NCRP REPORT No. 82
SI UNITS IN RADIATION PROTECTION A N D MEASUREMENTS Recommendations of the NATIONAL COUNCIL O N RADIATION PROTECTION AND MEASUREMENTS
Issued August 13,1985 First Reprinting February 28,1994 National Council on Radiation Protection and Measurements 7910 WOODMONT AVENUE / Bethesda, MD 20814
LEGAL NOTICE This report was prepared by the National Council on Radiation Protection and Measurements (NCRP). T h e Council strives to provide accurate, complete and useful information in its reports. However, neither the NCRP, the members of NCRP, other persons contributing to or assisting in the preparation of this report, nor any person acting on the behalf of any of these parties (a) makes any warranty or representation, express or implied. with respect to the accuracy, completeness or usefulness of the information contained in this report, or that the use of any information, method or process discloeed in this report may not infringe on privately owned rights; or (b) assumes any liability with respect to the use of, or for damages resulting from the use of, any information, method or process disclosed in this report.
L i b r a r y of Congress Cataloging i n Publication D a t a National Council on Radiation Protection and Measumments. SI Units in radiation protection and measurements. (NCRP report ; no. 82) "Issued March 13, 1985." Bibliography: p. Includes index. 1. Radiation-Measurement. 2. Units. 3. Metric system. I. Title. 11. Series. QC795.42.N37 1985 616.07'57'0287 85-3052 ISBN 0-913392-74-X
Copyright O National Council on Radiation Protection and Measurements 1985 All rights reserved. This publication is protected by copyright. No part of this publication may be reproduced in any form or by any means, including photocopying, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotation in critical articles or reviews.
Preface In 1948, the General Conference on Weights and Measures (Confkrence Ginirale des Poids e t Mesures, CGPM), a diplomatic conference responsible for the "international unification and development of the metric system," instructed its International Committee for Weights and Measures to develop a set of rules for the units of measurement. The "International System of Unitsn (SI) was developed under this charge, adopted by the CGPM in 1960, and accepted by all signatories to the Meter Convention in 1977. The special units, curie, roentgen, and rad are not coherent with this system and were listed among those units to be used for a limited time. The corresponding SI units are reciprocal second, coulomb per kilogram, and joule per kilogram, respectively. Recognizing that this shift to different units might cause difficulty, particularly in radiation therapy, the International Commission on Radiation Units and Measurements (ICRU) solicited comments on this matter in 1973 and 1974. From these comments, it appeared that the majority of workers in the field would find SI units acceptable if the transition period was sufficiently long and if there could be special names a t least for reciprocal second and joule per kilogram. Therefore, the ICRU proposed special names for these units and the 1975 meeting of the General Conference adopted, for us'e with ionizing radiation, the special names of becquerel for reciprocal second and gray for joule per kilogram. The ICRU will use SI units and, where pertinent, special names. Currently, it will also include the relevant special units, but it plans to drop such usage by 1985; i.e., after a 10 year transition period.' This action of the ICRU was followed by a joint action of the ICRU and the.Internationa1 Commission on Radiological Protection (ICRP) which resulted in the approval by the CGPM in 1977 of a special name-sievert-for the SI unit of dose equivalent. The ICRP has used only SI units in all of its reports since 1977. In view of these actions internationally, but mindful of the sometimes special problems in the U.S.A., the National Council on Radiation Protection and Measurements felt it appropriate to consider its own position with respect to the adoption of SI units in radiation uses iii
' For further details see ICRU Report 33 (1980).
iv
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PREFACE
and applications, in radiation protection and measurement and indeed in NCRP reports themselves. To assist the Council in this matter, an Ad Hoc Committee on Policy in regard to SI was formed. This report is the result of that Ad Hoc Committee's deliberations, suitably modified in the Council's review and approval process. The report therefore states the Council's position on this matter. Basically, the Council has decided to recommend to all that the SI be used and the special names for the SI units be employed where indicated. To accomplish this, the Council recommends (noting that the ICRU's 10-year period has essentially elapsed) a further transition period ending in five years, December 1989. For approximately a two year period through 1986, the NCRP recommends simultaneous use of SI and the present units, the present units being reported first and SI in brackets. During 1987-89, SI units will be quoted first with present units in brackets. Thereafter, only SI will be used. The NCRP recognizes that some will find the transition more difficult than others. It solicits the cooperation of all in making this transition, which experience indicates is less formidable than many suppose. The report was draftRd initially by the following Ad Hoc Committee: Randall S. Caswell, Choirman National Bureau of Standards Gaithenburg. Maryland
Edward R. Epp Massachusetts General Hospital Boston, Massachusetts
William A. McCarthy Cleveland Clinic Foundation Cleveland, Ohio
Fred A. Mettler, Jr. Veterans Administration Hospital Albuquerque, New Mexico
IWph H. Thomas Lawrence Berkeley Laboratory Berkeley, California
Harold 0. Wyckoff International Commieaion on Radiation Units and Measurements Bethe&. Maryland NCRP Seeretariot--Thomas M. Koval Thomas Fearon James Walker
Henry N. Wagner. Jr. The Johne Hopkins University Baltimore, Maryland
The Council wishes to express its appreciation to the members of the Committee and reviewers for the time and effort they devoted to the preparation of this report. Bethesda, Maryland 8 December, 1984
Warren K. Sinclair President, NCRP
Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Concepts of Quantities and Units . . . . . . . . . . . . . . . . . 1.2 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 SI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Base Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Supplementary Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Derived Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Special Names for Units . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Units for Use with SI . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Units Accepted Temporarily . . . . . . . . . . . . . . . . . . . . . . 2.7 Coherence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 SI Prefixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . Relationship Between Conventional and SI Units for Selected Quantities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Specific Energy. Absorbed Dose. and Kerma . . . . . . . . 3.1.1 Specific Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Absorbed Dose . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Kerma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Dose Equivalent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 SI Units for Nonionizing Radiation . . . . . . . . . . . . . . . . 4 Considerations Concerning Adoption of SI Units . . . . . . . . . 4.1 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Radiation Science . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Radiation Physics . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Radiation Chemistry . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Radiation Biology . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Radiation Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Radiation Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Diagnostic Radiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Nuclear Medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1 3 3 4 8 8 9 9 9 9 10 10 10 12 12 12 12 13 14 16 18 18 20 20 22 22 23 23 23 25 25 26
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CONTENTS
4.7 Environmental Radiation Measurement . . . . . . . . . . . . 4.8 Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.1 General Commercial Considerations . . . . . . . . . 4.8.2 Radionuclide Assay Devices . . . . . . . . . . . . . . . . 4.8.3 Radiation Therapy Instrumentation . . . . . . . . . 4.8.4 Instrument Modification . . . . . . . . . . . . . . . . . . . 4.9 Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 Regulatory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Discussion and Recommendations . . . . . . . . . . . . . . . . . . . . . APPENDIX A. Definitions of the SI Base Units . . . . . . . . . . . . . APPENDIX B . Conversion Between SI and Conventional
.
Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . APPENDIX C. Conversion Tables for Activity, Absorbed Dose. and Dose Equivalent Between SI and Conventional Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The NCRP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NCRP Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Executive Summary The National Council on Radiation Protection and Measurements recognized the need to consider its position with regard to the use of SI units in the fields of radiation protection and measurement and in NCRP reports. The present report is the result of its examination of these matters. The report considers the concepts of quantities and units, and gives a brief history of the International System (Le Syst6me International d'unitks, SI). The structure of the SI is then discussed, including base units, supplementary units, derived units, and some special categories of units. The meaning of coherence, which is an advantage of the SI, is explained, as well as the use of prefixes in the SI. The relation between conventional units and SI units for some quantities used in radiation measurement is discussed. Examples are given of calculations in both customary units and SI units. Next, arguments are considered for and against the adoption of SI units. Such questions as the experience with the adoption of the SI in other nations, safety considerations in the adoption of new units, and the impact of SI units on various fields of radiation protection and measurement are considered. A chief argument in favor of the adoption of the SI is that this system, with the desirable feature of coherence, is the consensus candidate for a single system of units to be used for all branches of science and engineering throughout the world. If we are to join the move toward a single system of units in the world, then at some time it will be necessary to change to SI units. Although it is difficult to estimate the economic costs of switching to the SI, it does seem clear that the cost of switching in the near future will be less than the cost of switching at any later time. The gradual adoption of SI units over a transition period will permit familiarization with the new units, provide time for necessary education and training to take place, and is generally consistent with the practice followed in other countries. The Council recommends the gradual adoption of SI units over a transition period beginning immediately and ending in about five years (December 1989). Experience indicates that, with proper educational processes in place, it is not difficult for individuals to change 1
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EXECUTIVE SUMMARY
to a new system of units. Available evidence does not indicate that safety is jeopardized by the introduction of a new unit system. For an approximately two-year period through 1986 the NCRP recommends simultaneous use of SI units and present units. During this period the Council recommends reporting of measurements in conventional units followed by the value in SI units in parentheses. During the period 1987-1989, it is recommended that measurements be reported with the value in SI units given first followed by the value in conventional units in parentheses. After 1989 it is recommended that SI units be used exclusively. In tables, graphs, and radiation records one system of units would be used with a footnote containing conversion factors to the other system. The NCRP recognizes that some organizations may find it more convenient for administrative or other reasons to make an abrupt change to SI units. In some cases it may not be practical to effect a transition in the recommended five-year period. In such cases the NCRP recommends that a carefully considered plan be developed to carry out the transition in an appropriate time period.
1. Introduction The subject of units for measurement is an important, complex, and sometimes emotional one. With the adoption of the modern consensus metric system, called SI for Systime International, throughout the greater part of the world and by many international organizations, the National Council on Radiation Protection and Measurements has recognized the need to consider its position with regard to the use of SI units in the fields of radiation protection and radiation measurement and to the adoption of SI units in NCRP reports. This report considers the concepts of quantities and units, discusses the International System, develops the relationships between conventional and SI units for radiation quantities, considers arguments for and against the adoption of S I units in terms of their use in various fields of activity, and provides recommendations for action. Emphasis in this report is given to ionizing radiation with some discussion of the use of the SI for nonionizing radiation.
1.1 Concepts of Quantities and Units
I t is necessary to distinguish between a physical quantity and a physical unit. " Aphysical quuntity characterizes a physical phenomenon in terms that are suitable for numerical specifications" (ICRU, 1980). " Aphysical unit is a selected reference sample of a quantity" (ICRU, 1980). The magnitude of a specified physical quantity can be expressed as a product of a pure number and a unit.' For example, let the symbol for length be L and the unit for length be meter (symbol, m).' If the 'Thus, if the quantity is divided by its unit, a pure number is obtained. For this reaeon the axes of graphs and the heading of tabular data are frequently given by the quotient of the symbol or name for the quantity and the symbol or name for its unit. In the following example the notation would be length L or - or L/m. meter
m
'Many international organizations use the spelling metre. 3
4
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1. INTRODUCTION
length, L, is measured and d is the symbol for the number of meters in L, Neither the physical quantity, nor the symbol used to denote it, implies a particular choice of unit. Note that symbols for quantities are italicized but those for units are not. As an example, consider the physical quantity called the wavelength, A. A particular measurement might lead to the specification of the "sizen of a wavelength as X
=
5.896 x lo-' m.
This may equally well be written X/m = 5.896 x lo-'. Given these definitions of a physical quantity and of a unit, one needs to set up a system of units so that the magnitude of the quantities of interest can be specified. One possible system might be to specify a unique unit for each quantity. However, some quantities are defined in terms of the product or quotient of other quantities. Thus a different name for the unit of each quantity leads to redundance because the unit for these quantities can also be expressed as the product or quotient of the units for the "other quantities." With the development of the field of quantities and units, the units for a selected few "other quantitiesn have been specified as "base quantities," and their units as "base units." The-unit for each additional quantity is then specified as the product or quotient of suitable powers of the base units. If this "product" or "quotient" contains no numerical values other than unity, the unit system is said to be coherent (see section 2.7).
1.2 History The sophistication and rigor associated with physical quantities and units has advanced over the centuries as commerce expanded and as the needed type and accuracy of measurements increased. Local units of well recognized quantities such as length and mass sufficed when commerce was restricted to local exchange. In early times, the standards for units of length were frequently defined in terms of portions of the human body or by agricultural products. According to a review by Zupko (1968), the inch as a unit of length was brought to England by the Romans and was commonly associated with a thumb's breadth. In the Middle Ages, the inch was defined as
1.2 HISTORY
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5
the length of three medium-sized barley corns placed end to end. The relatively wide possible variations in such a standard would indeed cause serious confusion in commerce. There were many other units of length in vogue in England in the Middle Ages. These included the "nail" which was the length of the last two joints of the middle finger and was later taken to be equivalent to about 2% inches. The "palm" was a length corresponding to a hand's breadth and was later made equal to a distance of 3 inches. The "hand" (equal to 4 inches) is still used for measurement of the height of horses. The "finger" was equal to two nails and therefore corresponded to a distance of about 4% inches. The "span," the distance between the tip of the small finger and the tip of the thumb of an outstretched hand, corresponds to a distance of 9 inches. For larger distances, units such as foot, yard, rod, perch3, furlong and mile were, and some still are, used. In Europe during the 17th and 18th centuries, a very large variety of weights and measures e.xisted. Weights and measures not only differed between countries-in 1742 the French "piedn and "livre" were found to be larger than the English "foot" and "poundn by six and eight percent, respectively (BIPM, 1975)-but many systems of measure existed in individual countries. For example, more than 50 different "livres" existed in France before the introduction of the metric system (Moreau, 1975). The industrial revolution increased the need for accurate and reproducible measures. Many proposals were put forth to resolve the difficulties resulting from varied measures. In 1791, the French General Assembly adopted the principle of a system of measures founded entirely on one base unit of length, the "meter," defined to be equal to one ten-millionth of the length of the quadrant of the earth's meridian. The unit of mass was to be the mass of a cubic decimeter of water at the temperature of maximum density (BIPM, 1975). Further development led to a system based on two artifact standards: a meter bar for length and a kilogram weight for mass. Following further spread of the system, the "Convention du Mitre" or Treaty of the Meter was A "perch of land" was a unit of land area "of no standard dimensions but usually the square of the linear perch common in the region" (Zupko, 1968). The size of a perch (of length) depended upon the region or type of measure for which it was used. For example, one perch was 12 feet when called a Tenant right or Court measure; was 18, 20, or 24 feet when called a Woodland Measure, and sometimes waa 21 feet when called a Church Measure. Perches of 16% feet or smaller were usually agricultural measures while perches of more than 16'/z feet were usually used in forest regions and by town craftsmen.
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1. INTRODUCTION
signed in 1875 by 20 countries including the United state^.^ Since that time both the metric and conventional English systems of units have been legal in the United States. The English units of length and weight are defined in terms of their metric equivalents in the United States and some other countries. Since 1893,the inch has been legally defined in the United States in terms of the meter. For a critical review of the metric system, see Danloux-Dumesnils (1969). Even with the adoption of the Treaty of the Meter, marked variations in the systems of units used throughout the world continued to exist. In fact, various metric systems of units were developed. The units systems known as esu (electrostatic units), emu (electromagnetic units), cgs (centimeter-gram-second) and mks (meter-kilogram-second) are all metric systems. They were evolved for use in limited branches of science. Giorgi in 1901 (Moreau, 1975; BIPM, 1975) made recommendations which led to the mksa (meter-kilogram-secondampere) system, a coherent unit system covering the whole field of electrical, magnetic, and mechanical phenomena. As an example we compare several units in the esu, emu, and mksa systems. Quantity charge potential difference force
esu 2.998 XYOO ' statcoulombs6 1 statvolt 1 dyne
= =
=
emu 1 a b z comb 2.998 X 101° abvoltss 1 dyne
=
mksa 10 c o x b s
=
299.8 volts
=
lo-' newtons
'Three organizations which have been established under the Treaty of the Meter should be mentioned: (1) The Conference Generale des Poids et Mesures (CGPM, General Conference of Weights and Measures) is a diplomatic-scientific body which now meets every four years, provides the budget for the BIPM (see below), and makes final decisions concerning the metric system; for example, names and values of units. (2) The Bureau International des Poids et Mesures (BIPM, International Bureau of Weights and Measures) is the central laboratory of the international metric system, located in SBvres, near Paris, France. It was set up for conservation of the international artifact standnrds and for their comparison with national standards. At present it ia the central focus for comparison of national and international standards of measurement. (3) The Comiti International des Poids e t Mesures (CIPM, International Committee of Weights and Measures) has scientific and management responsibility for overseeing the metric system and the BIPM on a continuing basis. Reporting to the CIPM are seven Consultative Committees in various technical areas. The Comiti Consultatif pour lee Unitis (CCU) advises CIPM on questions of quantities and units. For ionizing rahations the Comiti Consultatif pour les Etalons de Mesure des Rayonnements Ionisants (CCEMRI) has been established with Sections on X and Gamma rays, and Electrons; Radionuclide Measurements; and Neutron Measurement. In the United States the National Bureau of Standards participates in a continuing series of measurement intercomparisons of radiation units through the BIPM and CCEMRI. 'The numerical factor is the velocity of light in cm s-I.
1.2 HISTORY Quantity
esu -
mass energy
1 gram
1 erg
1 gram 1 erg
7
mksa
emu = =
/
= =
lo-' kilograms 10-'joules
The International Union of Pure and Applied Physics and its Symbols, Units and Nomenclature (S.U.N.) Commission expressed the need for the international adoption of an "international practical system of units" for international communication, to be based on the meter, the second, the kilogram, and an electrical unit of the absolute practical system. A similar request was made by the French government (BIPM, 1975). This led the General Conference, during its 1948 meeting, to instruct the CIPM: "to study the establishment of a complete set of rules for units of measurement"; "to find out for this purpose, by official inquiry, the opinion prevailing in scientific, technical, educational circles in all countries"; and "to make recommendations on the establishment of a practical system of units of measurement suitable for adoption by all signatories to the Meter Convention" (NBS, 1981). The 10th General Conference decided in 1954 that such an inter. national system (a modernization of the mksa system) was to be basec on six units: meter, kilogram, second, ampere, kelvin, and candela. 11 1960, the 11th General Conference adopted the name "The Interna tional System of Units" (le Systeme International &Unit&) and issuec rules for prefixes. In addition, the conference divided SI units int three classes: base units, supplementary units, and derived units. As science evolves and develops it is expected that the Internationr System of Units will concurrently develop. The system has bee designed as a dynamic system. For example, in 1971 the Gener Conference added a seventh base quantity, with the unit mole, as measure of the "amount of substance." It is apparent that the use the SI will increase over the years, and will gradually supplant 0th systems. Most countries have adopted or are adopting the Intern tional System as their exclusive legal system.
2.1 Base Units T o form a system of units, a limited set of base units is arbitrarily chosen, in general, to enhance accuracy and simplicity. Once the choice of these base units has been made, an entire system of units can be constructed logically. From a scientific viewpoint, the division of these units into the three classes (base units, supplementary units, and derived units) is arbitrary. During the development of the present metric system of quantities and units the number of base units has gradually increased. The metric system probably came into being because of the suggestion that three concepts-length, mass, and time could be expressed in terms of a single unit-meter. It can be used to specify a unit of time by means of the period of a pendulum of special length. This unit of length can also be used to define a volume and therefore a mass of water (at a given temperature). Probably because of variations of water density with temperature and variations of the period of a pendulum with location on the earth, the three base units (for length, mass, and time) have been defined independently. When the base units for length, mass, and time were used to provide a derived unit for electrical and magnetic quantities, fractional exponents of some of the three units were necessary. Id 1901 Giorgi pointed out that such fractional exponents could be eliminated by adding another base unit-i.e., one for an electrical quantity (BIPM, 1975). Such a base unit-ampere-was adopted in 1948. For treatment of thermal phenomena another base unit-kelvinwas adopted in 1948 and its scale defined in 1954. The inclusion of a base unit-candela-for luminous intensity was approved in 1948. In calculations of the amounts (masses) of different chemical species involved in a given chemical reaction, the ratio of the masses of the two species is needed. As the mass ratio of quantities of each of two different species can be determined from chemical or atomic reactions much more accurately than by means of the separate determinations of their respective masses, it is useful to provide a base unit for the amount of substance of a chemical species, the "mole." Thus, presently, 8
2.5 UNITS FOR USE WITH T H E SI
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9
there are seven base SI units: meter, kilogram, second, ampere, kelvin, candela, and mole (see also Appendix A).
2.2 Supplementary Units There are two supplementary units, the unit of plane angle, the "radian," and that of solid angle, the "steradian."
2.3 Derived Units In addition to base units and supplementary units, there are derived units which are the products or quotients of powers of the base and supplementary units. Examples of SI derived units are given in Appendix B, which is based on National Bureau of Standards (NBS) Publication 330 (NBS, 1981). The base units, derived units, and supplementary units are all termed "SI units."
2.4 Special Names for Units Several of the derived units have special names and symbol8 restricted to use with specified quantities. For example, for absorbed dose, the special name gray (Gy) is given to joule per kilogram (J kg-'). For activity of a radionuclide the special name becquerel (Bq) is given to reciprocal second (s-I). The SI derived units, becquerel, gray, and sievert (for dose equivalent), have been "admitted for reasons of safeguarding human health" (NBS, 1981).
2.5 Units for Use with the SI Some units exist outside the International System that are used with the system. Examples of these are minute and hour of time, liter, and barn. The combination of such units with SI units results in the loss of coherence inherent in the International System. Additionally, some other units continue to exist outside the International System simply because their value in terms of SI units must be obtained by experiment. An example of such a unit is the electron volt (eV).
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2. SI
2.6 Units Accepted Temporarily
In 1969, the CIPM accepted the use of some special units on a temporary basis. Of importance for the present document is that four of the units accepted temporarily are roentgen, rad, curie, and barn. No definition of "temporary" is given. However, many nations have already discontinued their use. 2.7 Coherence A major advantage of the SI is its coherence. A system is coherent when no conversion factors other than unity are needed for the formation of units derived from the base and supplementary units. For example, in the coherent SI for absorbed dose (see Table B.11, 1J 1 Gy = -= 1 J kg-' = 1 J/kg? 1 kg
(2.1)
Whereas, in the conventional system, 1 rad
100 erg
= -=
1g
100 erg g-'
=
100 erg/g.
(2.2)
Similarly, in the coherent SI, for activity of a radionuclide, 1 1s
1 Bq = - = 1 s-'.
(2.3)
In the customary system,
The conversion factors 100 and 3.7 x 101° which occur in Equations 2.2 and 2.4 by definition cause the conventional system to be incoherent. For other examples of calculations in coherent and non-coherent systems of units, see Section 3. 2.8 SI Prefixes Prefixes may be used for convenience to form decimal multiples and submultiples of SI units (NBS, 1981). The currently adopted prefixes are given in Table 2.1. 'The notations such as J/kg and J kg-' are equivalent and both are accepted.
/
2.8 SI PREFIXES
11
TABLE 2.1-SI prefixes
-.
Factor
Prefiw
Symbol
Factor
Prefix
E P
lo-'
deci
d
Pta
tera
T
centi milli micro
c m
nano
n P
10'" 1Ol6 10l2 loB
exa
gigs
G
lo6
mega kilo hecto deka
M
103
lo2 10'
k
h da
lo4 lo3 lo-'* 10-l6 lo-''
pic0 femto
atto
Symbol
P
f a
Use of prefixes is indicated by the following example:
Compound prefixes, formed by the juxtaposition of two or more SI prefixes, are not to be used. For example: 1 nm but not: lmpm.
When prefixes are used, there is lack of coherence. The magnitude of a quantity is most simply expressed as the product of a pure number and unit (see Section 1.1).When a prefix is used, part of the pure number is included in the prefixed unit. The advantages of coherence in calculations may be retained simply by converting from prefixed units to coherent units, performing the calculation, and converting back to prefixed units, if desired. Example: What is the power, P, on the target of an accelerator operating at 3 MV terminal potential, E, with a beam current, I, of 10 mA?
P = (3 MV) x (10 mA)
3. Relationship Between Conventional and SI Units for Selected Quantities Some definitions of radiation quantities and sample calculations are presented in this section as examples of the use of SI units in radiation problems. The quantities treated here are widely used in radiation work.
3.1 Specific Energy, Absorbed Dose, and Kerma Specific energy, absorbed dose, the kerma are all physical quantities whose units are given with dimensions of energy per unit mass. For convenience, the definitions of these quantities as given by the ICRU are reprinted here. The reader is referred to ICRU Reports 25 (ICRU, 1976) and 33 (ICRU, 1980) for more precise details and explanations.
3.1.1 Specific Energy The quantity specific energy (imparted), z, is the quotient of c by m, where t is the energy imparted by ionizing radiation to matter of mass m,
3.1.2 Absorbed Dose The absorbed dose, D, is the quotient of dS by dm, where d t is the mean energy imparted by ionizing radiation to matter of mass dm,
NOTE: The absorbed dose is the limit of the mean specific energy as the mass in the region under consideration approaches zero, i.e., 12
3.1 SPECIFIC ENERGY, ABSORBED DOSE, AND KERMA
/
13
D = lim 2. m-0
This equation, which indicates the relationship between D and z, could serve as an alternative definition of D.
3.1.3 Kerma The kerrna, K, is the quotient of dE,, by dm, where dE,, is the sum of the initial kinetic energies of all the charged ionizing particles liberated by uncharged ionizing particles in a material of mass dm,
The coherent unit of specific energy, absorbed dose, and kerma in the cgs system of units is the erg g-' and in the International System of Units is the J kg-'. The unit rad is not coherent in either the cgs or the International System of Units, 1 rad = 100 erg g-' = lo-* J kg-' The historical reason for the choice of the size of this special unitthe rad-is that, under conditions of charged particle equilibrium, a specific energy absorption of 100 erg g-' (to within about 10 percent) results from the exposure of a small volume of soft tissue to 1 roentgen (see Section 3.2). This is true over a wide range of photon energy and was a useful numerical equivalence in radiation protection. This numerical equivalence may, however, have led to misunderstandings of the radiation quantities and units used in radiation protection. Such equivalence does not hold in the SI between the units for exposure and absorbed dose, but does hold for the units of air kerma and absorbed dose. The coherent unit in the International System of Units for the quantities discussed in this section is the J kg-' which is given the special name "gray" (symbol Gy). Thus it follows that, 1 Gy = 100 rad. Exampk The absorbed dose, D, in a small mass of tissue resulting from irradiation by charged particles, is given by the formula,
14
/
3. CONVENTIONAL AND SI UNITS
where 9 is the charged-particle fluence, (dE/dz),,l is the linear collision stopping power of the charged particles in tissue, p is the density of tissue, and k is a constant depending upon the units used. Assume the following magnitudes for the quantities involved:
(3col
= 2 MeV cm-' = 3.2 x lo-" J m-'
The results in three systems of units are: SI (non-coherent)
1.602 x lo-' rad g MeV-' 45 108cm-~ p Ig~ m - ~ d E 2 - MeV cm-'
10" m-' 103 kg m-3 2 MeV cm-'
dx D
3.2 x
k
3.2 rad
Since 1 rad =
1.602 X lo-"
Gy
SI (coherent)
1.0 Gy kg cm MeV-' m-I 10" m-2 103 kg m-3 3.2 x lo-'' J m-' 3.2 x lo-' Gy
Gy, all results are equivalent.
3.2 Exposure The quantity exposure, X,is defined as the quotient of dQ by dm where dQ is the absolute value of the total charge of the ions of one sign produced in air when all the electrons liberated by photons in a volume element of air having mass dm are completely stopped in air,
3.2 EXPOSURE
/
15
The special unit of exposure in the cgs system of units is the roentgen (R) defined by the International Committee for Radiological Units (ICRU, 1938) as "the quantity of X- or gamma-radiation such that the associated corpuscular emission per 0.001293 gram of air produces, in air, ions carrying 1 e.s.u. of quantity of electricity of either sign." "0.001293 gram of air" is the mass of 1 cm3 of air a t 0°C and 760 mm mercury pressure (standard temperature and pressure). This definition of the roentgen therefore leads to a non-coherent unit in the cgs system of units. In more recent definitions of the size of the unit roentgen, it is usual to convert units and write (ICRU, 1980): 1 R = 2.58 x
C kg-'.
In the International System of Units, the coherent unit for the quantity exposure is the coulomb per kilogram (C kg-'). No special name has been given to this unit. Example
The exposure rate due to photons with energy greater than 6, X 6 ,a t distance L from a radioactive nuclide of activity A is given by ICRU (1971):
In the conventional system Xbis in roentgens per hour (R h-') when A is in curies, and L is in meters. r s , the exposure-rate constant, is in units of R m2 h-' Ci-'. Calculation in conventional units Calculate the exposure rate 3 meters from a 10-curie cobalt-60 source. The value of r, for 60Co (NCRP, 1974) is: where contributions from low-energy gamma-ray photons and x rays below a 6 of 11.3 keV have not been included. Substituting into Equation 3.2 we have:
16
/
3. CONVENTIONAL AND SI UNITS
Calculation in International System units Calculate the exposure rate a t 3 meters from a 1 TBq source.
rd= 2.53 X
lo-''
C kg-' m2 s-' Bq-'
= 2.81 x lo-" C kg-' s-'.
3.3 Dose Equivalent T h e quantity dose equivalent is defined by the ICRU (1980) as follows: The dose equivalent, H, is the product of D, Q, and N a t the point of interest in tissue where D is the absorbed dose, Q is the quality factor and N is the product of all other modifying factors,
H = DQN. T h e special name sievert, symbol Sv, has been adopted for the SI unit of dose equivalent in the field of radiation protection. For a given irradiation, the numerical value in joules per kilogram for the two quantities D and H may differ, depending on the values of Q and N. T o avoid any risk of confusion, the special names for the respective units should be used; i.e., D should be expressed in grays and H should be expressed in sieverts, 1 sievert = 100 rem.
Further ICRU reports which are helpful in understanding the definition of the quantity "dose equivalent" are ICRU Report 33 entitled Radiation Quantities and Units (ICRU, 19801, and ICRU Report 25 entitled Conceptual Basis for the Determination of Dose Equivalent (ICRU, 1976), and ICRU Report 39 entitled Determination of Dose Equivalents Resulting from External Radiation Sources (ICRU, 1985). An absorbed dose of 1 rad from photons results approximately in a dose equivalent of 1 rem. This leads to the numerical relationship that an exposure of 1 R t o soft tissue produces approximately an absorbed dose of 1 rad and a dose equivalent of 1 rem. This convenient "rule of thumb" associated with conventional units, however, can lead to
3.3 DOSEEQUIVALENT
/
17
confusion since it may obscure the differences among the quantities exposure, absorbed dose, and dose equivalent.
Example of dose equivalent calculation The fluence rate of neutrons a t middle latitudes and sea level, produced by the iilteraction of cosmic radiation with the earth's atmosphere may be taken as 7 x cm-2 s-'. Calculate the maximum dose equivalent in a semi-infinite tissue-equivalent slab from a year's exposure t o cosmic ray neutrons.
Calculation i n conventional units For the cosmic ray spectrum the fluence-to-dose equivalent conversion is taken as (Shaw et al. 1969): H/
lo-'
rem cm2
This is based on the annual maximum dose equivalent in the 30-cm thick slab from cosmic ray neutrons. Remembering that the number of seconds in one year is about 3.16 x lo7, this becomes: ~ r n s-' - ~ x 1.27 x lo-' rem cm2
H =7x X
3.16
= 2.8
X
lo7 s
x
rem.
Calculation i n SI units Recalling that there are cosmic ray neutrons is:
lo4 cm2 in
one m2, the annual fluence of
The fluence to dose equivalent conversion, HI@, for the spectrum of cosmic ray neutrons is: and the annual dose equivalent is H = 2.21 x
lo9 m-2 X
1.27 X 10-l4 Sv m2
Comparing the two calculations and remembering that 1 SV= lo2 rem we see that they are in agreement.
18
/
3. CONVENTIONAL AND SI UNITS
3.4 Activity Based upon the recommendations of the International Commission on Radiation Units and Measurements (ICRU), the 15th CGPM adopted a special name for the SI derived unit of activity. The special name is becquerel (symbol Bq). The becquerel is intended to replace the curie as a measure of the rate of spontaneous nuclear transformation of a radioactive nuclide. At the time of the definition of the curie, it was recognized that a unit for activity was needed. The choice of curie was originally based on the amount of radon in equilibrium with 1 g of '%Ra. As the accuracy of the determination increased the value changed. An arbitrary value was finally chosen for general use, 3.7 x 10'' s-'. One Bq equals 1 s-'. One curie, therefore, is equal to 3.7 x 10'' Bq.7 For example, if one wishes to convert the activity of a radiopharmaceutical, -Tc pertechnetate, with an activity of 20 mCi to SI units, the calculation would be as follows: since 1mCi equals 3.7 x lo7 s-', 20 times that number equals 74 x lo7 s-' or 7.4 x 10' Bq or 740 MBq.
3.5 SI Units for Nonionizing Radiation The importance of nonionizing radiation is increasing due to the widespread use of diagnostic ultrasound and the heightened interest in effects of ultraviolet, radiofrequency, and microwave radiation on living systems. The physical description of nonionizing radiation and its interaction with matter can be specified in terms of the base and derived units of the International System of Units. Quantities used for microwave radiation include: electric field strength in volts per meter (Vm-I), magnetic field strength in amperes per meter (A m-I), power density in watts per square meter (W m-*), and specific absorption rate, SAR, in watts per kilogram (W kg-') (NCRP, 1980). The use of the term "power density" may be represented by "energy flux density" or "irradiance." In some instances, the term power density refers to power per unit volume rather than unit area. However, its association with surfaces has a widespread application and
'Becquerel is a epecial name for s-' to be uaed for activity of a radionuclide.Hertz ia the epecial name for a-' to be used for frequency.
3.5 SI UNITS FOR NONIONIZING RADIATION
1
19
therefore terms such as current density, expressed in amperes per square meter, are retained in the SI. In NCRP Report No. 67, use of specific absorption rate (SAR) is recommended with units "W kg-'" (NCRP, 1980).More complete information is contained in that report and the forthcoming report of NCRP Scientific Committee 53. For ultrasound, useful quantities include pressure in pascals (Pa, N m-2) and intensity, synonymous with power density, in watts per square meter (Wm-*).NCRP Report No. 74 treats ultrasound (NCRP, 1984).
4. Considerations Concerning Adoption of SI Units 4.1 General Considerations
It seems clearly desirable that a common system of units be used for all branches of science and engineering throughout the world. Only then can the many different branches of science and engineering use a single common language. (It would also be desirable that the same name be used for a given quantity in different fields of study-by way of unfortunate example, energy flux density for ionizing radiation is the same quantity as irradiance in radiometry.) The consensus candidate for a world system is the Systeme International, accepted by 45 of the major nations of the world (NBS, 1981, p. 44; IUPAP, 1978; IUPAC, 1979; Metric Commission Canada, 1982). If the SI is adopted, radiation units rather than being special units (see Section 2.6), will be coherent with other units in science and engineering throughout the world. While there used to be international adherence to the conventional radiation units (R, rad, rem, Ci) this is no longer true. The SI has already replaced the conventional system of units in Sweden, Australia, and in the Comecon (Eastern Europe) countries. The conventional units will no longer be authorized in the European Economic Community after a date to be fixed, not later than Dec. 31, 1985 (EEC, 1980). The International Commission on Radiological Protection has, since 1977, been using the SI exclusively (ICRP, 1977). The International Commission on Radiation Units and Measurements has recommended adoption of the SI by 1985, and currently is preparing its reports in dual notation (both SI and conventional units given), or only in coherent SI units. The International Electrotechnical Commission study committee SC45B, meeting in Warsaw in 1979, however, recommended (1) suspension of the abandonment of the current units (rad, curie, rem), (2) utilization simultaneously and in transition of the two systems (the new SI unit preceding the former unit which would be placed in parentheses), and (3) rounding off as much as possible the values expressed in curies or becquerels. 20
4.1 GENERAL CONSIDERATIONS
/
21
A growing trend toward requiring the use of SI units is appearing in U.S. journals. SI units are now required by Medical Physics. The Journal of Nuclear Medicirw states that units should be in the SI. Present policies of Radiology and the American Journal of Roentgenology call for conventional units followed by SI units in parentheses. Manuscripts submitted in SI units are not changed. Health Physics now requires SI units, with or without traditional units in parentheses (Roessler, 1984). American manufacturers wishing to sell instruments to customers elsewhere in the world must frequently provide scales in SI units, which may require double scale numbering or other modifications if conventional radiation units are to be used as well. A major argument in favor of the SI is the simplicity and coherence of the system. Units are derived from combinations of seven base units with two supplementary units. A calculation using SI units throughout will give an answer in SI units. The system is simple to learn and is less prone to error than an incoherent system. For example, practical units of the same quantity are decimal multiples of each other (for example, centimeter and meter), unlike inch, foot, and yard. An argument which can be considered either for or against the adoption of SI units, depending upon the point of view, is the question of safety and the avoidance of errors in dose determinations and radiation measurements. The argument in favor says that once the SI is in general use, the chance for error will be lessened due to the simplicity of calculations (absence of numerical factors in formulae), the consistency of the whole measurement system, and the lack of need to convert from one system to another. The argument against says that, during the transition period from the conventional units to SI units, opportunities for error will increase due to untrained personnel not understanding the new system, or simply due to confusion between new and old units. On the other hand, reduction in errors could result from more care used in dealing with unfamiliar units. A study made in Australia indicates no significant change in the rate of errors on introduction of SI units (Sandeman et al., 1979). On the other hand, Eichholz et al. (1980) sent questionnaires to health physicists, professionals in nuclear medicine, and the nuclear instrument industry. They reported that a high proportion of the respondents anticipate hazards to patients and personnel during a transition period to the SI. No numerical estimate could be obtained for the actual magnitude of this risk, which they considered to be largely associated with relearning lapses and fatigue. Eichholz et al. (1980) also reviewed the scientific literature for evidence to support the belief that a person
22
/
4. ADOPTION OF SI UNITS
may unconsciously revert to earlier training concepts under the effects of fatigue, nervous strain, pressure, or frequent disturbance. "However, the literature search failed to support the presumed existence of studies of transfer effects in applied fields" (Eichholz et al., 1980). An argument made against the adoption of SI units is that a large amount of training and cost is involved in the transition to SI units. Costs would arise from the retraining of personnel, the changing of computer codes, the recalibrating or rescaling of instruments, and making changes in tables, figures, reference data, etc. Such costs can be minimized but not completely eliminated by planning for an orderly transition period, such as 5 years or 10 years, so that managers could systematically plan the changeover process. Since the amount of technology increases faster than the population, the cost of changeover would be larger per capita a t a later time. In the meantime, the maintenance cost of two systems is higher than for one. Some of the cost outlays mentioned here would be counterbalanced by improved international communication and, eventually, by simpler training resulting from the use of a single system of units. Another argument against the adoption of SI units is the one of familiarity. Many people, consciously or subconsciously, prefer that which is familiar, and are less comfortable with that which is new or different or strange.
4.2 Radiation Science
The impact of adoption of the SI on various branches of radiation science needs to be assessed. In this connection, radiation physics, radiation chemistry and radiation biology might be examined. 4.2.1 Radiation Physics Absorbed dose would be expressed in grays (J kg-') instead of rads. This should cause no problems for approaches which determine dose either absolutely (e.g., calorimetry) or indirectly (e.g., ionization chamber measurements, thermoluminescence dosimetry). Exposure can be expressed in C kg-' instead of R. Similarly, the sievert would be used for expressing dose equivalent instead of the rem. Use of the becquerel (s-') in physics as a unit of measurement is more natural than the somewhat arbitrary curie. The use of the eV (keV, MeV, GeV) is
4.3 RADIATION PROTECTION
/
23
widely ingrained in radiation and nuclear physics; its magnitude is obtained experiment all^, and its use is permitted with the SI. With cm2 = lo-'' m2), its use is permitted regard to the barn (1barn = temporarily with the SI. Of course, particle energies can be expressed in joules (rather than eV) and nuclear cross sections in m2 (rather than barns), which would have the advantage of coherence. 4.2.2
Radiation Chemistry
In radiation chemistry the radiation chemical yield has often been expressed as the G value (the number of molecules changed per 100 eV of energy absorbed). The radiation chemical yield is frequently expressed as C(x), for which the SI unit is "mol J-I." "x" refers to the entity produced, destroyed, or changed by the energy imparted from the ionizing radiation. The use of SI units would not present a problem. As 1molecule/100 eV = 1.036 x lom7mol J", G(x) = 1.036 X lo-' G. For example, the G value for Fe3+ of 15.5 (100eV)-' for cobalt-60 gamma rays becomes 1.61 ~ m oJ-'. l 4.2.3
Radiation Biology
In radiation biology, apart from quantities already discussed, one of the most commonly used quantities is linear energy transfer (LET) expressed in keV/pm. This unit can be retained since eV is permitted. The coherent SI unit is J m-'. 1keVlrm = 1.602 x 10"'J m-'.
4.3
Radiation Protection
As.previouslymentioned, there are some apprehensions in the health physics community concerning the adoption of the radiation units of the International System. These concerns range from those of mere inconvenience to suggestions that safety programs may be impaired (Eichholz et al., 1980). It cannot be denied that there would be some inconvenience in the adoption of the new units, but its degree has, perhaps, been overstated. Experience in Canada (see, for example, issues of Metric Monitor, By a measurement of the charge of the electron.
24
/
4.
ADOPTION OF SI UNITS
published by the Metric Commission of Canada, Ottawa, 1974-present) and the United Kingdom (Metrication Board, 1978, 1980) has shown that the adoption of metric units of measurement was achieved without great difficulty using adequate educational programs. T h e experience in the conversion to a decimal system of currency in the United Kingdom (Moore, 1973), or in converting to driving on the right-hand side of the road in Sweden (Statens Trafiksakerhetsverk, c. 1977), shows that such changes may be achieved with minimal difficulty. For some period it would certainly be possible for errors to occur in the estimation of dose equivalent rates and other quantities used in radiation protection. At the doses and dose rates usually encountered in well-supervised programs, however, it seems unlikely that such errors could be so pervasive, or so prolonged, as to endanger seriously human health or life. The consequences of such errors in the calculation of absorbed dose to patients in the use of ionizing radiation in diagnosis or therapy are, however, of much greater significance and are discussed in Sections 4.4 through 4.6. Spokesmen for some U.S. government agencies have argued against the adoption of SI units for radiation quantities, because they feel the adoption does nothing to improve the practice of radiation safety. This argument should only be true in the short term. Radiation-safety practices within the United States are inevitably influenced by practices in other countries. Most major industrial countries in the world are committed to the adoption of the SI. In the long term, it should be to the benefit of the United States to conform to internationally accepted radiation units. Young health physicists trained in the use of the International System tend to see very real advantages in a coherent system of units, which reduces the probability of errors in calculation. Advantages may be expected eventually to accrue to radiation protection by the adoption of SI units. The importance of educational programs cannot be overestimated. Professional societies, learned journals, government agencies, universities, and industry must provide information for their members, contributors, students, and employees if the adoption of the SI is to be efficient. Fields closely related to radiation protection are those of radiological emergency preparedness and radiological defense. These fields are characterized by large numbers of instruments and large numbers of non-professional personnel being involved. To persons in these fields, replacement of instruments and training of personnel in SI units represent major endeavors and significant costs. Careful planning of a changeover to SI units would be needed to insure that personnel are
4.5
DIAGNOSTIC RADIOLOGY
/
25
properly trained in advance of a changeover and that a change to SI units is properly timed in connection with needed instrument replacements to minimize the costs involved. 4.4 Radiation Therapy
By far the greatest impact on radiation therapy would come from the use of the gray for the unit of absorbed dose. Since treatment regimens using external beams are most commonly given in fractionated form (200 rads per daily fraction as a typical example), the prescription of dose in fractions of a gray (e.g., doses of less than 100 rads per treatment for whole abdomen irradiation) could lead to problems with possible resistance to acceptance by radiation therapy departments. The use of centigray (1 cGy = 1 rad) in daily clinical practice of radiation therapy would serve as a practical means of implementing the introduction of the gray into radiation therapy departments during a transition period. Such use has already been adopted by a number of departments within the U.S. No numerical changes thus need be introduced either into dose prescription or into the records of doses accumulated by patients during a treatment regimen. The use of the centigray would also mean that during a transition period, monitoring systems that are used in dose delivery with therapy machines (e.g., linear accelerators), would not have to undergo any numerical change. Since a typical dose treatment delivered by external radiation beams over a six-week period may be on the order of 6,000 rads, this dose expressed as 60 grays falls within a convenient and practical numerical range. For interstitial or intracavitary treatments, the use of the becquerel would not cause problems since radiation therapists presently do not specify doses from radionuclides in terms of curies, but in terms of rads. Thus the physicist computes the desired strength of the source and this could be done in terms of becquerels instead of curies. However, in view of the many orders of magnitude difference between curies and becquerels, great care in calculation would have to be exerted, together with attention to training of individuals responsible for these calculations. 4.5 Diagnostic Radiology
The S I would be of importance to the diagnostic radiologist in terms
26
/
4. ADOPTION OF SI UNITS
of calculations of exposure, kerma, absorbed dose, and dose equivalent. The SI unit for exposure is the coulomb per kilogram (C kg-'). Exposure rate in amperes per kilogram (A kg-') or air kerma rate in watts per kilogram (W kg-') or equivalently absorbed dose in grays per second (Gy s-') may be used for testing diagnostic radiation parameters where higher accuracy is required than for radiation protection. Absorbed dose has been expressed in rads and in SI would be expressed in grays (Gy). Dose equivalent, previously expressed in rems, would be expressed in sieverts (Sv). Since most diagnostic x-ray equipment indicates target current in milliamperes, time in seconds, and tube potential in kilovolts, all of which will remain unchanged, the significant accommodation that would have to be made would be in the calculation of dose equivalent from various procedures. At the present time, the level of dose equivalent from usual diagnostic procedures is in the range of 20 to 500 millirem. Conversion factors are quite simple, as one millirem is equal to lo-' Sv. One millirem equals 10 microsieverts and one millirad equals 10 micrograys. Energy fluence rates in diagnostic ultrasound are expressed in watts per square centimeter (W ~ m - ~ For ) . practical purposes, these units may continue to be used, although for SI coherence, watts per square meter would be used. The frequency of present diagnostic transducers is on the order of 2 to 10 megahertz (MHz). Megahertz is already in the SI and needs no alteration.
4.6. Nuclear Medicine In diagnostic and therapeutic nuclear medicine, the conventional unit of activity is the curie (Ci), the SI unit being the becquerel (Bq). One becquerel is one reciprocal second or 1 s-'. Therefore, 1 Ci equals 3.7 x 10'' Bq. Administration of radiopharmaceuticals t o patients in quantities useful for imaging procedures currently ranges from 250 lrCi to 20 mCi. This roughly corresponds to activities ranging from lo7 to 10' becquerels. It may be convenient to express such activities in MBq where 1 MBq = lo6 Bq. If the SI were adopted, administered activities of radiopharmaceuticals would need to be converted to SI units (see Appendix C and the example below).
4.6 NUCLEAR MEDICINE
/
27
Example A common administered amount for scanning is 20 mCi of 99mTcmethylene diphosphonate. In order to convert this activity to SI units, we proceed as follows: Since 1 Ci = 3.7 x 10'' s-' then 1 mCi = 3.7 x lo's-' and 20 mCi = 20 x 3.7 x 10' s-'
and since then 20 mCi = 7.4 x lo8 Bq = 740 MBq. In the use of the SI, such activities would normally be rounded, in this case t o 750 MBq. As with diagnostic radiology, the calculation of absorbed dose will also need to be considered with the guidelines and conversion factors outlined in Section 4.5. A convenient reference for use in nuclear medicine, which gives absorbed dose per unit of administered activity for various nuclear medicine procedures in both mrad/pCi and pGy/ MBq, is Roedler et al. (1978). A more comprehensive tabulation of absorbed doses in S I units is available (SNIRP, 1981).
Example For a uniform distribution of a radionuclide in an infinite, homogeneous absorbing medium, a well-known formula relates the absorbed dose t o the time integral of activity per unit mass and the energy per transition of a radionuclideg:
c
D = 2.13 A = 2.13 n E where D is the absorbed dose in rad, is the time integral of activity per unit mass in pCi h g-',
c
'This holds when the energy is absorbed in the same region in which it is emitted. For other cases see. for example, ICRU (1979).
28
/
4.
ADOPTION OF SI UNITS
A is the energy emitted per unit time integral
of activity (rad g pCi-' h-'), n is the number of particles emitted per nuclear transition (for simplicity this number is assumed to be one), and E is the average energy per particle in MeV. The non-coherence is represented in this equation by the numerical coefficient 2.13 g. rad/(MeV pCi h) which is the product of: sS rad erg x 10-2 x 3.70 x lo4 - x 3.60 x lo3 -. MeV erg g-' cccl h
1.602 x
-
In coherent units the numerical coefficient is unity, thus:
As a simple example, compute the absorbed dose from an administration of 32P with a cumulated concentration (time integral of the activity per unit mass) of lo8 transformations per gram. Coherent SI Units
Non-coherent Units D = 2.13 C n E C = 0.751 pCi h g-' n = 1.00 E = 0.695 MeV
D
=
D
=
2.13 x 0.751 rCi h g-' X 1.00 X 0.695 MeV 1.11 rad
D = C n E C = 1.00 x lo8 g-I = 1.00 X 10" kg-' n = 1.00 J E = 0.695 MeV x 1.602 x MeV = 1.11 x 10-l3 J D = 10" kg-' x 1.00 x 1.11 x 10-l3 J D
=
0.0111 J kg-' = 0.0111 Gy
Since 1 rad = Gy, the results are equal. Note that expressing the cumulated concentration in pCi h g-' (or in Bq s g-') does not indicate its true nature as a number of transitions per gram. Values of A tabulated in g rad/(pCi h) may be converted to the energy emitted per nuclear transition in picojoules (pJ) by dividing by 13.32. T h e Medical Internal Radiation Dose (MIRD) Committee of the Society for Nuclear Medicine practice is to tabulate A in Gy kg MBq-' s-' and in rad g mCi-' h-'. The quantity used here is equivalent to ~ / in m MIRD notation. A useful conversion factor relating absorbed doses to activity is 1 rad/mCi = 0.27 mGy/MBq, or slightly more accurately 1 rad/mCi = (1/3.7) mGy/MBq. 4.7 Environmental Radiation Measurement
Naturally-occurring external y-ray exposure rates in conventional
4.8 INSTRUMENTS
/
29
units are -10 pR h-'. Conversion to SI units of exposure would yield the value of 0.72 pC kg-' s-'. Alternatively, if air kerma rates were used, the external y-ray field could be quantified in S I units such as pGy s-'. Examples of changes that would occur with the adoption of SI units are: Activity concentrations of water samples are usually reported in units of pCi I-'. One pCi 1-' equals 37 Bq m-3. In the SI one could report activity concentrations in water in Bq 1-' or Bq m-3. Similarly, the per unit volume concentration of air samples is measured in units of pCi m-"n customary units which corresponds to 0.037 Bq m-= in SI units. The SI units would be Bq m-3. The conventional units for radioactivity concentration in soil are pCi g-'; in the SI, the unit would be Bq kg-'. Maximum permissible concentration (MPC's) would be expressed as follows: for unidentified alpha-emitters the corresponding MPC's in air are 20 x 10-'"Ci ml-' (customary units) and 740 ctBq m-3 (SI units).
4.8
4.8.1
Instruments
General Commercial Constderations
Manufacturers will continue to find it prudent to design instruments to measure quantities and express results in units which meet their customer's desires. Historically, nuclear instruments made in the United States have had a relatively large percentage of sales outside the U.S. (20 percent in 1977).1° T h e nuclear industry in other developed countries, along with growing programs in nuclear and radiological medicine in the developing nations, have put strong competitive pressure on the U.S. export market for nuclear instruments, especially in the past five years. This pressure is expected to increase in the future. If quantities and units are different in the United States from other parts of the world, higher prices for U.S. instruments will result from the necessity to cover the cost to design, build, inventory, and distribute two or more different versions of the same basic device. Alternatively, U.S. manufacturers could double-scale instruments or provide a switch to choose between readings in customary or S I units. lo
U.S. Department of Commerce, Bureau of the Census, Current Industrial Report: Nov. 1978.
Selected Instruments and Related Products, 1977. MA-38B (77)-1, issued
30
/
4.
ADOPTION OF SI UNITS
4.8.2 Radionuclide Assay Devices Most manufacturers calibrate radionuclide assay devices by direct or indirect comparison to a standard furnished by the National Bureau of Standards (NBS). It would appear to make little practical difference to the manufacturer whether his devices indicate activity in terms of becquerels or curies. Some instruments read in either unit. Because most radionuclide assay equipment employs a digital readout, redesign to accommodate the significant difference in the numbers and decimal point placement between the two units is not a difficult problem. The usual activity levels in nuclear medicine fall between 0.1 and 10,000 MBq which makes MBq a convenient unit. 4 -8.3 Radiation Therapy Instrumentation
A committee meeting at the International Bureau of Weights and Measures (CCEMRI Section I, 1979, 1981) indicated that a t some time in the future photon calibrations for instruments used in radiotherapy may be given in terms of absorbed dose to water. Until that time, NBS will calibrate radiation therapy instruments in air in terms of exposure, and later, air kerma. Instrument users will probably continue practices close to present ones until the absorbed-dose-towater calibrations are available. At that time, instrument manufacturers will undoubtedly find their customers interested in equipment which measures in terms of absorbed dose. The "entigray" might be useful for scales of instruments calibrated in terms of absorbed dose in water. 4.8.4 Instrument Modification
The simplest procedure for changing instrumentation to SI units is to purchase an instrument scaled in SI units, or having both conventional and SI scales, or a switch which selects between SI and conventional readout. If an old analog-type instrument is to be retained, in many cases an SI scale or scale overlay can be added at small cost. In some cases, for example self-reading pocket dosimeters, it may not be practical to change the scale. However, one could inexpensively wrap a tape around the dosimeter giving, for several significant levels, the conventional reading, the SI equivalent, and the significance of the level, if desired. Another such case would be instruments with digital readouts. Similarly, a tape with a conversion factor or a conversion chart to SI equivalents could be made handy for the instrument user.
4.10
REGULATORY
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31
4.9 Publications The style for SI usage in publications may be summarized as follows. Names of units in the SI are not capitalized, thus: meter, ampere, gray, becquerel, sievert. Symbols for units are capitalized if they are based on a person's name: A, Gy, Bq, Sv. They are not capitalized otherwise: m, kg. Capitalization of prefixes is as specified in Table 2.1. For example: MGy, mGy, cGy, MBq, GBq. During a transition period from conventional units to SI units, the customary unit may be given first, followed by the SI unit in parentheses, for example: 5,000 rad (50 Gy); 2.7 mCi (100 MBq); 500 mrem (5 mSv). In a later stage of transition the order could be reversed: 50 Gy (5,000 rad). Axis labels on graphs, and column headings in tables may be written, for example: absorbed dosejGy or absorbed dose in Gy; activity/Bq; range/m; thickness/mm or thickness in mm, etc. During a transition period, for tables and graphs, the appropriate conversion factor to the other system of units could be given in a footnote. Prefixes may be used for convenience, for example, in column headings of tables, to distinguish whether the tabulated values should be multiplied or divided by 10". However, for calculations it will usually be easiest to use the coherent units without prefixes. Because it is common practice to use the single word "dose" rather than the proper terms "absorbed dose" or "dose equivalent," possible ambiguity may be alleviated if the special names of the units for these two quantities used, thus: the "absorbed dose in Gy," and "dose equivalent in Sv."
4.10 Regulatory At present, a wide variety of federal and state regulatory agencies exists to regulate ionizing and nonionizing radiation. For an appropriate and orderly transition to the coherent SI units for regulatory purposes, governmental cooperation would be essential. A uniform approach would probably be feasible with the collaboration of major federal agencies. Several points need specific consideration. Revision of existing regulatory guides would probably not be necessary although forthcoming documents or legislation would need to allow for transition and subsequent total change to SI units. Records kept by agencies could be kept and printed in such a way as to be compatible with the scheduled transition.
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4.
ADOPTION OF SI UNITS
4.11 Training Training is an important element of any plan for a transition toward wider use of SI units. Training could emphasize SI units but cover the relationship to customary units. College-level courses and textbooks could explain both systems of units and use SI units. Training often can be included as part of regular refresher courses needed for maintenance and improvement of skills in the military, health physics practice, medical professions, and so forth. Audio-visual training courses are available. Sources of information on SI units include NBS (1981), ICRU (1980),WHO (1977), and this report.
5. Discussion and Recommendations 1. The NCRP recommends the gradual adoption of SI units over a transition period which should begin immediately and be completed by December 31, 1989. Use of a single system of units will facilitate good worldwide communication in medicine, science, engineering, and commerce. Adoption of SI units is increasing throughout the world. It is highly desirable that the United States participate in a single world system. If the United States is to change to SI units, it will be easier to change now rather than later. Available experience indicates that, with proper educational processes in place, it is not difficult for individuals to change to a new system of units, once an orderly timetable is established for doing so. Evidence in other countries (Sandeman e t al., 1979) does not indicate that safety is jeopardized by the introduction of a new unit system. Manufacturers of instruments can plan necessary changes in a fixed schedule for conversion if it is known in advance. The choice of a several-year period for gradual conversion allows time for the educational, administrative, and equipment design processes to take place. The NCRP recognizes that some organizations may find it more convenient for administrative or other reasons to make an abrupt change to SI units. 2. During the transition period, the NCRP recommends simultaneous use of SI units and conventional units. Starting immediately and extending until December 31, 1986, we recommend reporting of measurements with the value in customary units given first followed by the value in SI units given in parentheses, thus: 200 rad (2 Gy). During the period from January 1, 1987 to December 31, 1989, it is recommended that measurements be reported with the value in SI units given first followed by the value in customary units in parentheses, thus: 2 Gy (200 rad). In tables, graphs and radiation records, one system of units would be used with a footnote containing a conversion factor to the other system. NCRP reports will follow this recommendation. We encourage professional and governmental publications to follow a similar policy. 33
34
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5. DISCUSSION AND RECOMMENDATIONS
3. In some cases, due to large investments in non-SI instrumentation or for other reasons, it may not be possible or practical for some organizations to effect a transition to SI units in the recommended five-year transition period. In such cases, the NCRP recommends that a carefully considered plan be developed to carry out the transition in an appropriate time period. Such a plan should include such elements as training, instrument replacement or modification or provision of pertinent conversion factors on tag or tape attached to the instrument. Coordination and assistance in metric conversion is available from the Office of Metric Programs, U. S. Department of Commerce, Washington, D.C.
APPENDIX A
Definitions of the SI Base Units (NBS, 1981) Unit of length (meter) The l l t h CGPM (1960) replaced the definition of the meter based on the international prototype of platinum-iridium, in force since 1889 and amplified in 1927, by the following definition: The meter is the length equal to 1 650 763.73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2plo and 5d5 of the krypton-86 atom. ( l l t h CGPM (1960), Resolution 6). The meter has recently been redefined in the 17th CGPM in 1983 in the following way: The meter is the length of the path traversed in vacuum by light during the period of 11299792458 of a second. Unit of muss (kilogram) The 1st CGPM (1889) legalized the international prototype of the kilogram and declared: this prototype shaU henceforth be considered to be the unit of mass. The 3rd CGPM (1901), in a declaration intended to end the ambiguity which existed as to the meaning of the word "weight" in popular usage, confirmed that the kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram. This international prototype made of platinum-iridium is kept at the BIPM under conditions specified by the 1st CCPM in 1889. Unit of time (second) The unit of time, the second, was defined originally as the fraction 35
36
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APPENDIX A
1/86 400 of the mean solar day. The exact definition of the "mean solar day" was left to astronomers, but their measurements have shown that on account of irregularities in the rotation of the Earth, the mean solar day does not guarantee the desired accuracy. In order to define the unit of time more precisely the 11th CGPM (1960) adopted a definition given by the International Astronomical Union which was based on the tropical year. Experimental work had however already shown that an atomic standard of time-interval, based on a transition between two energy levels of an atom or a molecule, could be realized and reproduced much more accurately. Considering that a very precise definition of the unit of time of the International System, the second, is indispensable for the needs of advanced metrology, the 13th CGPM (1967) decided to replace the definition of the second by the following: The second is the duration of 9 192 631 770periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom. (13th CGPM (1967), Resolution 1).
Unit of electric current (ampere) Electric units, called "international," for current and resistance, had been introduced by the International Electrical Congress held in Chicago in 1893, and the definitions of the "international" ampere and the "international" ohm were confirmed by the International Conference of London in 1908. Although it was already obvious on the occasion of the 8th CGPM (1933) that there was a unanimous desire to replace those "international" units by so-called "absolute" units, the official decision to abolish them was only taken by the 9th CGPM (1948), which adopted for the unit of electric current, the ampere, the following definition:
The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2 x newton per meter of length. (CIPM (1946), Resolution 2 approved by the 9th CGPM, 1948). Unit of thermodynamic temperature (kelvin) The definition of the unit of thermodynamic temperature was given
DEFINITIONS OF T H E SI BASE UNITS
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37
in substance by the 10th CGPM' (1954, Resolution 3) which selected the triple point of water as the fundamental fixed point and assigned to it the temperature 273.16 K by definition. The 13th CGPM (1967, Resolution 3) adopted the name kelvin (symbol K) instead of "degree Kelvin" (symbol OK) and in its Resolution 4 defined the unit of thermodynamic temperature as follows:
The kelvin, unit of thermodynamic temperature, is the fraction 11273.16 of the thermodynamic temperature of the triple point of water. (13th CGPM (1967), Resolution 4). The 13th CGPM (1967, Resolution 3) also decided that the unit kelvin and its symbol K should be used to express an interval or a difference of temperature. Note-In addition to the thermodynamic temperature (symbol T ) expressed in kelvins, use is also made of Celsius temperature (symbol t ) defined by the equation where To= 273.15 K by definition. Note that 273.16 K is the triple point of water, but 273.15 K is the ice point.
Unit of amount of substance (mold Following proposals of the International Union of Pure and Applied Physics, the International Union of Pure and Applied Chemistry and the International Organization for Standardization, the CIPM gave, in 1967, and confirmed in 1969, the following definition of the mole, adopted by the 14th CGPM (1971, Resolution 3):
The mole is the amount of substance of a system which contains as many elementary entities as there are atoms i n 0.012 kilogram of carbon 12. W h e n the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
Unit of luminous intensity (candela) Because of the experimental difficulties in realizing a Planck radiator at high temperatures and the new possibilities offered by radiome-
38
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APPENDIX A
try, i.e. the measurement of optical radiation power, the 16th CGPM adopted in 1979 the following new definition: The candela is the luminous intensity, in agiven directwn, of a source that emits monochromatic radiation of frequency 540 X 10'' hertz and that has a radiant intensity in thut direction of (11683) watt per steradian. (16th CGPM (1979), Resolution 3).
APPENDIX B
Conversion Between SI and Conventional Units
Symbol Quantity
for
Quantity
Activity Absorbed Dose Absorbed Dose Rate Average Energy Per Ion Pair Dose Equivalent Dose Equivalent Rate Electric Current Electric Potential Difference Exposure Exposure Rate Fluence Fluence Rate r b
Kerma Kerma Rate Lineal Energy Linear Energy Transfer Mass Attenuation Coefficient Mass Energy Transfer Coefficient Mass Energy Absorption Coefficient Maas Stopping Power Power Pressure Radiation Chemical Yield SDecific Enerw
Expression in SI Units
1 per second joule per kilogram joule per kilogram second joule
Expreaaion in Symbols for St Unitn
Sp8ei.l Name for SI Unit
Symbols Using Special
Unit
Name
J kg-' s-'
curie rad rad
J
electron volt
s-'
J kg-'
joule per kilogram joule per kilogram second ampere watts per ampere
J kg-' J kg-' s-'
coulomb per kilogram coulomb per kilogram second 1 per meter squared 1 per meter squared second joule per kilogram joule per kilogram second joule per meter
C kg-'
A WA-'
becquerel gray
sievert
volt
rern rern per second
Ci rad rad s-'
3.7 X 10'' Bq 0.01 Gy 0.01 Gy s-I
rem rem s-'
0.01 s v 0.01 Sv s-'
R
2.58
X
10- C kg-'
R s-I
2.58
X
lo-'
rad rad s-'
0.01 Gy s-'
ern2 g-'
0.1 mZkg-'
cma ('
0.1 mZkg-'
cmP p1
0.1 m2 kg-'
MeV em9 g-I
1.602
molecules
1.04 X
ampere volt roentgen
C kg-' s-'
C kg-' a-'
1per centimeter
,-a
m-'
Valw of Conventioml Unit in SI Units
Symbol for Conventional Unit
squared *-I
J kg-' J kg-' s-'
1per centimeter
gray
kiloelectronvolt per micrometer kioelectronvolt per micrometer centimeter squared per gram centimeter squared per gram centimeter squared per gram MeV centimeter squared per gram
J m-'
joule per meter
J rn-'
meter squared per kilogram meter squared per kilogram meter squared per kilogram joule meter squared per kilogram joule per second newton per meter squared mole per joule
m' kg-' mz kg-'
d kg-' J m' kg-' J s-' N m-'
watt peal
watt torr
gray
molecules per 100 electron volts rad
mol J-'
joule Der kilogram J k g '
squared second rad rad per second
0.01 Gy
X
J ma kg-'
lo-' mol J-'
(100 eV)-'
rad
lo-''
0.01 Gy
APPENDIX C
Conversion Tables for Activity, Absorbed Dose, and Dose Equivalent Between SI and Conventional Units TABLE C.l-Conversion of mdioo~tiuityunits fmm MBg to mCi and pCi MBa mCi MBq pCi
TABLEC.2-Conversion of radioactivity units from mCi and mCi
MBq
100 TBq 10 TBq 1 TBq 100 GBq 10 GBq 1 GBq 100 MBq
lo
1 MBq 100 kBq 10 kBq 1 kBq 100 Bq 10 Bq 1 Bq 100 mBq 10 mBq 1 mBq
(10" Bq) = 2.7 kCi (10" Bq) = 270 Ci (10" Bq) = 27 Ci (10" Bq) = 2.7 Ci (I@' Bq) = 270 mci (10' Bq) = 27 mCi ( l d Bq) = 2.7 mCi (lo' Bq) = 270 rCi ( l b Bq) = 27 rCi Bq) = 2.7 rCi (lo4Bq) = 270 nCi (1@ Bq) = 27 nci (I@ Bq) = 2.7 nCi (10' Bq) = 270 pCi (100 Bq) = 27 pCi (lo-' Bq) = 2.7 pCi (lo-' Bq) = 270 fCi (lo-' Bq) = 27 fCi
pCi
(2.7 x (2.7 x (2.7 X (2.7 X (2.7 X (2.7 X (2.7 X (2.7 x (2.7 x (2.7 X (2.7 X (2.7 X (2.7 X (2.7 X (2.7 x (2.7 x (2.7 x (2.7 x
1d Ci) 1d Ci) 10' Ci) 10' Ci) lo-' Ci) lo-' Ci) lo-' Ci) lo4 Ci) lod Ci) lod Ci) lo-' Ci) lo4 Ci) lo4 Ci) lo-'' Ci) lo-'' Ci) lo-" Ci) lo-'' Ci) lo-'' Ci)
to MBq MBq
CONVERSION TABLES
TABLE C.4--Conversion of absorbed dose units SI Units Canventional 100 Gy (10I Gy) = 10.000 rad (10' rad) 10 Gy (10' Gy) = 1,000 rad (10d rad) 1 Gy ( I d G y ) = 100 rad (ldrad) 100 mGy (lo-' Gy) = 10 rad (10' rad) 10 mGy (lo-' Gy) = 1 rad (10'' rad) 1 mGy (lo-' Gy) = 100 mrad (lo-' rad) 10 mrad (lo-' rad) 100 pGy (lo-' Gy) = 10 pGy (lo-' Gy) = 1 mrad (10" rad) 1 pGy (10" Gy) = 100 prad (lo4 rad) 100 nGy (lo-' Gy) = 10 prad (lo-' rad) 10 nGy Gy) = 1 prad (lo4 rad) 1 nGy (lo-' Gy) .= 100 nrad (lo-' rad) of dose equivalent units T ~ B LC.5-Conversion E 100 Sv 10 Sv 1 Sv 100 mSv 10 mSv 1 mSv 100 pSv 10 1Sv 1 pSv 100 nSv 10 nSv 1 nSv
(1O'Sv) = 10,000 rem (10' Sv) = 1,000 rern (lOOSv) = 100 rern (lo-' Sv) = 10 rem 1 rern (10" Sv) = (10- Sv) = 100 mrem (lo4 Sv) = 10 mrem (10d Sv) = 1 mrem (lOdSv) = 100 prem (lO-'Sv) = 10 prem (lo" Sv) = 1 prem /lo-@Sv) = 100 nrem
(10' rem)
(Idrem) ( I d rem) (10' rem) ( I d rem) (lo-' rem) (lo-' rem) (lo-' rem) (lo4 rem) (10-"em) (lo4 rem) (lo-' reml
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43
References BIPM (1975). Le Bureau International des Poids et Mesures. The Internat w m l Bureau of Weights and Measures, 1875-1975,translation of the BIPM Centennial Volume, NBS Special Publication 420, Page, D. H. and Vigoureux, P., Eds. (National Bureau of Standards, Washington, D.C.). CCEMRI Section I (1979). Comith Consultatif pour les Etalons de Mesure des Rayonnements Ionisants, Section I.-Rayons X a n d y, electrons, 5' %union, 1979. (OFFILIB, Paris). CCEMRI Section I (1981). Comiti Consultatif pour Les Etalons de Mesure des Rayonnements Ionisants, Section I.-Rayons X a n d y, electrons, 6'%union, 1981. (OFFILIB, Paris). DANLOUX-DUMESNILS, M. (1969). The Metric System, translated by Garrett and Rowlinson (Athlone Press, London). EEC (1980). Council Directive of 20 December 1979. Official Journal of the European Communities No. L 39/40, 15 February 1980. G.G., POSTON,J. W., FAIR,M. F., A N D AUXIER,J. A. (1980). Cost EICHHOLZ, Benefit Effects of Conversion to SI Units in Health Physics. U. S. Nuclear Regulatory Commission Report NUREG/CR-1419 (National Technical Information Sewice, Springfield, Virginia). ICRP (1977). International Commission on Radiological Protection. Recommendations of the International Commission on RadiologicalProtection. 1977, ICRP Publication 26 (Pergamon Press, Oxford, U.K.). ICRU (1938). International Committee for Radiological Units. "Recommendations of the International Committee for Radiological Units (Chicago19371," Am. J. Roentgenol. Radium Ther. 39, 295. ICRU (1971). International Commission on Radiation Units and Measurements. Radiation Quantities and Units, ICRU Report 19 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). ICRU (1976). International Commission on Radiation Units and Measurements. Conceptual Basis for the Determination of Dose Equivalent, ICRU Report 25 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). ICRU (1979). International Commission on Radiation Units and Measurements. Methods of Assessment of Absorbed Dose in Clinical Use of Radwnuclides, ICRU Report 32 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). ICRU (1980). International Commission on Radiation Units and Measurements. Radiation Quantities and Units, ICRU Report 33 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). 44
REFERENCES
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45
ICRU (1985) International Commission on Radiation Units and Measurements. Determination of Dose Equivalents Resulting from External Radiation Sources, ICRU Report 39 (International Commission on Radiation Units and Measurements, Bethesda, Maryland). IUPAC (1979). International Union of Pure and Applied Chemistry. Manual of Symbols and Terminology for Physico-Chemical Quantities and Units, 1979 Edition (Pergamon Press, Oxford, U.K.). IUPAP (1978). International Union of Pure and Applied Physics. Symbols, Units, and Nomenclature in Physics, Document U.I.P. 20 (International Union of Pure and Applied Physics, Quebec, Canada). METRICCOMMISSION CANADA (1982). The SI Manual in Health Care, 2nd edition, (Publication Services Section, Ontario Government Bookstore, 880 Bay Street, Toronto). METRICAT~ON BOARD(1978). Going Metric: Progress in 1977178 (Her Majesty's Stationery Office, London). METRICATION BOARD(1980). Final Report of the Metrication Board (Her Majesty's Stationery Office, London). MOORE,N. E. A. (1973). The Decimalisation of Britain's Currency (Her Majesty's Stationery Office, London). H. (1975). Le Syskrne Metrique, des Anciennes Mesures au Systeme MOREAU, International d'Uni.tis (Chiron, Paris). NBS (1981). National Bureau of Standards. The International System of Units G I ) , translation approved by the International Bureau of Weights and Measures (BIPM) of its publication "Le Systime International d'UnitCsm, NBS Special Publication 330, 1981 edition (National Bureau of Standards, Gaithersburg, Maryland). NCRP (1974). National Council on Radiation Protection and Measurements. Specification of Gamma-Ray Brachytherapy Sources, NCRP Report No. 41 (National Council on Radiation Protection and Measurements, Bethesda, Maryland). NCRP (1980). National Council on Radiation Protection and Measurements. Radiofrequency Electromagnetic Fields: Properties, Quantities and Units, Biophysical Interaction, and Measurements, NCRP Report No. 67 (National Council on Radiation Protection and Measurements, Bethesda, Maryland). NCRP (1983). National Council on Radiation Protection and Measurements. Biological Effects of Ultrasound: Mechanisms and Clinical Implications, NCRP Report No. 74 (National Council on Radiation Protection and Measurements, Bethesda, Maryland). ROEDLER, H. D., KAUL,A., A N D HINE,G. J. (1978). Internal Radiation Dose in Diagnostic Nuclear Medicine (Verlag H. Hoffmann, Berlin). ROESSLER, G. S. (1984). "The Editor Responds," HPS Newsletter, 12.5. J. D. (1979). "SI Units SANDEMAN, T. F., MILLAR,R. M., A N D FRUMMOND, in Radiotherapy," Br. J. Radiology 52, 162. SHAW, K. B., STEVENSON, G. R., A N D THOMAS, R. H. (1969). "Evaluation of Dose Equivalent from Neutron Energy Spectra," Health Physics 17,459.
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REFERENCES
SNIRP (1981). Strildoser fr6n radiwktiva iunnen i medicinskt bruk (Swedish National Institute of Radiation Protection, Stockholm, Sweden). English glossary is provided. (c. 1977). Tio ar I Huger Trafik (Fack, 171 STATENS TRAFIKSAKERHETSVERK 20 Solna, Sweden). [The National Traffic Bureau (c. 1977). Ten Years of Traffic on the Right.] ZUPKO, R E. (1968).A Dictionaryof English Weights and Measures, University of Wisconsin Press (Madison, Wisconsin). WHO (1977).World Health Organization, The SI for the Hedth Professions, (World Health Organization, Geneva).
The NCRP The National Council on Radiation Protection and Measurements is a nonprofit corporation chartered by Congress in 1964 to: 1. Collect, analyze, develop, and disseminate in the public interest information and recommendations about (a) protection against radiation and (b) radiation measurements, quantities, and units, particularly those concerned with radiation protection; 2. Provide a means by which organizations concerned with the scientific and related aspects of radiation protection and of radiation quantities, units, and measurements may cooperate for effective utilization of their combined resources, and to stimulate the work of such organizations; 3. Develop basic concepts about radiation quantities, units, and measurements, about the application of these concepts, and about radiation protection; 4. Cooperate with the International Commission on Radiological Protection, the International Commission on Radiation Units and Measurements, and other national and international organizations, governmental and private, concerned with radiation quantities, units, and measurements and with radiation protection. The Council is the successor to the unincorporated association of scientists known as the National Committee on Radiation Protection and Measurements and was formed to carry on the work begun by the Committee. The Council is made up of the members and the participants who serve on the eighty-two scientific committees of the Council. The scientific committees, composed of experts having detailed knowledge and competence in the particular area of the committee's interest, draft proposed recommendations. These are then submitted to the full membership of the Council for careful review and approval before being published. The following comprise the current officers and membership of the Council: Offkers President Vice President
WARRENK . SINCLAIR S. JAMES ADELSTEIN 47
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T H E NCRP
Secretary and Treasurer Assistant Secretary Assistant Treasurer
SEYMOUR ABRAHAMSON S. JAMESADELSTEIN ROYE. ALBERT PETERR. ALMOND EDWARD L. ALPEN JOHNA. AUXIER W~LL~A J .M BAIR J O H ND. BOICE,JR. ROBERTL. BRENT ANTONEBROOKS THOMAS F. BUDINCER MELVINW. CARTER GEORGEW. C A S A R ~ RANDALL S. CASWELL GERALDD. DODD PATRIC~A W. DURBIN JOE A. ELDER MORTIMER M. ELKIND THOMAS S. ELY EDWARD R. EPP JACOB I. FABRIKANT R. J. MICHAELFRY ROBERTA. GOEPP ROBERT0.GORSON ARTHURW. GUY ERIC J . HALL NAOMIH. HARLEY JOHNW. HEALY WILLIAMR. HENDEE JOHNM. HESLEP SEYMOUR JABLON DONALDG. JACOBS A. EVERETTE JAMES,JR. BERNDKAHN JAMESG. KEREIAKES CHARLESE. LAND
Members GEORGER. LEOPOLD RAY D. LLOYD ARTHURC. LUCAS CHARLESW. MAYS ROGER0.MCCLELLAN JAMESMCLAUGHLIN J . MCNEIL BARBARA THOMAS F. MEANEY CHARLESB. MEINHOLD MORTIMERL. MENDELSOHN WILLIAME. MILLS DADEW. MOELLER A. ALANMOGHISSI ROBERTD. MOSELEY,JR. WESLEYNYBORC MARYELLENO'CONNOR FRANKL. PARKER ANDREWK. POZNANSKI NORMANC. RASMUSSEN WILLIAMC. REINIG CHESTERR. RICHMOND JAMESS. ROBERTSON LEONARD A. SAGAN WILLIAMJ . SCHULL GLENNE. SHELINE ROYE. SHORE WARRENK. SINCLAIR LEWISV. SPENCER JOHN B. STORER WILLIAML. TEMPLETON ROYC. THOMPSON JOHNE. TILL ARTHURC. UPTON GEORGEL. VOELZ EDWARD W. WEBSTER GEORGEM. WILKENING H. RODNEYWITHERS
Honorary Members LAURISTON S. TAYLOR,Honom~yPresident
EDGARC. BARNES VICTOR P. BOND
THE NCRP REYNOLD F. BROWN AUSTINM. BRUES FREDERICK P. COWAN JAMES F. CROW MERRILL EISENBUD ROBLEYD. EVANS
J O H NH. HARLEY LOUISH. HEMPELMANN, JR. PAULC. HODGES GEORGEV. LEROY WILPRIDB. MANN KARL2. MORGAN f o l l o w i n g subgroups are
Currently, the lating recommendations:
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49
HAROLDH. ROSSI WILLIAM G. RUSSELL JOHNH. RUST EUGENE L. SAENGER J. NEWELLSTANNARD HAROLD 0 . WYCKOFF
actively engaged i n f o r m u -
Basic Radiation Protection Criteria Medical X-Ray, Electron Beam and Gamma-Ray Protection for Energies Up to 50 MeV (Equipment Performance and U+e) X-Ray Protection in Dental Offices Standards and Measurements of Radioactivity for Radiological Use Waste Disposal Task Group on Krypton-85 Task Group on Disposal of Accident Generated Waste Water Task Group on Disposal of Low-Level Waste Task Group on the Actinides Task Group on Xenon Task Group on Definitions of Radioactive Waste Levels Biological Aspects of Radiation Protection Criteria Task Group on Atomic Bomb Survivor Dosimetry Subgroup on Biological Aspects of Dosimetry of Atomic Bomb Survivors Natural Background Radiation Radiation Associated with Medical Examinations Radiation Received by Radiation Employees Operational Radiation Safety Task Group 1 on Warning and Access Control Systems Task Group 2 on Uranium Mining and Milling-Radiation Safety Programs Task Group 3 on ALARA for Occupationally Exposed Individuals in Clinical Radiology Task Group 4 on Calibration of Instrumentation Task Group 5 on Maintaining Radiation Protection Records Task Group 6 on Radiation Protection for Allied Health Personnel Task Group 7 on Emergency Planning Instrumentation for the Determination of Dose Equivalent Apportionment of Radiation Exposure Conceptual Basis of Calculations of Dose Distributions Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Radiation Bioassay for Assessment of Control of Intake of Radionuclides Internal Emitter Standards Task Group 2 on Respiratory Tract Model Task Group 3 on General Metabolic Models
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THE NCRP
Task Group 5 on Gastrointestinal Tract Models Task Group 6 on Bone Problems Task Group 8 on Leukemia Risk Task Group 9 on Lung Cancer Risk Task Group 10 on Liver Cancer Risk Task Group 11 on Genetic Risk Task Group 12 on Strontium Task Gmup 13 on Neptunium SC-59: Human Radiation Exposure Experience SC-61: Radon Measurements SC-63: Radiation Exposure Control in a Nuclear Emergency SC-64: Radionuclides in the Environment Task Group 5 on Public Exposure from Nuclear Power Task Group 6 on Screening Models Task Group 7 on Contaminated Soil as a Source of Radiation Exposure SC-65: Quality Assurance and Accuracy in Radiation Protection Measurements SC-66: Biological Effects and Exposure Criteria for Ultrasound SC-67: Biological Effects of Magnetic Fields SC-68: Microprocessors in Dosimetry SC-69: Efficacy of Radiogaphic Procedures SC-70: Quality Assurance and Measurement in Diagnostic Radiology SC-71: Radiation E x p u r e and Potentially Related Injury SC-72: Radiation Protection in Mammography SC-74: hdiation Received in the Decontamination of Nuclear Facilities SC-75: Guidance on Radiation Received in Space Activities SC-76: Effects of Radiation on the Embryo-Fetus SC-77: Guidance on Occupational and Public Exposure Resulting from Diagnostic Nuclear Medicine Procedures SC-78: Practical Guidance on the Evaluation of Human Exposures to Radiofrequency Radiation SC-79: Extremely Low-Frequency Electric and Magnetic Fields SC-BO: Radiation Biology of the Skin (Beta-Ray.Dosimetry) SC-81: Assessment of Exposure from Therapy SC-82: Control of Indoor Radon Committee on Public Education Committee on Public Relations Ad HOCCommittee on Comparison of Radiation Exposures Study Group on Comparative Risk Task Group on Comparative Carcinogenicity of Pollutant Chemicals Task Force on Occupational Exposure Levels Ad Hoc Group on Model Used for Assessing Transport of Low-LevelRadioactive Waste Ad HOCGroup on Medical Evaluation of Radiation Workers Task Gmup on Ocean Dumping of Radioactive Waste
In recognition of its responsibility to facilitate and stimulate cooperation among organizations concerned with the scientific and related aspects of radiation protection and measurement, the Council has created a category of NCRP Collaborating Organizations. Organiza-
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51
tions or groups of organizations that are national or international in scope and are concerned with scientific problems involving radiation quantities, units, measurements, and effects, or radiation protection may be admitted to collaborating status by the Council. The present Collaborating Organizations with which the NCRP maintains liaison are as follows: American Academy of Dermatology American Association of Physicists in Medicine American College of Nuclear Physicians American College of Radiology American Dental Association American Industrial Hygiene Association American Institute of Ultrasound in Medicine American Insurance A m i a t i o n American Medical Association American Nuclear Society American Occupational Medical Association American Pediatric Medical Association American Public Health Association American Radium Society American Roentgen Ray Society American Society of Radiologic Technologists American Society for Therapeutic Radiology and Oncology Association of University Radiologists Atomic Industrial Forum Bioelectromagnetics Society College of American Pathologists Federal Comrnunicationa Commission Federal Emergency Management Agency Genetics Society of America Health Physics Society National Bureau of Standards National Electrical Manufacturers Aesociation Radiation Research Society Radiological Society of North America Society of Nuclear Medicine United States Air Force United States Army United States Department of Energy United States Department of Housing and Urban Development United States Department of Labor United States Environmental Proteetion Agency United Statea Navy United States Nuclear Regulatory. Commission United States Public Health Service
The NCRP has found its relationships 'with these organizations to be extremely valuable to continued progress in its program.
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T H E NCRP
Another aspect of the cooperative efforts of the NCRP relates t o the special liaison relationships established with various governmental organizations that have an interest in radiation protection and measurements. This liaison relationship provides: (1) an opportunity for participating organizations to designate an individual to provide liaison between the organization and the NCRP; (2) that the individual designated will receive copies of draft NCRP reports (at the time that these are submitted to the members of the Council) with an invitation to comment, but not vote; and (3) that new NCRP efforts might be discussed with liaison individuals as appropriate, so that they might have an opportunity to make suggestions on new studies and related matters. The following organizations participate in the special liaison program: Commission of the European Communities Commisariat a I'Energie Atomique (France) Defense Nuclear Agency Federal Emergency Management Agency Japan Radiation Council National Bureau of Standards National Radiological Protection Board (United Kingdom) National Research Council (Canada) Office of Science and Technology Policy Office of Technology Assessment United States Air Force United States Army United States Coast Guard United States Department of Energy United States Department of Health and Human Services United States Department of Labor United States Department of Transportation United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission
The NCRP values highly the partici~ ion of these organizations in the liaison program. The Council's activities are made possible by the voluntary contribution of time and effort by its members and participants and the generous support of the following organizations: Alfred P. Sloan Foundation Alliance of American Insurers American Academy of Dental Radiology American Academy of Dermatology American Association of Physicists in Medicine
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American College of Nuclear Physicians American College of Radiology American College of Radiology Foundation American Dental Association American Hospital Radiology Administrators American Industrial Hygiene Association American Insurance Association American Medical Association American Nuclear Society American Occupational Medical Association American Osteopathic College of Radiology American Podiatric Medical Association American Public Health Association American Radium Society American Roentgen Ray Society American Society of Radiologic Technologists American Society for Therapeutic Radiology and Oncology American Veterinary Medical Association American Veterinary Radiology Society Association of University Radiologists Atomic Industrial Forum Battelle Memorial Institute Center for Devices and Radiological Health College of American Pathologists Commonwealth of Pennsylvania Defense Nuclear Agency Edison Electric Institute Edward Mallinckrodt, Jr. Foundation Electric Power Research Institute Federal Emergency Management Agency Florida Institute of Phosphate Research Genetics Society of America Health Physics Society James Picker Foundation National Aeronautics and Space Administration National Association of Photographic Manufacturers National Bureau of Standards National Cancer Institute National Electrical Manufacturers Association Radiation Research Society Radiological Society of North America Society of Nuclear Medicine United States Department of Energy United States Department of Labor United States Environmental Protection Agency United States Navy United States Nuclear Regulatory Commission
To all of these organizations the Council expresses its profound appreciation for their support.
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THE NCRP
Initial funds for publication of NCRP reports were provided by a grant from the James Picker Foundation and for this the Council wishes to express its deep appreciation. The NCRP seeks to promulgate information and recommendations based on leading scientific judgment on matters of radiation protection and measurement and to foster cooperation among organizations concerned with these matters. These efforts are intended to serve the public interest and the Council welcomes comments and suggestions on its reports or activities from those interested in its work.
NCRP Publications NCRP publications a r e distributed by t h e NCRP Publications Office. Information on prices and how to order may be obtained by directing a n inquiry to: NCRP Publications 7910 Woodrnont Avenue Suite 800 Bethesda, MD 20814-3095 The currently available publications are listed below.
No.
NCRP Reports Title Control and Removal ofRadioactive Contamination in Laboratories (1951) Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupatioml Exposure (1959) [Includes Addendum 1 issued in August 19631 Measurement of Neutron F l w and Spectra for Physical and Biological Applications (1960) Measurement of Absorbed Dose ofNeutrons, and of Mixtures of Neutrons and Gamma Rays (1961) Stopping Powers for Use with Cavity Chambers (1961) Safe Handling of Radioactive Materials (1964) Radiation Protection in Educational Institutions (1966) Dental X-Ray Protection (1970) Radiation Protection in Veterinary Medicine (1970) Precautions i n the Management o f Patients W h o Have Received Therapeutic Amounts of Radionuclides (1970) Protection Against Neutron Radiation (1971) Protection Against Radiation from Brachytherapy Sources (1972)
Specification of Gamma-Ray Brachytherapy Sources (1974) Radiological Factors A f f e c t i n g Decision-Making i n a Nuclear Attack (1974)
1
NCRP PUBLICATIONS
Krypton-85 in the Atmosphere-Accumulation, Biological Significance, and Control Technology (1975) Alpha-Emitting Particles in Lungs (1975) Tritium Measurement Techniques (1976) Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV (1976) Environmental Radiation Measurements (1976) Radiation Protection Design Guidelines for 0.1-100 MeV Particle Accelerator Facilities (1977) Cesium-137 from the Environment to Man: Metabolism and Dose (1977) Medical Radiation Exposure of Pregnant and Potentially Pregnant Women (1977) Protection of the Thyroid G h n d i n the Event of Releases of Radioiodine (1977) Instrumentation and Monitoring Methods for Radiation Protection (1978) A Handbook of Radioactivity Measurements Procedures, 2nd ed. (1985) Operational Radiation Safety Program (1978) Physical, Chemical, and Biological Properties of Radiocerium Relevant to Radiation Protection Guidelines (1978) Radiation Safety Training Criteria fir Industrial Radwgmphy (1978) Tritium i n the Environment (1979) Tritium and Other Radionuclide Labeled Organic Compounds Incorporated in Genetic Material (1979) Influence of Dose and Its Distribution in Time on DoseResponse Relationships for Low-LET Radiations (1980) Management of Persons Accidentally Contaminated with Radionuclides (1980) Radiofrequency Electromagnetic Fields-Properties, Quantities and U n i t s , Biophysical Interaction, and Measurements (1981) Radiation Protection in Pediatric Radiology (1981) Dosimetry of X-Ray and Gamma-Ray Beams for Radiation Therapy in the Energy Range 10 keV to 50 MeV (1981) Nuclear Medicine-Factors Influencing the Choice and Use of Radionuclirles in Diagnosis and Therapy (1982) Operational Radiation Safety-Training (1983.) Radiation Protection and Measurement for Low-Voltage Neutron Generators (1983)
NCRP PUBLICATIONS
1
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Protection i n Nuclear Medicine and Ultrasound Diagnostic Procedures i n Children (1983) Biological Effects of Ultrasound: Mechanisms and Clinical Implications (1983) Iodine-129: Evaluation of Releases from Nuclear Power Generation (1983) Radiological Assessment: Predicting the Transport, Bioaccumulation, a n d Uptake by M a n o f Radionuclides Released to the Environment (1984) Exposures from the Uranium Series with Emphasis o n Radon and Its Daughters (1984) Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters i n the United States (1984) Neutron Contamination from Medical Electron Accelerators (1984)
Induction of Thyroid Cancer by Ionizing Radiation (1985) Carbon-14 in the Environment (1985) SI Units in Radiation Protection and Measurements (1985) The Experimental Basis for Absorbed-Dose Calculations in Medical Uses of Radionuclides (1985) General Concepts for the Dosimetry of Internally Deposited Radionuclides (1985) Mammography-A User's G u d e (1986) Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields (1986) Use of Bioassay Procedures for Assessment o f Internal Radionuclide Deposition (1987) Radiation Alarms and Access Control Systems (1986) Genetic Effects from Internally Deposited Radionuclides (1987)
Neptunium: Radiation Protection Guidelines (1988) Public Radiation Exposure from Nuclear Power Generation in the United States (1987) Ionizing Radiation Exposure of the Population of the United States (1987) Exposure of the Population in the United States and Canada from Natural Background Radiation (1987) Radiation Exposure of the U.S. Population from Consumer Products and Miscellaneous Sources (1987) Comparative Carcinogenicity o f Ionizing Radiation and Chemicals (1989) Measurement of Radon and Radon Daughters in Air (1988) Guidance on Radiation Received in Space Activities (1989) Quality Assurance for Diagnostic Imaging (1988)
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NCRP PUBLICATIONS
Exposure of the U.S. Population fiom Diagnostic Medical Radiation (19891 101 Exposure of the U . S . Population from Occupational Radiation (1989) 102 Medical X-Ray, Electron Beam and Gamma-Ray Protection for Energies U p to 50 MeV (Equipment Design, Performance and Use) (1989) 103 Control of Radon in Houses (1989) 104 The Relative Biological Effectiveness ofRadiations ofDifferent Quality (1990) 105 R a d i a t i o n Protection for Medical a n d Allied Health Personnel (1989) 106 Limit for Exposure to "Hot Particles" on the Skin (1989) 107 Implementation of the Principle of A s Low A s Reasonably Achievable (ALARA) for Medical and Dental Personnel (1990) 108 Conceptual Basis for Calculations o f Absorbed-Dose Distributions (1991) 109 Effects of Ionizing Radiation on Aquatic Organisms (1991) 110 Some Aspects of Strontium Radwbiology (1991) 111 Developing Radiation Emergency Plans for Academic, Medical or Industrial Facilities (1991) 112 Calibration of Survey Instruments Used in Radiation Protection for the Assessment of Ionizing Radiation Fields and Radioactive Surface Contamination (1991) 113 Exposure Criteria for Medical Diagnostic Ultrasound:I. Criteria Based on Thermal Mechanisms (1992) 114 Maintaining Radiation Protection Records (1992) 115 Risk Estimates for Radiation Protection (1993) 116 Limitation of Exposure to Ionizing Radiation (1993) 117 Research Needs for Radiation Protection (1993) 118 Radiation Protection in the Mineral Extraction Industry (1993) Binders for NCRP reports are available. Two sizes make it possible to collect into small binders the "old series" of reports (NCRP Reports Nos. 8-30)and into large binders the more recent publications (NCRP Reports Nos. 32-118). Each binder will accommodate from five to seven reports. The binders carry the identification "NCRP Reports" and come with label holders which permit the user to attach labels showing the reports contained in each binder. The following bound sets of NCRP reports are also available: 100
Volume I. NCRP Reports Nos. 8, 22 Volume 11. NCRP Reports Nos. 23, 25, 27, 30 Volume 111. NCRP Reports Nos. 32, 35, 36, 37
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Volume IV. NCRP Reports Nos. 38,40, 41 Volume V. NCRP Reports Nos. 42,44,46 Volume VI. NCRP Reports Nos. 47, 49, 50, 51 Volume VII. NCRP Reports Nos. 52, 53, 54, 55, 57 Volume VIII. NCRP Report No. 58 Volume IX. NCRP Reports Nos. 59, 60, 61, 62,63 Volume X. NCRP Reports Nos. 64, 65,66, 67 Volume XI. NCRP Reports Nos. 68, 69, 70, 71, 72 Volume XII. NCRP Reports Nos. 73, 74, 75, 76 Volume XIII. NCRP Reports Nos. 77, 78, 79, 80 Volume XIV. NCRP Reports Nos. 81, 82,83, 84, 85 Volume XV. NCRP Reports Nos. 86, 87, 88, 89 Volume XVI. NCRP Reports Nos. 90, 91,92,93 Volume XVII. NCRP Reports Nos. 94, 95, 96, 97 Volume XVIII. NCRP Reports Nos. 98, 99, 100 Volume XIX. NCRP Reports Nos. 101,102, 103, 104 Volume XX. NCRP Reports Nos. 105, 106, 107,108 Volume XXI. NCRP Reports Nos. 109, 110, 111 Volume XXII. NCRP Reports Nos. 112, 113, 114 (Titles of the individual reports contained in each volume are given above.) NCRP Commentaries
No. 1
2
3 4
5 6 7
Title Krypton-85 i n the Atmosphere-With Specific Reference to the Public Health Significance of the Proposed Controlled Release a t Three Mile Island (1980) Preliminary Evaluation of Criteria for the Disposal o f Transuranic Contaminated Waste (1982) Screening Techniques for Determining Compliance with Environmental Standards-Releases o f Radionuclides to the Atmosphere (1986), Revised (1989) Guidelines for the Release o f Waste Water from Nuclear Facilities with Special Reference to the Public Health Significance of the Proposed Release of Treated Waste Waters at Three Mile Island (1987) Review of the Publication, Living Without Landfills (1989) R a d o n Exposure of t h e U.S. Population-Status o f the Problem (1991) Misadministration of Radioactive Material i n MedicineScientific Background (1991)
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NCRP PUBLICATIONS
Uncertainty i n NCRP Screening Models Relating to Atmospheric Transport, Deposition and Uptake by Humans (1993)
Proceedings of the Annual Meeting No.
Title
1
Perceptions of Risk, Proceedings of the Fifteenth Annual Meeting held on March 14-15, 1979 (including Taylor Lecture No. 3) (1980) Critical Issues i n Setting Radiation Dose Limits, Proceedings of the Seventeenth Annual Meeting held on April 89, 1981 (including Taylor Lecture No. 5) (1982) R a d i a t i o n Protection a n d N e w Medical Diagnostic Approaches, Proceedings of the Eighteenth Annual Meeting held on April 6-7, 1982 (including Taylor Lecture No. 6) (1983) Environmental Radioactivity, Proceedings of the Nineteenth Annual Meeting held on April 6-7,1983(including Taylor Lecture No. 7) (1983) Some Issues Important i n Developing Basic Radiation Protection Recommendations, Proceedings of the Twentieth Annual Meeting held on April 4-5,1984 (including Taylor Lecture No. 8) (1985) Radioactive Waste, Proceedings of the Twenty-first Annual Meeting held on April 3-4,1985 (including Taylor Lecture No. 9) (1986) Nonionizing Electromagnetic Radiations and Ultrasound, Proceedings of the Twenty-second Annual Meeting held on April 2-3, 1986 (including Taylor Lecture No. 10) (1988) New Dosimetry at Hiroshima and Nagasaki and Its Implications for Risk Estimates, Proceedings of the Twenty-third Annual Meeting held on April 8-9,1987 (including Taylor Lecture No. 11)(1988) Radon, Proceedings of the Twenty-fourth Annual Meeting held on March 30-31, 1988 (including Taylor Lecture No. 12) (1989) Radiation Protection Today-The NCRP at Sixty Years, Proceedings of the Twenty-fifth Annual Meeting held on April 5-6, 1989 (including Taylor Lecture No. 13) (1990) Health and Ecological Zmplications of Radioactively Contaminated Environments, Proceedings of the Twenty-
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sixth Annual Meeting held on April 4-5, 1990 (including Taylor Lecture No. 14) (1991) Genes, Cancer and Radiation Protection, Proceedings of the Twenty-seventh Annual Meeting held on April 3-4,1991 (including Taylor Lecture No. 15) (1992) Radiation Protection in Medicine, Proceedings of the Twentyeighth Annual Meeting held on April 1-2,1992 (including Taylor Lecture No. 16) (1993) Lauriston S. Taylor Lectures No.
Title
1
The Squares of the Natural Numbers in Radiation Protection by Herbert M. Parker (1977) Why be Quantitative about Radiation Risk Estimates? by Sir Edward Pochin (1978) Radiation Protection-Concepts and Trade Offs by Hymer L. Friedell (1979) [Available also in Perceptions of Risk, see abovel From "Quantity of Radiation" and "Dose" to "Exposure" and "Absorbed Dose"-An Historical Review by Harold 0. Wyckoff (1980) How Well Can We Assess Genetic Risk? Not Very by James F. Crow (1981) [Available also in Critical Issues in Setting Radiation Dose Limits, see abovel Ethics, Trade-offs and Medical Radiation by Eugene L. Saenger (1982) [Available also in Radiation Protection and New Medical Diagrwstic Approaches, see abovel The Human Environment-Past, Present and Future by Merril Eisenbud (1983) [Available also in Environmental Radioactivity, see abovel Limitation and Assessment in Radiation Protection by Harald H . Rossi (1984) [Available also in Some Issues Important in Developing Basic Radiation Protection Recommendations, see abovel Truth (and Beauty) in Radiation Measurement by John H. Harley (1985) [Available also in Radioactive Waste, see abovel Biological Effects of Non-ionizing Radiations: Cellular Properties and Interactions by Herman P. Schwan (1987) [Available also in Nonionizing Electromagnetic Radiations and Ultrasound, see abovel How to be Quantitative about Radiation Risk Estimates by
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NCRP PUBLICATIONS
Seymour Jablon (1988) [Available also in New Dosimetry at Hiroshimu and Nagasaki and its Implications for Risk Estimates, see abovel How Safe is Safe Enough? by Bo Lindell(1988) [Available also in Radon, see abovel Radiobiology and Radiation Protection: The Past Century and Prospects for the Future by Arthur C. Upton (1989) [Available also in Radiation Protection Today, see abovel Radiation Protection and the Internal Emitter Saga by J . Newel1 Stannard (1990) [Available also in Health and Ecological Implications of Radioactively Contaminated Environments, see abovel When is a Dose Not a Dose? by Victor P. Bond (1992) [Available also in Genes, Cancer and Radiation Protection, see above] Dose and Risk in Diagnostic Radiology: How Big? How Little? by Edward W. Webster (1992)[Available also in Radiation Protection in Medicine, see abovel
Symposium Proceedings The Control of Exposure of the Public to Ionizing Radiation in the Event ofAccident orAttack, Proceedings of a Symposium held April 27-29, 1981 (1982)
NCRP Statements No.
Title
1
"Blood Counts, Statement of the National Committee on Radiation Protection," Radiology 63, 428 (1954) "Statements on Maximum Permissible Dose from Television Receivers and Maximum Permissible Dose to the Skin of the Whole Body," Am. J. Roentgenol., Radium Ther. and Nucl. Med. 84, 152 (1960) and Radiology 75, 122 (1960) X-Ray Protection Standards for Home Teleuision Receivers, Interim Statement of the National Council on Radiation Protection and Measurements (1968) Specification of Units ofNatural Uranium and Natural Thorium, Statement of the National Council on Radiation Protectwn and Measurements, (1973) NCRP Statement on Dose Limit for Neutrons (1980) Control of Air Emissions of Radionuclides (1984)
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The Probability That a Particular Malignancy May Have Been Caused by a Specified Irradiation (1992) Other Documents
The following documents of the NCRP were published outside of the NCRP Report, Commentary and Statement series:
Somatic Radiation Dose for the General Population, Report of the Ad Hoc Committee of the National Council on Radiation Protection and Measurements, 6 May 1959, Science, February 19, 1960, Vol. 131, No. 3399, pages 482-486 Dose Effect Modifying Factors In Radiation Protection, Report of Subcommittee M-4 (Relative Biological Effectiveness) of the National Council on Radiation Protection and Measurements, Report BNL 50073 (T-471) (1967) Brookhaven National Laboratory (National Technical Information Service Springfield, Virginia) The following documents are now superseded and/or out of print:
NCRP Reports No. 1 2 3 4 5
Title X-Ray Protection (1931) [Superseded by NCRP Report No. 31 Radium Protection (1934) [Superseded by NCRP Report No. 41 X-Ray Protection (1936) [Superseded by NCRP Report No. 61 Radium Protehbn (1938) [Supersededby NCRP Report No. 131 Safe Handling of Radioactive Luminous Compound (1941) [Out of Printl Medical X-Ray Protection Up to Two Million Volts (1949) [Superseded by NCRP Report No. 181 Safe Handling of Radioactive Isotopes (1949) [Superseded by NCRP Report No. 301 Recommendations for Waste Disposal ofPhosphorus32 and Zodine-131 for Medical Users (1951) [Out of Print] Radiological Monitoring Methods and Instruments (1952) [Superseded by NCRP Report No. 571 Maximum Permissible Amounts of Radioisotopes i n the Human Body and Maximum Permissible Concentrations in Air and Water (1953) [Superseded by NCRP Report No. 221 Recommendations for the Disposal of Carbon-14 Wastes (1953) [Superseded by NCRP Report No. 811
NCRP PUBLICATIONS
Protection Against Radiations from Radium, Cobalt-60 and Cesium-137 (1954) [Superseded by NCRP Report No. 241 Protection Against Betatron-Synchrotron Radiations U p to 100 Million Electron Volts (1954) [Superseded by NCRP Report No. 511 Safe Handling of Cadavers Containing Radioactive Isotopes (1953) [Superseded by NCRP Report No. 211 Radioactive-Waste Disposal i n the Ocean (1954) [Out of Print] Permissible Dose from External Sources of Ionizing Radiation (1954) including Maximum Permissible Exposures to Man, Addendum to National Bureau of Standards Handbook 59 (1958) [Superseded by NCRP Report No. 391 X-Ray Protection (1955:)[Superseded by NCRP Report No. 261 Regulation of Radiation Exposure by Legislative Means (1955) [Out o f Print] Protection Against Neutron Radiation Up to 30 Million Electron Volts (1957) [Superseded by NCRP Report No. 381 Safe Handling of Bodies Containing Radioactive Isotopes (1958) [Superseded by NCRP Report No. 371 Protection Against Radiations from Sealed Gamma Sources (1960) [Superseded by NCRP Reports No. 33,34 and 401 Medical X-Ray Protection Up to Three Million Volts (1961) [Superseded by NCRP Reports No. 33,34,35 and 361 A Manual of Radioactivity Procedures (1961) [Superseded by NCRP Report No. 581 Exposure to Radiation in a n Emergency (1962) [Superseded by NCRP Report No. 421 Shielding for High-Energy Electron Accelerator Installations (1964) [Superseded b y NCRP Report No. 51.1 Medical X-Ray and Gamma-Ray Protection for Energies up to 10 MeV-Equipment Design and Use (1968) [Superseded by NCRP Report No. 1021 Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 MeV-Structural Shielding Design and Evaluation Handbooh (1970) [Superseded by NCRP Report No. 493 Basic Radiation Protection Criteria (1971) [Superseded by NCRP Report No. 911 Review of the Current State of Radiation Protection Philosophy (1975) [Superseded by NCRP Report No. 911 Natural Background Radiation in the United States (1975) [Superseded by NCRP Report No. 941
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Radiation Protection for Medical and Allied Health Personnel (1976) [Superseded by NCRP Report No. 1051 Review ofNCRP Radiation Dose Limit forEmbryo and Fetus in Occupationally-Exposed Women (1977) [Out of Print] Radiation Exposure from Consumer Products and Miscellaneous Sources (1977) [Superseded by NCRP Report No. 951 A Handbook ofRadioactivity Measurements Procedures, 1st ed. (1978) [Superseded by NCRP Report No. 58,2nd ed.1 Mammography (1980) [Out of Print] Recommendations on Limits for Exposure to Ionizing Radiation (1987) [Superseded by NCRP Report No. 1161
NCRP Proceedings No. 2
Title Quantitative Risk in Standards Setting, Proceedings of the Sixteenth Annual Meeting held on April 2-3, 1980 [Out of Print]
Index Absorbed Dose 12, 13,16,22,26-28.41, CCU 6 CGPM 6 CIPM 6 English systems of units 6 Meter 5 Treaty of the Meter 5,6
43
Activity 18, 26, 27, 29, 41, 42 Ampere 7,8 Barn 10,23 Base Units 4,7-9,35-38 Ampere 7-9,36 Candela 7,9,37,38 Definitions 35-38 Kelvin 7,9,36, 37 Kilogram 7,9,35 Meter 7-9,35 Mole 7-9,37 Second 7,9,35,36 Becquerel9, 10, 18, 22, 26, 27, 41, 42 BIPM 6,35 Candela 7 CGPM 6, 36 Coherence 4,6, 10, 11, 14, 15, 21, 23, 26, 28
Conversion Tables 39-43 Coulomb per Kilogram 26 Curie 10, 18, 26, 27, 41, 42 Derived Units 7-9 Diagnostic Radiology 25, 26 Dose Equivalent 16, 17, 26,41,43 Electron Volt 9 Environmental Radiation Measurement
Instrumenta 21,29.30 Modification 30 Radiation therapy 30 Radionuclide assay devices 30 Joule 23 Kelvin 7 Kerma 12,13, 29 Kilogram 7 Linear Energy Transfer 23 Meter 5, 7, 8, 23 Mole 7, 8 Nonionizing Radiation Units 18, 19 Nuclear Medicine 26-28 Prefixes 10, 11 Publications 31 Quantities and Units 3,4, 12-18, 22, 23, 26-29.35-37,4143
Absorbed dase 12, 13,16,22,26-28,41,
28,29
43
Examples 11, 13, 15,17, 27, 28 Exposure 14-16,26,29
Activity 18, 26, 27, 29, 41, 42 Amount of substance 37 Base units 4 Coulomb per kilogram 26 Dose equivalent 16, 17, 26.41, 43 Electric current 36 Exposure 14-16.26.29 Kerma 12.13, 29
G Value 23 Gray 9, 10, 13, 22.25, 26,43 History 4-7 BIPM 6 CCEMRI 6
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INDEX
Quantities and Units (Continued) Length 35 Linear energy transfer 23 Luminous intensity 37 Mass 35 Quantity 3 Specific Energy 12 Temperature 36,37 Time 35 Unit 3 Rad 10, 13, 16,22,25,26.43 Radiation Biology 23 Radiation Chemical Yield 23 Radiation Chemistry 23 Radiation Physics 22, 23 Radiation Protection 23-25 Radiation Science 22 Radiation Therapy 25 Recommendations 33,34 Regulatory 31 Rem 16,43 Roentgen 10, 15 Safety 21 Second 7 Sievert 9, 16,22,26,43 Simplicity 21 Specific Energy 12 Supplementary Units 7-9 Systems of Units 6 cgs 6 emu 6 esu 6 mks 6
mksa 6 Training 22,32 Treaty of the Meter 5.6 Units (see also Base Units) 3,4, 7,9,10, 12,13,15,16-18,22,23,25-28,35-
38,40-43 Accepted temporarily 10 Ampere 36 Barn 10.23 Base units 4, 8 Becquere19, 18, 22,26, 27,41,42 Candela 37,38 Conventional 12, 15,21, 28, 40,41 Conversion 39-43 Curie 10,18,26,27,41,42 Derived 7,9 Electron volt 9 For use with the SI 9 Gray 9,13, 22, 25,26,43 Joule 23 Kelvin 36,37 Kilogram 35 Meter 23,35 Mole 37 Nonionizing radiation 18 Prefixes 10 Rad 10,13, 16,22, 25, 26,43 Rem 16,43 Roentgen 10,15 Second 35, 36 Sievert 9, 16,22, 26, 43 Special names 9 Supplementary 7,9
