Sources and Magnitude of Occupational and Public Exposures from Nuclear Medicine Procedures (N C R P Report)

NCRP REPORT No. 124

SOURCES AND MAGNITUDE OF OCCUPATIONAL AND PUBLIC EXPOSURES FROM NUCLEAR MEDICINE PROCEDURES Recommendations of the NATIONAL COUNCIL O N RADIATION PROTECTION AND MEASUREMENTS

Issued March 11, 1996

National Council on Radiation Protection and Measurements I Bethesda, MD 20814-3095 7910 Woodmont Avenue

LEGAL NOTICE This report was prepared by the National Council on Radiation Protection a n d Measurements (NCRP). The 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 i n this Report, or that the use of any information, method or process disclosed i n 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, under the Civil Rights Act of 1964, Section 701 et seq, as amended 42 U.S.C. Section 2000e et seq. (Title VII) or any other statutory or common law theory governing liability.

Library of Congress Cataloging-in-Publication Data National Council on Radiation Protection and Measurements. Sources and magnitude of occupational and public exposures from nuclear medicine procedures / recommendations of the National Council on Radiation Protection and Measurements. cm. - (NCRP report ; no. 124) p. "Prepared by Scientific Committee 77 on Guidance on Occupational and Public Exposure Resulting from Diagnostic Nuclear Medicine Proceduresn-Pref. "Issued March 1996." Includes bibliographical references and index. ISBN 0-929600-51-7 1. Nuclear medicine-Safety measures. 2. Radiation-Dosage. I. National Council on Radiation Protection and Measurements. Scientific Committee 77 on Guidance on Occupational and Public Exposure Resulting from Diagnostic Nuclear Medicine Procedures. 11. Title. 111. Series. [DNLM: 1. Nuclear Medicine. 2. Occupational Exposure. 3. Radiation Effects. 4. Risk. 5. Radiation Protection. WN 440 N2765s 19961 RA569.N355 1996 616.9'897-dc20 DNLMfDLC for Library of Congress 96-690 CIP

Copyright O National Council on Radiation Protection and Measurements 1996 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 This Report addresses the sources of exposures incurred in the practice of nuclear medicine and provides the necessary data to evaluate the magnitude of exposures to those directly associated with that practice and to those who provide nursing care to the patients containing radiopharmaceuticals. Exposure to members of the public are also addressed. The primary emphasis of this Report is on these individuals and not on the patient, since the patient receives the direct benefit from the nuclear medicine procedure. I t is recognized that the patient also receives the bulk of any potential radiation decrement. This Report was prepared by Scientific Committee 77 on Guidance on Occupational and Public Exposure Resulting from Diagnostic Nuclear Medicine Procedures. Serving on the Scientific Committee were:

Kenneth L. Miller, Chairman Pennsylvania State University Hershey, Pennsylvania Members

Frank P. Castronovo, Jr. Brigham & Women's Hospital Boston, Massachusetts

Martin L. Nusynowitz University of Texas Medical Branch at Galveston Galveston , Texas

Arnold P. Jacobson University of Michigan School of Public Health Ann Arbor, Michigan

Dennis D. Patton University of Arizona College of Medicine Tucson, Arizona

Sheila I. Kronenberger Stanford University Stanford, California Consultant

Edward W. Webster Massachusetts General Hospital Boston, Massachusetts

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PREFACE

NCRP Secretariat James A. Spahn, Jr., Senior Staff Scientist Cindy L. O'Brien, Editorial Assistant The Council wishes to express its appreciation to the Committee members for the time and effort devoted to the preparation of this Report. Charles B. Meinhold President

Contents .

1 Introduction ........................................................................ 1.1 Scope ................................................................................ 1.2 Quantities and Units .......................... ........................ 2 Public SigniGcance of Nuclear Medicine ..................... 2.1 Nature and Advantages .................................................. 2.2 Size and Growth .............................................................. 3 Radiation Risk in Perspective ........................................ 3.1 Introduction ..................................................................... 3.2 Risk ................................................................................ 3.3 Radiation Risks ............................................................... 3.3.1 Low-Level Radiation Doses ................................. 3.3.2 Dose Limits ........................................................... 3.3.3 Radiation Effects a t Low Doses .......................... 3.3.3.1 Hereditary Defects .................................. 3.3.3.2 Developmental Defects ........................... 3.3.3.3 Cancer Induction ..................................... 3.3.4 Comparative Risks ............................................... 4 Receipt and Delivery of Radioactive Materials ......... 4.1 Introduction .................................................................... 4.2 Shipment of Radioactive Sources ................................... 4.3 Receipt of Radionuclides ................................................. 4.4 "In-House" Transportation of Radioactive Materials ... 4.5 Transport of Patients ...................................................... 4.6 Transport of Specimens from Nuclear Medicine Patients ............................................................................ 5 Radiation Exposure from Nuclear Medicine Practice ................................................................................. 5.1 Nuclear Medicine Personnel Exposure .......................... 5.2 Radiation Doses to Patients and Persons Nearby and Members of the Public .................................................... 5.3 Exposure of Nurses and Other Medical Personnel ....... 5.4 Exposure of the General Public ..................................... 6 Radiopharmaceutical Handling Procedures in Nuclear Medicine ............................................................... 6.1 Introduction ..................................................................... 6.2 Radiopharmaceutical Dosage Preparation ....................

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CONTENTS

6.2.1 Commercial Radiopharmacy Unit Dosages ........ 6.2.2 "In-House" Radiopharmacy ................................. 6.2.3 Generators ............................................................ 6.2.4 Chemical Formulation ......................................... 6.2.5 Xenon .................................................................... 6.2.6 Nebulizers ............................................................. 6.2.7 Iodine (Diagnosis and Therapy) .......................... 6.3 Dosage Calibrations ...................................................... 6.4 Radiopharmaceutical Administration ............................ 6.5 Imaging ............................................................................ 6.6 Contamination Control ........ .......................................... 6.7 Misadministration ........................................................... 6.8 Safety Considerations with Nursing Mothers ............... 6.9 Radioactive Waste Disposal ............................................ 7 Radiation Safety Considerations for the Nursing

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Staff .......................................................................................

7.1 Radiopharmaceutical Administrations .......................... 7.2 Notification of Radiopharmaceutical Administration ... 7.3 When Radioactive Precautions Are Necessary ............. 7.3.1 The Patient ........................................................... 7.3.1.1 For Diagnostic Purposes ......................... 7.3.1.2 For Therapeutic Purposes ...................... 7.3.2 Collection and Handling of Excreta .................... 7.3.2.1 From Diagnostic Dosages ....................... 7.3.2.2 From Therapeutic Dosages .................... 7.3.3 Collected Specimens ............................................. Glossary .................................................................................... References ................................................................................. The NCRP ................................................................................ NCRP Publications .............................................................. Index .........................................................................................

1. Introduction 1.1 Scope

The medical use of unsealed radioactive materials, generally referred to as nuclear medicine, subjects four classes of persons to radiation exposure. These are patients, health care radiation workers, health care nonradiation workers, and members of the general public who are in the vicinity of these materials before, during or after their medical use. Considerations of patient exposure have been included in two previous reports of the National Council on Radiation Protection and Measurements (NCRP), namely NCRP Report No. 70, Nuclear Medicine-Factors Influencing the Choice and Use of Radionuclides in Diagnosis and Therapy (NCRP, 1982) and NCRP Report No. 73, Protection in Nuclear Medicine and Ultrasound Diagnostic Procedures in Children (NCRP, 1983). Estimates of the quantities of radionuclides administered to patients in nuclear medicine procedures together with evaluations of the equivalent dose to the gonads and effective dose, and their contribution to the population exposure and dose are included in NCRP Report No. 100, Exposure of the U.S. Population from Diagnostic Medical Radiation (NCRP, 1989a). A primary concern is the evaluation and control of occupational exposures to nuclear medicine and allied health personnel and to members of the public other than the patient. Since the general public would potentially receive exposure from patients containing radioactive material, t h e radiation levels close t o these patients are also important. Many groups of medical personnel may receive radiation exposure from radioactive materials used in medical practice. The principal groups are physicians, technologists, radiopharmacists and others who handle the radioactive material and radioactive waste or provide care for the nuclear medicine patient. In addition, other physicians, nurses, x-ray technologists, receiving room personnel, security staff, those who transport patients within the hospital, operating room staff, maintenance workers and others, may occasionally be exposed. Specific radiation protection guidelines for these and other allied health personnel have been given in NCRP Report No. 105, Radiation Protection for Medical and Allied Health Personnel (NCRP,

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1. INTRODUCTION

1989b). Members of the general public who might receive small exposures include other patients in waiting rooms, wards or multibed rooms, visitors and persons close to radioactive patients while in transit or in the home. Section 2 of this Report addresses the impact of nuclear medicine on the practice of medicine and on the diagnosis and treatment of disease. Its ability to image parts or organs of the body or, when necessary, the whole body and to treat cancers without performing surgery was a major public health accomplishment. The use of radioimmunoassay techniques was another major accomplishment that aided in a more complete understanding of diseases and disease processes. The advent of single photon emission computed tomography (SPECT) and positron emission tomography (PET) have added to the number and kind of nuclear medicine procedures being performed. Section 3 focuses on radiation risk and presents a few comparisons which will help to improve understanding of risk and provide some perspective on the importance of comparing risks of radiation exposure to other risks faced by our society. There is a brief discussion of limits of radiation exposure followed by an equally brief discussion of radiation effects. Section 4 traces the path of radioactive materials from receipt at a facility through delivery of the material to the nuclear medicine department, preparation of a dosage for administration to the patient, and dosage of the patient. Since, when the patient receives the radioactive material, he or she becomes a source of exposure to others, the patient is then followed through the facility. Another aspect examined is the movement of specimens from the patient to the laboratory for examination or testing. This may or may not represent another source of exposure. The subject of radiation exposure to individuals is further developed in Section 5. There are three principal sources to radiation workers-dosage preparation and assay, administration, and patient imaging or treatment. The details of each of these areas is analyzed and techniques useful to reduce exposures are examined. Finally, the exposure of those not involved in administration of radiopharmaceuticals to patients is examined. This group includes patients other than nuclear medicine patients who may walk through the halls or share a patient room, waiting room or elevator with a nuclear medicine patient, nurses or other providers of care to the patient, and members of the public. The more detailed examination of the handling procedures used in nuclear medicine are covered in Section 6. The two areas for preparation of dosages for administration to the patient are a

1.2 QUANTITIESANDUNITS

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commercial radiopharmacy or the nuclear medicine department. The exposures from these two sources and the advantages and disadvantages are discussed. The calibration and use of dosage calibrators are reviewed. The techniques of the administration of the radiopharmaceuticals to the patient by injection, inhalation or oral administration a r e reviewed. The subjects of contamination control, misadministration and safety consideration for nursing mothers are discussed. There is also a brief review of radioactive waste disposal. Section 7 treats the very important topic of radiation safety in the care of the hospitalized patient. These are generally patients who have received therapeutic amounts of radionuclides and, at least in the early times after administration, represent a significant source of exposure.

1.2 Quantities and Units In NCRP Report No. 116 (NCRP, 1993a),the NCRP recommended the use of a new quantity to be known as effective dose. By combining doses to radiosensitive organs in the body in a manner that accounts for their relative contributions to the total radiation detriment, the effective dose provides a single measure of dose that is directly related to detriment. The unit for this effective dose is sievert (Sv). Wherever in this Report the term dose is used, unless otherwise qualified, its meaning is effective dose. The energy absorbed per unit mass at a point in the human body exposed to radiation is known as the absorbed dose in tissue. The unit of absorbed dose is gray (Gy). For this Report, the quantity air kerma, and its special unit Gy, will be used in place of the quantity exposure. The two quantities are not interchangeable as the unit for air kerma is joules per kilogram and the unit for exposure is coulombs per kilogram. Since they are not interchangeable, the conventional unit name, roentgen, will not be used but, until such time as radiation detection and survey meters are calibrated in air kerma, the numerical value of exposure in roentgens may be assumed to be approximately equal to the numerical value of air kerma in rads, which is equal to air kerma in centigray. For a more complete discussion ofthese concepts see ICRU Reports 33 and 51 (ICRU, 1980; 1993) and for a more complete discussion of Systeme Internationale (SI) units see NCRP Report No. 82 (NCRP, 1985a).

2. Public Significance of Nuclear Medicine 2.1 Nature and Advantages Radiopharmaceuticals (drugs containing radionuclides) a r e administered to patients in order to make a physiologic measurement, to obtain images of organs or organ systems, or to provide treatment. Drugs or compounds tagged with specific radionuclides will deposit within the human body in a predictable manner (both as to location and amount). The advantages of using these techniques are that spatial distributions and physiologic behavior may be studied simply, noninvasively, a t low cost and withlow risk to the patient. As a n example, nuclear medicine imaging of the heart and studies of function are frequently used to provide information otherwise obtainable only by cardiac catheterization, an invasive procedure. The latter usually requires hospitalization and is accompanied by higher radiation dose, mortality, morbidity and cost. Another example is the determination of whether newly discovered breast cancer has metastasized (spread) to the bone. The nuclear bone imaging procedure is the most cost effective method available for making such a determination. If metastases in bone are found, they provide information important for developing a n appropriate treatment protocol for breast cancer. Numerous similar applications exist which illustrate the impact of this technology on clinical decision making in the management of patient problems. Although treatment (as distinct from diagnosis) with radiopharmaceuticals is a small part of the practice of nuclear medicine, it is very effective for certain medical conditions. The dosage administered for therapeutic purposes is 10 to 50 times the dosage administered for diagnostic purposes. The treatment of hyperthyroidism, (overactivity of the thyroid gland), is a routinely used procedure in nuclear medicine. In contrast, surgery requires hospitalization and has higher associated mortality, morbidity and expense. A third segment of nuclear medicine is radioimmunoassay laboratory testing. Such procedures do not require the administration of radioactive materials to the patient. In these tests, a biological

2.1 NATURE AND ADVANTAGES

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specimen, usually blood, is analyzed in the test tube usingradioactive materials for determination of the content of hormones. vitamins, drugs, enzymes, viral particles or products, cancer antigens or other chemicals. The methods are sensitive and precise and, since their advent a few decades ago, have revolutionized the understanding of disease and disease processes by the medical profession. These tests employ small quantities of radioactive materials and result in radiation exposures to the technologists involved in their performance that are so low the technologists need not be considered radiation workers, if that is their sole source of exposures. Information on the physical characteristics of commonly used radionuclides is set out in Table 2.1. The activity of radioactive materials used in diagnostic nuclear medicine examinations varies with the particular radionuclide employed and the purpose of the examination. In general, larger activities are used with radionuclides of shorter half-life. The range is from kBq for vitamin B-12absorption tests with 57Co(physical half-life 272 d) to GBq for PET studies of brain blood flow with 150(physical half-life, 2 min). Typical organ doses from diagnostic procedures are in the range of 10 to 30 mGy, and for therapy procedures, can exceed 100 Gy. In vitro radioimmunoassay procedures typically employ about 300 Bq of radioactive material. Since the tests are conducted in the laboratory on samples, e.g., blood, that have been removed from the patient, there is no accompanying radiation dose to the patient. Federal and state authorities have been involved in the regulation of nuclear medicine since its inception. All facilities responsible for medical use of by-product material must be licensed, for radionuclide use, by the U.S.Nuclear Regulatory Commission (NRC) or by an TABLE 2.1-Physical characteristics of radionuclides used in nuclear medicine. Radionuclide

Physical Half-Life

99mTc 6 h '=I 13 h la11 8d aolll 73 h 67Ga 78 h l%e 5.3 d "'In 68 h 82Rb 1.25 min l50 2.04 min llC 20.48 min 18F 109.74 min laN 9.97 min " k o m an unshielded point source in air. bFormrad h-I at 1 m from 1 mCi multiply by 0.037.

Air Kerma Rate Constant' (pGy h-I 100 MBq-I@ 1 mIb

2.0 3.8 5.5 1.2 4.0 1.1 3.4 16.7 15.7 15.7 15.1 15.7

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2. PUBLIC SIGNIFICANCE OF NUCLEAR MEDICINE

agreement state (see Glossary). For accelerator produced or naturally occurring radionuclides, many states regulate their use. Radiopharmaceuticals intended for medical use must be approved by the U.S. Food and Drug Administration. Major aspects of radiopharmaceutical production, transportation, application and disposal are regulated by various federal and state agencies.

2.2

Size and Growth

NCRP estimated in 1989 that about 100 million procedures using radioactive materials are performed each year in the United States for diagnostic and therapeutic medical purposes (NCRP, 1989a). Approximately 10percent of these procedures involve administration of radioactive pharmaceuticals directly to patients for diagnostic or therapeutic procedures. The remaining 90 percent are radioirnmunoassay procedures that involve the use of small amounts of radioactivity in analysis of patient urine, blood, etc. There are over 150 diagnostic and therapeutic nuclear medicine procedures involving the administration of radiopharmaceuticals to patients (AMA, 1991). According to a survey of full-time nuclear medicine clinics,' only 10 in vivo diagnostic procedures comprised over 90 percent of all such procedures performed in a typical nuclear medicine clinic, and only one therapeutic procedure constitutes the bulk of all nuclear medicine treatments. These results are qualitatively similar to those of Mettler et al. (1986) who showed that in the early 19809, nine categories of studies accounted for over 90 percent of diagnostic in vivo examinations (see Table 2.2). Witherspoon and Shuler2 obtained similar results in a survey of nuclear medicine facilities in the southwestern United States, but the distribution of studies has shifted significantly over the years. Cardiac and pulmonary nuclear medicine studies (pathophysiologic in nature) have doubled their share of total studies, whereas hepatic 94"T~ sulfur colloid imaging has disappeared from the top ten list. This change reflects two simultaneously occurring trends over the past decade. Radiologic imaging has significantly improved with the advent and application of high contrast, high resolution modalities (computed tomography, ultrasound, magnetic resonance imaging, 'Personal communications (1991) from Martin L.Nusynowitz, University of Texas Medical Branch at Galveston, Galveston, Texas. 2Unpublished survey (1991) from Lynn Witherspoon and Stanton Shuler of the Ochsner Clinic, Metairie, Louisiana.

2.2 SIZE AND GROWTH T

m 2.2-Relative

Procedure

Diagnostic Bone Gastric emptying Heart: Equilibrium radiocardiography Heart: Myocardial perfusion

Hepatobiliary Kidney

Relative Fkeauencv of Procedu&ss (percent)

740

1.3

40

0.2

110

4.5

mlT1thallous chloride 99"Tc sestamibi ""Tc teboroxime 99"Tcdisofenin 1311iodohippurate ""Tc pentetate *mTcmertiatide 99mTc macroaggregated albumin lS%e gas *Tc pentetate aerosol "31Na iodide '311Na iodide 99"Tc pertechnetate aG@ ' citrate

110 1,110 1,850

6.3 5.0 8.3

300 15 370 370 110

1.3 0.4 0.6 0.7 0.5

370 740

0.14 1.6

11.8

17.9 2.9

8.2

5.6 3.8 5.7

Activity Typical Administered Dose per Procedure to Patient (MBq) (mGy)

""Tc medronate or oxidmnate *Tc sulfur colloid *Tc red cells

4.6

7.3

Tumorlinfedion Other Therapeuticb Hyperthyroidism Thyroid cancer

Radiopharmaceutical

20.6

Lung ventilation

Thyroid (25% uptake of iodine)

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frequency of nuclear medicine procedures (1991), typical activities administered and typical dose.

9.6 Lung perfusion

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( {

{ {

15 4 185 190

0.4 0.7 0.7 13.0

1.8 I3lI Na iodide 740 0.2 '311Na iodide 3,700 "Based on an unpublished survey (1991)of nuclear medicine facilities by Martin L. Nusynowitz, University of Texas Medical Branch a t Galveston, Galveston, Texas. Treatment for hyperthyroidism and thyroid cancer estimated at 2 per 100 diagnostic procedures. 'Typical dose is meaningless in therapy. Dose to region of concern is the only consideration because that dose provides the benefit.

and digital subtraction angiography) for anatomic definition, thereby supplanting the poorer-resolution nuclear medicine techniques in the detection and definition of pathologic anatomy. On the other hand, pathophysiologically-oriented nuclear medicine studies have made significant progress with the availability of newer

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2. PUBLIC SIGNIFICANCE OF NUCLEAR MEDICINE

radiopharmaceuticals (e.g., myocardial perfusion agents, regional cerebral blood flow agents), instrumentation (e.g.,SPECT), and computers and software (e.g., renal function evaluation). The number of in vivo nuclear medicine examinations performed in hospitals in the United States increased about 16 percent from approximately 6.4 million to 7.4 million from 1980 to 1990 (Mettler et al., 1993). The projected growth rate of eight percent per year was not realized over this 10 y period mainly as a result of the virtual disappearance of 99"Tcpertechnetate brain scintigraphy and %Tc sulfur colloid liver imaging, which have been replaced by other modalities, such as computed tomography (CT) and magnetic resonance imaging. Meanwhile, nuclear cardiology studies have increased. As would be expected, the work load and procedure distribution a t any one facility depends, in large measure, on the size and nature of the facility, the patient population and on the interests of the medical community. Nevertheless, for all but small general hospitals, approximately 8 to 10 in vivo diagnostic studies on in- and outpatients are performed per year per occupied hospital bed. The relative frequency of performance of these procedures and typical amounts of radioactivity administered to a n adult are presented in Table 2.2. The coming decade will witness further changes as new procedures and techniques are developed and applied clinically. Likely to be among these are PET for the spatial mapping of functional parameters of the brain, including brain blood flow, metabolism, receptor activity, tumor metabolism and response to therapy, and cardiac flow and metabolism, using radiopharmaceuticals of the positron emitters "C, 150, 18F,82Rband 13N.Representative dosages and radiation absorbed doses (Kearfott, 1982a; 1982b) are listed in Table 2.3. TABLE2.3-Radiation absorbed dose for various PET studies (adapted from Kearfott, 1982a; 1982b). Radiopharmaceutical

Activity Administered

"CO C150

(MBq) 740 1,850

coi50

1,850

H ~ ~ ~ o 1,850 lBF-FDG 82Rb

370 1,850

Organ of Interest

Spleen, lungs, intestine Spleen, lungs, intestine Lungs Blood, kidneys, liver, lungs Bladder Heart, kidneys

Organ &sorbed Dose to Patient Absorbed Dose (pGy MBq-') (PGYMBg-')

14 to 23 4, 3, 4 1.3 3

5.0 0.4 0.4 0.4

120 3.5 to 5

10.5 0.4

3. Radiation Risk in Perspective 3.1 Introduction

The rapid growth in development and use of radiation and radioactive materials parallels the development of a large body of knowledge concerning the measurement of radiation, its interaction with matter, and its biological effects. Of special importance in connection with effects is the evidence that has been obtained from studies of human populations that have been exposed to radiation (ICRP, 1991a; 1991b; NCRP, 1993a; 1993b; UNSCEAR, 1993; 1994) There is much information and general agreement about risks following exposures to large radiation doses. In contrast, there is very little direct information about the effects on humans of low absorbed doses of radiation ((0.2 Gy) received by many radiation workers and the lower doses received by the public. The available data for humans do not allow direct estimates of risk from radiation doses below 0.2 Gy.

3.2 Risk

There is no such thing as a risk-free life. For most people, risk is an inherent and accepted part of daily life. Death is one risk we all face to some extent every day. The probability of death occurring ultimately in every person is unity. The risk from one source, exposure to radiation, should therefore be judged in comparison with the other risks which we face continuously throughout our lives.

3.3 Radiation Risks 3.3.1 Low-Level Radiation Doses

Numerous groups have estimated that medical radiation workers in the United States receive annual effective doses between 2.5 and

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3. RADIATION RISK IN PERSPECTIVE

5 mSv (NASNRC, 1980; UNSCEAR, 1988). Doses will vary with the individual and the task. Table 3.1 provides a summary of radiation doses routinely encountered by the public in various medically related procedures. It should be noted that the average annual dose to the public from nuclear power plants is