Report of the Inter-Society Commission for Heart Disease Resources: Optimal Resource Guidelines for Radioactive Tracer Studies of the Heart and Circulation

S. James Adelstein, Chairman, Carl Jansen, and Henry N. Wagner, Jr.

The status of radioactive tracer studies in cardio­ of nuclear cardiovascular examinations. Some, such as vascular diagnosis is summarized. Planning guidelines are central nervous system (CNS) and renal studies, relate suggested for a hospital nuclear medicine service in­ to standard techniques for determining the state of the cluding a central nuclear medicine facility and satellite peripheral circulation, but other procedures have only units, and resource criteria are given for professional recently become clinically possible. Many applications, personnel including training and duties, equipment, space, while extremely promising, are still investigational and and support systems. The administrative organization of a at present occupy an intermediate stage between early nuclear medicine service and case loads are discussed. clinical testing and broad clinical or routine use. A few, Guidelines for equipment maintenance and quality con­ such as acute myocardial infarct scanning, are em­ trols are described. bryonic but, considering the pace of trial and acceptance in this field, they too may soon be in widespread use. The particular examinations included in these guidelines Radionuclide techniques are of growing importance are, in our judgment, those most likely to have an im­ in the field of diagnostic cardiology. Among the earliest pact on patient care. noninvasive procedures for obtaining quantitative We have also reviewed, updated, and expanded our physiologic information about the cardiovascular resource guidelines for organizing a hospital nuclear system, they currently provide diagnostic data medicine program. The space, equipment, and man­ unavailable by other means-such as measurements of power requirements will provide services for all kinds of regional blood flow-as well as important information diagnostic problems, not only those associated with car­ supplementary to hemodynamic and angiographic diovascular diseases. In large institutions with heavy examinations during cardiac catheterization. cardiac case loads, special cardiovascular nuclear units An increasing number of community hospitals have may be both medically and economically practical. We established nuclear medicine facilities or are in the also propose training qualifications for the professional process of doing so. The convenient availability of such and technical staff, appropriate case loads and utiliza­ facilities is, in fact, a requirement of the Joint Com­ tion levels, methods of quality control, and procedures mission on Accreditation of Hospitals. There are 1,700 for protecting the safety of both patients and staff from physicians in the United States certified as specialists in excessive exposure to ionizing radiation. nuclear medicine and many others are using radioactive These resource guidelines are directed to tech­ tracers as part of the. diagnostic process. Radioactive nologists, physicians, and hospital administrators t,racers play a role in the care of approximately one out responsible for planning and organizing nuclear of every three hospitalized patients and in the next few medicine programs who anticipate either current or years at least an equal number of outpatients will also future needs for such services in their community. It is be candidates for such examinations. This report is an · assumed that the selection and use of these procedures overview of the status of cardiovascular radionuclide will be the joint responsibility of a nuclear medicine spe­ diagnostic studies and a guideline to the hospital cialist and one or more cardiologists who accept the ob­ resources, both physical and human, required for a nu­ ligation to keep abreast of advances in this rapidly clear medicine service of high quality. In a previous statement (J) we outlined resource specifications for two nuclear medicine examinations, Supported under Contract No. HSM-110-73-362 from the Re­ regional pulmonary perfusion and blood pool imaging, gional Medical Programs Service, Health Services and Mental Health and we anticipated the development of two others, re­ Administration, Department of Health, Education and Welfare. For reprints contact: Irving S. Wright or Donald T. Fredrickson, gional myocardial perfusion and regional pulmonary Inter-Society Commission for Heart Disease Resources, Suite 316, ventilation. In this guideline we report on 11 categories 44 E. 23rd St., New York, N.Y. 10010.

VOLUME 3, NUMBER 3 141 changing field, particularly with regard to instru­ that of contrast angiography, useful information con­ mentation and methodology. cerning cardiac anomalies, intracardiac shunts, valve positions, chamber size and location, pericardia! effusions, and aneurysms and coarctations of the aorta Syllabus of Cardiovascular Radionuclide can be obtained. In addition to providing a graphic dis­ Procedures play of the passage of a bolus through the heart, great Radiocardiography. Single crystal, simply colli­ vessels, and lungs, the use of the scintillation camera mated, and portable radiation detectors or probes can with computer capabilities permits selection of areas of be used for the determination of cardiac output, trans­ interest, such as the right and left ventricles, and display pulmonary transit time, and ejection fraction. Determi­ of regional time-activity curves. These curves provide nation of cardiac output by the radioactive indicator di­ quantitative information such as the transit times be­ lution technique requires measurement of the blood tween various points in the circulation and the mag­ volume, and measurement of the change in arterial or nitude of intracardiac shunts. If the recording system <:ardiac blood concentration of a radioactive tracer as a has adequate resolution, the stroke volume and ejection function of time after its injection into the circulatory fraction of the ventricles can also be calculated. system. Measurements are made by direct arterial Technetium-99m-labeled albumin or red blood cells sampling or by external monitoring of a vascular pool, are the preferred tracers. Pertechnetate, which is com­ usually the heart itself. Tracers include radiolabeled monly employed, is less desirable since it diffuses albumin, transferrin, or red blood cells. Indium-113m rapidly out of the vascular compartment. and 131 I require greater shielding than 99mTc. Cardiopulmonary activity can be continuously Radioisotope tracers have not been used commonly recorded on film, on magnetic tape, or directly into a for measuring cardiac output during catheterization computer, which is required for quantitative work. procedures because they offer no significant advantage The technique is helpful in the diagnosis of congenital over nonradioactive tracer dyes, which can be ac­ and acquired cardiac and pulmonary conditions and, curately measured spectrophotometrically. They are, when done with a portable camera, has proven useful in however, most appropriate for this purpose in con­ bedside evaluation of cardiopulmonary function. junction with other radiotracer studies such as radionu­ Ventricular wall motion and performance. A clide angiocardiography, and their short physical half­ number of methods have been introduced recently for life facilitates serial determinations. the study of ventricular performance and regional wall Transpulmonary transit time measurements, the motion. As stated previously, ejection fraction can be oldest of radiotracer measurements of the circulation, measured with a nonimaging detector, but evaluation of can be made by positioning the detector so that the ventricular wall motion requires a scintillation camera. activity from both ventricles is recorded. The Usually, the scintillation camera is activated (gated) to cardiopulmonary activity can be instantaneously dis­ record images only during selected portions of the played in analog form on a strip chart recorder or con­ cardiac cycle. Technetium-99m-albumin or ionic 113min tinuously recorded on magnetic tape or directly into a are commonly used since these tracers remain within computer. When both cardiac output and trans­ the vascular compartment. Technetium-99m-red blood pulmonary transit time are measured, the pulmonary cells are preferred by some. Both right and left ven­ vascular volume can be estimated. tricular function can be determined. Serial studies are When the ventricular activity is recorded on mag­ possible since the technique requires only an netic tape or directly into a computer, the left ven­ intravenous injection. tricular ejection fraction can be estimated from analysis Simple inspection of the end-systolic and end­ of the first-transit time-activity curve. diastolic images of the two ventricles in the 45-deg left The external detector probe can also measure the anterior oblique position often permits estimation of the activity in an area of the lungs and thus can estimate the ejection fraction of each ventricle and the detection of size of left-to-right intracardiac shunts from the regional contraction abnormalities. Other views, such pulmonary time-activity curve generated by an in­ as the anterior, are often helpful. Alternation of end­ travascular indicator. It can also estimate the size of pe­ systolic and diastolic images on the same viewing screen ripheral arteriovenous shunts from successive arterial facilitates perception of hypokinesis, akinesis, and dys­ and venous microsphere injections. The instrument has kinesis. proven useful for the bedside evaluation of cardio­ Quantification of end-diastolic volume and ejection pulmonary disorders. fraction can be accomplished by geometric projections Radionuclide angiocardiography. In radionuclide of ventricular contours using formulas developed for angiocardiography, the scintillation camera is used to contrast angiography or by analysis of time-activity depict the course' ol an intravenously injected radio­ curves in the flagged area of the left ventricle. pharmaceutical as it passes through the heart and great The timing of the events of the cardiac cycle (gating) vessels. Although the structural detail is far inferior to is usually obtained from the electrocardiogram, al-

142 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY though the carotid pulse or the phonocardiogram can at rest. During exercise, the myocardium supplied by a also be used. An alternative to gating the scintillation stenotic artery becomes ischemic and less tracer is ob­ camera is the continuous recording of both cardiac ra­ served in the involved region compared to that of the dioactivity and the electrocardiogram on magnetic tape surrounding nonischemic myocardium. Such changes or directly into a computer. Subsequently, the activity may not be observed when the tracer is injected at rest, at various regions and phases of the cardiac cycle are se­ when even major degrees of stenosis may exist withOut lected for data processing and display. Usually an image visible focal defects. If acute infarction or scar tissue of the tracer distribution is obtained at 0.1-sec intervals (old infarction) is present, however, the damaged area during a specific fraction of the R-R interval. Images does not accumulate radioactivity either during exercise obtained during the same time intervals after the R or at rest. When used in combination with radionuclide waves are summed until 200,000 or more counts have angiocardiography, and ventricular wall and ventricular been recorded during systole and diastole. The end-sys­ performance studies, the noninvasive relative perfusion tolic and end-diastolic images are usually recorded in examination is useful both in identifying patients with both the left anterior oblique and the anterior position, heart disease and in differentiating diffuse from focal and each position requires separate recording intervals pathology of the left ventricle. of perhaps lO min each. Multiple images of greater fre­ Relative regional myocardial perfusion can be dem­ quency throughout the cardiac cycle can also be formed onstrated at the time of coronary angiography by the in­ by specially programmed computers. It is essential that jection of albumin microspheres or macroaggregates the patient lie absolutely still during the data recording. tagged with 99mTc or other radionuclides directly into An important use of these procedures to date has the coronary arteries, left ventricle, or aortic root. Such been to differentiate diffuse hypokinesis from localized studies reveal the functioning capillary bed in the terri­ dysfunction and aneurysm in patients with myocardial tory distal to the point of injection. The distribution of infarction and heart failure. This differentiation is vital radioactivity within the myocardium can be determined in selecting patients for subsequent contrast angiog­ for several hours after the patient has left the raphy and aneurysmectomy. These procedures are also angiographic laboratory. The safety of this technique useful in the evaluation of patients with congestive heart has been widely accepted, when appropriate attention is failure and in the differentiation of left, right, and biven­ paid to the number and size of particles injected. tricular failure. They are also used to monitor the status Regional myocardial blood flow estimates per unit of patients with acute myocardial infarcts and to assess weight of myocardium are provided by the washout of a the response to pharmacologic intervention as well as to diffusable indicator, usually 133Xe injected into the coro­ coronary bypass surgery. nary arteries. The technique is particularly useful in that Facilities for these studies should be immediately ad­ serial measurements can be made before and after a jacent to a coronary care unit if patients with suspected physiologic or pharmacologic intervention, and quanti­ or proven myocardial infarction are to be studied, par­ tative measurements of flow can be provided. (Similar ticularly those in shock or congestive heart failure. In serial measurements can also be made with hospitals with many coronary heart disease patients, a microspheres by using two or more radionuclides.) The scintillation camera kept in the coronary care unit can interventions employed are usually rapid atrial pacing, be dedicated to these and other studies. This camera drugs such as papaverine, or radiographic contrast ma­ may also serve other patients in adjacent medical/sur­ terial. The data can be displayed as a grid of derived gical intensive care units. In smaller hospitals, portable numbers on the cardiac silhouette or as a functional equipment may be more desirable so that when not in image with intensities proportional to the calculated re­ use for patients with coronary heart disease it can be gional blood flow. This procedure requires a camera in used in other locations. the angiocardiographic laboratory. El'aluation of myocardial perfusion. Regional Acute myocardial infarct l'isualization. The prop­ myocardial perfusion can be determined noninvasively erty of certain technetium-tin chelates to localize in from peripheral intravenous injection of radioactive acutely infarcted myocardium has been employed to de­ tracers or by direct injection into the coronary cir­ termine the size, location, and extent of acute damage culation at the time of cardiac catheterization. These during the first 3 or 4 days after an infarction. These techniques are useful for differentiating diffuse and focal studies complement those of regional myocardial per­ myocardial disease and for estimating perfusion deficits fusion and ventricular wall motion, which document the associated with stenosis of the coronary arteries. presence and location of myocardial damage but cannot Relative myocardial perfusion can be determined by distinguish acute from chronic disease. Agents such as imaging the distribution of intravenously injected 43K or technetium-labeled tetracycline, pyrophosphate, a~d its analogs, 81Rb, 129Cs, and 201Tl. The location, size, glucoheptonate that accumulate in regions (}f acute in­ and extent of myocardial infarcts can be estimated in farction help solve this problem. Since the studies are the majority of patients. Regional ischemia can be positive only in fresh infarcts of 4-8 days' duration, this identified by comparing such studies after exercise and test also helps identify the extension and recurrence of

VOLUME 3. NUMBER 3 143 infarction. It is of particular value in patients in whom studies are usually performed as an aid in the the diagnosis of acute infarction is clinically difficult, differential diagnosis of pulmonary embolism but are those with left bundle branch block, previous infarction, also useful for detecting pulmonary venous hyperten­ subendocardial infarction, true posterior infarction, and sion, congestive heart failure, and other cardiovascular intraoperative infarction. abnormalities such as hypoplastic pulmonary arteries. Either a dedicated or a portable scintillation camera Perfusion lung scanning performed after intravenous is required since the majority of studies are performed administration of 99mTc-microspheres or other particles on patients in coronary care units. It is often desirable depicts regional distribution of pulmonary arterial to determine ventricular function at the same time in a blood flow. When properly interpreted, such in­ patient with a documented myocardial infarct. formation can often help confirm or exclude pulmonary Radionuclide arteriography and venography: Ar­ embolism suspected on clinical grounds, particularly teriography. Following the intravenous injection of when regional ventilation is also measured with 133Xe 99mTc-pertechnetate, the activity in the abdominal gas. aorta may be visualized. The presence of suspected ab­ To perform a perfusion lung scan, an injection of the dominal aneurysm and its effects on distal perfusion to radiopharmaceutical is made intravenously and its dis­ extremities or kidneys can be determined. This tech­ tribution throughout the lungs is determined by means nique may also be used to determine the vascularity of of either a scintillation camera or rectilinear scanner space-occupying lesions within the liver or kidneys. since the radioactive microspheres or particles remain The distribution of perfusion in the extremities can in situ for a sufficient length of time. Regional be determined during peripheral arteriography by intra­ pulmonary arterial blood flow can also be estimated arterial injection of labeled albumin particles or following an intravenous injection of 133Xe gas dissolved microspheres of albumin. Diffuse disease of the vessels in saline. In the latter instance, measurements are is indicated by a generalized decrease in blood flow to limited to the first 10 sec after injection, however, and muscle as compared to skin; stenotic lesions of large usually only one view can be obtained. vessels cause regional decreases in blood flow that are It is necessary to use a scintillation camera to indicated by regional decreases in activity. Healing of measure regional ventilation since all regions of the lung skin ulcers can often be predicted on the basis of the must be examined simultaneously to monitor the initial degree of associated hyperemia. Quantification of the arrival of the radioactive gas and its rate of washout size of arteriovenous fistulas can be made by measuring during exhalation. The qualitative relationship between pulmonary activity after arterial injection of regional perfusion and ventilation can be obtained by microspheres. Increased sensitivity of the method can comparing the distribution of technetium-labeled parti­ be achieved by injecting microspheres during reactive cles with a single breath of xenon gas. Valuable in­ hyperemia resulting 5-15 sec after injection of ra­ formation can also be obtained by computer and diographic contrast media. quantification of the distribution, arrival, andjor Venography. gadionuclide venography of the legs washout of the tracers. The most precise quantitative and pelvis is performed by injecting labeled albumin relationship is obtained using radioxenon for both per­ particles or microspheres into a foot vein and moni­ fusion and ventilation measurements, but clinically toring them as they ascend the leg into the inferior vena useful data are obtained by comparing the distribution cava. An obstruction with collateral flow can be de­ of radiotechnetium (perfusion) with radioxenon (venti­ termined by serial scintigrams of the area to evaluate lation). The administration of 133Xe gas requires a spi­ the presence of thrombi. ]>articles of albumin (espe­ rometer or other delivery system as well as a collection cially macroaggregated) easily adhere to thrombi. apparatus that can be a self-contained charcoal system, Radioiodinated fibrinogen has been used to detect oc­ a collection bag, or a vent with an exhaust into a hood. cult thrombosis in the legs, especially in postoperative Experience has shown that it is possible to move patients, and to evaluate the efficacy of various anticoa­ patients suspected of pulmonary embolism to the gulant regimens. The detector most frequently used is a central nuclear facility. Perfusion scanning may also be small hand-held nonimaging crystal probe attached to a used to detect pulmonary venous hypertension in rate meter. certain patients with coronary artery disease so it would The course of large veins (superior and inferior vena be desirable to do such studies at the bedside of cavae) can also be determined by visualization of non­ critically ill patients as well. Portable equipment can be particulate technetium-labeled tracers. used but intermediate storage of the recorded data is de­ The arterial studies can be imaged in the central nu­ sirable to permit use of the data processing and display clear medicine facility because there is ample time after capability in the core facility. injection while the tagged particles are temporarily Central nervous system studies. Regional cerebral blocked. A scintillation camera is needed for the dy­ blood flow can be estimated by recording with a scin­ namic portion of the venous studies. tillation camera the first passage of an intravenous Regional pulmonary perfusion and ventilation. These bolus of sodium pertechnetate through the cerebral

144 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY circulation, usually employing the vertex or anterior nosis of suspected renal masses, such as cysts, tumors, projection. Interpretation can be based on visual assess­ and fetal lobulation; in decisions regarding steroid ment of serial timed images (usually at 1- or 2-sec inter­ therapy or removal of transplanted kidneys; and in vals) or on quantitative analysis of regional time­ serial evaluation of renal function in children with a va­ activity curves. Quantitative analysis requires the use of riety of postrenal obstructive diseases. either a general purpose or a special purpose computer Compartmental volumes. Measurements of red system. If carotid arterial disease is suspected, it is best blood cell and plasma volumes are based on dilutional to visualize the carotid arteries by slightly extending the measurements in which known volumes and activities of neck and pointing the camera to this region. tracer are injected into the circulation and, after an ap­ The technique is useful in distinguishing serious propriate period of mixing, samples are withdrawn for cerebrovascular disease from more benign conditions measurement of radioactivity. Red cells are labeled with causing neurologic symptoms, in determining the 51Cr or 99mTc. Chromium-51 can also be used to deter­ relative vascularity of mass lesions of the brain detected mine red cell survival. Technetium-99m may be em­ by conventional scanning techniques, and in assessing ployed when simultaneous radionuclide angiocardiog­ the size and location of cerebral infarcts. Many patients raphy and/or blood pool imaging is to be performed. A can be examined in the central facility although it is de­ number of labeled human plasma proteins can also be sirable to combine cerebral, cardiac, and pulmonary used for plasma volume measurements, e.g., 131I­ studies in a satellite nuclear facility in the vicinity of a albumin, 99mTc-albumin, and 113min-transferrin (autolo­ medical/surgical intensive care area. gous). Renal studies. Renal perfusion can be estimated by In addition to determining blood volumes, dilutional recording the first passage of an intravenous bolus of a measurements can be used to study electrolyte and fluid technetium radioindicator used for renal scanning. In­ compartments such as exchangeable sodium and total­ terpretation is usually based on visual assessment of body water. serial timed images (usually at 5- or 10-sec intervals) or Measurements of compartmental volumes, particu­ on quantitative analysis of regional time-activity curves. larly red cell and plasma volumes, are useful in deter­ The procedure is used to estimate the relative blood flow mining the extent of hypo- and hypervolemia in patients to both kidneys and as an index of obstruction to flow at in shock, from other than recent blood loss, or with the arterial, venous, and microcirculatory levels. In the acute congestive heart failure, particularly after sur­ transplanted kidney, it can be used as a qualitative esti­ gery. mate of perfusion and sequentially as a guide to changes Drug and hormone assays. The development of in flow with time. radioimmunoassay methodology makes it possible to A number of technetium chelates are bound by the measure extremely low serum concentrations of bio­ kidney and can be used for obtaining structural in­ logically active substances, some of which are of im­ formation. The images can be employed to determine portance in the management of patients with cardio­ renal size, location, and anatomy; to delineate renal vascular disorders. pathology, especially in patients who have demon­ Digoxin (and digitoxin) serum assays are a strated or suspected sensitivity to iodinated radio­ reasonable estimate of the drug's pharmacologic graphic contrast agents; to supply anatomic informa­ activity and reflect variations in bioavailability, com­ tion on patients with azotemia in whom radiographic partmental distribution, and rates of metabolism and visualization cannot be obtained; to assess the amount excretion. The assay, which depends on interaction with of residual functioning tissue in hydronephrotic kidneys; an antibody raised by coupling the drug to bovine serum and to assess postrenal patency and obstruction. albumin, can be performed with simple clinical chem­ In addition to visual methods for assessing perfusion istry equipment and either a gamma or beta scintillation and urinary tract morphology, quantitative methods are counter. Several commercial kits are now available. available for estimating renal function. A number of The digoxin assay's major c!inical use is in the substances are excreted primarily or only by the differential diagnosis of digitalis toxicity, especially in kidneys, so, by labeling one of these substances with a patients with diminished renal function. It can also be suitable radionuclide and monitoring the pattern of ra­ used to investigate the bioavailability of certain pharma­ dioactivity over the kidney as a function of time, it is ceutical preparations. Facilities for this assay should be possible to obtain an evaluation of renal function. available 24 hr a day. Radioactive tracer studies are helpful in assessing Although it is still not possible to assay renin relative function of the kidneys in patients with directly, an indirect estimate can be made by measuring suspected renovascular hypertension and in evaluating the serum concentration of angiotensin I, an inter­ the adequacy of renal arterial surgery; in the diagnosis, mediate between the conversion of angiotensinogen and treatment, and monitoring of patients with obstructive its biologically active form, angiotensin II; renin pro­ uropathy; in the early diagnosis of disease affecting one motes the conversion of angiotensinogen to angiotensin kidney, such as pyelonephritis; in the differential diag- I. Antibody to angiotensin I is raised by coupling the

VOLUME 3, NUMBER 3 145 Director and

Nuclear Medical Physicisls

FIG. 1 . Staff relationships in central nuclear medicine facility.

peptide hormone to poly-1-lysine to make an effective Central nuclear medicine facility: Administra­ antibody-producing substance. The antigen-antibody tion. The central facility should be established as an complex is soluble and free antigen must be fixed to an independent administrative unit with a separate budget added adsorbent. Commercial kits are available to and a physician-director qualified to assume clinical, perform the assay and the basic equipment is essentially technologic, and administrative responsibility for the that required for digoxin radioimmunoassays. service. Laboratory policy should be developed by the The angiotensin test is useful in the differential diag­ director and his staff, reviewed by appropriate hospital nosis of primary aldosteronism and renovascular authorities, and published in the written statement of hypertension. Renal vein assays can be used in the hospital policy. investigation of unilateral renovascular disease. Professional staff. Figure 1 illustrates staff rela­ This assay need not be available in the hospital but tionships in the central nuclear medicine facility. can be perfomed in a reliable and easily accessible out­ The director should be certified by the American side laboratory. Board of Nuclear Medicine or have the equivalent in Although these radioimmunoassays are the principal training and experience. He must have sufficient back­ ones relating to cardiovascular disease in use today, ground in the clinical, technologic, and administrative others such as a radioimmunoassay for serotonin and aspects of a nuclear medicine service to assume vasopressin are rapidly appearing. responsibility for-but not necessarily limited to­ granting clinical privileges, review and approval of phy­ sician performance, establishment of quality controls, Hospital Resource Guidelines training of physicians and laboratory support personnel, Because of the complexity and common features of development of an annual budget, purchase of equip­ much nuclear diagnostic equipment and the medical and ment, and scheduling of procedures. technical expertise required for its proper use, hospitals Staff physicians should have the same professional developing nuclear medicine services should begin by es­ qualifications as the director with the exception that tablishing a central nuclear medicine facility capable of they need not necessarily be experienced in the areas of providing a broad range of diagnostic studies. These will administration and training. If a staff physician restricts include but will not be limited to cardiovascular studies. his activities to in vivo or in vitro procedures, his As case loads and staff capabilities expand, it may be competence can be limited to these areas. desirable to establish one or more satellite nuclear The principal functions of a staff nuclear medicine medicine units remote from the central facility to pro­ physician will be appropriate patient evaluation before mote the interaction of nuclear medicine with other the diagnostic study; supervision of the technical as­ di,agnostic and therapeutic modalities and to help meet pects of the study including advising the nuclear the needs of patients in special care areas-emergency medicine technologist on the adequacy of the data ob­ rooms, intensive care units, operating and recovery tained; interpretation and reporting of examination re­ rooms, catheterization laboratories, and noninvasive sults; and consultation with the referring physicians. If a cardiac diagnostic laboratories. Satellite units should physician's duties are restricted to these activities, he always be functionally and administratively related to should be able to examine between 12 and 15 patients a the central facility to facilitate consultation, and to day. Other responsibilities such as administration, provide for equipment backup and more sophisticated education, research, and the development and imple­ data processing. In small hospitals, and in large institu­ mentation of new diagnostic techniques will reduce this tions during the early phases of program development, case load capability. an alternative to on-site satellite units is portable diag­ In the development and implementation of cardio­ nostic equipment originating from the central facility. vascular procedures, close cooperation between car-

146 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY FIG. 2. Nuclear medicine examination flow diagram. diologists and the nuclear medicine staff is essential for technologist can assume responsibility for 8-10 major meaningful patient care evaluation. in vivo procedures per day. The technologist staff should include a chief The services of a full-time radiopharmacist or ra­ technologist and an assistant chief technologist, both diopharmaceutical chemist will be required only by skilled in the administrative as well as technologic as­ major medical centers although every hospital with a pects of nuclear medicine. In collaboration with the nuclear medicine program will benefit from the consul­ physician-director he should develop the technical tative services of such professionals. The daily com­ operational budget and be responsible for its expen­ pounding of radiopharmaceuticals from commercial diture; develop and maintain statistical records appro­ kits can be accomplished by a trained nuclear medicine priate to budget administration and long-range plan­ technologist. ning; purchase necessary supplies and approve related The services of a nuclear medicine physicist should invoices for payment; actuate institutional personnel be available on a full- or part-time basis. His or her policies for the technical staff; interview, hire, and responsibilities include radiation safety, quality control perform regular evaluations of employee performance of instrumentation, the teaching of medical radiation and maintain related personnel files. physics and nuclear instrumentation to the medical and Technologists should be certified by the American technical trainees and staff, and the evaluation of new Registry of Radiologic Technologists (ARRT), the instrumental techniques. Skills in computer program­ American Society of Clinical Pathologists (ASCP), or a ming are particularly desirable. As an alternative, the conjoint registry currently under consideration.* They function of the physicist can be filled by an engineer with should understand the general principles of radiation special training in nuclear instrumentation. physics, radiopharmaceutical chemistry, and the Location and space. A major characteristic of nu­ function of nuclear instrumentation. They should be fa­ clear medicine procedures is that they are noninvasive. miliar with the operation of nuclear instruments and be Thus, they are used early in the diagnostic process. Al­ capable of calibration checks, general quality control, though the majority of patients seen in a central nuclear and minor maintenance. They should understand the medicine facility today come from the inpatient problems of caring for sick people and of their families, medical service, it is likely that increasing numbers of be skilled in patient positioning, and know sufficient patients in the future will come from the ambulatory anatomy and physiology to understand the mor­ outpatient service. Therefore, the central facility phophysiologic basis of nuclear procedures and the con­ should be easily accessible to outpatients. Radiation sequences of patient and position variation. They should shielding and structural requirements are minimal and know sufficient radiation hygiene to minimize the should not be considered obstacles to its being located patients' and their own radiation exposures and to close to patient areas. perform simple decontamination procedures. The sequence of events involved in the performance Experience suggests that excessive specialization, of a nuclear medicine diagnostic examination, illus­ such as performing only one type of study, can trated in Fig. 2, can be grouped into three phases: those eventually result in morale problems as well as overde­ occurring before the technical performance of the pendence on a single individual. To achieve maximum study; the technical performance of the study; and the flexibility and to provide services outside the normal interpretation and reporting of results to the referring working schedule and during vacations and illness, it is physician. Figure 3 illustrates spatial relationships and preferable that all technologists should be competent in staff-patient traffic flow patterns for the central facility. the performance of all procedures. On the average, one To accommodate one camera or scanning system, examination table, stretcher, storage area, and small writing desk, the minimum size for an imaging room *For information contact the Council on Medical Education, should be from 250 to 300 sq ft. Arrangement should be American Medical Association, 535 Dearborn St., Chicago Ill. 60610. such that a technologist can move freely around the

VOLUME 3, NUMBER 3 147 Phase I Phase II Phase Ill

"'c:: Secretary '2 File Storage c:: and Transcription .. Referring Patient~ iL and Staff Offices Traffic 7~ ___... ~- 1-'- .L---~ Physician --~"""""""'"""""""'"""'"""'""""""""~...,_..,...,...,...,...,...,~...,..... ~ t ,_ ~ Traffic 'tl.,"' 'tl"'c.!: e Q. ..c 'fti- .!!c.c., ==., - .,-u ·- a:~ I Interpretation l' Reporting and \ Consultation \

FIG. 3. Spatial relationships and traffic flow in central nuclear medicine facility. table during the examination procedure. Both oxygen should be adequately shielded; either built-in lead bins and suction should be available with emergency equip­ or removable modular containers are acceptable. If ment located close by. hundred-millicurie quantities of radioxenon or The value of many cardiovascular procedures is radioiodine are to be stored, a hood should be located in greatly enhanced by processing and display of the data the storage room. by a computer. There are two basic types of computers Preparation rooms should be 150 sq ft and include a used in nuclear medicine-general (programmable) and shielded and ventilated radionuclide hood with a face ve­ special (hard wire) purpose units. The general purpose locity of 100 ft/min, a safely located exhaust, and ade­ systems are more flexible and programs can be de­ quate filtration. A protective barrier with direct (lead veloped and changed by the users. Special purpose glass) or indirect viewing of compounding of radiophar­ systems have fixed programs and are more limited in maceuticals should be provided as well as syringe capability. Many computer systems are small and can shields, lead bricks, and pigs. Lead aprons should also be operated immediately adjacent to the imaging de­ be available for personnel who handle large amounts of vices, usually in the same room. An additional 50 sq ft radioactive substances. Ten square feet of countertop should be added to the procedure room to accom­ space should be provided for dose calibration. If modate such devices. Alternatively, an intermediate properly shielded, the preparation room may be within data storage system may be introduced between the the storage area. Both rooms, however, should be plan­ imaging device and the computer. The controls of this ned in accordance with federal and, where appropriate, intermediate storage device should be in the procedure state radiation safety standards and in consultation with room to facilitate collection of the data; the computer a qualified health physicist. Access to the radiophar­ itself may be located either in the procedure room or in macy should be limited to those engaged in the prep­ a central data-processing area. The central data­ aration and transport of radiopharmaceuticals. processing unit should be immediately adjacent to, but An area should be provided for administration of ra­ acoustically isolated from, a consultation room for the diopharmaceuticals to patients when studies do not re­ nuclear medicine staff and referring physicians. The size quire patient injection in the procedure room. This area of the data-processing and display area will range from should be large enough to accommodate a stretcher, 200 to 400 sq ft depending on the complexity of the unit examining table, counter tops, and two staff members­ and the number of imaging devices. It should be large approximately 150 sq ft. Prepared radiopharmaceuti­ enough to contain a central processing unit and pe­ cals will often be stored temporarily in various locations ripherals, a writing desk, and a storage area for disks where patient examinations are conducted so there and tapes. must also be adequate shielding and monitoring instru­ The functions of the radiopharmacy are to store ra­ mentation in these areas. dioactive materials, prepare them for administration, The size of the in vitro radioassay laboratory will be and to assay individual patient doses. The storage room determined by the number and type of in vitro assays should be approximately 50 sq ft and geographically performed. Usually a minimum of 400 sq ft is sufficient. separated from the preparation area to reduce radiation Adequate space should be provided for patient re­ exposure to the staff. All stored radioactive materials ception and waiting areas, which may be shared with

148 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY other hospital services. It is highly desirable to separate dible signal as well as a rate meter. In addition, there inpatients from outpatients, and children from adults. should be survey equipment for monitoring incoming Since many procedures will require patients to be kept packages, storage space, and contaminated areas (3-5). in the central nuclear medicine facility for considerable Devices known as dose calibrators are available com­ periods after an injection, the waiting area should be mercially for measuring the activities of different ra­ sufficient to contain an adequate number of chairs for diopharmaceutical preparations, and such a device ambulatory patients; separate space should be provided must be located in the radiopharmaceutical supply or for stretcher patients and a receptionist's desk. preparation rooms. Most dose calibrators incorporate a The physician's examination room should be close to high-pressure ionization chamber, the ionization-cur­ the reception area where the nuclear medicine physician rent response of which, per unit of activity of a gamma can evaluate patients in preparation for studies. It ray emitter placed in the re-entrant cavity of the should be large enough to contain a chair, small desk, chamber, is a well-defined and reproducible function of examination table, and instrument cabinet; about 120 sq the gamma ray energies. This function is approximately ft. linear, increasing with energy, for 100% abundant For secretarial and transcribing facilities and files, monoenergetic gamma rays, except at low energies 150-250 sq ft should be allocated. (below - 200 keY). By appropriate electrical circuitry Many nuclear medicine procedures require si­ the ionization-current response is converted into a multaneous conventional radiographs for proper in­ direct reading of activity, in multiples of curies, on a terpretation of results. In large departments this may digital voltmeter, which reads the voltage drop across a justify a radiographic unit within the central facility resistance in the electrical circuit. The response of the while, in other circumstances, these services may be dose calibrator is adjusted to different radionuclides by shared with diagnostic radiology. Automatic film means of different plug-in resistance modules (labeled processing should be available for both radiographic for the radionuclide in question), or by altering a and nuclear medicine procedures. variable resistor to calibrated values supplied by the A minimum of 350 sq ft should be allocated for a manufacturer. data interpretation and consultation room, which A variant of the ionization-chamber dose calibrator should contain projectors for viewing nuclear medicine is the plastic scintillator, which, in turn, generates a data and conventional viewers for radiographic data. It varying current response from an electron-multiplier is also desirable that a computer terminal and display phototube. unit be available here. In using any dose calibrator, great care must be At present, approximately 10,000 studies may be taken to follow the manufacturer's instructions, par­ stored in 30 sq ft of file space using conventional x-ray ticularly with regard to geometry corrections for folders. In the future, it is probable that storage of nu­ different sizes and shapes of containers, and to possible clear medicine data will be in the 35-250 mm format so recombination effects at high gamma ray emission space requirements will be greatly reduced; as many as rates. Daily monitoring of the dose calibrator, using a 150,000 studies in the 35 mm format can be stored in sealed preparation of a long-lived radionuclide, such as 137 137 226 approximately 30 sq ft of floor space. Thus, filing can Cs- m Ba, or Ra in equilibrium with its daughters, be conveniently combined with the secretarial and is essential. Periodic recalibration of the dose cali­ transcribing functions. brator, with standards of the radionuclides in general There should be adequate office space for staff phy­ use, is desirable. In the event of unexpectedly large dis­ sicians, nuclear medicine physicists and chemists, ra­ crepancies between the suppliers' assays stated on the diopharmacists, and supervisory technologists in accor­ label of the radiopharmaceutical container and the dose dance with the needs of the hospital. Space should also calibrator assays, it is essential to make an immediate be provided for storing linens and general supplies and recalibration with a standard of the radionuclide in for an employees' rest area (toilets, locker space, question. lounge), janitorial area, and educational facilities Equipment for beta and gamma scintillation (conference rooms, library and study room, teaching counting of liquid samples should be available in the aids and files), all of which may be shared with other radioassay laboratory. Sample changers should be au­ hospital services.· tomated and interfaced to a general or special purpose Equipment. The following specifications relate pri­ computer when a large number of samples are marily to equipment required for optimal cardio­ processed. vascular studies. A useful guide to equipment specifica­ At times, these devices are used instead of scin­ tions and maintenance has been published (2). tillation cameras for measurement of cardiac output, Area monitors should be located where there is a ejection fraction, left-to-right shunts, transpulmonary potential for high radiation exposure, such as the transit time, and arteriovenous shunting in the pe­ storage and radiopharmaceutical preparation rooms. ripheral circulation. When a probe is to be used for ra­ They should be operated continuously and have an au- diocardiography, it must be equipped with special colli-

VOLUME 3, NUMBER 3 149 mators, a short time constant, and high speed strip cilitate inspection of results before patients leave the chart or other recorder or computer interface. examination area. Varieties available include 35 mm, 70 The resolution of currently available scintillation mm, and 105 mm, as well as those designed to process camera systems is 8 mm or better in the range of 120- larger (14 x 17) radiographic film. Daylight loading 200 keV when measured from FWHM of line-spread systems are available. functions at the face of the collimator. Count rates of A general purpose computer is useful for permanent up to 100,000 cps have been obtained without excessive storage of patient data, such as identification numbers losses. Spatial linearity measured with a bar source or and type and date of study. Permanent storage of adsMber shows a deviation of less than 0.5 em from the images is best achieved photographically using 35 mm, center line of the bar. Uniformity, as measured with a 70 mm, 105 mm, or standard radiographic film sizes 64 x 64 digitized matrix, usually does not deviate by with single or multiple format. Direct inspection is more than ± 10% in the useful field of view. Older possible with 70-mm or larger film; but for viewing 35- cameras, however, cannot achieve this level of perfor­ mm film, projection is desirable. Recording on Polaroid mance; therefore, each instrument must be evaluated film has the advantage of immediate availability of each for its adequacy in performing the desired studies. For view, but this method is more expensive than celluloid example, many older cameras have inadequate special film and less desirable for conference viewing. Auto­ resolution for the low-energy photons of 201Tl; however, matic processing of conventional celluloid film also per­ such cameras may be satisfactory for radionuclide mits evaluation of the examination shortly after its angiocardiography and gated studies. Uniformity, spa­ completion. tial resolution, and sensitivity should be checked on a Interpretation of scintigrams frequently requires regular basis. Spectral resolution of the crystal should correlation with radiographs and with ultrasound be better than 18% FWHM at 140 keV, and overall studies (1, 6). Particularly when studying the lung, sensitivity should also be sustained within 10% of the isolated interpretation of the scintigram without corre­ level set at the time of the purchase of the instrument lating the study with the roentgenographic appearance when measured under identical conditions. of the chest may lead to misinterpretation. Therefore, Computers are not necessary- -for many cardio­ the location of the scanning rooms and the adminis­ vascular nuclear medicine procedures but they enhance trative arrangements concerning inter-relationship with the quality of most of them. For example, initially only diagnostic radiology and ultrasound should be such that the scintillation camera and cardiac gate are needed for films and ultrasound scans are immediately available radionuclide angiocardiography and ventricular wall for viewing at the time the scintigrams are being in­ motion and performance studies. The next step should terpreted. be the addition of computer capabilities. Each imaging Nuclear medicine technologists should perform daily device should be interfaced to a data storage system equipment checks including evaluation of uniformity of such as magnetic tape, disks, or cassettes. For many field, spatial resolution, and sensitivity of cameras. studies, special purpose (hard wire) computational Scanners should be checked daily for sensitivity and equipment is adequate but, for maximum flexibility and monthly for adequacy of contrast. Provision should be incorporation of new technology, general purpose made for periodic preventive maintenance for all equip­ (programmable) digital computational equipment is de­ ment (Table l ). Monitoring of personnel for radiation sirable. Ideally, the computer system should have 10,- exposure should conform with state and federal regula­ 000 or more image cells with a capability of various ma­ tit>ns. There should be weekly checks for radionuclide trix sizes down to 4,000 image cells (64 x 64 array) for contamination of all working areas. use when count rates during specific periods of the Quality control for sterility and pyrogenicity should cardiac cycle are limited. Magnetic tape or disk re­ be available if radiopharmaceutical's are prepared in the cording devices should meet industry standards com­ laboratory from other than commercial kits. monly used for larger digital computers. Some of the Emergency resuscitation. Essential patient medica­ commercially available imaging systems in nuclear tions and monitoring and resuscitation equipment medicine employ a television screen for displaying the should be available. data. The advantages of television display include better Satellite nuclear medicine units: Types of examina­ gray scale, ready adaptability for use with color, and tions. Table 2 outlines the cardiovascular nuclear relatively low cost. medicine examinations that, under optimal conditions, The use of rectilinear scanners in cardiovascular nu­ should be available in each satellite unit. A priority clear medicine is limited almost entirely to pulmonary rating has been assigned each examination based on its perfusion studies with particles and to the diagnosis of utility in the satellite under consideration. cerebral infarction. These studies can also be Administration. Approaches for managing satellite performed, however, with the scintillation camera. The units will vary, and hospitals must tailor administrative use of a dual detector rectilinear scanner substantially structure to local circumstances. Whatever the ar­ reduces examination time. rangement, it is important to emphasize that close Automatic film processors are highly desirable to fa- working relationships between the professional staff of

!50 JOURNAL OF NUCLEAR-MEDICINE TECHNOLOGY TABLE 1. Quality Control for Patients, Radiopharmaceuticals, and Equipment*

Who is What monitored How monitored When monitored responsible

Patient Is the correct study being performed? Consultation with referring physician Before scheduling Physician Satisfactory information Requisition/report form; clinical evaluation After study Physician Accurate interpretation Followup When information becomes available Physician Positive identification Verbal or personal communication, wrist Before nuclide is administered Technologist band if available Correct preparation Verbal request Before nuclide is administered Technologist Radiopharmaceutical Pyrogens Pyrogen test (USP) Micro-organisms Sterility test ( USP) Efficacy Tissue distribution Chemical and radiochemical purity Chromatographic and spectroscopic analysis Radionuclidic purity Beta/gamma spectroscopy Physical properties Microscopy Radionucl idic concentration Ionization chamber assay Commercially compounded Before use Manufacturer Commercial kit preparations Before use Manufacturert and generators Pharmacist+ In-house preparations Before use Pharmacist Equipment Well counters and external detectors System resolution FWHM Monthly Technologist System linearity Two nuclides with widely separated Monthly photopeaks Background Background control chart Daily Stability of count rate Long-lived standard control chart Daily Spectrometer calibration Peak with nuclide with photopeak Daily near nuclide to be counted Rectilinear scanners Photorecorder calibration Counts/cm2 /film density Three monthly Effect of contrast enhancement Three monthly Spatial resolution Phantom studies Initial evaluation only Scintillation cameras Stability of count rate Long-I ived standard control chart Daily Spectrometer calibration Peak with nuclide to be used Daily Field uniformity check Disk source 57 co or 99mTc Daily Spatial resolution Lead bar phantom or line source phantom Daily Ionization chambers Contamination Background count Daily Stability of count rate Long-lived standard count Daily

*Modified from Ref. 7. t Responsible for pyrogen- and micro-organism-free radiopharmaceuticals. +Responsible for efficacy, chemical and radiochemical purity, physical properties, and radionuclidic concentration of radiopharmaceutica/s.

TABLE 2. Cardiovascular Nuclear Medicine Examinations in Satellite Facilities

Location of satellite nuclear medicine facility Cardiovascular nuclear Central nuclear Noninvasive Cath-angio Cardiac medical examinations medicine lab CCU/ICU* cardiac lab lab E.R. O.R.

Radiocardiography + + + + ± ± Radionuclide angiocardiography + + + + + + Ventricular wall motion and performance + + + + + + Acute infarct visualization + + + Regional myocardial perfusion + + + + + + Radionuclide arteriography and venography + + ± + + + Pulmonary perfusion and ventilation + + + + + CNS studies + + + + + Renal studies + + ± + + ± Compartmental volumes + _t ±t ±t Drug and hormone assays + _t ±t ±t

*Includes cardiac surgical /CU. tstudies should be available; equipment need not be. Priority rating: Based on utility of examination in the area indicated, (+),highly desirable;(±), optional; (-),not desirable.

VOLUME 3, NUMBER 3 151 the central and satellite facilities is essential to ensure mating the size and location of acute myocardial in­ high-quality diagnostic examinations and patient safety. farcts, for delineation of regional ischemia during exer­ Equally important is a clear delineation of adminis­ cise, and for the evaluation of regional and total right trative, clinical, and technologic responsibility of phy­ and left ventrical function are rapidly being developed. sicians and technical staff. These should take the form Special purpose instrumentation specifically designed of written policies and should include a mechanism for for patients with cardiovascular disorders will soon be resolving professional disputes. available including lightweight, portable imaging instru­ A cardiovascular nuclear medicine unit that is ments capable of use at the bedside, in the operating located in the coronary care unit or in some other lo­ room, intensive care and coronary care units; emission cation in the hospital should be administered jointly by a and transmission tomographic systems capable of pro­ cardiologist and by a nuclear medicine physician. In ducing transverse sections of the heart to help locate most institutions the unit ·should be an administrative regions of infarction or dyskinesis; and single purpose, satellite of a central nuclear medicine facility while in hard-wire systems such as a device for radiocardiog­ other institutions alternative administrative arrange­ raphy with capability for the computation of ejection ments may be made. Regardless of where the cardio­ fraction for use in the cardiac clinic. In addition, vascular nuclear medicine unit is physically or adminis­ efficient computer codes are being developed that, in tratively housed, the nuclear medicine physician with his conjunction with radionuclide angiocardiography, specialized training should be responsible for the safety, provide a wide range of indices of ventricular function technical performance, and quality control of the unit. including cardiac output, pulmonary vascular volume, If either cardiologist or nuclear medicine physician at­ stroke volume, ejection fraction, and shunt flow tempt to operate this satellite service independently, it measurements. will either fail or, at best, perform ineffectively to the Progress in the development of cardiovascular nu­ detriment of both the patients and the professional staff. clear medicine will be facilitated by close cooperation Equipment. Most in vivo nuclear medicine between cardiologists and nuclear medicine physicians procedures can be performed in satellite units with a in the planning, performance, and interpretation of scintillation camera. Interfacing of the camera to a these diagnostic examinations. The special require­ computer-processing system simplifies some proce­ ments of patients with acute cardiovascular disorders dures and aids in obtaining quantitative data. The often necessitate supplementation of the central nu­ operation of the satellite units differs principally in the clear medicine facility of the hospital with one or more type and number of patients rather than in the tech­ satellite units in or near the coronary care unit, nologic requirements of the study. emergency room, and cardiac operating suite. In ad­ Utilization. An average daily case load of at least dition, the newly emerging noninvasive cardiac diag­ four major in vivo studies is desirable to maintain the nostic laboratories should be equipped to perform clinical and technical competence of the diagnostic certain nuclear medicine procedures. Moreover, se­ team in a satellite unit. The high cost of equipment and lected nuclear diagnostic procedures will provide useful the necessity of amortizing it over a 5-year period (be­ supplemental information during cardiac catheteriza­ cause of rapid technologic developments) also will re­ tion and angiocardiography. quire this level of utilization in a free-standing satellite. The major instrument involved in the important ad­ At the present state of technology, eight to ten studies vances in cardiovascular nuclear medicine is the scin­ per 8-hr day can be performed with each instrument. tillation camera. Many studies can be performed by Quality control. Each nuclear medicine service using this instrument alone, but their number and should establish and maintain a quality control program quality is increased by interfacing the camera to a to include adequate records for documentation of digital computer. continued high-quality performance. Excellent We have presented guidelines for planning cardio­ guidelines for quality control are available (7). vascular nuclear medicine procedures both in a central A potential danger associated with noninvasive nuclear medicine facility and in satellite units such as studies with minimal complication rates is that inade­ the coronary care unit. They are suggested -as optimal quately trained individuals may be tempted to perform criteria rather than minimal standards and they should these examinations. This can result in improper conduct be read with this in mind. of the study resulting in inadequate data, faulty retrieval, and misleading results that may lead to inap­ Acknowledgments propriate or even dangerous therapy. We gratefully appreciate the detailed critiques and the many helpful suggestions from those who reviewed Summary and Conclusions drafts of this statement: William L. Ashburn, Daniel S. The use of radioactive tracers for studying the heart Berman, Larry P. Elliott, Richard H. Greenspan, B. and circulation is increasing daily. Procedures for esti- Leonard Holman, Philip C. Johnson, Robert Jones,

152 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY Denis L. Kirsch, Wilfrid B. Mann, Dean T. Mason, 2. Harris CC: The care and feeding of medical nuclear instru- Henry D. McIntosh, Richard N. Pierson, Jr., Bertram rneatatiaasemin Nucl Med 3:225-238, 1973 3. National Committee on Radiation Protection: Radiological Pitt, Richard Reba, Antone F. Salel, Donald Van Dyke, Monitoring Methods and Instruments. Report No. 10, 1952 and Manuel Viamonte, Jr. 4. International Commission on Radiological Protection: Princi- During the preparation of this statement William L. ples of Environmental Monitoring Related to the Handling of Ra- Ashburn served as liaison-consultant between the dioactive Materials. Publication No. 7, Elmsford, NY, Pergamon Press, 1966 Commission and The Society of Nuclear Medicine. 5. International Commission on Radiological Protection: Han- dling and Disposal of Radioactive Materials in Hospitals and Medical Research Establishments. Publication No. 5, Elmsford, NY, References Pergamon Press, 1966 6. Report of the Inter-Society Commission for Heart Disease I. Report of Inter-Society Commission for Heart Disease. Resources: Optimal Resource for Ultrasonic Examination of the Resources: Optimal radiologic facilities for examination of the chest Heart. Circulation 5 1:A- I, 1975 and the cardiovascular system. Circulation 43:A-135, 1971; revised 7. Lovegrove F, Langan J, Wagner HN: Quality control in nu- 1975 Circulation: to be published clear medicine procedures. J Nucl Med Tech 244-5 1, 1974

VOLUME 3. NUMBER 3