Thirteen radionuclides involved: iodine-131, zinc-65, strontium-85, calcium-47, gold-198, iodine-125, cobalt-60, technetium 99m, copper-67, manganese-54, xenon 133, indium-113m and fluorine-18
UCLA-1. Early Experimental Imaging of the Thyroid Gland Using Iodine 131
IN 1951, the University of California, Los Angeles conducted a series of tests on humans to study the uptake of radioiodine into the thyroid gland. Additional tests were made on patients at the Sawtelle Veteran’s Hospital. The main purpose of this study was to test a new automatic scanner and recorder.
Initial scans were made using a collimated gamma scintillation counter. This equipment enabled a record to be obtained on which an image of the gland was visible and which the researchers concluded was better than a total activity count for clinical studies of thyroid disease.
The second set of scans was made on a frozen tissue preparation obtained from a terminal patient who had been given 3 millicuries of iodine-131, 14 hours before his death. The measured total activity of the thyroid gland at the time it was scanned was about 50 microcuries.
The results of these tests led to increased use of this equipment for clinical diagnostic scans in other patients with thyroid disorders. This work was supported by the U.S. Atomic Energy Commission.
UCLA-2. Zinc Metabolism Studies Using Zinc-65
DURING THE LATE 1950s, researchers at the University of California, Los Angeles; Boston University School of Medicine; and the Massachusetts Memorial Hospitals conducted studies on the metabolism of zinc using zinc-65 (Zn65).
Twenty-one patients with neoplastic disease and one patient with generalized arteriosclerosis participated as subjects. Each was intravenously administered Zn65 as zinc ammonium citrate. The amounts of activity administrated were not reported.
These studies showed that zinc appeared rapidly in white blood cells and persisted for several weeks. It appeared less rapidly in red cells, but persisted much longer. The injected zinc concentrated in the liver and other major organs and was excreted slowly in urine and feces. This study was supported by the U.S. Atomic Energy Commission.
UCLA-3. A Study of Strontium-85 and Calcium-47 Metabolism in Patients with Osteoporosis, Paget’s Disease, and Metastatic Bone Tumors
IN 1959, RESEARCHERS at the University of California Medical School, Los Angeles conducted a series of studies on strontium-85 (Sr85) metabolism using hospital patients with osteoporosis, other skeletal disorders (such as Paget’s disease), and various cancers to determine the uptake and retention of strontium in selected tissues.
The study population included nine hospital patients and six normal volunteers. Five to 15 microcuries of Sr85 as the chloride were administered intravenously to each subject. The rates of Sr85 accumulation were determined for selected parts of the body, using a shielded sodium iodide gamma scintillation counter. Strontium-85 injections were repeated in some of the patients. Excretion rates of Sr85 in urine and stool were determined in one patient. Some of the patients also received tracer amounts of human serum albumin labeled with iodine-131 (I131) by intravenous injection to determine the uptake and retention of protein-bound I131 for comparison to Sr85.
These studies indicated that Sr85 uptake was normal in Anonsenile osteoporotic patients, but reduced in patients with Asenile osteoporosis, due presumably to reduced capillary blood flow. These studies continued from 1959 to 1962 and included additional injections of Sr85 and calcium-47 in other hospital patients with multiple myeloma and other diseases to improve understanding of the metabolism of strontium and calcium in man. The effects on strontium metabolism and calcium balance of administered prednisone, testosterone propionate, and adrenocorticotropic hormone were also studied in one patient. This work was supported by the U.S. Atomic Energy Commission.
UCLA-4. Studies of Liver Function and Blood Flow Using Rose Bengal Iodine-131 and Colloidal Gold 198 in Normal and Diseased Subjects
IN THE LATE 1950s AND EARLY 1960s, researchers at University of California Medical School, Los Angeles and at the Los Angeles County Harbor General Hospital conducted tracer studies using iodine-131 (I131)B labeled rose bengal (a sodium salt stain) and colloidal gold-198 (Au198). The purpose of this study was to determine whether the I131-labeled rose bengal hepatogram provided an improved method for diagnosing jaundice.
At least 120 patients with a variety of liver and hepatobiliary tract diseases, and 45 subjects with normal liver functions participated in the study. Blood clearance half-times for intravenously injected rose bengal I131 and colloidal Au198 were studied to assess liver blood flow and cell function. This allowed researchers to correlate functional abnormalities of the liver with vascular defects. The colloidal radiogold test was found useful for diagnosis of severe jaundice, ascites(fluid accumulation in the abdominal cavity) of unknown origin, and acute gastrointestinal tract hemorrhage.
In 1959, blood clearance stress tests using I131-labeled rose bengal were performed on 23 subjects with normal liver function and compared with tests on 39 nonjaundiced patients having probable liver disease, and on 25 other patients with confirmed liver disease. This study confirmed that this test was more sensitive than tests then in use. Tracer studies using I131-labeled rose bengal and colloidal Au198 were continued in 1960 to assess liver blood flow and cellular function in patients with congestive heart failure. Clearance rates of I131 and Au198 were determined. At least 13 subjects participated in these studies, including patients with congestive heart failure, hepatitis, jaundice, cirrhosis, and 1 subject with a normal liver.
The investigators showed that reduced blood flow occurred in liver cirrhosis but not in jaundice. This work was supported by the U.S. Atomic Energy Commission.
UCLA-5. Tracer Studies Using Iodine-125, Iodine-131, and Gold-198 to Evaluate Functions of the Reticuloendothelial System
STUDIES WERE CONDUCTED in 1960 at the University of California Medical School, Los Angeles to develop tracer methods for evaluating the phagocytic (engulfing foreign matter and breaking it down chemically) and digestive functions of the reticuloendothelial system (a defensive mechanism against foreign materials) in man.
Experiments were conducted using iodine-131 (I131) colloidal agents administered to 8 normal subjects and 13 patients with various renal disorders. The amounts of I131 tracer administered as iodinated albumin aggregates were not stated. Blood clearance half-times for I131 were determined. Colloidal gold-198 (Au198) was also administered to patients to evaluate uptake in liver cells for comparison with the metabolism of I131-labeled proteins.
A study in 1961 at the Laboratory of Nuclear Medicine and Radiation Biology, University of California, Los Angeles used heat-treated serum albumin labeled with I131 to determine blood flow and reticuloendothelial system functions. The number of subjects involved in this study was not stated. A further study in 1961 involved clinical trials with colloidal suspensions of I131-labeled human serum albumin to estimate phagocytic and proteolytic digestive functions of the reticuloendothelial system. Fifteen healthy subjects and an unstated number of patients with diseases involving the organs of the reticuloendothelial system participated.
In 1964, patients with cirrhosis of the liver were injected with albumin microaggregates labeled with I125. The purpose of this study was to determine the extraction efficiency of the liver. After injection, samples of blood were obtained from catheters in the hepatic vein and a peripheral vein. It was determined that the extraction efficiency of the liver in cirrhosis is dependent to a large extent on the degree of portal hypertension. These studies were funded by the U.S. Atomic Energy Commission.
UCLA-6. Retention of Vitamin B12 Labeled with Cobalt-60
IN 1960, RESEARCHERS at the Laboratory of Nuclear Medicine and Radiation Biology at the University of California, Los Angeles conducted studies on the whole-body retention of vitamin B12 labeled with cobalt-60 (Co60). In the first study, four normal volunteer subjects received an oral administration of 0.02 microcurie of Co60-labeled vitamin B12. The subjects were then monitored in the whole-body counter over a period of 7 days. The purpose of the study was to determine the retention of vitamin B12 in the whole body, liver, and intestinal tract, and to demonstrate the whole-body counter’s sensitivity for measuring small amounts of gamma radioactivity in humans. The measurements showed a retention of 50 to 81 percent of the administered activity at 7 days post-ingestion of vitamin
The results of this study were compared with results of the routine Schilling test performed on four other hospital patients with pernicious anemia. These patients were injected with 0.5 microcurie of Co60, which was accompanied by an injection of a flushing dose of nonlabeled vitamin B12.
The conclusion of the study was that similar diagnostic information could be obtained using this Co60-B12 whole-body counting technique with 96 percent less Co60 than that used with the Schilling test. These studies were funded by the U.S. Atomic Energy Commission.
UCLA-7. Retention of Iodine-131B-Labeled Human Serum Albumin
IN THIS 1962 STUDY at the University of California, Los Angeles the body retention of human serum albumin labeled with iodine-131 (I131) was determined by frequent measurements of hospital patients and normal volunteers in the UCLA total-body counter.
Twenty subjects received an intravenous administration of approximately 5 microcuries of I131-labeled human serum albumin (HSA). This study included normal subjects in addition to patients with various disorders, including: duodenal ulcer, hepatitis, lymphosarcoma, ulcerative colitis, and regional enteritis. Potassium iodide was given prior to I131-labeled HSA administration to minimize thyroid uptake of the radioiodine. The subjects with ulcerative colitis retained only 14 to 31 percent of the human serum albumin after 14 days, while all other subjects retained over 40 percent after 14 days. This study was funded by the U.S. Atomic Energy Commission.
UCLA-8. Study of Calcium Metabolism Using Calcium-47 as a Tracer
BETWEEN 1962 AND 1964, staff of the University of California Medical School, Los Angeles conducted calcium metabolism studies using calcium-47 (Ca47) to determine the gastrointestinal absorption of calcium by humans.
Calcium-47 was administered orally to 11 patients at the Veterans Administration Hospital in Los Angeles. The administered activity is not stated. Some of the patients suffered from cirrhosis of the liver, osteoporosis, or hyperparathyroidism. Four were on calcium balance, and three were normal, healthy subjects. The investigators assayed the Ca47 in stool, urine, and blood and conducted total-body counts.
This study showed that calcium absorption rates in normal and osteoporotic subjects were highly variable and overlapped between groups. This study was funded by the U.S. Atomic Energy Commission.
UCLA-9. Study of Lung Imaging Techniques Using Albumin Labeled with Iodine-131 and Iodine-125
BETWEEN 1963 AND 1965, the University of California Medical School, Los Angeles conducted studies to develop new methods for imaging the lungs.
In these studies, albumin (a simple protein found in the body), labeled with 100 to 200 microcuries of iodine-131 (I131) or iodine-125 (I125), was administered by intravenous injection. The subjects’ lungs were then scanned to produce an image to determine where the albumin deposited. Areas of impaired lung function were indicated by low uptake of I131 or I125-albumin. Using this technique, lung tumors and other abnormalities were detectable before they were apparent on traditional x rays.
These methods were tested on patients with a variety of lung disorders, including pneumonia, tuberculosis, and lung cancer. Subjects with normal lung function were also used for comparison. Approximately 100 subjects were used in these studies. This research was supported by the U.S. Atomic Energy Commission.
UCLA-10. Strontium-85 Retention in Humans
A STUDY WAS CONDUCTED in 1964 at the University of California, Los Angeles on the skeletal retention of strontium-85 (Sr85) in subjects after intravenous injection. The purpose of this study was to develop a correlation between body depositions of strontium and the amount excreted in urine at various times after injection. It was hoped that this information could be used to estimate the amounts of strontium-90 (Sr90) fallout in people exposed to radioactive fallout from atmospheric weapons testing.
Twenty-three subjects, both men and women, were selected to participate in this study. The subjects ranged in age from 11 to 76 years and included 10 patients with osteoporosis, 4 cancer patients, 6 patients with other illnesses, and 3 normal healthy subjects. These subjects were each injected with 5 to 10 microcuries of Sr85 chloride.
The amount of Sr85 retained in the subjects bodies was measured in the University’s total-body counter at frequent intervals for up to several months post-injection. Radiation measurements were also selectively made over the knee and tibia midshaft (shin) areas of nine subjects to estimate the fraction of the total-body deposition in skeletal tissue. Complete collections of all urine and feces were obtained from 11 patients on metabolic balance regimens to determine calcium/strontium ratios.
The study showed that strontium intake and body deposition could be evaluated by urinalysis measurements. Funding for the study was provided by the National Institutes of Health and the U.S. Atomic Energy Commission.
UCLA-11. Lung Scanning of Inhaled Radiopharmaceuticals Using Iodine-131and Technetium 99m
DURING THE PERIOD 1964 TO 1968, the Laboratory of Nuclear Medicine and Radiobiology at the University of California, Los Angeles conducted studies on the use of radiolabeled compounds for the diagnosis of various pulmonary diseases in man. While most of these studies were intended for the diagnosis of conditions in patients with disease, some of the studies were conducted using normal, healthy volunteer subjects.
Aerosols of albumin aggregate labeled with iodine-131 (I131) and administered by inhalation were used to diagnose bronchial obstructions in patients with lung cancers and in normal volunteer subjects. The lungs of each subject were imaged using a gamma camera after administration of the aerosol. The number of subjects and the amounts of activity administered were not stated. The diffusion of gases across alveolar (air cells in the lungs) membranes was studied in an unstated number of normal, healthy subjects using ethylenediaminetetraacetic acid labeled with technetium-99m (Tc99m-EDTA) administered by inhalation. The distribution of the Tc99m-EDTA in the lungs was then determined by gamma camera imaging. The amount of Tc99m-EDTA administered to each subject was not stated. These studies were funded by the U.S. Atomic Energy Commission.
UCLA-12. Measurement of Loss of Iodine 131B-Labeled Human-Serum Albumin in Children
IN 1967, nine healthy children aged 6 months to 12 years, and seven ill children aged 18 months to 14 years, participated in a study at the University of California, Los Angeles to determine the rate of loss of iodine-131 (I131)B labeled human serum albumin by using total-body counting. The study was designed to compare the retention between healthy and ill children and between children and adults.
After their thyroid uptake was blocked with Lugol’s solution, the children were intravenously injected with 0.05 to 0.10 microcurie of I131-albumin, estimated to impart an absorbed dose of about 10 millirads. Whole-body retention was studied for 3 weeks following injection.
This study showed that I131 was retained in healthy children with half-times ranging from 2 to 13 days, a period shorter than the 13- to 18-day adult retention period. The study was funded by the U.S. Atomic Energy Commission.
UCLA-13. Copper-67 Absorption in Patients with Disorders of Iron Metabolism
IN APPROXIMATELY 1968, a preliminary study of copper absorption was conducted at the University of California, Los Angeles. Copper-67 (Cu67) was used to measure total-body absorption and retention of elemental copper in seven patients with disorders of iron metabolism, and in two normal volunteers.
Subjects were orally administered an unstated amount of Cu67 with a small amount of stable copper. The absorption and retention were measured in the Total-Body Counter Facility over a period of 15 days. Due to the variability between patients of day-to-day measurements, the experiment produced only rough estimates of copper absorption and retention. This study was funded by the U.S. Atomic Energy Commission.
UCLA-14. Total-Body Counting of Iodine 131B-Labeled Gamma Globulins
AROUND 1968, researchers at the University of California, Los Angeles conducted a study of metabolic kinetics of gamma globulins. Gamma globulins labeled with an unstated amount of iodine-131 (I131) or iodine-125 (I125) were administered intravenously to 11 hospital patients. The rates of loss of these substances from the blood and from the body were measured over a period of 3 to 4 weeks.
This study showed that the blood concentrations of the g-type gamma globulin labeled with I131 cleared with a half-time of 10 to 32 days. The time range for complete clearance of I131 from the body was 9 to 60 days. In patients who also received the m-type gamma globulin, the rate of metabolism was faster, showing a clearance half-time of 1.3 to 20 days. This work was funded by the U.S. Atomic Energy Commission.
UCLA-15. Study of Manganese-54 and Copper-67 Absorption and Retention
IN A 1969 STUDY conducted at the University of California, Los Angeles, 14 subjects were administered isotopes of manganese and copper to determine the absorption and retention rates of these elements. The subjects were seven patients with hemochromatosis (excessive iron in the body) and seven normal, healthy volunteers.
Each subject was orally administered manganese-54 (Mn54) as manganese chloride and measured for body retention with a whole-body counter two to three times a week. Eight subjects were counted for 3 weeks, and six subjects were counted for 60 days. Whole-body counting also was used to evaluate copper absorption and retention in the hemochromatosis patients who had been administered 20 to 25 microcuries of copper-67 (Cu67).
These studies showed that Mn54 absorption ranged from 6 to 34 percent, with a mean of 13 percent. The Cu67 absorption ranged from 46 to 84 percent. Further study was needed to determine whether increased Mn54 absorption in two patients was associated with hemochromatosis or related to an iron deficiency produced by repeated phlebotomy (therapeutic bleeding). This research was funded by the U.S. Atomic Energy Commission.
UCLA-16. Study of Inhaled Pollen-Associated Asthma Using Technetium-99m and Xenon 133
IN THE EARLY 1970s, researchers at the University of California Medical School, Los Angeles conducted a study of the distribution of inhaled grass pollen to understand how large pollen grains are able to induce bronchospasm reactions in sensitive subjects.
Four normal subjects and five asymptomatic allergic subjects inhaled pollen grains labeled with technetium-99m (Tc99m). Gamma camera scintiphotos of their head, chest, and abdominal regions were then obtained. Standard lung function studies, which included administration of xenon-133 (Xe133), were conducted before and after the pollen inhalation. The results of the study indicated that the inhaled pollen grains were too large to reach the bronchial mucosa; and therefore the pollens deposited mostly in the mouth and pharynx and produced clinical asthma 4 to 8 hours later. This research was funded by the U.S. Atomic Energy Commission.
UCLA-17. Liver Blood Flow Study Using Gold-198 and Technetium-99m
IN THE EARLY 1970s, researchers at the University of California, Los Angeles conducted studies on venous blood flow to the liver. The purpose of this study was to show that certain disease conditions tend to localize in the liver’s right lobe.
Twelve volunteer patients without liver disease who were undergoing abdominal surgery participated as subjects. Each subject was administered 200 to 300 microcuries of gold-198 (Au198)B colloid intravenously. The uptake and retention of Au198 in lobes of the liver were then measured by scintiscan. Immediately thereafter, 2 to 5 millicuries of technetium-99m (Tc99m)B microaggregated albumin were injected into an arm vein and a second liver scan was performed. The distribution in blood flow of Au198 from the mesenteric vein was compared to the control injection using Tc99m.
Results showed that streamlining to the right lobe did occur, but that it was dependent on which mesenteric vein (cecal, terminal ileal, mid-jejunal, or sigmoid) was injected. This experiment was funded by the U.S. Atomic Energy Commission.
UCLA-18. Thrombophlebitis Scanning Using Technetium-99m and Iodine-125
IN THE EARLY 1970s, researchers at the Laboratory of Nuclear Medicine and Radiation Biology of the University of California, Los Angeles conducted studies using technetium-99m (Tc99m) to diagnose and study thrombophlebitis (inflammation of a vein associated with clot formation) in veins of the legs. The purpose of this study was to see whether thrombophlebitis could cause pulmonary embolisms (obstructions caused by transported clots).
The subjects for the first study included 73 patients with thrombophlebitis (many of whom also had pulmonary emboli) and 90 control subjects without disease. This study involved injecting 1.5 millicuries of Tc99m-albumin in the veins and measuring its accumulation. The results of this study showed that 80 percent of patients with pulmonary embolisms also had positive scans for thrombophlebitis.
In a related follow-on study involving additional normal subjects (10 or more) and hundreds of patients with actual or suspected thrombophlebitis, comparisons were made between two different diagnostic techniques. The first technique involved injection of 1.5 millicuries of Tc99m-labeled albumin to detect areas of thrombophlebitis in 32 additional patients. The second technique involved injection of 100 microcuries of iodine-125 (I125)Blabeled blood clotting factor (fibrinogen) in an additional 50 patients. Scans of the lower legs of each subject were then performed over a 7 to 30-day post-injection period to measure accumulation.
Both the Tc99m-albumin and the I125-fibrinogen uptake tests were found to be useful for detecting blood clots. This work was supported by the U.S. Atomic Energy Commission.
UCLA-19. Studies of Liver Circulation and Metabolism in Normal and Diseased Subjects Using Technetium-99m Albumin Microaggregates
IN 1970 AND 1971, researchers at the Laboratory of Nuclear Medicine and Radiation Biology of the University of California, Los Angeles conducted gamma camera studies of the liver=s dual circulation. The purpose of these studies was to investigate the utility of technetium-99m (Tc99m)Blabeled albumin (a simple protein found throughout the body) aggregates for measuring the digestive capacity of the reticuloendothelial system.
Studies were conducted on an unspecified number of normal subjects, hospital patients with tumors, and patients with liver cirrhosis. Subjects underwent several tracer studies, each of which consisted of injection with unspecified amounts of Tc99m microaggregates of albumin. Gamma camera images were then obtained to compare uptakes in the normal versus abnormal liver and in the liver versus heart.
A related study investigated the usefulness of Tc99m albumin microaggregates for measuring the protein-digesting capability of the normal versus the diseased liver. Seventy-one studies were conducted on 47 patients with various liver and reticuloendothelial system disorders.
Twelve hospital patients and one healthy volunteer with no known liver or infectious disorders were considered as the comparison group.
This study showed that diseased patients exhibited a more rapid excretion of Tc99m-albumin via the biliary pathway and greater amounts of albumin degradation products in the intestines than comparison subjects. These studies were supported by the U.S. Atomic Energy Commission.
UCLA-20. Studies of Hip Socket Vascularity Using Technetium-99mBSulfur Colloid
IN 1971 AND 1972, researchers at the Laboratory of Nuclear Medicine and Radiation Biology of the University of California, Los Angeles conducted studies using technetium-99m (Tc99m) sulfur colloid. The purpose of these studies was to gain information about the blood supply to the hip socket for use in treating hip diseases and fractures.
Subjects for these studies were an unspecified number of hospital patients with normal hips and patients with hip disease. Technetium-99m sulfur colloid was administered intravenously and the pelvis was studied by gamma photoscan techniques. Scans were then correlated with pelvic x rays for each patient.
These studies showed that uptake of Tc99m sulfur colloid occurred symetrically in both hip sockets of patients with no known hip disease and that uptake was asymmetric in patients with hip disease. These studies were supported by the U.S. Atomic Energy Commission.
UCLA-21. Test of Lung Scans in Normal Subjects Using Technetium-99m, Indium-113m, and Xenon 133
DURING THE PERIOD 1972 to 1973 , researchers at the Laboratory of Nuclear Medicine and Radiation Biology of the University of California at Los Angeles conducted studies to learn more about abnormal lung scans from subjects with normal lung function. The study group consisted of 46 nonsmoking volunteers, aged 21 to 34 years, without history of asthma, emphysema, or other lung disease.
The subjects were administered an unstated amount of albumin macroaggregates labeled with technetium-99m (Tc99m), either by inhalation or intravenous injection and were then given a chest image using a rectilinear scanner. The subjects also received pulmonary standard function tests. Thirteen percent of the scans indicated various perfusion defects such as pulmonary emboli, which were not present. It was concluded that these apparent anomalies could not be related to any pathologic origin.
In a later study, normal volunteer subjects and patients with suspected chronic bronchitis with normal results after pulmonary function testing were selected for gamma camera lung imaging using Tc99m-albumin macroaggregates and albumin labeled with indium-113m (In113m). In selected cases, the lung closing volumes were also measured with a xenon-133 (Xe133) inhalation test. The number of subjects and amounts of radioisotope administered during these tests were not stated. This study showed a relation between abnormality of closing volume and the degree of unevenness of the inhalation scan, and indicated that the chest scan provided a more useful diagnostic tool than routine pulmonary function tests. These studies were supported by the U.S. Atomic Energy Commission.
UCLA-22. Study of Cranial Development Defects Using Fluorine-18
A STUDY IN 1973 was conducted at the Laboratory of Nuclear Medicine and Radiation Biology of the University of California, Los Angeles to determine the usefulness of fluorine-18 (F18) in the study of cranial closure development in small children. Since x ray and other clinical examinations can fail to detect the premature closing of the cranium in children, it was thought that cranial imaging with F18 might provide a more effective diagnostic tool for early detection.
Subjects included 15 children with abnormal skulls, ages newborn to 4 years, and 7 children with normal skull development, ages 7 weeks to 16 years. Each subject was administered an unstated amount of F18 and then imaged in the nuclear medicine clinic.
The study provided an explanation for mechanisms involved in the premature closing of the cranium. This study was supported by the U.S. Atomic Energy Commission.
UCLA-23. Study of Heart Chamber and Pulmonary Dilution Curves in Normal Subjects and Patients with Shunts Using Xenon-133 and Technetium-99m
A 1973 STUDY conducted by researchers at the Laboratory of Nuclear Medicine and Radiation Biology of the University of California, Los Angeles compared heart chamber dilution curves and dilution curves for blood vessels in the lungs in the diagnosis of congenital heart disease.
Thirteen normal patients (i.e., patients without heart disorders) and 33 patients with cardiac shunts were included in the study. The normal subjects ranged in age from 2 to 40 years and the patients with heart disease from 3 months to 48 years.
Unstated amounts of xenon-133 (Xe133) in saline and technetium-99m (Tc99m) sulfur colloid were intravenously administered. The flow of the isotopes was followed into the heart and blood vessels of the lungs, and images were made of Xe133 and Tc99m uptake. Dilution curve measurements were also made using flow data. Differences between normal subjects and patients with shunts were observed. This study was funded by the U.S. Atomic Energy Commission.