Julia W. Buchanan

RADIOACTIVE ALBUMIN MICROSPHERES FOR STUDIES OF THE PULMONARY CIRCULATION.

Since its introduction into clinical medicine in 1963 (12), lung scanning has become a widely used method for determining the distribution of pulmonary arterial blood flow (13). The most common radiopharmaceutical for this purpose is 131 -labeled macroaggregates of human serum albumin (MAA), but more recently both 113mIn-labeled floes of iron hydroxide (10) and 99mTc-labeled MAA (4) have also been used. Attempts to extend the labeled particle distribution method to the study of the systemic circulation and to the measurement of arteriovenous shunting have failed because these particles are too irregular in size and too fragile (5). Such studies have been carried out in experimental animals with labeled ceramic or carbonized microspheres (2, 5, 7–9, 11). Although these microspheres have been used in man for in situ radiation therapy (1, 14), they have not been employed in diagnostic studies because they are not metabolized. To extend the methods which employ radioactive microspheres to the study of the hum...

Monitoring cardiac function with nuclear techniques

Noninvasive imaging with radioactive tracers has become widely used since its introduction in the early 1970s. Improvements continue to be made in the techniques and the clinical applications. Much of the information provided by these techniques is new. The first transit studies are used mainly in the evaluation of pulmonary transit time, detection of intracardiac shunting, evaluation of right ventricular function, measurement of ejection fraction and detection of wall motion abnormalities at rest and after exercise. The gated blood pool study is found to be most useful in assessment of global left ventricular function, regional wall motion, valve regurgitation and right ventricular function. The techniques of nuclear cardiac imaging are noninvasive, simple, successfully performed in almost 100 percent of cases. They are easy to interpret, able to be quantified and able to be almost totally automated. Their use is likely to become more widespread in the future.

Radioimmunotherapy in Non-Hodgkin Lymphoma: Opinions of Nuclear Medicine Physicians and Radiation Oncologists

Despite approval by the Food and Drug Administration and consistent reports of the efficacy and safety of 90Y-ibritumomab tiuxetan and 131I-tositumomab, these therapies are infrequently used. This study investigates the opinions and patterns of the use of radioimmunotherapy by nuclear physicians, affiliated researchers, nuclear medicine technologists, and radiation oncologists and aims to identify possible barriers to the use of this promising therapy. Methods: An e-mail–based survey with 13 broad questions related to radioimmunotherapy was sent electronically to 13,221 Society of Nuclear Medicine members and radiation oncologists throughout the United States. Results: Six hundred thirteen individuals (4.6%) responded to the electronic survey. Two hundred fifty-one responders (40.9%) had treated patients with non-Hodgkin lymphoma (NHL) with radioimmunotherapy in the last 24 mo. Of the responders, 29.5% used only 90Y-ibritumomab tiuxetan, 7.6% used only 131I-tositumomab, and 24.9% used both radiopharmaceuticals; 37.9% did not treat NHL with radioimmunotherapy. Most responders said their patients came from university hospitals (33.9%) or private offices (25.6%), and they mainly treated in a second-line (42.9%), third-line (35.6%), or consolidation (23.5%) setting. Major concerns were that referring oncologists and hematologists wanted to treat by themselves with nonradioactive compounds (mean ± SD, 3.418 ± 1.49) and that 90Y-ibritumomab tiuxetan and 131I-tositumomab were expensive (mean ± SD, 3.413 ± 1.35). Of the responders and involved physicians, 40.4% and 35.2%, respectively, did not know if their institution accepted Medicare patients for radioimmunotherapy. Almost 30% (29.6%) of the responders thought radioimmunotherapy would probably grow and 38.0% thought it would grow in importance in the future. Responders who did not administer radioimmunotherapy for NHL thought it took too much time to administer radioimmunotherapy (P < 0.01) and had concerns about the dosimetry procedure (P < 0.01) and radiation safety (P < 0.01). Individuals who perceived a negative future for radioimmunotherapy had significantly more concerns about the time-consuming administration process (P < 0.05) and the high cost of radioimmunotherapy (P < 0.05). Responders from academic centers had significantly fewer concerns about payment (P < 0.01), dosimetry (P < 0.01), and radiation safety (P < 0.01). Conclusion: Radioimmunotherapy was generally viewed positively by the surveyed population. However, limited referrals due to alternative nonradioactive therapies and logistic, educational, and economic concerns played an important role for subgroups in the perception of radioimmunotherapy for NHL.

Frontiers in Nuclear Medicine

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Automatic drawing of the left epicardial region of interest on Thallium 201 scintigraphic images

An algorithm has been written which automatically selects a left epicardial region of interest on 201Tl myocardial images. It accomplishes a radial search from the geometric center of the myocardium. On each of the 30 profiles, the local maximum of the 1st derivative is selected as the epicardial edge. The algorithm has been tested in 40 patients at stress and redistribution. In ten patients, conventional planar images were obtained in three views. In 30 patients conventional short axis tomographic images were obtained after reconstruction of 32 projections acquired over 180°.The rate of success is 97% for both imaging modalities. This procedure is another step towards fully automated assessment of myocardial defects and redistribution.

Radioactive Tracers and the Heart

The most widely used tracer for the study of the heart muscle is thallium-201. The principal advantage of radioactive tracers in the study of the heart is that they tell us about regional as well as a overall function. In some cases a regional abnormality may be detected before the overall function of the heart is impaired.

Regional Phagocytosis in Man

The phagocytic function of the reticuloendothelial cells in the liver, spleen, bone marrow, and lymph nodes can be examined by nuclear imaging. Since approximately 85–95% of the body’s phagocytic cells are located in the liver and spleen, most intravenously injected particulate or colloidal material is taken up rapidly by these organs (Saba, 1970). Larger particles are removed from the circulation faster than smaller particles. The splenic uptake of labeled colloidal material depends on the characteristics of the particles, especially their size (Colombetti et al, 1969; Nelp, 1975). The functional status of the phagocytic cells in the liver, as well as the spleen, and the relative liver and splenic blood flow are the major factors responsible for the eventual distribution of the radioactivity within the body when tracer quantities of radiocolloids are injected intravenously. Tech- netium-99m sulfur colloid is currently the most widely used radiopharmaceutical for imaging the reticuloendothelial system. Liver, spleen, bone marrow, and lymph gland imaging is used in clinical medicine to reveal both global and regional phagocytic function.