Abstract: Myocardial perfusion imaging with thallium-201 and gated cardiac blood pool scanning are finding increasing use in clinical cardiology. These noninvasive techniques have been found useful in detecting myocardial infarction independent of the electrocardiogram and determining the site and extent of the infarct as well as its effect on left ventricular function. These studies provide important prognostic data and are proving to be of value in evaluating patients with cardiogenic shock. Neither the thallium-201 myocardial perfusion image nor the gated cardiac blood pool scan can distinguish between acute and chronic myocardial damage. In clinical situations where this is important, infarct avid imaging with technetium-99m pyrophosphate allows determination of whether a given perfusion defect or wall motion abnormality is acute. Myocardial perfusion imaging with thallium-201 at rest and after exercise is also proving to be of value in evaluating patients with suspected ischemic heart disease. Initial studies suggest that the technique may be more sensitive than exercise electrocardiography and is of special value in minimizing the occurrence of false positive exercise tests for the diagnosis of ischemic heart disease. The combined tracers technique is also of value in the evaluation of patients undergoing coronary bypass graft surgery and those with cardiomyopathy.

Abstract: A brief description is given of imaging techniques to record and analyze the myocardial perfusion scan, study changes in segmental wall motion, measure ejection fraction and ventricular volumes and detect acute myocardial infarction. Attention to the details of collimation, pulse height analyzer settings, intrinsic resolution of the imaging device and quality of the tracers utilized for these studies will permit information of high quality to be obtained from subjects with use of these noninvasive techniques.

Abstract: Two cases of heptatic hemangioma are reported in which multiple-radionuclide and ultrasound techniques were combined in the diagnostic process. Blood pool imaging rather than perfusion imaging proved to be the most definitive diagnostic procedure. The application of radionuclide and ultrasound studies in the differential diagnosis of focal lesions of the liver is discussed.

Abstract: This report proposes that perfusion scanning in combination with arteriography be included in the diagnostic work-up of the diabetic patient who, because of peripheral vascular complications, is a candidate for surgery. Two cases are reported which illustrate the extremes of the findings: abnormal arteriogram-normal scan indicating large-vessel disease without significant small-vessel involvement. It is suggested that these patients are candidates for vascular reconstruction. The other extreme is the normal arteriogram-abnormal scan indicating small-vessels disease without significant large-vessel involvement. It is apparent that these patients are not candidates for vascular reconstruction.

Abstract: A new technique for in vivo renal perfusion is described which eliminates the need for autotransplantation. In short term ischemia studies using three solutions, Sacks' solution was found to provide the optimal renal ischemia protection.

Abstract: OVER the past decade, advances in nuclear cardiology have provided a range of diagnostic tools for the practicing clinician. The development of new radionuclides, high-resolution γ scintillation cameras, and sophisticated small computers have been responsible for improvement in the quality and scope of nuclear cardiologic techniques. The following is a brief review of these techniques, their applications and limitations. Perfusion Imaging Normal Myocardium.— Perfusion imaging of normal myocardium is performed by administration of a radioactive tracer that is extracted by normally functioning myocardial cells. Agents such as thallium 201 exhibit the biological behavior of potassium and presumably are pumped into the cell by activating membranebound (Na + , K + )-adenosine triphosphatase. Their myocardial uptake is dependent on two factors: (1) regional myocardial blood flow and (2) cell function. The normal myocardial image appears homogeneous in count distribution. Areas of decreased uptake in the resting study reflect areas of myocardial fibrosis or infarction

Abstract: The effects of inspiring low O2 or high CO2, or low-O2-high-CO2 gas mixtures on tissue perfusion and tissue Po2 of brain and muscle were studied in 76 anesthetized rats. Under control conditions, relative tissue Po2 of cerebral white matter measured polarographically averaged 16.4 mmHg and 18.7 mmHg in the biceps brachii. With low-O2 gas mixtures, tissue Po2 declined in both brain and muscle, but more in muscle. Tissue Po2 increased under high-CO2 conditions, with the brain increasing to a greater extent. Control cerebral cortex tissue perfusion averaged 23.5 ml/min per 100 g and muscle was 18.3 ml/min per 100 g measured by H2 clearance. Brain perfusion increased under all experimental conditions. Muscle perfusion did not change with low O2 alone, but increased with low-O2-high-CO2 or high-CO2 gas mixtures. Brain perfusion increased under all conditions significantly more than muscle. The brain appeared better protected compared to skeletal muscle in terms of tissue Po2 and perfusion under the stress of hypoxia and hypoxic-hypercapnia. The effects of hypercapnia are also greater on the brain.