[en] To assess the validity of myocardial imaging with potassium-43 (⁴³K) early after the onset of ischemia, the left anterior descending artery was occluded with a balloon tip catheter in 32 intact anesthetized dogs. /sup 99m/Technetium ventriculograms localized the left ventricle. ⁴³K was administered intravenously and serial images were obtained in four views using an Anger camera with a pinhole collimator. The heart was arrested after 60 minutes and removed for imaging and tissue counts to ascertain extracardiac and geometric factors. In normals (group 1) left ventricular images were relatively homogeneous, except for the thin walled apex, both in vivo and in the isolated heart. Equilibration with ⁴³K prior to ischemia (group 2) gave similar images to group 1, associated with a small reduction in tissue counts after one hour of ischemia. Group 3 was infused with ⁴³K after initiation of ischemia. Despite a reduction of ⁴³K counts in the ischemic area to less than one-fourth of the nonischemic site (P < 0.001), demonstration of a ''cold area'' in vivo was inconstant, occurring in only 34 percent of studies. Lead shielding did not improve accuracy. In the isolated heart the ability to detect the cold area was improved to 73 percent. However, when the left ventricle was incised and spread flat, so that low and high activity areas were contiguous rather than superimposed, a widespread area of ischemia was present without exception in the anterior wall. Use of a rectilinear scanner in seven animals failed to improve diagnostic yield; areas of reduced radioactivity were seen at the apex in normals by both techniques. Thus, while detection of low flow areas in the isolated heart is feasible by isotopic imaging early after the onset of ischemia, both extracardiac and geometric factors can contribute to qualitative and quantitative errors in vivo

No abstract available

[en] ⁴³K has been found to be useful in medical applications such as body space and potassium transport measurements and myocardial function studies. Unfortunately ⁴³K is difficult to produce, especially in a pure form free from ⁴²K. A method of producing ⁴³K using an argon gas target is described. (UK)

[en] Two categories of radionclides are used for myocardial scintiscanning: potassium and its analogues which myocardial uptake is a function of cell integrity and of coronary blood flow; and technetium 99m labelled pyrophoshates suitable for studying uptake in myocardial infarcts

[en] Fourteen patients with transmural myocardial infarction were studied by gated cardiac blood pool scanning (to determine regional ventricular function) and ⁴³K myocardial imaging (to determine the regional distribution of myocardial perfusion). An akinetic area on the gated scan and an area of decreased tracer concentration on the ⁴³K image were detected. The area of reduced ⁴³K concentration averaged 33.5 percent of the left ventricular circumference which correlated (r = 0.74, p < 0.01) with the area of infarction determined by the zone of akinesis, 34.2 percent of left ventricular circumference. The extent of akinesis and left ventricular ejection fraction were significantly different in those patients with left ventricular failure than in those without failure. (U.S.)

[en] To determine the variables that might affect interpretability of myocardial perfusion images in patients with acute myocardial infarctions, images obtained following intravenous administration of potassium-43 or cesium-129 were evaluated in 68 patients with nonacute coronary or noncoronary heart diseases, who were undergoing cardiac catheterization. Severe coronary arterial disease usually produces no distinctive perfusion defects in the resting state. Remote infarcts likewise tend to remain undetectable unless accompanied by wall-motion disturbances that can be detected by ventriculography. Left ventricular hypertrophy or cardiac dilatation can produce perfusion patterns indistinguishable from the ischemic defects of infarction. Right ventricular hypertrophy can cause image alterations that mimic infarcts in the left ventricle. In patients with acute myocardial infarction, sequential imaging studies with perfusion indicators should be of value in determining the effects of various therapeutic maneuvers on regional myocardial perfusion, but variations caused by conditions other than acute vascular occlusion limit the usefulness of perfusion imaging for diagnosing acute infarction. In suspected acute infarction, perfusion imaging will be used most effectively in conjunction with other imaging or nonimaging procedures that show the presence of damaged or necrotic myocardium. The information derived from this study should be generally applicable to the interpretation of imaging results obtained with the newer indicators of myocardial perfusion now in use or under development

No abstract available

[en] Noninvasive myocardial imaging with potassium-43 and rubidium-81 has been used successfully to identify areas of infarction and exercise-induced ischemia as regions of decreased radioactivity. The image defects observed are believed to be due to a decreased radionuclide uptake in regions of myocardial scar or to heterogeneous myocardial accumulation of tracer as a result of regional ischemia. Of 27 patients with left bundle branch block studied with noninvasive imaging at rest and during exercise, 25 manifested at rest reduced radioactivity in the region of the interventricular septum. This pattern is similar to that seen in patients with anteroseptal myocardial infarction. Sixteen of the 27 patients underwent diagnostic coronary arteriography and left ventriculography. Only five of these patients had evidence of either previous infarction or significant obstructive coronary artery disease as assessed with clinical or angiographic criteria, or both

[en] Progress in myocardial perfusion imaging has been slowed by the lack of radiopharmaceuticals with suitable physical and biologic characteristics. Hexadecanoic acid, terminally labeled with ¹²³I, partially overcomes these limitations by providing a compound that concentrates in the myocardium in proportion to relative regional blood flow and carries a gamma-emitter with desirable detection and imaging qualities. After intravenous injection in experimental animals, the clearance half-times of hexadecanoic acid for blood and myocardium are 1.7 and 20 min, respectively. These values compare favorably with 18-carbon fatty-acid analogs labeled with ¹¹C. In acute and chronic infarction, similar distribution patterns are found for hexadecenoic acid and ⁴³K, which indicates that hexadecenoic acid is a suitable substitute for the potassium analogs now in use for myocardial imaging. Because of the high count rates obtainable with ¹²³I-hexadecanoic acid, good-quality images can be acquired in as little as 2--3 min per view. Iodine-123-hexadecanoic acid is potentially a useful radiopharmaceutical for clinical application

[en] β-decay measurement has importance in both basic nuclear physics and in the applied field. The excited states in the neutron-rich nuclei can be studied by β-decay using low intensity radioactive ion beams (RIB). Decay spectroscopy and T_1_/_2 measurement of the neutron-rich "4"3K were performed to address the anomalous beta-feeding intensities to some of the levels in the "4"3Ca daughter nucleus