[The determination of the left ventrical volume curve without background correction and its validation by direct intercomparison with the ejection fractions as determined by biplane laevocardiography (author's transl)]. / Nuklearmedizinische Bestimmung linksventrikulärer Volumenkurven ohne Untergrundkorrektur und ihre Validisierung durch direkten Vergleich mit biplan laevokardiographisch ermittelten Auswurffraktionen.

Background corrections applied on the left ventricular volume curve determined by the "gated blood pool"--method are based on an estimated rather than on a directly measured background. This imposes an uncertainty on the values determined from the volume curve, especially on the ejection fraction. A method which does not require background correction may be applied if all available measurement and evaluation facilities are utilized fully. High temporal and spatial resolution is of fundamental importance, permitting the exact determination of the time-dependent scintigraphic contour variations of the left ventricle during the mechanical action of the heart. A good criterion of the validity of the volume curves with respect to interfering background radiation is the ejection fraction calculated from these curves. The direct intercomparison of 10 ejection fractions obtained by an expanded "gated blood pool"-method, employing cardiac catheterization, immediately before a biplane laevocardiography demonstrated very good agreement. A small systematic underestimation of the ejection fraction by the nuclear method was observed. This understimulation shows that the influence of the true background is small if other interfering count rate contributions or methodical uncertainties are excluded systematically.

[Quantitative exercise scintigraphy of the myocardium with 201Tl--methods and normal values (author's transl)]. / Quantitative Belastungs-Szintigraphie des Myokards mit 201Tl--Methodik und Normalverhalten.

Quantitative myocardial scintigraphy was performed in 20 normal individuals after maximum exercise and after two hours of rest. A mobile Anger camera with converging collimator and a Data-General computer with a 128 x 128 matrix were used. Quantitative analysis of data was performed on the basis of a 14-halfsegment model. Quantitative normal values after exercise and after redistribution of activity during rest are presented.

Predictive value of thallium scintigraphy in coronary artery disease.

To verify the predictive value of thallium exercise scintigraphy, 20 normal individuals and 60 patients with coronary artery disease (CAD) were examined, using a quantitative standard technique and receiver operating characteristic analysis. The sensitivity of thallium scintigraphy for the presence of CAD was 97% for patients with previous infarction and 85% for those without infarction. The sensitivity for the extent of CAD was 93% for vessels perfusing infarcted areas and only 67% for vessels without infarction. In patients without myocardial infarction, sensitivity for the number of diseased vessels decreased with increasing extent of CAD. An underestimation of hemodynamically significant stenoses was proven by a comparison with the results of exercise ventriculography. The predictive value of a normal scintigram at a high prevalence of CAD is as low as the predictive value of an abnormal scintigram at a low prevalence level (screening). Thallium scintigraphy is indicated in patients with a medium prevalence of CAD, e.g., in patients with atypical angina and in asymptomatic patients with pathologic ECG.

Visualization of an acoustic neurinoma by radioisotope cisternography.

A case of acoustic neurinoma is reported. Clinical symptoms were typical, but brain scan, EEG, X-rays and the first CT failed to demonstrate the expected tumor.

[Results of quantitative myocardial scintigraphy with thallium-201 at rest and after maximum exercise--critical analysis of predictive value and clinical application (author's transl)]. / Ergebnisse der quantitativen Myokardszintigraphie mit Thallium-201 in Ruhe und unter maximaler Belastung--Kritische Analyse des prädiktiven Wertes und der klinischen Anwendung.

In 20 normal individuals and 60 patients with CAD, myocardial scintigraphy with thallium-201 was performed after maximum exercise and two hours later at rest. The evaluation of digitized scintigrams was performed quantitatively by means of a 14-halfsegment model. Using ROC analysis, sensitivity and specificity were estimated. Furthermore the predictive value of a thallium scintigram was evaluated by means of the bayesian theorem, comparing the data with coronary angiography and partly also with exercise ventriculography. At a specificity of 90%, sensitivity of scintigraphy for CAD was 97% in 34 patients with previous myocardial infarction and 85% in 26 patients without infarction. Sensitivity for the extent of CAD was 93% for 44 vessels, perfusing infarcted myocardium and 67% for 96 vessels, perfusing non-infarcted myocardium. Sensitivity decreased with increasing extent of CAD and was higher for Cx than for LAD. The predictive value of a positive or negative scintigram was analyzed for different prevalences of CAD. At a low prevalence, e.g. 5%, the predictive value of a pathological scintigram is only 32%, consequently thallium scintigraphy is not applicable as a general screening procedure. At a high prevalence, e.g. 90%, the predictive value of a normal scintigram is only 40%. Therefore thallium scintigraphy seems not to be able to differentiate whether a coronary artery stenosis is hemodynamically significant or not. This was in agreement with the data from exercise cineventriculography. A high predictive value of thallium scintigraphy of about 85% is obtained only in the case of a medium prevalence of CAD, e.g. in asymptomatic patients with pathological Ecg or in patients with atypical angina pectoris. An improvement of the predictive value of myocardial scintigraphy would require other radionuclides than thallium-201, to use higher activities and to allow Ecg-gated myocardial scintigraphy.