Detection of lesions in thallium-201 myocardial perfusion scintigraphy

Experimental studies have been made of the lesion detectability in myocardial perfusion studies using thallium-201. A series of images (AP-view) was generated using a convolution of a mathematical model of the left ventricular myocardium and an experimentally determined point spread function. Background was added. Images were simulated with 100k, 200k, and 300k counts for the complete image. Each image contained a lesion with either 0% or 50% of the normal tracer concentration. All images were interpreted by five experienced observers, independently of each other. Their interpretations were analysed using the Kolmogorov-Smirnov two sample test. The true positive fraction (TPF) was hardly affected by changes in count density. The TPF decreased significantly if the lesion tracer concentration changed from 0% to 50% of the normal myocardial tracer concentration. The decrease was independent of the count density. The false positive fraction (FPF) decreased significantly if the count density increased; no difference in FPF was found for a change in lesion tracer concentration. In addition, plots were generated with the TPF and the FPF versus lesion location and of the TPF versus lesion volume. The TPF was lowest for locations far from the camera; FPF was high for these segments. Increase of the count density mainly improved the FPF in these segments. Small lesion were more difficult to detect.