NORMAL QUALITATIVE AND QUANTITATIVE TC-99M SESTAMIBI MYOCARDIAL SPECT- SPECTRUM OF INTRAMYOCARDIAL DISTRIBUTION DURING EXERCISE AND AT REST

Exercise myocardial perfusion imaging with Tc-99m sestaMIBI is routine ly used to detect underlying coronary stenoses. Ischemia is diagnosed in regions that display decreased tracer uptake during exercise as com pared to rest. Tc-99m sestaMIBI SPECT images of 42 healthy volunteers were assessed both qualitatively (tomographic slices) and quantitative ly (sectored polar map) for potential sources of misinterpretation. On the myocardial tomographic slices, the most common culprit artifacts were diaphragmatic attenuation and bowel interposition, which caused f ixed or reversible ''perfusion defects'' in the inferior and posterior regions (in 19/35 abnormal segments), and artifacts related to the pr esence and shift of hot spots (observed in 11/28 men; in women, they w ere more difficult to demonstrate because of the overriding effect of breast attenuation). Hot spots shifts between exercise and rest usuall y resulted in pseudo-reversible defects in the anterolateral and later al walls. The quantified polar map display of the myocardium showed a physiologic decrease in sestaMIBI activity in the basal anterolateral and basal posterolateral areas in men during exercise. There are many normal variants that may mimic coronary artery disease on tomographic sestaMIBI images. Before reporting an area of decreased activity as ei ther a fixed or reversible perfusion defect, the interpreter should en sure that it does not represent an artifact or a normal variation in t he intramyocardial distribution of sestaMIBI during exercise.