Three-dimensional demarcation of perfusion zones corresponding to specific coronary arteries: application for automated interpretation of myocardial SPECT.

UNLABELLED: In this study, three-dimensional maps of specific coronary artery territories were derived and combined with normal distribution maps as a reference for automated characterization of defects, including location and size. METHODS: One hundred sixty-eight 99mTc-sestamibi myocardial perfusion SPECT scans from normal patients and patients with single-vessel disease were selected according to angiographic data. Five separate groups were established for men and women: normal, proximal left anterior descending (PLAD), distal left anterior descending (DLAD), right coronary artery (RCA) and left circumflex (LCx). All myocardial perfusion studies were aligned and sized to the same three-dimensional orientation using a previously developed automated image registration technique. Mean and variation three-dimensional templates were constructed from stress images in each group. Normal templates were demarcated with hypoperfusion regions obtained from disease templates. The defects were detected in the individual patient's images by a region-growing algorithm which identified abnormal voxels by comparison to the corresponding voxels in the mean and variation templates. RESULTS: Defects were quantified with respect to volume, location relative to the expected hypoperfusion zones and severity index. Abnormal regions could be marked directly on tomographic slices and visualized in various orientations. Single defects greater than 2% of the myocardium positioned within demarcated perfusion territories were detected in 105/119 abnormal patients and in 3/49 normal patients. CONCLUSION: Maps of myocardial perfusion zones created from images of angiographically selected patients provide a reference for automated localization of myocardial perfusion defects. A template-based region-growing is a robust technique for volumetric quantification and localization of abnormal regions.

Myocardial uptake and washout kinetics of T1-201 with the VEX (vasodilator plus exercise) test: contribution of stress mode components and coronary stenosis severity.

OBJECTIVE: To assess the vasodilator plus exercise (VEX) test as an adjunct to myocardial perfusion imaging with respect to the accuracy of kinetics of thallium-201 (Tl-201) and other indicators of ischemia. SETTING: A nuclear medicine laboratory in which patients referred for myocardial scintigraphy are triaged to undergo the stress component with symptom-limited bicycle exercise, dipyridamole or VEX as appropriate. DESIGN: Cases having correlating scintigraphy and angiography (n = 425) were selected retrospectively. Immediate poststress and redistribution images were quantified using a circumferential profile analysis with interpolative background subtraction. For each of nine sectors on the left anterior oblique image, multivariate analyses were performed, comparing the relative uptake and net washout of Tl-201 to the exercise workload attained, use of dipyridamole, time to redistribution, gender, and the angiographic presence and severity of stenoses at five key sites. Washout values standardized according to gender, exercise level and time to redistribution, were compared with relative uptake profiles and ST depression using receiver operating curves. RESULTS: For each sector, a significant contribution to Tl-201 washout was made by the exercise level (P < 0.001) and by at least one site of stenosis (P < 0.0001), but not by use of dipyridamole (P > 0.5); female gender was associated with increased washout (P < 0.01) except for the three lateral sectors. For each stress modality, standardized washout performed better than ST depression but not as well as relative uptake profiles in detecting coronary artery disease. CONCLUSIONS: For combined pharmacological-exercise stress, quantitative uptake profiles may assist in confirming subjective scan interpretation; washout profiles, even when standardized for gender and stress level, are suboptimal for confirming defect reversibility.