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Quantification of Myocardial Perfusion by Contrast-Enhanced 64-MDCT: Characterization of Ischemic Myocardium

¹ Department of Radiology, Prefectural Ehime Imabari Hospital, Ishii-cho 4-5-5, Imabari-city, Ehime 794-0006, Japan.
² Department of Cardiology, Prefectural Ehime Imabari Hospital, Ehime, Japan.
³ Department of Radiology, Ehime University Medical School, Ehime, Japan.
⁴ Department of Medical Engineering, Division of Allied Health Sciences, Osaka University Medical School, Osaka, Japan.

OBJECTIVE. Assessment of hemodynamic changes in ischemic cardiac segments at rest using CT has yet to be performed. We hypothesized that variations in subendocardial perfusion during the cardiac cycle might be related to the appearances of ischemia. The purpose of this study was to investigate myocardial perfusion in ischemic segments using contrast-enhanced 64-MDCT.

SUBJECTS AND METHODS. We performed cardiac MDCT at rest and stress/rest ²⁰¹Tl myocardial perfusion scintigraphy (MPS) in 34 patients with suspected coronary artery disease. We reconstructed 2D long- and short-axis cardiac images in diastolic and systolic phases using raw data from coronary CT angiography. The attenuation value (in Hounsfield units) in the myocardium was used as an estimate of myocardial perfusion. We measured the subendocardial intensity of 17 segments according to the American Heart Association classification. Systolic perfusion or diastolic perfusion was calculated by dividing the subendocardial intensity at systole or diastole, respectively, for each segment by the mean value across all segments for each patient. We used stress/rest MPS to evaluate the variation in myocardial perfusion at systole and diastole for the segments diagnosed as ischemic or nonischemic.

RESULTS. Systolic perfusion for ischemic segments was significantly lower than that for nonischemic segments in 15 of 17 segments. The difference between systolic perfusion and diastolic perfusion in ischemic segments was significantly lower than that in nonischemic segments (14 of 17 segments). There was no significant difference in diastolic perfusion between ischemic and nonischemic segments (15 of 17 segments).

CONCLUSION. Our results suggest that a pattern of subendocardial hypoperfusion at systole and normal perfusion at diastole characterizes ischemic myocardium.

Keywords: cardiac imaging • coronary artery disease • ischemia • myocardium • perfusion imaging

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