Normal myocardial perfusion on 64-detector resting cardiac CT

Background Computed tomography (CT) of the heart is increasingly used to characterize not only the coronary arteries but also cardiac structure and function. The performance of CT in depicting myocardial perfusion is under active investigation. Objective We describe the pattern of normal myocardial perfusion on resting 64-detector cardiac CT. Methods Patients (n = 33; 20 women, 13 men; mean age, 52 years) with normal radionuclide myocardial perfusion imaging and normal coronary arteries on CT angiography (120 kVp) comprised the study population. Segmental myocardial perfusion on CT was measured in Hounsfield units (HU) with manual and semiautomated methods for the 17-segment American Heart Association model in both systole and diastole. Segments were aggregated into coronary artery territories, from apex to base and by myocardial wall. The relationships between myocardial perfusion and various patient factors were evaluated. Results Overall mean myocardial perfusion was 98 HU in systole and 94 HU in diastole with the manual method ( P = .011) and 92 HU in systole and 95 HU in diastole with the automated method ( P = .001). The septum showed significantly higher mean attenuation values than the other walls in systole and diastole with both methods. Generally, attenuation values were lower in the left circumflex artery territory and in the apex. Bivariate analysis showed higher mean myocardial attenuation values for women than men, although this difference did not persist on multivariate analysis adjusted for patient size. Conclusion Normal mean resting myocardial perfusion correlates with CT attenuation values of approximately 92–98 HU on CT angiography in the coronary arterial phase. The septum consistently shows greater attenuation values than the other walls.