Abstract 2547: Quantification of Myocardial Perfusion in Patients Using 256-Row Multidetector Computed Tomography: Evaluation of Endocardial vs. Epicardial Blood Flow
Introduction: The advent of 256x0.5 mm high resolution multidetector computed tomography (MDCT) created the potential to quantify subendocardial myocardial blood flow (MBF) reduction, the hallmark of ischemia. The purpose of this study was to test the hypothesis that adenosine stress / rest 256x0.5mm MDCT can detect ischemia by measuring differences in subendo-cardial versus subepicardial MBF.
Methods: Nineteen patients with abnormal SPECT perfusion studies underwent adenosine (140μg/kg/min) stress 256x0.5mm MDCT perfusion imaging (CTP): 120kV, 100mAs, 3 gantry rotations at 0.5 secs, followed by rest 256x0.5mm MDCT angiography (CTA): 120kV, 175mAs, 3 gantry rotations at 0.5 secs. CT perfusion images were reconstructed in the short axis with a 3 mm slice thickness. Endocardial and epicardial borders were defined, myocardium was sectored according to the standard 17 segment model, and divided circumferentially into endocardial and epicardial layers. The transmural perfusion ratio (TPR) was calculated by dividing the endocardial attenuation density (AD) by the epicardial AD in each sector. Ischemia was defined as TPR <0.8 in more than one sector. The TPR results were compared to the presence or absence of stenoses ≥50% on CTA and perfusion deficits on SPECT.
Results: Mean TPR in abnormal and normal sectors was 0.71±0.05 and 1.01±0.06, respectively (p<0.01). Mean number of abnormal sectors for patients with no stenoses, 1-vessel, and multi-vessel disease were 1.6, 2.5, and 6.3; respectively (p<0.05). The sensitivity and specificity of TPR for detecting a stenosis ≥50% severity was 62% and 86% compared with 62% and 71% for SPECT (NS). When defining territorial ischemia as a SPECT perfusion abnormality plus a stenosis ≥50%, the sensitivity, specificity, positive and negative predictive values were 75%, 95%, 75%, and 95% for combined CTA/CTP imaging, respectively.
Conclusions: The transmural perfusion ratio measured from 256x0.5mm MDCT perfusion images can detect the presence of obstructive atherosclerosis with similar accuracy compared with SPECT imaging. The combination of 256x0.5mm MDCT angiography and perfusion imaging may avoid the high false positive rate seen with SPECT imaging alone as well as improve its prediction of territorial ischemia.