Purpose: CT coronary angiography (CTCA) is a non invasive technique which allows acquisition of high resolution images of the heart and coronary vessels. CTCA may also be used to examine myocardial perfusion. The gold standard technique for the absolute quantification of myocardial blood flow (MBF) is positron emission tomography (PET). The aim of the present study was to compare CTCA with PET in the evaluation of myocardial perfusion. Methods: Twenty five patients (mean age 62±0.7 years, 72% male) underwent both CTCA and N13-ammonia PET for the evaluation of coronary artery disease (CAD). CTCA was performed in normal sinus rhythm with 110 ml of contrast medium injected at 8 ml/sec. Offline analysis of myocardial perfusion was carried out according to the following steps: 1) long-axis reformatting and interactive selection of ventricular VOI 2) extraction of the left ventricular cavity by thresholding and blob growing 3) segmentation of the left ventricle 4) calibration of myocardial enhancement by subtracting the baseline attenuation (estimated from standard calcium score scans) 5) generation of 17-segment bull's eye maps depicting the spatial distribution of myocardial contrast enhancement (MCE) expressed in Hounsfield Units, corrected for aortic attenuation. PET imaging was performed in basal conditions and after intravenous administration of dipyridamole; 17-segment polar maps of MBF were then constructed and compared with bull's eye maps obtained through CTCA. Correlations between CTCA MCE and PET MBF were analyzed with Spearman's rank correlation, under the weak assumption of monotonic dependence. Results: Average values of myocardial blood flow measured by PET were 0.55±0.19 ml/min/g (min=0.12, max=1.37) in basal conditions and 1.16±0.49 ml/min/g (min=0.20, max=2.81) during pharmacological vasodilatation. Average MCE at CTCA was 0.14±0.08 (min=0.01, max=0.36). Using Spearman's analysis, a strong association was observed between segmental values of MCE and MBF at rest (rho 0.89, p<10-15), which became more evident when MCE was compared with MBF during vasodilatation (rho 0.94, p<10-15). Conclusions: CTCA allows accurate determination of myocardial perfusion. More specifically, myocardial perfusion assessed through CTCA is more closely linked to MBF values obtained during vasodilatation induced by dipyridamole. CTCA may, therefore, become a valuable tool not only for the examination of coronary anatomy and myocardial contractile function, but also for the evaluation of the physiological significance of epicardial stenoses and for the study of microvascular function.
Myocardial perfusion assessed through CT coronary angiography: a comparison with positron emission tomography
Favilla R;Coppini G;Marraccini P
2010
Abstract
Purpose: CT coronary angiography (CTCA) is a non invasive technique which allows acquisition of high resolution images of the heart and coronary vessels. CTCA may also be used to examine myocardial perfusion. The gold standard technique for the absolute quantification of myocardial blood flow (MBF) is positron emission tomography (PET). The aim of the present study was to compare CTCA with PET in the evaluation of myocardial perfusion. Methods: Twenty five patients (mean age 62±0.7 years, 72% male) underwent both CTCA and N13-ammonia PET for the evaluation of coronary artery disease (CAD). CTCA was performed in normal sinus rhythm with 110 ml of contrast medium injected at 8 ml/sec. Offline analysis of myocardial perfusion was carried out according to the following steps: 1) long-axis reformatting and interactive selection of ventricular VOI 2) extraction of the left ventricular cavity by thresholding and blob growing 3) segmentation of the left ventricle 4) calibration of myocardial enhancement by subtracting the baseline attenuation (estimated from standard calcium score scans) 5) generation of 17-segment bull's eye maps depicting the spatial distribution of myocardial contrast enhancement (MCE) expressed in Hounsfield Units, corrected for aortic attenuation. PET imaging was performed in basal conditions and after intravenous administration of dipyridamole; 17-segment polar maps of MBF were then constructed and compared with bull's eye maps obtained through CTCA. Correlations between CTCA MCE and PET MBF were analyzed with Spearman's rank correlation, under the weak assumption of monotonic dependence. Results: Average values of myocardial blood flow measured by PET were 0.55±0.19 ml/min/g (min=0.12, max=1.37) in basal conditions and 1.16±0.49 ml/min/g (min=0.20, max=2.81) during pharmacological vasodilatation. Average MCE at CTCA was 0.14±0.08 (min=0.01, max=0.36). Using Spearman's analysis, a strong association was observed between segmental values of MCE and MBF at rest (rho 0.89, p<10-15), which became more evident when MCE was compared with MBF during vasodilatation (rho 0.94, p<10-15). Conclusions: CTCA allows accurate determination of myocardial perfusion. More specifically, myocardial perfusion assessed through CTCA is more closely linked to MBF values obtained during vasodilatation induced by dipyridamole. CTCA may, therefore, become a valuable tool not only for the examination of coronary anatomy and myocardial contractile function, but also for the evaluation of the physiological significance of epicardial stenoses and for the study of microvascular function.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
