Assessment of myocardial viability in a reperfused porcine model: evaluation of different MSCT contrast protocols in acute and subacute infarct stages in comparison with MRI.

OBJECTIVE: To assess myocardial viability in acute and subacute infarcts using different multislice spiral computed tomography contrast protocols with magnetic resonance imaging (MRI) correlation. METHODS: Seven pigs were studied with 64-multislice spiral computed tomography and MRI (1.5 T) at a median of 1 and 21 days after temporary occlusion of the second diagonal branch. Computed tomography was performed at 3, 5, 10, and 15 minutes after injection of contrast medium. Contrast agent was applied either as a bolus (protocol 1; n = 7 for the first; n = 5 for the second scan) or as a bolus plus 30 mL of subsequent 0.1 mL/s low-flow (protocol 2; n = 7 for the first; n = 6 for the second scan). Finally, histological sections were obtained. Volumes of infarcted myocardium were assessed as the percentage of the left ventricle. Computed tomography attenuation values were obtained, and image quality was assessed. RESULTS: When compared with protocol 1, protocol 2 provided greater Hounsfield unit attenuation difference between viable and nonviable myocardium at 5, 10, and 15 minutes (P = 0.19; 0.003; 0.0006) and an additional significant contrast between nonviable myocardium and ventricular blood at 3 and 5 minutes (P < 0.001). Image quality was rated significantly higher with the use of protocol 2 at 5, 10, and 15 minutes (P < or = 0.027) and for all time points use of protocol 2 resulted in improved correlation of acute and subacute infarct size with MRI. CONCLUSIONS: Good correlation of infarct zones with MRI was achieved for both acute and subacute infarcts. With the use of a bolus/low-flow protocol, image quality was substantially improved by means of a higher tissue contrast.

Coronary artery bypass grafts: assessment of graft patency and native coronary artery lesions using 16-slice MDCT.

The objective of this study was to evaluate the accuracy of electrocardiography (ECG)-gated 16-slice multidetector-row computed tomography (MDCT) in detection of stenosis of bypass grafts and native coronary arteries in patients who have undergone coronary artery bypass grafting (CABG). ECG-gated contrast-enhanced MDCT using 12 x 0.75-mm collimation was performed in 20 patients with recurrent angina 4.75 years after undergoing CABG. A total of 50 grafts, 16 arterial and 34 venous, were examined. All graft and coronary segments were evaluated for stenosis in comparison with conventional coronary angiography (CCA). Among the 80 arterial graft segments, 62 could be assessed (77.5%). Sensitivity, specificity, and positive and negative predictive values for stenosis were 96.2%, 97.2%, 96.2%, and 97.2%, respectively. In a total of 180 venous graft segments, 167 could be assessed. Sensitivity, specificity, and positive and negative predictive values for stenosis were 98.5%, 93.9%, 91.8%, and 98.9%, respectively. MDCT could assess 179 of 260 native coronary artery segments (68.8%). Sensitivity, specificity, and positive and negative predictive values for stenosis were 92.1%, 76.9%, 87.5%, and 84.7%, respectively. Sixteen-slice MDCT provides excellent image quality and diagnostic accuracy in detection of graft and coronary artery lesions in patients with suspected graft dysfunction.

Assessment of left ventricular myocardial function using 16-slice multidetector-row computed tomography: comparison with magnetic resonance imaging and echocardiography.

OBJECTIVE: To assess functional parameters using multidetector-row computed tomography (MDCT) and echocardiography and to compare the results with magnetic resonance imaging (MRI). MATERIALS AND METHODS: End-diastolic-volume (EDV), end-systolic-volume (ESV), stroke-volume (SV), ejection-fraction (EF), and myocardial mass (MM) were calculated based on CT data sets from 52 patients. Echocardiography was performed in 24 of the 52 patients. The results from MDCT and echocardiography were compared with MRI. RESULTS: A strong correlation between MDCT and MRI (r=0.66-0.90) was found for all parameters. Echocardiography revealed a low or moderate correlation (0.05-0.59). Compared to MRI the average differences with MDCT were for EDV 15.1 ml, ESV 10.6 ml, SV 4.5 ml, EF 1.8%, and MM 8.2 g, for EDV determined by echocardiography 36.2 ml, ESV 6.8 ml, and EF 13.9%. Bland-Altman analysis revealed acceptable limits of agreement between MRI and MDCT. CONCLUSIONS: MDCT enables reliable quantification of left ventricular function. Echocardiography was found to have only a moderate agreement of functional parameters with MRI.

ECG-gated 16-MDCT of the coronary arteries: assessment of image quality and accuracy in detecting stenoses.

OBJECTIVE: The aim of this study was to investigate image quality and diagnostic accuracy in detecting coronary artery lesions using a 16-MDCT scanner. MATERIALS AND METHODS: Thirty-seven patients (28 men, nine women) underwent unenhanced helical CT and MDCT angiography of the coronary arteries. After patients received oral beta-blocker medication, CT scans were obtained during a single breath-hold with a 16-MDCT scanner using ECG-gating (0.75-mm collimation, 2.8-mm table feed/rotation, 0.42-sec rotation time). The image quality was assessed in terms of artifacts and segment visibility by two reviewers. Stenosis severity was compared with the results of conventional invasive coronary angiography. RESULTS: The data evaluation of the image quality was based on a total of 488 segments, of which 380 segments were considered to have diagnostic image quality. One hundred eight segments (22.1%) could not be sufficiently evaluated because of severe calcifications (35 segments) and motion artifacts (73 segments). The mean calcium score (Agatston score equivalent [ASE]) was 524.3 +/- 807.6. Twenty-eight (75.7%) of the 37 patients had an ASE of less than 1,000 (mean ASE, 90.8 +/- 152.3 [SD]), and nine (24.3%) patients had an ASE of 1,000 or greater (mean ASE, 1,761.0 +/- 637.6). For detecting lesions 50% or greater (without any exclusion criteria), the overall sensitivity, specificity, positive predictive value, and negative predictive value were 59%, 87%, 61%, and 87%, respectively. When limiting the number of patients to those with a calcium score of less than 1,000 ASE, the threshold-corrected sensitivity for lesions 50% or greater was 93%; specificity, 94%; positive predictive value, 68%; and negative predictive value, 99%. CONCLUSION: In patients with no or moderate coronary calcification, MDCT of coronary arteries using 16-MDCT technology allows the reliable detection of coronary artery stenoses with high diagnostic accuracy. Obtaining an initial unenhanced scan was found to be mandatory to avoid performing useless examinations in patients with severe calcifications.