A novel model to test accuracy and reproducibility of MDCT scan protocols for coronary calcium in vivo.

OBJECTIVES: We compared the accuracy and reliability of prospectively triggered, retrospectively ECG gated, and non-gated CT image reconstruction for measurements of coronary artery calcification (CAC) in vivo using a novel animal model. MATERIALS AND METHODS: In six Yorkshire farm pigs, prefabricated chains of cortical bone fragments were sutured over the epicardial bed of the major coronary arteries. Using a 4-slice MDCT scanner, each animal was imaged with two different protocols: sequential acquisition with prospective ECG triggering, and spiral acquisition with retrospectively ECG gated image reconstruction- non-gated reconstructions were also generated from these latter scans. Two independent observers measured the 'Agatston score' (AS), the calcified volume (CV), and mineral mass (MM). To calculate accuracy of MM measurements the ash weight of the burned bone fragments was compared to MDCT derived MM. RESULTS: Six pigs successfully underwent surgery and CT imaging (mean heart rate: 86+/-12 bpm). MM measurements from prospectively ECG triggered CT sequential scans were more accurate (p<0.02) and reproducible (p=0.05) than sequential CT scans without ECG triggering or spiral acquisition using retrospective ECG gating. CONCLUSIONS: At high heart rates prospective ECG triggered image reconstruction is more accurate and reproducible for CAC scoring than retrospective ECG gated reconstruction and non-gated reconstruction.

Acute myocardial infarction: contrast-enhanced multi-detector row CT in a porcine model.

PURPOSE: To assess the role of contrast material-enhanced retrospectively electrocardiographically (ECG) gated multi-detector row computed tomography (CT) in the detection of acute myocardial infarction in a porcine model of total coronary occlusion. MATERIALS AND METHODS: Seven Yorkshire farm pigs were studied with contrast-enhanced retrospectively ECG-gated multi-detector row CT 3 hours after total occlusion of the distal left anterior descending artery (n = 5) or the second diagonal branch (n = 2). Reformatted short-axis end-systolic and end-diastolic CT data sets were assessed for myocardial perfusion deficits, coronary occlusion, and abnormal myocardial wall motion. Perfusion deficits were compared with microsphere-determined blood flow and triphenyltetrazolium chloride (TTC)-stained tissue samples for infarct assessment by using Bland-Altman analysis and analysis of variance. RESULTS: Myocardial perfusion deficits, occlusion of the left anterior descending artery or second diagonal branch, and akinesis of the infarcted segment were identified in all five animals that completed the study. One animal died, and one data set had nondiagnostic image quality. The CT end-diastolic (mean, 16.1% +/- 4.8 [SD]; range, 8.6%-22.2%) and end-systolic (mean, 17.0% +/- 6.4; range, 8.7%-26.8%) volume of perfusion deficit was similar to that of infarcted tissue at TTC staining (mean, 13.6% +/- 6.0; range, 7.8%-30.9%). Infarcted myocardium at CT demonstrated a 76.1% reduction in microsphere-determined blood flow and a significant reduction of myocardial CT attenuation compared with normal myocardium (P <.01). Myocardial wall motion analysis demonstrated absence of systolic wall thickening in infarcted myocardium. CONCLUSION: Multi-detector row CT with retrospective ECG gating permits the detection and further characterization of acute myocardial infarction in a porcine model of complete coronary occlusion.