The effect of iterative reconstruction on quantitative computed tomography assessment of coronary plaque composition.

To compare coronary plaque size and composition as well as degree of coronary artery stenosis on coronary Computed Tomography angiography (CCTA) using three levels of iterative reconstruction (IR) with standard filtered back projection (FBP). In 63 consecutive patients with a clinical indication for CCTA 55 coronary plaques were analysed. Raw data were reconstructed using standard FBP and levels 2, 4 and 6 of a commercially available IR algorithm (iDose(4)). CT attenuation and noise were measured in the aorta and two coronary arteries. Both signal-to-noise-ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The amount of lipid, fibrous and calcified plaque components and mean cross-sectional luminal area were analysed using dedicated software. Image noise was reduced by 41.6% (p < 0.0001) and SNR and CNR in the aorta were improved by 73.4% (p < 0.0001) and 72.9% (p < 0.0001) at IR level 6, respectively. IR improved objective image quality measures more in the aorta than in the coronary arteries. Furthermore, IR had no significant effect on measurements of plaque volume and cross-sectional luminal area. The application of IR significantly improves objective image quality, and does not alter quantitative analysis of coronary plaque volume, composition and luminal area.

Diagnostic efficacy of coronary calcium score in the assessment of significant coronary artery stenosis.

BACKGROUND: Coronary artery calcium score (CCS) is a quantitative assessment of calcifications detectable by multidetector computed tomography (MDCT). AIM: To evaluate diagnostic accuracy of CCS to detect significant stenosis in coronary arteries in symptomatic patients. METHODS: The study population included consecutive symptomatic patients with suspected coronary artery disease (CAD) who were referred for coronary angiography. The group included 158 patients (64.6% males) who were all evaluated by unenhanced 64-slice computed tomography where calcium was quantified according to the Agatston method. The ROC curves were constructed to evaluate the discriminating power of the total CCS and CCS for each individual coronary artery in predicting the presence of significant stenosis. RESULTS: The prevalence of significant CAD strongly increased with higher CCS. The area under the curve (AUC) for total CCS for diagnosing significant stenosis (> or = 50%) in at least one coronary artery was 0.83 (95% CI 0.74-0.92). Using the cut-off value of CCS > or = 7.7 at least one significant coronary stenosis was detected with the sensitivity and specificity of 86% and 71%, respectively. Significant coronary artery stenosis was better predicted by measuring CCS for individual coronary arteries than total CCS. The AUC of CCS for significant stenosis of each coronary artery was 0.80 for the right coronary artery (RCA), 0.72 for the left main (LM), 0.73 for the left anterior descending (LAD) and 0.76 for the left circumflex arteries (LCX). The optimal cut-off point was estimated for CCS of each coronary artery. It was set at > or = 3.1 for RCA, > or = 7.7 for LM, > or = 9.5 for LAD and > or = 4.5 for LCX. Positive and negative predictive values for an intact artery using a CCS of zero were 92.8% and 83.8%, respectively. Diagnostic performance of CCS for predicting stenosis of LM and LCX arteries was better in patients over age 65 than in younger patients. CONCLUSIONS: Coronary artery calcium score is useful in predicting coronary artery stenosis, especially in subjects in whom invasive diagnostic or therapeutic utilities seem to be used untimely. The current study suggests an optimal cut-off value of total CCS > or = 7.7 for detecting significant stenosis, and underlines the better predictive value for CCS of individual arteries.

Assessment of regional myocardial oxygenation changes in the presence of coronary artery stenosis with balanced SSFP imaging at 3.0 T: theory and experimental evaluation in canines.

PURPOSE: To examine the dependence of steady-state free-precession (SSFP) -based myocardial blood-oxygen-level-dependent (BOLD) contrast on field strength using theoretical and experimental models. MATERIALS AND METHODS: Numerical simulations using a two-pool exchange model and a surgically prepared dog model were used to assess the SSFP-based myocardial BOLD signal changes at 1.5T and 3.0T. Experimental studies were performed in eight canines with pharmacological vasodilation under various levels of left circumflex coronary artery stenosis. Experimentally obtained BOLD signal changes were correlated against microsphere-based true flow changes. RESULTS: Theoretical results showed that, at 3.0T, relative to 1.5T, a threefold increase in oxygen sensitivity can be expected. Experimental studies in canines showed near similar results-a 2.5 +/- 0.2-fold increase in BOLD sensitivity at 3.0T relative to 1.5T (P < 0.05). Based on the scatter gram of BOLD data and microsphere data, it was found that the minimum regional flow difference that can be detected with SSFP-based myocardial BOLD imaging at 1.5T and 3.0T were 2.9 and 1.6, respectively (P < 0.05). CONCLUSION: This study demonstrated that SSFP-based myocardial BOLD sensitivity is substantially greater at 3.0T compared with 1.5T. The findings here suggest that SSFP-based myocardial BOLD imaging at 3.0T may have the necessary sensitivity to detect the clinically required minimum flow difference of 2.0.