Abstract 18634: Quantification of Coronary Volume to Left Ventricular Mass Ratio Using CT Angiography

Abstract

Introduction: Coronary volume to left ventricular mass ratio (V/M) is a promising parameter that can detect physiological imbalances between coronary vasculature and the supplied myocardium. However, the existing method that assesses the V/M using epicardial vascular volume based on coronary CT angiography (CCTA) is labor intensive and prone to variability due to its dependence on coronary vasculature visualization. Hypothesis: A new technique based on CCTA and its associated bolus tracking data enables an efficient semi-automated approach that can reproducibly measure the V/M with less variability compared to the existing manual approach. Methods: The V/M was assessed by both existing manual and the new semi-automated techniques in 6 Yorkshire swine (49.1 ± 9.0 kg). Using a 320-slice CT scanner, 9 pairs of repeated CT measurements were made (100 kVp; 200 mA) with a 5-minute delay between each acquisition. Contrast (0.5 mL/kg; 370 mgI/mL) and a diluted contrast/saline chaser (0.5 mL/kg; 30:70contrast/saline) were injected peripherally at 5mL/s. Bolus tracking and triggering were followed by a single scan acquired at the peak of the aortic enhancement. Using a first-pass analysis model, the bolus tracking and single volume scan data were used to derive the total vascular blood volume (mL). Standard myocardial segmentation was used for myocardial mass (g) measurement. The V/M was also calculated from CCTA using the manual technique, by segmenting coronary luminal volume and myocardial mass. The reproducibility of the V/M was assessed using regression analysis. The variability of the two techniques for determining normal V/M was quantified using the coefficient of variation. Results: The first ((V/M) 1 ) and second ((V/M) 2 ) measurements were related by (V/M) 2 = 1.039 (V/M) 1 + 0.002 (Pearson’s r = 0.90; RMSE = 0.01 mL/g). The coefficient of variation was 0.13 and 0.24 for the V/M calculated from the new semi-automated and existing manual techniques, respectively. Conclusion: A novel semi-automated technique can be used for quantification of V/M with low variability. This technique can potentially be used for early detection of physiological imbalances between coronary vasculature and the supplied myocardium following coronary artery disease.