Quantitative analysis of regional endocardial geometry dynamics from 4D cardiac CT images: endocardial tracking based on the iterative closest point with an integrated scale estimation

Effect of the ratio of vessel-specific volume to fractional myocardial mass on fractional flow reserve

This study aimed to examine whether the ratio of vessel-specific coronary arterial lumen volume to the fraction of myocardial mass (V_R/M_R) affects myocardial ischemia. We proposed a calculation method for V_R/M_R, and compared the ratio of total epicardial coronary arterial lumen volume to left ventricular myocardial mass (V/M) with V_R/M_R in predicting myocardial ischemia. V_R/M_R and V/M were computed using data from 205 patients with 241 stenosis vessel who underwent coronary computed tomography angiography (CTA), quantitative coronary angiography, and fractional flow reserve. The vessel-specific coronary arterial lumen volume (V_R) was obtained from CTA by segmenting the coronary arterial lumen volume, while the vessel-specific fraction of myocardial mass (M_R) was obtained by allometric scaling. The V_R/M_R was then calculated. The cut-off values of V/M (23.55 mm³/g) and V_R/M_R (12.98 mm³/g) were used to define equal groups of ischemic and non-ischemic patients, respectively. Using these cut-off values, the accuracy, specificity, sensitivity, positive predictive value, and negative predictive value of V/M were 60%, 76%, 45%, 57%, and 66%, and of V_R/M_R were 87%, 92%, 77%, 89%, and 83%, respectively. Patients have different V_R/M_R values in different stenotic coronary arteries. Clinically, V_R/M_R is a quantitative indicator of the risk of myocardial ischemia.

Estimation of coronary artery movement using a non-rigid registration with global-local structure preservation

BACKGROUND

At present, coronary artery disease (CAD) is the leading cause of death worldwide. Many studies have shown that CAD is strongly associated with the motion characteristics of the coronary arteries. Although cardiovascular imaging technology has been widely used for the diagnosis of CAD, the motion parameters of the heart and coronary arteries cannot be directly calculated from the images. In this paper, we propose a point set registration method with global and local topology constraints to quantify coronary artery movement.

METHODS

The global constraint is the motion coherence of the point set which enforces the smoothness of the displacement field. The local linear embedding based topological structure and the local feature descriptor i.e., the 3D shape context, are designed to retain the local structure of the point set. We incorporate these constraints into a maximum likelihood framework and derive an expectation-maximization algorithm to obtain the transformation function between the two point sets. The proposed method was compared with four existing algorithms using simulated data and applied to the real data obtained from 4D CT angiograms.

RESULTS

For the simulation data, the proposed method achieves a lower registration error than the comparison algorithms. For the real data, the proposed method shows that, in most cases, the right coronary artery achieves a larger velocity than the left anterior descending and left circumflex branches, and there are three well-defined velocity peaks, during the cardiac cycle for these branches.

CONCLUSION

The proposed approach is feasible and effective in quantifying coronary artery movement and thus adds to the diagnostic power of coronary imaging.