Determination of aortic distensibility using non-rigid registration of cine MR images

A novel method for the estimation of areas in 2D MR images of the aorta is presented. The method uses spatio-temporal non-rigid registration in order to obtain the 2D deformation fields of the vessels during the cardiac cycle. This is accomplished by aligning all time frames in the image sequence simultaneously to the first one. The determinant of the Jacobian of the 2D deformation fields are then computed to obtain the expansion (or contraction) at each time frame, with respect to the first time frame. By using 3D splines, the method exploits the relation between time frames in order to obtain continuous and smooth distensibility measurements throughout the cardiac cycle. Validation was carried out with MR images of the aorta. Experiments for the registration and estimation of areas in the aorta are presented in 60 data sets corresponding to three different sections of the aorta (proximal, mid and distal) in 20 different subjects, where each set consisted of 17 to 38 time frames. Manually estimated areas are compared to the areas estimated automatically in 8 data sets where the average error is 2.3% of the area manually obtained.