Abstract:
This study was conducted to align images of a beagle’s heart obtained from in vivo cardiac tagged magnetic resonance imaging (MRI) and ex vivo diffusion tensor MRI (DTMRI), provided by our collaborators at NIH. Such data will be used in a mathematical modelling framework in order to analyse regional left ventricular (LV) mechanics, which will provide important insight to pathological conditions such as myocardial infarction. DTMRI data provide the myocardial fibre orientations for each pixel of an image. The tagged MRI and DTMRI images were orientated and scaled differently, since the shape of the heart was different when imaged in vivo versus ex vivo. Image re-sampling was required to obtain new DTMRI images with the heart in the same orientation as the tagged images. A graphical user interface was developed for the segmentation of the surface contours and readily identifiable landmark points on the re-sampled DTMRI images, together with the corresponding landmark target points on the tagged MRI images. Based on this geometrical data, a free-form deformation is used to warp the fibre orientation data from the DTMRI images to an end-diastolic geometrical model determined from the tagged MRI images. Cardiac mechanics simulations will be validated against data obtained from the tagged images throughout the cardiac cycle. We conclude by assessing the effectiveness of using DTMRI fibre data for cardiac mechanics modelling. This type of modelling will be useful for analysing cardiac mechanics during diseased states and can be extended for biventricular modelling.