Construction of a cardiac motion atlas from MR using non-rigid registration

In this paper we present a technique for constructing a cardiac motion atlas using the myocardial motion fields derived from 4D MR image sequences of a series of subjects. This is achieved by transforming the motion field of each subject into a the coordinate system of a reference subject, and then averaging the transformed fields to give a vector field representing the mean motion of the heart. The motion fields of each subject are calculated by registering each of the frames in the sequence of tagged short-axis and long-axis MRI images to the end-diastolic frame using a non-rigid registration technique based on multi-level free-form deformations. The end-diastolic untagged short-axis images of each subject, which are acquired shortly after the tagged images, are registered to the corresponding image of a designated reference subject using non-rigid registration to determine reference-subject mappings, which are then used to transform the corresponding motion fields into that of the reference subject. Finally, the mean transformed motion field is calculated to give the cardiac motion atlas.