  In this paper, we propose an enhanced 3D myocardial strain estimation
procedure, which combines complementary displacement information from multiple
orientations of a single imaging modality (untagged CMR SSFP images). To
estimate myocardial strain across the left ventricle, we register the sets of
short-axis, four-chamber and two-chamber views via a 2D non-rigid registration
algorithm implemented in a commercial software (Segment, Medviso). We then
create a series of interpolating functions for the three orthogonal directions
of motion and use them to deform a tetrahedral mesh representation of a
patient-specific left ventricle. Additionally, we correct for overestimation of
displacement by introducing a weighting scheme that is based on displacement
along the long axis. The procedure was evaluated on the STACOM 2011 dataset
containing CMR SSFP images for 16 healthy volunteers. We show increased
accuracy in estimating the three strain components (radial, circumferential,
longitudinal) compared to reported results in the challenge, for the imaging
modality of interest (SSFP). Our peak strain estimates are also significantly
closer to reported measurements from studies of a larger cohort in the
literature and our own ground truth measurements using Segment Strain Analysis
Module. Our proposed procedure provides a relatively fast and simple method to
improve 2D tracking results, with the added flexibility in either deforming a
reconstructed mesh model from other image modalities or using the built-in CMR
mesh reconstruction procedure. Our, proposed scheme presents a deforming
patient-specific model of the left ventricle, using the commonest imaging
modality , routinely administered in clinical settings, without requiring
additional or specialized imaging protocols.
