Cardiac motion estimation by joint alignment of tagged MRI sequences.

Image registration has been proposed as an automatic method for recovering cardiac displacement fields from tagged Magnetic Resonance Imaging (tMRI) sequences. Initially performed as a set of pairwise registrations, these techniques have evolved to the use of 3D+t deformation models, requiring metrics of joint image alignment (JA). However, only linear combinations of cost functions defined with respect to the first frame have been used. In this paper, we have applied k-Nearest Neighbors Graphs (kNNG) estimators of the α-entropy (H(α)) to measure the joint similarity between frames, and to combine the information provided by different cardiac views in an unified metric. Experiments performed on six subjects showed a significantly higher accuracy (p<0.05) with respect to a standard pairwise alignment (PA) approach in terms of mean positional error and variance with respect to manually placed landmarks. The developed method was used to study strains in patients with myocardial infarction, showing a consistency between strain, infarction location, and coronary occlusion. This paper also presents an interesting clinical application of graph-based metric estimators, showing their value for solving practical problems found in medical imaging.

Echocardiography at diagnosis of antiphospholipid syndrome provides prognostic information on valvular disease evolution and identifies two subtypes of patients.

The evolution of valvular disease in antiphospholipid syndrome (APS) is barely known. In order to evaluate whether the presence or absence of valvular disease at the time of diagnosis of APS, assessed by an initial echocardiogram, predicts its subsequent evolution, we performed a prospective cohort study. We included 53 patients with APS. An initial transthoracic echocardiogram was performed on patients at the time of diagnosis of APS. Serial echocardiograms were conducted along a 12-year follow-up. Final echocardiograms were used for comparative purposes. We started with 29 patients (54%) with and 24 (45%) without valvulopathy at initial echo. At the final echocardiogram, 27 of 29 patients with initial valvulopathy continued to have valvular disease (a 93% observed likelihood), and 22 of 24 patients without initial valvulopathy demonstrated an absence of valvular disease (a 91% observed likelihood). Patients with valvulopathy in comparison with those without presented more arterial thrombotic events (69% vs. 20%, P < 0.001), atherosclerotic risk factors (62% vs. 29%, P = 0.01), livedo (48% vs. 16%, P = 0.01) and migraine (41% vs. 12%, P = 0.02). We have identified two subtypes of APS patients with and without valvulopathy by defining differential clinical features and with little crossover in valvular involvement over a long follow-up period, giving a high prognostic value to the initial echocardiographic assessment.