  We present a robust method to correct for motion and deformations for
in-utero volumetric MRI time series. Spatio-temporal analysis of dynamic MRI
requires robust alignment across time in the presence of substantial and
unpredictable motion. We make a Markov assumption on the nature of deformations
to take advantage of the temporal structure in the image data. Forward message
passing in the corresponding hidden Markov model (HMM) yields an estimation
algorithm that only has to account for relatively small motion between
consecutive frames. We demonstrate the utility of the temporal model by showing
that its use improves the accuracy of the segmentation propagation through
temporal registration. Our results suggest that the proposed model captures
accurately the temporal dynamics of deformations in in-utero MRI time series.
