We present a novel method for correction of geometric distortions induced by main B0 field in fetal EPI. The method estimates distortion by making the EPI data consistent with reconstructed T2 weighted ssFSE volume. The algorithm consists of two interleaved registration processes: rigid registration of EPI slices with T2 volume to correct for motion; and deformable registration with Laplacian constraint to correct for geometric distortion of EPI slices in a manner consistent with a source free

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... ackground B0 field. Our results show that the Laplacian constraint significantly improves estimation of the distortion field and EPI volume reconstructed using the proposed method achieves better consistency with T2 weighted volume than EPI volume reconstructed from data corrected by B0 field map.