AbstractPurposeDiffusion weighted (DW) echo-planar imaging (EPI) is prone to geometric and intensity distortions due to B0 inhomogeneities. Pulse sequences that excite spins within a reduced field-of-view (FOV) in the phase encoding (PE) direction have been developed to decrease such distortions. In addition, use of the reverse polarity gradient (RPG) method, a retrospective approach to correct distortion artifacts, has been shown to improve the localization of tumor lesions. The purpose of this work was to evaluate the performance of reduced-FOV acquisition and RPG in decreasing distortion artifacts for breast imaging.MethodsEPI data were acquired with full and reduced-FOV in a breast phantom and in a group of 170 women at 3T. The performance of RPG in correcting distortion artifacts in EPI data was evaluated using the mutual information (MI) metric between EPI and anatomical low-distortion images before and after distortion correction.ResultsRPG corrected distortions by 61% in full-FOV EPI and 48% in reduced-FOV EPI in a breast phantom. In patients, MI increased on average 13±8% and 8±6% for both full and reduced-FOV EPI data after distortion correction, respectively. The 95th percentile and maximum displacement between uncorrected and corrected full-FOV EPI datasets were 0.8±0.3cm and 1.9±0.3cm, and for reduced-FOV were 0.4±0.2cm and 1.3±0.3cm.ConclusionMinimal distortion was achieved with RPG applied to reduced-FOV EPI data. RPG improved distortions for full-FOV, but with more modest improvements and limited correction near the nipple.
Robust 2D phase correction for echo planar imaging under a tight field-of-view
