Improved correction of B0 inhomogeneity-induced distortions in prostate diffusion images

Motivation: The Jacobian intensity correction (JIC) of conventional EPI-distortion correction methods can conceal severe under-correction and even create false anatomical structure. Goal(s): Demonstrate the shortcomings of JIC methods and present an alternative distortion-correction technique that obviates the need for a JIC. Approach: Acquiring DWI images with opposite phase-encoding polarity at multiple b-values and normalizing prior to estimating tissue displacement eliminates the need to account for intensity scaling with the JIC. This approach, referred to as mRPG, was compared against conventional distortion correction methods. Results: mRPG significantly improved the estimation and removal of spatial distortions compared to conventional methods. Impact: Jacobian intensity correction (JIC) can generate misleading improvement of EPI distortion and create false structure in prostate diffusion images. Eliminating the JIC, by acquiring opposed-phase images at multiple b-values and normalizing prior to correction, results in improved EPI distortion correction.