Pre‐excitation gradients for eddy current nulled convex optimized diffusion encoding (Pre‐ENCODE)

Abstract

AbstractPurposeTo evaluate the use of pre‐excitation gradients for eddy current–nulled convex optimized diffusion encoding (Pre‐ENCODE) to mitigate eddy current–induced image distortions in diffusion‐weighted MRI (DWI).MethodsDWI sequences using monopolar (MONO), ENCODE, and Pre‐ENCODE were evaluated in terms of the minimum achievable echo time (TE) and eddy current‐induced image distortions using simulations, phantom experiments, and in vivo DWI in volunteers ().ResultsPre‐ENCODE provided a shorter TE than MONO (71.0 17.7ms vs. 77.6 22.9ms) and ENCODE (71.0 17.7ms vs. 86.2 14.2ms) in 100 of the simulated cases for a commercial 3T MRI system with b‐values ranging from 500 to 3000 s/mm and in‐plane spatial resolutions ranging from 1.0 to 3.0mm. Image distortion was estimated by intravoxel signal variance between diffusion encoding directions near the phantom edges and was significantly lower with Pre‐ENCODE than with MONO (10.1 vs. 22.7, ) and comparable to ENCODE (10.1 vs. 10.4, ). In vivo measurements of apparent diffusion coefficients were similar in global brain pixels (0.37 [0.28,1.45] mm/s vs. 0.38 [0.28,1.45]mm/s, ) and increased in edge brain pixels (0.80 [0.17,1.49] mm/s vs. 0.70 [0.18,1.48]mm/s, ) for MONO compared to Pre‐ENCODE.ConclusionPre‐ENCODE mitigated eddy current–induced image distortions for diffusion imaging with a shorter TE than MONO and ENCODE.