Online motion correction for diffusion‐weighted imaging using navigator echoes: Application to RARE imaging without sensitivity loss

Abstract

This article describes the first application of true online motion correction to diffusion‐weighted RARE imaging. Two orthogonal navigator echoes were acquired and zeroth and first‐order phase corrections applied in less than 8 ms between a diffusion‐weighted magnetization preparation and data acquisition using the RARE sequence. The zeroth‐order phase correction was realized by pulsing the system's B₀‐coil: the first‐order error corrected with appropriate magnetic field gradient pulses. Online correction ensured that no irreversible signal loss could occur in the imaging experiment. Diffusion‐weighted images of the brain were obtained from healthy volunteers. EGG‐triggered acquisition was applied at 400 ms after the R‐wave. Data were acquired on a matrix of 256 × 256 with a RARE factor of 16 and a b‐value of 804 smm⁻². The images obtained with online motion correction showed a remarkably high image quality, while those acquired without motion correction were severely degraded by artifacts. Magn Reson Med 45:729–733, 2001.