Improvement of accuracy of diffusion MRI using real-time self-gated data acquisition

Diffusion-weighted and diffusion tensor MR imaging (DWI, DTI) techniques are generally performed with signal averaging of multiple measurements to improve the signal-to-noise ratio (SNR) and the accuracy of the diffusion measurement. Any discrepancy in the images between different averages causes errors which reduce the accuracy of the diffusion MRI measurements. In this report, a motion artifact reduction scheme with a real-time self-gated (RTSG) data acquisition for diffusion MRI using two-dimensional echo planar imaging (2D EPI) is described. A subject's translational and rotational motions during application of the diffusion gradients induce an additional phase term and a shift of the echo-peak position in the k-space, respectively. These motions also reduce the magnitude of the echo-peak. Based on these properties, we present a new scheme which monitors the position and the magnitude of the largest echo-peak in the k-space. The position and the magnitude of each average is compared to those of early averaging shot to determine if the differences are within or beyond the given threshold values. Motion corrupted data are reacquired in real time. Our preliminary results using RTSG indicate an improvement of both SNR and the accuracy of diffusion MRI measurements.