Simultaneous phase-correction and denoising for diffusion-weighted MRI

Diffusion-weighted imaging (DWI) suffers from low SNR when compared to regular MRI images. To attain reasonable SNR levels with high spatial resolution, multiple acquisitions of each slice have to be acquired. These repetitions are then averaged, with the goal of increasing the SNR. However, subject motion during diffusion-sensitizing gradients creates varying phases between repeated acquisitions. When direct complex averaging is performed, these phase offsets can cause unpredictable phase cancellations and local signal drops. Here, we propose a technique that simultaneously corrects phase and performs a non-local means filtering to reduce noise. The success of the proposed technique is demonstrated in vivo at 3T with DWI of the cervical spinal cord.