T. Benner, V. Jellus, R. Wang, V. J. Wedeen, A. J. van der Kouwe, G. C. Wiggins, A. G. Sorensen Radiology, Athinoula A. Martinos Center, Charlestown, MA, United States, Siemens Medical Solutions, Erlangen, Germany Introduction Diffusion-weighted MR images (DWI) typically exhibit low SNR due to the diffusion gradients, which are applied during image acquisition. This effect is pronounced at low field strength, when using high b-values or high spatial resolution. Higher field strength and phased array coils can be used to regain SNR. The use of phased array coils has the additional benefit of enabling parallel imaging techniques such as sensitivity encoding (SENSE) [1] or generalized auto-calibrating partially parallel acquisitions (GRAPPA) [2] for increased imaging speed and reduced susceptibility distortion artifacts. However, combination of signals from the coil elements is typically performed as sum-of-squares (SoS), which is near optimal only in the case of high SNR.