Abstract: Diffusion-weighted data are acquired with an MRI system. From the diffusion-weighted data, a comprehensive diffusion tensor distribution (CDTD) is generated. The provides a proportional weighting, at the voxel level, of different diffusion tensors that could describe the water diffusion occurring in the voxel. The CDTD provides insight into tissue microstructure without making assumptions about the structure of a diffusion tensor used to characterize diffusion occurring in tissues of interest. Water pool images, corresponding to different subsets of diffusion tensors in the CDTD, may be generated to assess different components of water diffusion in tissue. Classification images can also be generated from the CDTD to depict different clusters of voxels having similar distributions of diffusion tensors.

Abstract: Radiation damping (RD) is employed to hasten the recovery of longitudinal magnetization after RF excitation and signal readout in a magnetic resonance measurement cycle. A switch driven by the pulse sequence that performs the measurement cycle energizes a feedback RF coil driven by an amplified and phase shifted portion of the received MR signal. The recovery of longitudinal magnetization is thus under direct control of the MR system and enables the reduction of the otherwise inefficient waiting times that are required for natural T1 recovery of the excited spin magnetization. This enables shortened acquisition times, improved sensitivity, better spatial and temporal resolution, and reduction of motion artifacts that result from long acquisition times.