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White matter fiber reconstructions based on seeking local maxima of Orientation Distribution Functions (ODFs) typically fail to identify fibers crossing at narrow angles below 45°. ODF-Fingerprinting (ODF-FP) replaces the ODF maxima localization mechanism with pattern matching, allowing the use of all information stored in ODFs. In this work, we study the ability of ODF-FP to reconstruct fibers crossing at varied angles spanning 10°-90° in physical diffusion phantoms composed of textile tubes with 0.8μm diameter, approaching the anatomical scale of axons. Our results show that ODF-FP is able to correctly identify 80 ± 8% of the crossing fibers regardless of the crossing angle and provide the highest average reconstruction accuracy.

Fitting of the multicompartment biophysical model of white matter is an ill-posed optimization problem. One approach to make it computationally tractable is through Orientation Distribution Function (ODF) Fingerprinting. However, the accuracy of this method relies solely on ODF dictionary generation mechanisms which either sample the microstructure parameters on a multidimensional grid or draw them randomly with a uniform distribution. In this paper, we propose a stepwise stochastic adaptation mechanism to generate ODF dictionaries tailored specifically to the diffusion-weighted images in hand. The results we obtained on a diffusion phantom and in vivo human brain images show that our reconstructed diffusivities are less noisy and the separation of a free water fraction is more pronounced than for the prior (uniform) distribution of ODF dictionaries.

Sodium MRI (sMRI) has undergone a tremendous amount of technical development during the last two decades that makes it a suitable tool for the study of human pathology in the acute setting within the constraints of a clinical environment. The salient role of the sodium ion during impaired ATP production during the course of brain ischemia makes sMRI an ideal tool for the study of ischemic tissue viability during stroke. In this paper, the current limitations of conventional MRI for the determination of tissue viability during evolving brain ischemia are discussed. This discussion is followed by a summary of the known findings about the dynamics of tissue sodium changes during brain ischemia. A mechanistic model for the explanation of these findings is presented together with the technical requirements for its investigation using clinical MRI scanners. An illustration of the salient features of the technique is also presented using a nonhuman primate model of reversible middle cerebral artery occlusion.

A new interface combining phased arrays and echo-planar imaging (EPI) technologies was developed for two channel breast MR EPI applications. A detailed design for a dual-channel, EPI-compatible, phased array breast coil is described. EPI digital data multiplexing, signal controlling and sampling schemes are also presented. Results from breast phantoms and patients demonstrate a 55% improvement in signal-to-noise ratio when compared to a conventional two-loop, single channel coil configuration. This method can be easily expanded to a four or more channel, EPI-compatible, phased array system to improve field-of-view coverage and signal-to-noise ratio.