Generalized ${ q}$-Sampling Imaging

TLDR

A new Fourier‑transform relation enables direct estimation of the spin distribution function from diffusion MR signals. The authors propose generalized q‑sampling imaging (GQI) to obtain the spin distribution function from shell or grid sampling schemes. GQI derives the spin distribution function from these sampling schemes, and its accuracy was evaluated by simulation and in vivo experiments compared with q‑ball imaging and diffusion spectrum imaging. Simulations and in vivo data show GQI’s accuracy matches QBI and DSI, its quantitative anisotropy correlates with fiber volume fraction, and its SDF patterns and tractography are comparable, demonstrating that GQI can provide directional and quantitative crossing‑fiber information from shell or grid sampling.

Abstract

Based on the Fourier transform relation between diffusion magnetic resonance (MR) signals and the underlying diffusion displacement, a new relation is derived to estimate the spin distribution function (SDF) directly from diffusion MR signals. This relation leads to an imaging method called generalized q-sampling imaging (GQI), which can obtain the SDF from the shell sampling scheme used in q-ball imaging (QBI) or the grid sampling scheme used in diffusion spectrum imaging (DSI). The accuracy of GQI was evaluated by a simulation study and an in vivo experiment in comparison with QBI and DSI. The simulation results showed that the accuracy of GQI was comparable to that of QBI and DSI. The simulation study of GQI also showed that an anisotropy index, named quantitative anisotropy, was correlated with the volume fraction of the resolved fiber component. The in vivo images of GQI demonstrated that SDF patterns were similar to the ODFs reconstructed by QBI or DSI. The tractography generated from GQI was also similar to those generated from QBI and DSI. In conclusion, the proposed GQI method can be applied to grid or shell sampling schemes and can provide directional and quantitative information about the crossing fibers.