Dependence of Temporal Diffusion Spectroscopy on Axon Size in White Matter Tracts of Rat Spinal Cord

Junzhong Xu¹, Kevin D. Harkins¹, R Adam Horch¹, Mark D. Does¹, John C. Gore¹

Conventional diffusion measurements use pulsed gradient spin echo methods with relatively long diffusion times, and require high b values to increase sensitivity to smaller axons. In the current work, an oscillating gradient spin echo (OGSE) method was used to acquire temporal diffusion spectra with relatively short diffusion times and low b values. The results show that the temporal diffusion spectrum is sensitive to the mean axon size of WM tracts of fixed rat spinal cord. A new parameter R, i.e. dispersion rate of ADC vs gradient frequency, is suggested as a sensitive indicator of mean axon size.