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Abstract #0130

Disentangling microscopic anisotropy and diffusion time dependence in the brain using oscillating gradients with spherical b-tensor encoding

Manisha Aggarwal1 and Lauren Jantzie2
1Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 2Departments of Pediatrics and Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

Synopsis

Keywords: Microstructure, Microstructure, Brain, Multidimensional diffusion MRI, Oscillating gradients

Motivation: Tensor-valued diffusion MRI allows estimation of microscopic fractional anisotropy (μFA) independent of orientation dispersion. However, diffusion time/frequency-dependence of μFA in the brain is not well understood.

Goal(s): To investigate the frequency dependence of diffusional variances and μFA in the rat brain using oscillating-gradient spherical (STE) and linear (LTE) b-tensor encoding waveforms.

Approach: Oscillating-gradient STE and LTE waveforms were implemented at frequencies of 65, 117, and 169 Hz. Tensor-valued dMRI data were acquired from fixed rat brains using the spectrally-matched STE and LTE gradients.

Results: Spectrally-modulated STE and LTE gradients revealed significant time/frequency-dependence of isotropic diffusivity, diffusional variances, and μFA in the rat brain.

Impact: We demonstrate that oscillating spherical and linear b-tensor encoding waveforms allow mapping of frequency-dependent isotropic diffusivity, diffusional variances, and μFA in the brain. The results are important to understand the effects of spectral content of the waveforms in tensor-valued dMRI.

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Keywords