Robust frequency-dependent diffusion kurtosis computation using an efficient direction scheme, axisymmetric modelling, and spatial regularization
arXiv (Cornell University)(2023)
摘要
Frequency-dependent diffusion MRI (dMRI) using oscillating gradient encoding
and diffusion kurtosis imaging (DKI) techniques have been shown to provide
additional insight into tissue microstructure compared to conventional dMRI.
However, a technical challenge when combining these techniques is that the
generation of the large b-values required for DKI is difficult when using
oscillating gradient diffusion encoding. While efficient encoding schemes can
enable larger b-values by maximizing multiple gradient channels simultaneously,
they do not have sufficient directions to enable fitting of the full kurtosis
tensor. Accordingly, we investigate a DKI fitting algorithm that combines
axisymmetric DKI fitting, a prior that enforces the same axis of symmetry for
all oscillating gradient frequencies, and spatial regularization, which
together enable robust DKI fitting for a 10-direction scheme that offers double
the b-value compared to traditional direction schemes. Using data from mice
(oscillating frequencies of 0, 60, and 120 Hz) and humans (0 Hz only), we first
show that axisymmetric modelling is advantageous over full kurtosis tensor
fitting in terms of preserving contrast and reducing noise in DKI maps, and
improved DKI map quality when using an efficient encoding scheme with averaging
as compared to a traditional scheme with more encoding directions. We also
demonstrate how spatial regularization during fitting preserves spatial
features better than using Gaussian filtering prior to fitting, which is an
oft-reported preprocessing step for DKI, and that enforcing consistent axes of
symmetries across frequencies improves fitting quality. Thus, the use of an
efficient 10-direction scheme combined with the proposed DKI fitting algorithm
provides robust maps of frequency-dependent directional kurtosis parameters
that can be used to explore novel biomarkers for various pathologies.
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关键词
diffusion,axisymmetric modelling,efficient direction scheme,frequency-dependent
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