Efficient experimental designs for isotropic generalized diffusion tensor MRI (IGDTI).
PURPOSE
We propose a new generalized diffusion tensor imaging (GDTI) experimental design and analysis framework for efficiently measuring orientationally averaged diffusion-weighted images (DWIs), which remove bulk signal modulations attributed to diffusion anisotropy and quantify isotropic higher-order diffusion tensors (HOT). We illustrate how this framework accelerates the clinical measurement of rotation-invariant tissue microstructural parameters derived from HOT, such as the HOT-Trace and the mean t-kurtosis.


THEORY AND METHODS
For a large range of b-values, we compare orientationally averaged DWIs measured with high angular resolution diffusion imaging to those obtained with the proposed isotropic GDTI (IGDTI) experimental design. We compare rotation-invariant microstructural parameters measured with IGDTI to those derived from HOTs measured explicitly with GDTI.


RESULTS
In both fixed-brain microimaging and in vivo clinical experiments, IGDTI accurately quantifies mean apparent diffusion coefficient (mADC)-weighted DWIs over a wide range of b-values and allows efficient computation of HOT-derived scalar tissue parameters from a small number of DWIs.


CONCLUSIONS
IGDTI provides direct and accurate estimates of orientationally averaged tissue water mobilities over a wide range of b-values. This efficient method may enable new, sensitive, and quantitative assessments for clinical applications in which changes in mADC can be observe,d such as detecting and characterizing stroke, cancers, and neurodegenerative diseases. Magn Reson Med 79:180-194, 2018. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.
['Avram|Alexandru V|AV|http://orcid.org/0000-0002-0295-601X', 'Sarlls|Joelle E|JE|', 'Hutchinson|Elizabeth|E|', 'Basser|Peter J|PJ|']
D000818:Animals D001921:Brain D001931:Brain Mapping D003198:Computer Simulation D038524:Diffusion Magnetic Resonance Imaging D056324:Diffusion Tensor Imaging D005289:Ferrets D006801:Humans D000860:Hypoxia D007091:Image Processing, Computer-Assisted D008297:Male D015233:Models, Statistical D008962:Models, Theoretical D009369:Neoplasms D019636:Neurodegenerative Diseases D015203:Reproducibility of Results D020521:Stroke
anisotropy HOT diffusion tensor imaging (DTI) higher-order tensor mean apparent diffusion coefficient (mADC) mean diffusivity trace