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In vivo demonstration of microscopic anisotropy in the human kidney using multidimensional diffusion MRI
Author(s) -
Nery Fabio,
Szczepankiewicz Filip,
Kerkelä Leevi,
Hall Matt G.,
Kaden Enrico,
Gordon Isky,
Thomas David L.,
Clark Chris A.
Publication year - 2019
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27869
Subject(s) - fractional anisotropy , diffusion mri , medulla , cortex (anatomy) , renal medulla , in vivo , nuclear magnetic resonance , anisotropy , chemistry , nuclear medicine , renal cortex , kidney , biomedical engineering , magnetic resonance imaging , medullary cavity , physics , pathology , anatomy , neuroscience , medicine , radiology , psychology , biology , optics , microbiology and biotechnology
Purpose To demonstrate the feasibility of multidimensional diffusion MRI to probe and quantify microscopic fractional anisotropy (µFA) in human kidneys in vivo. Methods Linear tensor encoded (LTE) and spherical tensor encoded (STE) renal diffusion MRI scans were performed in 10 healthy volunteers. Respiratory triggering and image registration were used to minimize motion artefacts during the acquisition. Kidney cortex–medulla were semi‐automatically segmented based on fractional anisotropy (FA) values. A model‐free analysis of LTE and STE signal dependence on b‐value in the renal cortex and medulla was performed. Subsequently, µFA was estimated using a single‐shell approach. Finally, a comparison of conventional FA and µFA is shown. Results The hallmark effect of µFA (divergence of LTE and STE signal with increasing b‐value) was observed in all subjects. A statistically significant difference between LTE and STE signal was found in the cortex and medulla, starting from b = 750 s/mm 2 and b = 500 s/mm 2 , respectively. This difference was maximal at the highest b‐value sampled ( b = 1000 s/mm 2 ) which suggests that relatively high b‐values are required for µFA mapping in the kidney compared to conventional FA. Cortical and medullary µFA were, respectively, 0.53 ± 0.09 and 0.65 ± 0.05, both respectively higher than conventional FA (0.19 ± 0.02 and 0.40 ± 0.02). Conclusion The feasibility of combining LTE and STE diffusion MRI to probe and quantify µFA in human kidneys is demonstrated for the first time. By doing so, we show that novel microstructure information—not accessible by conventional diffusion encoding—can be probed by multidimensional diffusion MRI. We also identify relevant technical limitations that warrant further development of the technique for body MRI.