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Dynamic brain ADC variations over the cardiac cycle and their relation to tissue strain assessed with DENSE at high‐field MRI
Author(s) -
Sloots JacobJan,
Froeling Martijn,
Biessels Geert Jan,
Zwanenburg Jaco J. M.
Publication year - 2022
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.29209
Subject(s) - effective diffusion coefficient , white matter , coefficient of variation , cardiac cycle , nuclear magnetic resonance , diffusion mri , brain tissue , nuclear medicine , magnetic resonance imaging , biomedical engineering , chemistry , materials science , medicine , physics , radiology , chromatography
Purpose The ADC of brain tissue slightly varies over the cardiac cycle. This variation could reflect physiology, including mixing of the interstitial fluid, relevant for brain waste clearance. However, it is known from cardiac diffusion imaging that tissue deformation by itself affects the magnitude of the MRI signal, leading to artificial ADC variations as well. This study investigates to what extent tissue deformation causes artificial ADC variations in the brain. Theory and Methods We implemented a high‐field MRI sequence with stimulated echo acquisition mode that simultaneously measures brain tissue deformation and ADC. Based on the measured tissue deformation, we simulated the artificial ADC variation by combining established theoretical frameworks and compared the results with the measured ADC variation. We acquired data in 8 healthy volunteers with diffusion weighting b = 300 and b = 1000 s/mm 2 . Results Apparent diffusion coefficient variation was largest in the feet‐to‐head direction and showed the largest deviation from the mean ADC at peak systole. Artificial ADC variation estimated from tissue deformation was 1.3 ± 0.37·10 −5 mm 2 /s in the feet‐to‐head direction for gray matter, and 0.75 ± 0.29·10 −5 mm 2 /s for white matter. The measured ADC variation in the feet‐to‐head direction was 5.6·10 −5 ± 1.5·10 −5 mm 2 /s for gray matter and 3.2·10 −5 ± 1.0·10 −5 mm 2 /s for white matter, which was a factor of 3.5 ± 0.82 and 3.4 ± 0.57 larger than the artificial diffusion variations. The measured diffusion variations in the right‐to‐left/anterior‐to‐posterior direction were a factor of 1.5 ± 1.0/1.7 ± 1.4 and 2.0 ± 0.91/2.5 ± 0.94 larger than the artificial diffusion variations for gray matter and white matter, respectively. Conclusion Apparent diffusion coefficient variations in the brain likely largely reflect physiology.