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An exploration of diffusion tensor eigenvector variability within human calf muscles
Author(s) -
Rockel Conrad,
Noseworthy Michael D.
Publication year - 2016
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.24957
Subject(s) - diffusion mri , fractional anisotropy , eigenvalues and eigenvectors , tensor (intrinsic definition) , anisotropy , nuclear magnetic resonance , mathematics , consistency (knowledge bases) , physics , mathematical analysis , geodesy , geometry , geology , medicine , optics , magnetic resonance imaging , quantum mechanics , radiology
Purpose To explore the effect of diffusion tensor imaging (DTI) acquisition parameters on principal and minor eigenvector stability within human lower leg skeletal muscles. Materials and Methods Lower leg muscles were evaluated in seven healthy subjects at 3T using an 8‐channel transmit/receive coil. Diffusion‐encoding was performed with nine signal averages (NSA) using 6, 15, and 25 directions (NDD). Individual DTI volumes were combined into aggregate volumes of 3, 2, and 1 NSA according to number of directions. Tensor eigenvalues (λ 1 , λ 2 , λ 3 ), eigenvectors (ε 1 , ε 2 , ε 3 ), and DTI metrics (fractional anisotropy [FA] and mean diffusivity [MD]) were calculated for each combination of NSA and NDD. Spatial maps of signal‐to‐noise ratio (SNR), λ 3 :λ 2 ratio, and zenith angle were also calculated for region of interest (ROI) analysis of vector orientation consistency. Results ε 1 variability was only moderately related to ε 2 variability ( r = 0.4045). Variation of ε 1 was affected by NDD, not NSA ( P < 0.0002), while variation of ε 2 was affected by NSA, not NDD ( P < 0.0003). In terms of tensor shape, vector variability was weakly related to FA (ε 1 : r = –0.1854, ε 2 : ns), but had a stronger relation to the λ 3 :λ 2 ratio (ε 1 : r = –0.5221, ε 2 : r = –0.1771). Vector variability was also weakly related to SNR (ε 1 : r = –0.2873, ε 2 : r = –0.3483). Zenith angle was found to be strongly associated with variability of ε 1 ( r = 0.8048) but only weakly with that of ε 2 ( r = 0.2135). Conclusion The second eigenvector (ε 2 ) displayed higher directional variability relative to ε 1 , and was only marginally affected by experimental conditions that impacted ε 1 variability. J. Magn. Reson. Imaging 2015. J. MAGN. RESON. IMAGING 2016;43:190–202.