Age-related differences in diffusion tensor indices and fiber architecture in the medial and lateral gastrocnemius.
OBJECTIVE
To investigate age related changes in diffusion tensor indices and fiber architecture of the medial and lateral gastrocnemius (MG and LG) muscles using diffusion tensor imaging (DTI).


METHODS
The lower leg of five young and five senior subjects was scanned at 3 Tesla and DTI indices extracted using three methods: region of interest, histogram, and tract based. Tracked fibers were automatically edited to ensure physiologically relevant tracks. Pennation angles were measured with respect to the deep and superficial aponeuroses of both muscles.


RESULTS
The three methods provided internally consistent measures of the DTI indices (correlation coefficient in the range of 0.90-0.99). The primary, secondary, and tertiary eigenvalues in the MG and LG increased significantly in the senior cohort (P < 0.05), while the small increase in fractional anisotropy with age was not significant (MG/LG: P = 0.39/0.85; 95% confidence interval: [-0.059/-0.056, 0.116/0.064]). Fiber lengths of MG fibers originating distally were significantly decreased in seniors (P < 0.05) while pennation angles decreased with age in the MG and LG but this was not significant.


CONCLUSIONS
Fiber atrophy and increased fibrosis have opposing effects on the diffusion indices resulting in a complicated dependence with aging. Fiber architectural changes could play a role in determining aging muscle function.
Department of Physics, San Diego State University, San Diego, California, USA.
Usha
U
Sinha
Robert
R
Csapo
Vadim
V
Malis
Yanjie
Y
Xue
Shantanu
S
Sinha
D000328:Adult; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D000465:Algorithms; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000166:cytology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
diffusion tensor imaging; gastrocnemius muscle; muscle aging; muscle fiber architecture