Diffusion-weighted magnetic resonance imaging of human skeletal muscles: gender-, age- and muscle-related differences...

To evaluate the apparent diffusion coefficient (ADC) of skeletal muscle based on signal intensity (SI) attenuation vs. increasing b values and to determine ADC differences in skeletal muscles between genders, age groups and muscles.

Diffusion-weighted images (b values in the range of 0-750 s/mm2 at increments of 50 s/mm2) of the ankle dorsiflexors (116 subjects) and the erector spinae muscles (86 subjects) were acquired with a 1.5-T MR device. From the two different slopes obtained in SI vs. b-value logarithmic plots, ADCb0-50 (b values=0 and 50 s/mm2) reflected diffusion and perfusion, while ADCb50-750 (b values in the range of 50-750 s/mm2 at increments of 50 s/mm2) approximated the true diffusion coefficient. Moreover, to evaluate whether this b-value combination is appropriate for assessing the flow component within muscles, diffusion-weighted images of the ankle dorsiflexors (10 subjects) were obtained before and during temporal arterial occlusion.

ADCb0-50 and ADCb50-750 were found to be 2.64x10(-3) and 1.44x10(-3) mm2/s in the ankle dorsiflexors, and 3.02x10(-3) and 1.49x10(-3) mm2/s in the erector spinae muscles, respectively. ADCb0-50 was significantly higher than ADCb50-750 in each muscle (P<.01). The erector spinae muscles showed significantly higher ADC values than the ankle dorsiflexors (P<.01). However, for each muscle, there were few significant gender- and age-related ADC differences. Following temporal occlusion, ADCb0-50 of the ankle dorsiflexors decreased significantly from 2.49 to 1.6x10(-3) mm2/s (P<.01); however, ADCb50-750 showed no significant change.

Based on the SI attenuation pattern, muscle ADC could be divided into ADC that reflects both diffusion and perfusion, and ADC that approximates a true diffusion coefficient. There were significant differences in ADC of functionally distinct muscles. However, we barely found any gender- or age-related ADC differences for each muscle.