Diffusion-weighted magnetic resonance imaging of human skeletal muscles: gender-, age- and muscle-related differences in apparent diffusion coefficient

PurposeTo 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.Materials and MethodsDiffusion-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.ResultsADCb0–50 and ADCb50–750 were found to be 2.64×10–3 and 1.44×10–3 mm2/s in the ankle dorsiflexors, and 3.02×10–3 and 1.49×10–3 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 1.6×10–3 mm2/s (P<.01); however, ADCb50–750 showed no significant change.ConclusionBased 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.