To elucidate changes in the diffusion properties of muscle fiber between rest and active contraction.
In 10 healthy adult volunteers (4 men, 6 women), we obtained diffusion tensor (DT) images (b=500 s/mm(2)) of bilateral calves using a 1.5-tesla clinical magnetic resonance (MR) imager. We first simultaneously scanned both calves at rest, then obtained scans of bilateral calves with plantar flexion of the right ankle using the same imaging parameters. We measured fractional anisotropy (FA) and lambda(1), lambda(2), and lambda(3) in the gastrocnemius medialis (GCM) and anterior tibialis (AT) muscles of both calves by seeding the region of interest at the thickest part, then calculated the right-to-left ratio of the FA and eigenvalues in each muscle and compared each ratio between rest and contraction by paired t-test.
In the GCM, the FA ratio increased from 1.05 at rest to 1.17 after contraction, and contraction elevated the lambda1 and 2 ratios from 0.99 in resting muscles to 1.06 (lambda(1)) and 1.07 (lambda(2)). In contrast, the AT showed a decrease of the lambda(1) ratio from 0.99 at rest to 0.96 at elongation and of the lambda(2) ratio, from and 1.01 at rest to 0.94 at elongation. Statistically significant differences were observed in the FA (P<0.05), lambda1 and lambda2 (P<0.01) in the GCM, and the lambda1 and lambda2 (P<0.05) in the AT.
The higher FA and lambda(1) and lambda(2) values of muscles at contraction than rest presumably reflect complicated changes, including microscopic morphological changes of the diffusion-restricting factor, focal temperature, and perfusion. We found that change in perfusion could affect the AT, and changes in focal perfusion and temperature could influence the GCM.
Magnetic Resonance in Medical Sciences 01/2010; 9(1):1-8. DOI:10.2463/mrms.9.1 · 1.04 Impact Factor
Tractography of skeletal muscle can clearly reveal the 3-dimensional course of muscle fibers, and the procedure has great potential and could open new fields for diagnostic imaging. Studying this technique for clinical application, we noticed differences in the number of visualized tracts among volunteers and among muscles in the same volunteer. To comprehend why the number of visualized tracts varied so that we could acquire consistently high quality tractography of muscle fiber, we started to examine whether differences in individual parameters affected tractography visualization.
To determine whether there are gender- and age-specific differences that differentiate the muscles by gender and age in MR tractography of skeletal muscle fiber.
We divided 33 healthy volunteers by gender and age among 3 groups, A (13 younger men, aged 20 to 36 years), B (11 younger women, 25 to 39 years), and C (9 older men, 50 to 69), and we obtained from each volunteer tractographs of 8 fibers, including the bilateral gastrocnemius medialis (GCM), gastrocnemius lateralis (GCL), soleus (SOL), and anterior tibialis (AT) muscles. We classified the fibers into 5 grades depending on the extent of visualized tracts and used Mann-Whitney U-test to compare scores by gender (Group A versus B) and age (Group A versus C).
Muscle tracts were significantly better visualized in women than men (median total visual score, 34 versus 24, P<0.05). In particular, the SOL muscles showed better visualization in the right (4.0 in women, 1.0 in men, P<0.05) and left (3.0 in women, 1.0 in men, P<0.05). Difference by age was not significant. The GCL was the highest scored muscle in all groups.
Our results suggest that group differences, especially by gender, affected visualization of tractography of muscle fiber of the calf.
Magnetic Resonance in Medical Sciences 01/2010; 9(3):111-8. DOI:10.2463/mrms.9.111 · 1.04 Impact Factor
To elucidate the difference of diffusion property of muscle fiber between active contraction and resting state
METHOD AND MATERIALS
Healthy four male and six female volunteers were recruited for this study. We obtained diffusion tensor (DT) images (b=500 s/mm²) of bilateral calves in 1.5 T clinical MRI. First, bilateral calves were scanned simultaneously at resting state. Next, we obtained images of bilateral calves with planter flexion of the right ankle inducing contraction of the dorsal side of the right calf muscles with the same imaging parameters. Pressing on a custom-made foot brake-like device placed under the right planter controlled extent of loading to the muscle. FA values were measured in the gastrocnemius medialis (GCM), gastrocnemius lateralis (GCL), soleus (SOL), and anterior tibialis (AT) muscles of bilateral calves by seeding the region of interest at the level of the maximum diameter of the calf. And we calculated the right to left ratio of FA value in each muscle, and compared each FA ratio between resting and contraction by student's t-test.
The mean FA ratio (right / left) was 1.05 in GCM, 1.05 in GCL, 1.08 in SOL, and 1.07 in AT at resting state. No statistical differences between right and left were observed in all muscles. At contraction state, the mean FA ratio was 1.17 in GCM, 1.33 in GCL, 1.32 in SOL, and 1.07 in AT. Statistical differences between FA ratios at rest and those in contraction were observed in GCM (P=0.038<0.05), GCL (0.001 <P), and SOL (0.001<P). The AT showed the same FA ratio in resting and contraction states.
FA values of muscles were higher at muscle contraction than in rest. We suppose this can reflect morphological changes of myofibril bundle, or changes of the interstitial space of the calf.
DTI has a possibility to reflect the microscopic morphological change of muscle fiber, and may contribute the clarification of the pathophysiologic basis of neuromuscular diseases.
Radiological Society of North America 2008 Scientific Assembly and Annual Meeting; 12/2008