Diffusion tensor imaging of the lower leg musculature during exercise

Echoplanar diffusion tensor imaging of musculature was performed using an adapted sequence with stimulated echo preparation and eddy current compensation. Reliable diffusion tensor data were obtained in short measuring time of 2 minutes. Image distortion problems due to eddy currents arising from long lasting diffusion sensitizing gradients could be overcome by insertion of additional gradient pulses in the TM interval of the stimulated echo preparation. In addition, a T 2 -weighted multi-contrast spin-echo sequence with seven echoes was applied for assessment of changes in T2 during exercise. The diffusion tensor and T2 in the musculature of the lower leg was investigated in 4 healthy subjects and maps of the trace and the three eigenvalues of the diffusion tensor, fractional anisotropy maps, and angle maps were calculated from examinations before and after 90 seconds of exhausting tiptoe exercises. For both fractional anisotropy and muscle fibre orientation obvious differences for the miscellaneous muscle groups could be observed, whereas the eigenvalues of the diffusion tensor were found rather homogenous in the whole calf musculature. All eigenvalues of the diffusion tensor of loaded muscles were significantly increased by 7-17% immediately after the exercise. Maximum increase (14-17%) was found in the smallest eigenvalue in gastrocnemius lateralis and soleus muscle.