Grading of rabbit skeletal muscle trauma by diffusion tensor imaging and tractography on magnetic resonance imaging.
OBJECTIVE
To distinguish the edema, injury, or rupture in the traumatic skeletal muscle fiber in vivo using diffusion tensor imaging (DTI) and tractography on magnetic resonance imaging (MRI).


METHODS
The skeletal muscle trauma models were made in 4 rabbits (eight hindlimbs) by iron discus (weight 1.0 kg, diameter 6 cm) falling down vertically from 45 cm height to rabbits' thighs. Conventional sequences and two-dimensional (2D) diffusion-weighted (DW) spin-echo (SE) echo planar imaging (EPI) sequence with fat suppression (b = 600 s/mm2) were performed on 1. 5T MRI scanner. The grading of edema, injury, and fiber rupture in the damaged muscle were made according to their histopathological views, which was consistent with the images. The mean apparent diffusion coefficient (ADC) values and fractional anisotropy (FA) values were measured from the region of interests (ROIs) of all groups on 2D DW images used for tractography. Analysis of variance test was performed to analyze all data.


RESULTS
ADC values of the areas in normal muscle, edema muscle, injury muscle, and ruptured muscle were (6.12 +/- 1.34) x 10(-3), (6.38 +/- 1.30) x 10(-3), (8.06 +/- 0.97) x 10(-3), and (9.57 +/- 0.93) x 10(-3) mm2/s, respectively. There was significant difference among groups (P < 0.001), but no difference between edema muscle and normal muscle group (P > 0.05). The FA values of normal muscle, edema muscle, injury muscle, and ruptured muscle were 0.42 +/- 0.12, 0.36 +/- 0.12, 0.26 +/- 0.09, 0.12 +/- 0.08, respectively, with a significant difference among groups (P < 0.001). In the edema muscle, the tracking cross-fiber could be seen but it decreased slightly. In the injury muscle, the tracking fiber decreased markedly. In the ruptured muscle, the transverse-orientation tracking fiber vanished, yet some interrupted longitudinal-orientation tracking fiber could be found.


CONCLUSIONS
The edema, injury, and rupture of muscle fiber in rabbit damaged skeletal muscle can be verified according to the ADC and the FA on DTI and tractography.
Zeng
Hui
H
Department of Radiology, Center of Medical Imaging, Guangdong Provincial People's Hospital, Guangzhou 510080.
Zheng
Jun-Hui
JH
Zhang
Jin-E
JE
Liu
Yan-Hui
YH
Tan
Shao-Heng
SH
Wang
Guang-Yi
GY
Liang
Chang-Hong
CH
D000818:Animals; D016880:Anisotropy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D017352:Echo-Planar Imaging; D004487:Edema / Q000175:diagnosis* / Q000473:pathology; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries* / Q000473:pathology; D011817:Rabbits; D012421:Rupture / Q000175:diagnosis / Q000473:pathology; D013848:Thigh / Q000293:injuries* / Q000473:pathology