In vivo assessment of pelvic floor muscles dysfunction using MR diffusion tensor imaging: fractional anisotropy and apparent diffusion coefficient as quantitative methods

Abstract Background Diffusion tensor imaging (DTI) techniques in magnetic resonance imaging (MRI) were found to provide quantitative insights into microstructural abnormalities in biological tissues. This study aimed to determine the significance of DTI-derived numerical values in quantifying pelvic floor muscle dysfunctions (PFD) by comparing fractional anisotropy (FA) and apparent diffusion coefficient (ADC) data between control subjects and patients with PFD. Thirty patients referred with PFD for MR Defecography (MRD) and 40 patients referred for MRI of pelvis with no pelvic floor symptoms underwent 2D spin-echo (SE) echo-planar imaging sequence of the pelvic floor using a 1.5-T MRI machine. Analysis of MRD was done by a single pelvic floor radiologist. Two radiologists selected the region-of-interest on muscles with active pelvic floor support in consensus. PFD patients were further classified based on MRD findings into dyssynergic and non-dyssynergic defecation. FA and ADC values were compared using ANOVA. Results Comparison of datasets of PFD and controls revealed statistically significant results in all pelvic floor muscles on both sides (except for the right iliococcygeus muscle), with the mean FA was found significantly higher in patients with PFD and the mean ADC was lower in the PFD group compared to the control group. Comparison of FA and ADC values between the subgroups of PFD was not statistically significant. None of the examined patients or controls had morphological muscle changes on MR images. Conclusions Fractional anisotropy and ADC values, known to be influenced by the fat and water content of muscles, suggesting that patients with PFD likely to have microstructural changes in the pelvic floor muscles' even in absence of visible muscle tears, possibly leading to the abnormalities observed during MRD. Differences in FA and ADC values between patients with dyssynergic and non-dyssynergic defecation are likely secondary to different underlying microstructural changes however, DTI parameters are incapable of differentiating them quantitatively. Combining DTI numerical datasets with abnormalities depicted on MRD could be particularly insightful in the follow-up of patients with pelvic dysfunctions especially patients managed conservatively through biofeedback and physiotherapy.