Evaluation of the injury of levator ani muscle in primipara after vaginal delivery using diffusion tensor imaging and fibre tractography

Abstract

Objective To investigate the clinical application of diffusion tensor imaging (DTI) and fibre tractography in evaluating the levator ani muscle injury after first vaginal delivery. It can provide objective evidence for clinical rehabilitation treatment after delivery and prevention of pelvic organ prolapse. Methods From June 2014 to January 2015, 50 primiparous six months after vaginal delivery and 33 normal women without experience of pregnancy and delivery as control group were prospectively studied in Tianjin First Center Hospital. All women underwent axial, coronal fast spin-echo T2-weighted imaging(FSE T2WI)sequences and DTI sequences of the pelvic floor. Offline fibre tractography of each major levator ani subdivision (pubovisceralis and iliococcygeus) and quality assessment of fibre tracking were performed. From accurate tracking results fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated. FSE-T2WI were evaluated for levator ani muscle abnormalities. And on the basis of the levator ani muscle defects, the primiparous were divided into two groups. The pubovisceralis normal group and pubovisceralis injured group, iliococcygeus normal group and iliococcygeus injured group respectively. FA, ADC values between the control group, levator ani muscle normal group and injured group were compared using ANOVA. Results The quality of the 3D representation was judged as accurate for all of the pubovisceralis and inaccurate for all of the iliococcygeus. Twelve (24.0%, 12/50) primiparous had injuries in their pubovisceralis, 9 primiparous had unilateral defects and three had bilateral amyotrophy. Four (8.0%, 4/50) primiparous had injuries in their iliococcygeus, all of them showed unilateral defects. No levator ani defects were identified in nulliparous women. The FA values of pubovisceralis among control group, pubovisceralis normal group and pubovisceralis injured group were 0.49±0.08, 0.52±0.11, and 0.53±0.13, respectively. The ADC values were (1.79±0.29)×10-3 mm2/s, (1.75±0.34)×10-3 mm2/s, and (1.93±0.35)×10-3 mm2/s. There was no statistical significance (F=1.217, 1.747 respectively, all P values>0.05). Conclusions DTI with fibre tractography provides a satisfactory 3D representation of pubovisceralis. The study of iliococcygeus is more difficult. DTI and fiber tractography cannot provide accurate quantified diagnostic evidence to differentiate normal and abnormal states of the levator ani muscle. Key words: Magnetic resonance imaging; Diffusion tensor imaging; Tractography; Levator ani muscle; Primiparous; Labor, obstetric