Reproducibility of dynamic MR imaging pelvic measurements: A multi-institutional study

Purpose: To assess the reproducibility of bone and soft-tissue pelvimetry measurements obtained from dynamic magnetic resonance (MR) imaging studies in primiparous women across multiple centers. Materials and Methods: All subjects prospectively gave consent for participation in this institutional review board-approved, HIPAA-compliant study. At six clinical sites, standardized dynamic pelvic 1.5-T multiplanar T2-weighted MR imaging was performed in three groups of primiparous women at 6-12 months after birth: Group 1, vaginal delivery with anal sphincter tear (n = 93); group 2, vaginal delivery without anal sphincter tear (n = 79); and group 3, cesarean delivery without labor (n = 26). After standardized central training, blinded readers at separate clinical sites and a blinded expert central reader measured nine bone and 10 soft-tissue pelvimetry parameters. Subsequently, three readers underwent additional standardized training, and reread 20 MR imaging studies. Measurement variability was assessed by using intraclass correlation for agreement between the clinical site and central readers. Acceptable agreement was defined as an intraclass correlation coefficient (ICC) of at least 0.7. Results: There was acceptable agreement (ICC range, 0.71-0.93) for eight of 19 MR imaging parameters at initial readings of 198 subjects. The remaining parameters had an ICC range of 0.13-0.66. Additional training reduced measurement variability: Twelve of 19 parameters had acceptable agreement (ICC range, 0.70-0.92). Correlations were greater for bone (ICC, >0.70 in five [initial readings] and eight of nine [rereadings] variables) than for soft-tissue measurements (ICC, >0.70 in three [initial readings] of 10 and four [rereadings] of 10 readings, respectively). Conclusion: Despite standardized central training, there is high variability ofpelvic MR imaging measurements among readers, particularly for soft-tissue structures. Although slightly improved with additional training, measurement variability adversely affects the utility of many MR imaging measurements for multicenter pelvic floor disorder research.