Relevance of open magnetic resonance imaging position (sitting and standing) to quantify pelvic organ prolapse in women.

INTRODUCTION: In pelvic organ prolapse (POP), posture and gravity impact organ position and symptom severity. The advanced magnet configuration in open magnetic resonance imaging (MRO) allows patients to be imaged when sitting and standing, as well in a conventional supine position. This study evaluated if sitting and standing MRO images are relevant as a means of improving quantification of POP because they allow differences in organ position not seen on supine imaging to be identified.
METHODS: Forty women recruited from a university urogynecology clinic had MRO imaging (0.5 T scanner) with axial and sagittal T2-weighted pelvic scans obtained when sitting, standing, and supine. Pelvic reference lines were used to quantify the degree of POP, and the relevance of imaging position on the detection of POP compared.
RESULTS: Images from 40 participants were evaluated (20 with POP and 20 asymptomatic controls). Our results indicate that the maximal extent of prolapse is best evaluated in the standing position using H line, M line, mid-pubic line, and perineal line as reference lines to determine POP.
CONCLUSIONS: MRO imaging of symptomatic patients in a standing position is relevant in the quantification of POP. Compared with supine images, standing imaging identifies that greater levels of downward movement in the anterior and posterior compartments occur, presumably under the influence of posture and gravity. In contrast, no appreciable benefit was afforded by imaging in the sitting position, which precluded use of some reference lines due to upward movement of the anorectal junction.