OPEN MAGNETIC RESONANCE IMAGING TO DEFINE THE AFFECT OF POSTURE ON THE PELVIC FLOOR IN ASSESSMENT OF PROLAPSE; REFERENCE LINES AND 3D PELVIC RECONSTRUCTIONS
ABDULAZIZ, L. STOTHERS, D. LAZARE, J. LOCKE, A. MACNAB;
Univ. of British Columbia, Vancouver, Canada.
Introduction: Standard magnetic resonance imaging (MRI) systems study women in the supine position. However, the position and posture of a patient are relevant and may play a significant role in staging of POP and the interplay of the structures of the pelvic floor. Recently developed open MRI technology allows imaging of the patients in different positions: standing, sitting, and supine. Also, it provides a comprehensive assessment of the entire pelvis, including supporting structures and organs.
Objective: The objectives of this study were: (1) to determine the anatomic differences in pelvic floor anatomy and to assess whether these anatomic differences depend on the position of the subject during imaging using open MRI, (2) to evaluate the changes of POP in different positions compared with non-prolapsed images by using validated reference lines and (3) to develop reconstructed 3D models using MRO to identify the morphologic changes in the pelvic floor in different stages of prolapse.
Methods: Open MRI (MRO) of the pelvis was performed using a 0.5 T dedicated research scanner at a tertiary care university centre. Manual segmentation and surface modeling was used to construct the 3D models of the pelvis. A cohort of 15 subjects including controls and those with clinically POPQ staged POP were recruited for MRO imaging. Physical examination was performed according to the ICS guidelines. Comparison was made to control volunteers who were free of symptoms and had not undergone previous pelvic surgery. Axial, sagittal, and coronal T2-weighted pelvic magnetic resonance scans were obtained with the subjects in the supine, seated, and upright positions. The extent of displacement of prolapse was determined in centimeters according to the validated reference lines (pubococcygeal line (PCL), horizontal line (HL), perineal line (PL), midpubic line (MPL), and sacrococcygeal-inferior pubic point line (SCIPP) drawn on the mid-sagittal image of the respective most extended organ descent in MRO.
Results: Considerable elongation along the PCL and lowest point of the bladder was evident in patients with POP, comparing supine and standing images (p = 0.03), but not in the control group (p = 0.07).
Image 1 shows a representative 3D reconstruction from a standing open MRI image.
Image 2 shows an example of POP observed in the standing position from a control subject evident in the standing position which was not observed supine.
Conclusions: The recent development of open-configuration MRI systems allows images in the sitting, standing, and lying positions. This provides additional anatomical landmarks, as it provides the internal relationship of the pelvic organs in the upright and sitting positions. The 3D reconstruction models will make it feasible for the effects of posture on the pelvic anatomy to be quantified.