**6. Proposed protocol for upright open MRI evaluation of POP**

technique is that it enables comprehensive definition of the full extent of organ prolapse due

Upright open MRI is currently only available as a research entity. A new clinical protocol for MRO image capture of the female pelvis has been created and introduced into clinical practice. This provides enhanced anatomic definition and allows more comprehensive evaluation

Image interpretation from conventional and upright open MRI evaluates the three compartments of the pelvic floor [43]. The three compartments are evaluated for morphologic changes such as POP at various pelvic floor positions. To define the existence and descent of POP, the use of a point of reference is beneficial. Several points and lines of reference for measuring POP have been reported [44]. The more commonly used lines are the pubococcygeal line (PCL) and the mid-pubic line (MPL), both applied on midsagittal images. The PCL is the line drawn from the inferior part of the symphysis pubis to the last coccygeal joint. Extending the posterior portion of the PCL to the sacrococcygeal joint also has been proposed because there is movability of the coccyx with straining [21]. The MPL is a line extending along the long axis of the symphysis pubis. The PCL represents the levator plate, while the MPL correlates with the level of the hymen, which is the landmark applied for clinical staging [45]. To measure pelvic organ prolapse a perpendicular line is drawn from the reference line (PCL or MPL) to the bladder base (anterior compartment), the cervix or vaginal vault (middle compartment), and the anal rectal junction (ARJ) (posterior compart-

Another classification system, H line, M line, organ prolapse (HMO), has been proposed for measuring prolapse [35]. The H line is drawn from the pubis to the posterior anorectal junction and measures the levator hiatus width. Organ prolapse is measured relative to that line. The M line measures the descent of the levator plate from the pubococcygeal line. The angle of the levator plate relative to the pubococcygeal line and the width and part of the pelvic hiatus

The choice of which reference line is used is mostly made by the radiologist and/or the referring clinician, as neither of the two lines has shown distinct superiority [44]. The PCL, however, is the most-used reference line, particularly by surgeons and gastroenterologists. The MPL is better known among urogynecologists, as it is compatible with their clinical staging system. Both reference lines display only moderate to poor agreement with clinical staging of pelvic organ prolapse [38]. This might be partly because anatomical landmarks used for MR measurements and for clinical examination differed in most of the studies [23]. Standards exist for diagnosing prolapse on physical examination [1]. Congruity between this clinical standard and MRI imaging analysis should be used to document the utility of MRI and the

to the effects of posture and gravity [40].

and staging.

26 Pelvic Floor Disorders

ment) [23].

on axial images can be measured as well [22].

success of treatment [22].

**5. Reference lines**

Based on our literature search research, the protocol we propose for upright open MRI evaluation of women with prolapse and stress urinary incontinence is as follows. (1) All women complete a history that includes validated symptom scores for bladder, bowel, and prolapserelated symptoms. (2) Patients have a physical examination that follows IUGA/ICS guidelines [10]; this examination includes POPQ staging. (3) Patients complete a screening assessment tool to ensure there are no contraindications for magnetic resonance imaging. Some metals and surgical hardware are ferromagnetic and, therefore, are not acceptable with MRI. (4). Imaging is then conducted.

Our images are obtained currently using a 0.5 T scanner located at a dedicated research facility at the Centre for Hip Health at the University of British Columbia, Canada. Each patient's preparation includes ensuring a full bladder; hence, they are asked to refrain from voiding for 2 h before imaging. For standing images, intermittent pneumatic compression devices are applied to the legs. A T2-weighted sagittal image of the midline structures, including the symphysis, urethra, and coccyx, is acquired. Women then empty the bladder, and images in the supine, seated, and upright position are obtained. Current settings based on pilot studies indicate successful imaging is obtained with the following: TR/effective TE, 2500/16; echo train length, 32; bandwidth, 32 kHz; excitation, one; matrix size, 256 × 160; field of view, 0.5 (24 cm); section thickness, 5 mm, slice gap, 1. Sagittal images for mobility of the bladder neck and urethra can be obtained during straining [46].
