# Upright 0.5 T open MR defaecating proctography proof of concept study: the inter- and intra-rater variability of pelvic floor measures using seated proctography

## TL;DR

A new upright MRI technique for studying pelvic floor function during defecation is shown to be reliable and feasible.

## Contribution

The study introduces and validates an upright 0.5 T MRI method for defaecating proctography with minimal preparation.

## Key findings

- PF landmarks were consistently identified with acceptable inter- and intra-rater variability.
- Intra-rater variation was low, with relative absolute differences ranging from 3.2–44%.
- Inter-rater correlation was strong (r² > 0.93), and bias was within acceptable limits.

## Abstract

We tested the feasibility, data quality, and reliability of an upright magnetic resonance defaecating proctography (uMRDP) technique using an Open 0.5 T ASG MRI scanner.

Eight healthy volunteers (2 males) performed seated defaecation on a purpose-built radio-frequency commode coil in an Open scanner. An optimised T2-weighted HASTE sequence captured dynamic changes during all three phases of the Kegel manoeuvre. Inter- and intra-rater variability was measured from the pelvic floor (PF) metrices (M-line, H-line, distances of landmarks) extracted by two radiologists.

All relevant PF landmarks could be identified and metrices were extracted with acceptable inter- and intra-rater variability. Intra-rater variation was marginal, with relative absolute differences ranging from 5 to 21% and 3.2–44%. Inter-rater variability was reported using correlation and Bland-Altman plots. Correlation between raters was satisfactory, with r2 > 0.93, and bias ranged from − 1.8 to 0.65 mm. Moreover, the limit of agreement in the Bland-Altman plot ranged from 5.8 to 20.4 mm, indicating satisfactory precision.

The proposed uMRDP technique can be used as a feasible and reliable alternative to supine MRDP, without the necessity of gadolinium injection and bowel preparation. It can capture defaecation in a regular seated posture and can provide information complementary to standard-of-care fluoroscopic proctography for clinicians.

The online version contains supplementary material available at 10.1007/s10334-025-01296-6.