Upright 0.5T Open MR Defaecating Proctography: an investigation into the inter- and intra-observer variability of pelvic floor measures using seated proctography

Object : We tested the feasibility, data quality, and reliability of an upright magnetic resonance defaecating proctography (uMRDP) technique using an Open 0.5T ASG MRI scanner Materials and Methods: 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 metrices extracted by two radiologists. Results: All relevant pelvic floor 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 5−21% and 3.2−44%. Inter-rater variability was reported using correlation and Bland-Altman plots. Correlation between raters was satisfactory, with r ² > 0.93, and bias ranged from -1.8−0.65 mm. Moreover, the limit of agreement in the Bland-Altman plot was small, ranging from 5.8−20.4 mm, indicating satisfactory precision. Discussion: The proposed upright MRDP 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 regular seated posture and can provide information complementary to standard-of-care fluoroscopic proctography for clinicians.