ABSTRACT
PURPOSE: Assess whether application of a micro-enema can reduce gas-induced susceptibility artefacts in Single-shot Echo Planar Imaging (EPI) Diffusion-weighted imaging of the rectum at 1.5â¯T. MATERIALS AND METHODS: Retrospective analysis of nâ¯=â¯50 rectal cancer patients who each underwent multiple DWI-MRIs (1.5â¯T) from 2012 to 2016 as part of routine follow-up during a watch-and-wait approach after chemoradiotherapy. From March 2014 DWI-MRIs were routinely acquired after application of a preparatory micro-enema (Microlax®; 5â¯ml; self-administered shortly before acquisition); before March 2014 no bowel preparation was given. In total, 335 scans were scored by an experienced reader for the presence/severity of gas-artefacts (on b1000 DWI), ranging from 0 (no artefact) to 5 (severe artefact). A score ≥3 (moderate-severe) was considered a clinically relevant artefact. A random sample of 100 scans was re-assessed by a second independent reader to study inter-observer effects. Scores were compared between the scans performed without and with a preparatory micro-enema using univariable and multivariable logistic regression taking into account potential confounding factors (age/gender, acquisition parameters, MRI-hardware, rectoscopy prior to MRI). RESULTS: Clinically relevant gas-artefacts were seen in 24.3% (no micro-enema) vs. 3.7% (micro-enema), odds ratios were 0.118 in univariable and 0.230 in multivariable regression (Pâ¯=â¯0.0005 and 0.0291). Mean severity score (±SD) was 1.19⯱â¯1.71 (no-enema) vs 0.32⯱â¯0.77 (micro-enema), odds ratios were 0.321 (Pâ¯<â¯0.0001) and 0.489 (Pâ¯=â¯0.0461) in uni- and multivariable regression, respectively. Inter-observer agreement was excellent (κ0.85). CONCLUSION: Use of a preparatory micro-enema shortly before rectal EPI-DWI examinations performed at 1.5â¯T MRI significantly reduces both the incidence and severity of gas-induced artefacts, compared to examinations performed without bowel preparation.