Gas-induced susceptibility artefacts on diffusion-weighted MRI of the rectum at 1.5T – Effect of applying a micro-enema to improve image quality

Publication date: Available online 28 December 2017
Source:European Journal of Radiology
Author(s): Joost J.M. van Griethuysen, Elyse M. Bus, Michael Hauptmann, Max J. Lahaye, Monique Maas, Leon C. ter Beek, Geerard L. Beets, Frans C.H. Bakers, Regina G.H. Beets-Tan, Doenja M.J. Lambregts
PurposeAssess 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 1.5T.Materials and MethodsRetrospective analysis of n = 50 rectal cancer patients who each underwent multiple DWI-MRIs (1.5T) from 2012-2016 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^®;5 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).ResultsClinically 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 (P = 0.0005 and 0.0291). Mean severity score (±SD) was 1.19 ± 1.71 (no-enema) vs 0.32 ± 0.77 (micro-enema), odds ratios were 0.321 (P < 0.0001) and 0.489 (P = 0.0461) in uni- and multivariable regression, respectively. Inter-observer agreement was excellent (κ0.85).ConclusionUse of a preparatory micro-enema shortly before rectal EPI-DWI examinations performed at 1.5T MRI significantly reduces both the incidence and severity of gas-induced artefacts, compared to examinations performed without bowel preparation.



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