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

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*

*Corresponding author for this work

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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 1.5 T. Materials and methods: Retrospective analysis of n = 50 rectal cancer patients who each underwent multiple DWI-MRIs (1.5 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 (R); 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 gasartefacts (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 (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 (kappa 0.85). Conclusion: Use of a preparatory micro-enema shortly before rectal EPI-DWI examinations performed at 1.5 T MRI significantly reduces both the incidence and severity of gas-induced artefacts, compared to examinations performed without bowel preparation.
Original languageEnglish
Pages (from-to)131-137
Number of pages7
JournalEuropean Journal of Radiology
Publication statusPublished - 1 Feb 2018


  • Diffusion-weighted imaging
  • Susceptibility artifacts
  • Micro-enema
  • Bowel preparation
  • Rectal imaging
  • Rectal cancer
  • COIL

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