Does microenema administration improve the quality of DWI sequences in rectal MRI?

Purpose To determine whether the administration of a microenema immediately prior to rectal magnetic resonance imaging (MRI) decreases the level of gas-related artifacts on diffusion-weighted imaging (DWI) sequences. Methods This retrospective analysis included 492 (183 baseline and 309 post-total neoadjuvant treatment [TNT]) consecutive MRI scans for rectal cancer from January 2019 to January 2020. Scan-related factors were identified including microenema use (yes or no), field of view (FOV) in DWI (b = 800 orb = 1500), and magnet strength (1.5 T or 3 T). Two readers scored DWI studies for gas-related artifacts and T2-weighted sequences for the amount of intraluminal gas on a 5-point scale. Fisher's exact test and the Rao-Scott Chi-squared test were used to examine associations between microenema use and other factors. Generalized estimating equation and multivariable regression models were performed to examine the effect of microenema use in subgroups of scans for each reader. Cohen's kappa was used to assess inter-reader agreement. Results Gas-related artifact levels decreased in scans with microenema overall (P < 0.001) as well as when scans were stratified by FOV (P <= 0.003). For both readers, post-TNT scans with microenema showed lower artifact levels overall (P < 0.014 andP < 0.001) and in post-TNT subgroups of axial DWI scans (P <= 0.006 andP < 0.001) and scans acquired with a 3 T magnet (P <= 0.001 for both FOV). No evidence of decreased artifact level was found for baseline studies. Decreased gas was seen with microenema use (P < 0.001 for both readers). Inter-reader agreement on artifact-level and gas-level assessments ranged from slight to substantial (kappa = 0.273-0.685). Conclusion Microenema use prior to rectal MRI reduces gas-related artifacts on DWI, including both large and small FOV sequences and particularly on post-TNT scans performed at 3 T, and offers a viable solution to improve DWI quality.

Automated summary

This study investigated the effect of using a microenema before rectal MRI to reduce gas-related artifacts on DWI sequences. Overall, there was a significant decrease in gas-related artifacts with microenema use, especially in post-TNT scans and scans conducted with a 3 T magnet. This method offers a promising solution to improve DWI quality.