Evaluating the effect of rectal distension on prostate multiparametric MRI image quality

- Rectal distension had a significant negative effect on the quality of DWI.
- There was a correlation between rectal distension and T2W motion artefact.
- Rectal distension had no significant effect on T2 sharpness and DCE image quality.
- Targeted biopsy PPV was higher for mild versus moderate/severe rectal distension.
- Bowel preparation prior to prostate MRI is advised to improve image quality.

PurposeTo evaluate the effect of rectal distension on the quality of anatomical and functional prostate multiparametric (mp) MRI.Materials and methodsMultiparametric (mp) 3T-MRI images of 173 patients were independently evaluated by two radiologists in this retrospective study. Planimetry rectal volumes were derived and a subjective assessment of rectal distension was made using a 5-point Likert scale (1 = no stool/gas, 5 = large amount of stool/gas). Image quality of diffusion-weighted imaging (DWI) was evaluated using a 5-point Likert scale. DWI was further scored for distortion and artefact. T2W images were evaluated for image sharpness and the presence of motion artefact. The stability of the dynamic contrast-enhancement acquisition was assessed by recording the number of corrupt data points during the wash-out phase.ResultsThere was a strong correlation between subjective scoring of rectal loading and objectively measured rectal volume (r = 0.82), p < 0.001. A significant correlation was shown between increased rectal distension and both reduced DW image quality (r = −0.628, p < 0.001), and increased DW image distortion (r = 0.814, p < 0.001). There was also a significant trend for rectal distension to increase artefact at DWI (r = 0.154, p = 0.042). Increased rectal distension led to increased motion artefact on T2 (p = 0.0096), but did not have a significant effect on T2-sharpness (p = 0.0638). There was no relationship between rectal distension and DCE image quality (p = 0.693). 63 patients underwent lesion-targeted biopsy post MRI, there was a trend to higher positive predictive values in patients with minor rectal distension (34/38, 89.5%) compared to those with moderate/marked distension (18/25, 72%), p = 0.09.ConclusionRectal distension has a significant negative effect on the quality of both T2W and DW images. Consideration should therefore be given to bowel preparation prior to prostate mpMRI to optimise image quality.