Effect on image quality of ultra-high b-values diffusion weighted imaging in patients with rectal cancer by using different bowel preparation methods
Objective: To investigate the effect of image quality of ultra-high b-values diffusion weighted imaging (DWI) with b=2000 s/mm2 (DWIb2000) and routine DWI with b=1000 s/mm2 (DWIb1000) by different bowel preparation (drinking folium sennae soup or dietary restrictions) in patients with rectal cancer (RC). Materials and Methods: The DWI (DWIb1000 and DWIb2000) image quality and related factors were analyzed in 203 patients with RC between the bowel preparation group with folium sennae soup and the dietary restrictions groups. The bowel preparation metrics (rectal dilatation, rectal contents, amount of gas in rectum and amount of gas around the tumor) and magnetic susceptibility artifacts (overall artifacts and artifacts of the tumor area) were independently assessed in the DWIb1000 and DWIb2000 by two radiologists. Between-group comparisons of bowel preparation metrics and DWI artifacts were calculated using Mann-Whitney U test or t-test. Subsequently, DWIb2000 artifact scores of less than or equal to 3 score in the tumor area was defined as clinical relevant artifacts. Univariate and multivariable logistic regression was used to assess related factors (bowel preparation methods, age, gender, tumor location, tumor circumferential percentage and thickness of posterior rectal mesentery) for DWIb2000 clinical relevant artifacts. Results: Inter-reader agreement was good [intra-class correlation coefficient (ICC) >0.70]. The rectal contents, amount of gas in rectum and amount of gas around the tumor in the bowel preparation group with folium sennae soup were higher than those of the dietary restriction groups (P<0.05), respectively. The degree of overall artifacts and artifacts of the tumor area (DWIb1000 and DWIb2000) in the bowel preparation group with drinking folium sennae soup were significantly higher than those of the dietary restriction groups (P<0.05), respectively. In the same bowel preparation group, the degree of overall artifacts and artifacts of tumor area in DWIb2000 were significantly higher than those of DWIb1000 (P<0.01), respectively. Multivariable logistic regression analysis demonstrated that the bowel preparation method was an independent related factor for DWIb2000 clinical relevant artifacts in tumor area (OR=3.463, 95% CI: 1.738-6.901, P<0.001). Conclusions: Compared with the dietary restriction group, patients with bowel preparation by drinking folium sennae soup can obtain good bowel preparation quality, reduce the DWI artifacts and improve the image quality of DWIb1000 and DWIb2000.