## 3 Results
### Qualitative Analysis  
The inter-reader agreement was excellent for lesion conspicuity (ICC = 0.843 (0.763-0.896), 0.947 (0.919-0.965) and 0.772 (0.669-0.846)), overall image quality (ICC = 0.895 (0.842-0.931), 0.847 (0.773-0.898) and 0.844 (0.768-0.896)), margin sharpness (ICC = 0.929 (0.891-0.954), 0.935 (0.901-0.957) and 0.942 (0.912-0.962)) in rs-EPI, 2 \(\times\) SMS rs-EPI and 3 \(\times\) SMS rs-EPI, respectively.  
The scores of lesion conspicuity, overall image quality and margin sharpness on DWI images and ADC map were significantly different among rs-EPI, 2 \(\times\) SMS rs-EPI, and 3 \(\times\) SMS rs-EPI (_p_ < 0.05), while there were no significant different between 2 \(\times\) SMS rs-EPI and rs-EPI (all \(p\) > 0.05). In the b = 1000 s/mm\({}^{2}\) DWI image of the 3 \(\times\) SMS rs-EPI sequence, parallel acquisition artifacts can be seen, and rectal structures were poorly visualized (Table 3 and Figures 2 and 3).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Clinicopathological** & & \(n\) **Percentile (\%)** \\ \hline Gender & Male & 55 (66.27) \\ Age (years) & Female & 28 (33.73) \\ BMI (kg\(\cdot\)m\({}^{-2}\)) & & 58.82 (11.71) \\ Location of tumor & Upper-middle segment & 34 (40.96) \\ Lower segment & 49 (59.04) \\ well & 13 (15.7) \\ differentiation grade & moderate & 64 (77.1) \\ poor & 6 (7.2) \\ CEA & + & 55 (66.27) \\ – & 28 (33.73) \\ + & 40 (48.19) \\ CA19-9 & – & 43 (51.81) \\ Nerve invasion & + & 56 (67.5) \\ – & 27 (32.5) \\ Vascular cancer embolus & + & 61 (73.5) \\ – & 22 (26.5) \\ Cancer nodules & + & 68 (81.9) \\ – & 15 (18.1) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Clinicopathological characteristics of the patients.  
Figure 3: Male, 53 years old with rectal cancer. (**a–c**) Diffusion-weighted and ADC maps of conventional rs-EPI sequences with b-values of 0 s/mm\({}^{2}\) and 1000 s/mm\({}^{2}\), respectively. (**d–f**) Diffusion-weighted and ADC maps of 2 \(\times\) SMS rs-EPI sequences with b-values of 0 s/mm\({}^{2}\) and 1000 s/mm\({}^{2}\), respectively. (**g–i**) Diffusion-weighted and ADC maps of 3 \(\times\) SMS rs-EPI sequences with b-values of 0 s/mm\({}^{2}\) and 1000 s/mm\({}^{2}\), respectively. The arrow in the figure points to a rectal cancer lesion.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Qualitative Parameters** & **rs-EPI** & **2 \(\times\) SMS rs-EPI** & **3 \(\times\) SMS rs-EPI** & **X\({}^{2}\) Value** & _p-Value_ \\ \hline
**Lesion Conspicuity** & & & & & \\ \hline b = 0 s/mm\({}^{2}\) & 3.57 \(\pm\) 0.41 & 3.58 \(\pm\) 0.41 & 3.54 \(\pm\) 0.44 ab & 11.143 & 0.004 \\ b = 1000 s/mm\({}^{2}\) & 3.46 \(\pm\) 0.31 & 3.47 \(\pm\) 0.30 & 3.43 \(\pm\) 0.36 ab & 9.579 & 0.008 \\ ADC map (\(\times 10^{-3}\) mm\({}^{2}\)/s) & 3.50 \(\pm\) 0.44 & 3.52 \(\pm\) 0.41 & 3.46 \(\pm\) 0.48 ab & 6.909 & 0.032 \\ Overall image quality & & & & & \\ b = 0 s/mm\({}^{2}\) & 3.63 \(\pm\) 0.32 & 3.60 \(\pm\) 0.27 & 3.56 \(\pm\) 0.29 ab & 9.579 & 0.008 \\ b = 1000 s/mm\({}^{2}\) & 3.55 \(\pm\) 0.36 & 3.51 \(\pm\) 0.39 & 3.47 \(\pm\) 0.46 ab & 11.273 & 0.004 \\ ADC map (\(\times 10^{-3}\) mm\({}^{2}\)/s) & 3.64 \(\pm\) 0.28 & 3.61 \(\pm\) 0.29 & 3.57 \(\pm\) 0.37 ab & 11.273 & 0.004 \\ Margin sharpness & & & & & \\ b = 0 s/mm\({}^{2}\) & 3.49 \(\pm\) 0.32 & 3.47 \(\pm\) 0.33 & 3.44 \(\pm\) 0.34 & 18.488 & \textless{}0.001 \\ b = 1000 s/mm\({}^{2}\) & 3.57 \(\pm\) 0.38 & 3.55 \(\pm\) 0.36 & 3.45 \(\pm\) 0.33 ab & 14.392 & 0.001 \\ ADC map (\(\times 10^{-3}\) mm\({}^{2}\)/s) & 3.33 \(\pm\) 0.43 & 3.36 \(\pm\) 0.40 & 3.24 \(\pm\) 0.51 ab & 18.588 & \textless{}0.001 \\ \hline \hline \end{tabular} Note. 1: compared with rs-EPI, \(p\) \(<\) 0.05; 2 compared with 2 \(\times\) SMS rs-EPI, \(p\) \(<\) 0.05.  
\end{table}
Table 3: Comparison of three rs-EPI sequences showing subjective scores of rectal image quality.  
Figure 2: Comparison of qualitative evaluation metrics of the three EPI sequences. (**a**) lesion conspicuity; (**b**) overall image quality; (**c**) margin sharpness.