Integrated slice-specific dynamic shimming diffusion weighted imaging (DWI) for rectal Cancer detection and characterization

PURPOSE: To compare integrated slice-specific dynamic shimming (iShim) diffusion weighted imaging (DWI) and single-shot echo-planar imaging (SS-EPI) DWI in image quality and pathological characterization of rectal cancer. MATERIALS AND METHODS: A total of 193 consecutive rectal tumor patients were enrolled for retrospective analysis. Among them, 101 patients underwent iShim-DWI (b = 0, 800, and 1600 s/mm(2)) and 92 patients underwent SS-EPI-DWI (b = 0, and 1000 s/mm(2)). Qualitative analyses of both DWI techniques was performed by two independent readers; including adequate fat suppression, the presence of artifacts and image quality. Quantitative analysis was performed by calculating standard deviation (SD) of the gluteus maximus, signal intensity (SI) of lesion and residual normal rectal wall, apparent diffusion coefficient (ADC) values (generated by b values of 0, 800 and 1600 s/mm(2) for iShim-DWI, and by b values of 0 and 1000 s/mm(2) for SS-EPI-DWI) and image quality parameters, such as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of primary rectal tumor. For the primary rectal cancer, two pathological groups were divided according to pathological results: Group 1 (well-differentiated) and Group 2 (poorly differentiated). Statistical analyses were performed with p < 0.05 as significant difference. RESULTS: Compared with SS-EPI-DWI, significantly higher scores of image quality were obtained in iShim-DWI cases (P < 0.001). The SD(background) was significantly reduced on b = 1600 s/mm(2) images and ADC maps of iShim-DWI. Both SNR and CNR of b = 800 s/mm(2) and b = 1600 s/mm(2) images in iShim-DWI were higher than those of b = 1000 s/mm(2) images in SS-EPI-DWI. In primary rectal cancer of iShim-DWI cohort, SI(lesion) was significantly higher than SI(rectum) in both b = 800 and 1600 s/mm(2) images. ADC values were significantly lower in Group 2 (0.732 ± 0.08) × 10(− 3) mm(2)/s) than those in Group 1 ((0.912 ± 0.21) × 10(− 3) mm(2)/s). ROC analyses showed significance of ADC values and SI(lesion) between the two groups. CONCLUSION: iShim-DWI with b values of 0, 800 and 1600 s/mm(2) is a promising technique of high image quality in rectal tumor imaging, and has potential ability to differentiate rectal cancer from normal wall and predicting pathological characterization. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40644-021-00403-9.