DWI of the rectum with deep learning reconstruction: comparison of PROPELLER, reduced FOV, and conventional DWI.

Purpose: To compare the image quality and diagnostic performance of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER), reduced field-of-view (rFOV), and conventional diffusion-weighted imaging (cDWI) combined with deep learning reconstruction (DLR) for evaluating rectal tumors.

Methods: This prospective study included 42 MRI examinations of 38 patients with rectal tumors who underwent initial staging and/or restaging MRI. PROPELLER-DWI, rFOV-DWI, and cDWI obtained with DLR were reviewed by two radiologists and compared for image quality and diagnostic performance for local tumor extent at staging and restaging and response to chemoradiotherapy at restaging.

Results: PROPELLER-DWI had significantly the least artifacts and distortions, but the worst perceptive noise, while rFOV-DWI had significantly the best sharpness for both readers (P < 0.01). For overall image quality and rectal/tumor conspicuity, PROPELLER-DWI and rFOV-DWI were significantly superior to cDWI in both readers (P < 0.01). The incidence of suboptimal image quality was significantly lower with PROPELLER-DWI and rFOV-DWI than with cDWI (5 and 1 patients with PROPELLER-DWI, 14 and 6 with rFOV-DWI, and 29 and 25 with cDWI by the 2 readers, P < 0.01). Although there were no significant differences in the accuracy of staging and restaging among the 3 types of DWI, inter-reader agreement was highest for PROPELLER-DWI (weighted kappa, 0.62-0.71) compared with cDWI (weighted kappa, 0.38-0.52) and rFOV-DWI (weighted kappa, 0.47-0.61).

Conclusions: PROPELLER-DWI and rFOV-DWI with DLR may improve the image quality of rectal DWI by reducing artifacts and distortions or increasing sharpness, although the impact on diagnostic accuracy was not significant.