Computed Diffusion-Weighted Images of Rectal Cancer: Image Quality, Restaging, and Treatment Response after Neoadjuvant Therapy.

Background: Computed diffusion-weighted images (cDWI) of random b value could be derived from acquired DWI (aDWI) with at least two different b values. However, its comparison between aDWI and cDWI images in locally advanced rectal cancer (LARC) patients after neoadjuvant therapy (NT) is needed.

Purpose: To compare the cDWI and aDWI in image quality, restaging, and treatment response of LARC after NT.

Study Type: Retrospective.

Population: Eighty-seven consecutive patients.

Field Strength/sequence: 3.0 T/DWI.

Assessment: All patients underwent two DWI sequences, including conventional acquisition with b = 0 and 1000 s/mm (aDWI ) and another with b = 0 and 700 s/mm on a 3.0-T MR scanner. The images of the latter were used to compute the diffusion images with b = 1000 s/mm (cDWI ). Four radiologists with 3, 4, 14, and 25 years of experience evaluated the images to compare the image quality, TN restaging performance, and treatment response between aDWI and cDWI .

Statistical Tests: Interclass correlation coefficients, weighted κ coefficient, paired Wilcoxon, and McNemar or Fisher test were used. A significance level of 0.05 was used.

Results: The cDWI images were superior to the aDWI ones in both subjective and objective image quality. In T restaging, the overall diagnostic accuracy of cDWI images was higher than that of aDWI images (57.47% vs. 49.43%, P = 0.289 for the inexperienced radiologist; 77.01% vs. 63.22%, significant for the experienced radiologist), with better sensitivity in determining ypT0-Tis tumors. Additionally, it increased the sensitivity in detecting ypT2 tumors for the inexperienced radiologist and ypT3 tumors for the experienced radiologist. N restaging and treatment response were found to be similar between two sequences for both radiologists.

Data Conclusion: Compared to aDWI images, the computed ones might serve as a wise approach, providing comparable or better image quality, restaging performance, and treatment response assessment for LARC after NT.

Level Of Evidence: 3 TECHNICAL EFFICACY STAGE: 2.