The Value of Multi-directional High b-Value DWI in the Assessment of Muscular Invasion in Bladder Urothelial Carcinoma: In Comparison with VI-RADS.

Rationale and objectives: To predict the muscular invasion status of bladder urothelial carcinoma (UCB) using quantitative parameters from multi-directional high b-value diffusion-weighted imaging (MDHB-DWI), and compare these parameters with the Vesical Imaging Reporting and Data System (VI-RADS).

Methods: In this prospective study, patients with pathologically confirmed UCB were enrolled between May 2023 and May 2024. All participants underwent preoperative MRI, including MDHB-DWI and conventional MRI. The average quantitative parameter values of MDHB-DWI (diffusion kurtosis imaging [DKI], diffusion tensor imaging [DTI], mean apparent propagator [MAP] and neurite orientation dispersion and density imaging [NODDI]) and apparent diffusion coefficient (ADC) values were compared between non-muscle invasive (NMIBC) and muscle-invasive (MIBC) groups using the T-test or rank sum test. Quantitative MRI models were developed using multivariate logistic regression analyses based on significant diffusion parameters obtained from MDHB-DWI. Receiver operating characteristic (ROC) curves were plotted, and DeLong's test was applied to compare the area under the curve (AUC) of the model with that of VI-RADS.

Results: A total of 76 patients with UCB (56 males; NMIBC/MIBC=51/25) were included. Axial diffusivity (AD) from DKI and mean diffusivity (MD) from DTI were identified as independent predictors for constructing a quantitative MRI model. The AUC of the model was 0.936, significantly outperforming VI-RADS (AUC=0.831) (p = 0.007).

Conclusion: DKI-AD and DTI-MD from MDHB-DWI demonstrate a robust ability to differentiate muscular invasion in UCB. Their combination significantly improves diagnostic efficiency compared to VI-RADS.