Detecting Muscle Invasion of Bladder Cancer: An Application of Diffusion Kurtosis Imaging Ratio and Vesical Imaging‐Reporting and Data System

Background Independent factors are needed to supplement vesical imaging‐reporting and data system (VI‐RADS) to improve its ability to identify muscle invasive bladder cancer (MIBC). Purpose To assess the correlation between MIBC and diffusion kurtosis imaging (DKI) ratio, VI‐RADS, and other factors (such as tumor location). Study Type Retrospective. Population Sixty‐eight patients (50 males and 18 females; age: 70.1 ± 9.5 years) with bladder urothelial carcinoma. Field Strength/Sequence 1.5 T, conventional diffusion‐weighted imaging (DWI), and DKI (single shot echo‐planar sequence). Assessment Three radiologists independently measured the diffusion parameters of each bladder cancer (BCa) and obturator internus, including the mean apparent diffusion coefficient (ADCmean), mean kurtosis (MK), and mean diffusion (MD). And the ratio of diffusion parameters between BCa and obturator internus was calculated (diffusion parameter ratio = bladder cancer:obturator internus). Based on the VI‐RADS, the target lesions were independently scored. Furthermore, the actual tumor‐wall contact length (ACTCL) and absolute tumor‐wall contact length (ABTCL) were measured. Statistical Tests Multicollinearity among independent variables was evaluated using the variance inflation factor (VIF). Multivariable logistic regression analysis was used to determine the independent risk factors of MIBC. The receiver operating characteristic curve was used to evaluate the efficacy of each variable in detecting MIBC. The DeLong test was used to compare the area under the curve (AUC). A P < 0.05 was considered statistically significant. Results MKratio (median: 0.62) and VI‐RADS were independent risk factors for MIBC. AUCs for MKratio, VI‐RADS, and MKratio combined with VI‐RADS in assessing MIBC were 0.895, 0.871, and 0.973, respectively. MKratio combined with VI‐RADS was more effective in diagnosing MIBC than VI‐RADS alone. Data Conclusions MKratio has potential to assist the assessment of MIBC. MKratio can be used as a supplement to VI‐RADS for detecting MIBC. Level of Evidence 4 Technical Efficacy Stage 2