Diffusion kurtosis imaging to assess correlations with clinicopathologic factors for bladder cancer: a comparison between the multi-b value method and the tensor method

Objectives To assess the efficacy of diffusion kurtosis imaging (DKI) in differentiating low-grade from high-grade tumors and evaluating the aggressiveness of bladder cancer. Methods From January 2017 to July 2017, 35 patients (28 males, 7 females; mean age 63 ± 9 years) diagnosed with bladder cancer underwent diffusion-weighted imaging (DWI) with two types of DKI protocols: (1) multi- b value ranging from 0 to 2000 s/mm 2 to obtain mean diffusivity/kurtosis (MD b /MK b ) and (2) the tensor method with 32 directions with 3 b values (0, 1000, and 2000s/mm 2 ) to obtain mean/axial/radial diffusivity (MD t /Da/Dr), mean/axial/radial kurtosis (MK t /Ka/Kr), and fractional anisotropy (FA) before radical cystectomy. Comparisons between the low- and high-grade groups, non-muscle-invasive bladder cancer (NMIBC), and muscle-invasive bladder cancer (MIBC) were performed with the areas under the receiver operating characteristic curves (AUCs). Results The MK t and Kr values were significantly ( p = 0.017 and p = 0.048) higher in patients with high-grade bladder tumors than in those with low-grade tumors. The MK t , Kr, and MK b values were significantly ( p = 0.022, p = 0.000, and p = 0.044, respectively) higher in patients with MIBC than in those with NMIBC, while no significant differences ( p > 0.05) were found in other values. The AUC of Kr (0.883) was the largest and was significantly higher than those of other metrics (all p