The Performance of MR Cytometry Imaging in Differentiating High- and Low-Grade Bladder Cancer

Accurate preoperative grading of bladder cancer is important for determining treatment and prognosis.

To investigate the diagnostic efficacy of MR cytometry imaging in differentiating high- and low-grade bladder cancer.

Prospective.

Sixty-participants (male: 27, mean age: 65 years) with pathologically confirmed bladder cancer (37 high-grade, 23 low-grade).

3.0 T, pulsed gradient spin-echo (PGSE) and oscillating gradient spin-echo (OGSE, 20 and 40 Hz) diffusion-weighted imaging.

All tumors were manually delineated independently by two radiologists, and inter-observer agreement was assessed using intraclass correlation coefficient (ICC). Time-dependent apparent diffusion coefficients (ADCs), including OGSE at 20 HZ (ADC_20HZ), OGSE at 40 HZ (ADC_40HZ), and PGSE (ADC_PGSE), and MR cytometry-derived microstructural parameters (cell diameter [ $d$ ], intracellular volume fraction [ $v_{\text{in}}$ ], extracellular diffusivity [ $D_{\mathrm{ex}}$ ], and cellularity [ $\rho$ ]) were calculated. Histopathological examination of surgical specimens served as the reference standard for tumor grading.

Mann-Whitney U test was used for group comparisons. Diagnostic performance was evaluated by logistic regression and receiver operating characteristic (ROC) analysis; area under the ROC curve (AUCs) was compared with the DeLong test. Statistical significance was set at p < 0.05.

High-grade tumors showed significantly higher $v_{\text{in}}$ (median: 0.31 vs. 0.20), $\rho$ (1.97 vs. 1.33 × 10^-2 μm^-1), and lower ADCs than low-grade tumors while $d$ (p = 0.85, 95% confidence interval [CI] of mean difference: -0.822 to -0.820) and $D_{\mathrm{ex}}$ (p = 0.053, 95% CI of mean difference: 0.025 to 0.352) were not different. $v_{\text{in}}$ demonstrated the highest AUC (0.89; 95% CI: 0.80-0.97) among single parameters, and the combined model of $v_{\text{in}}$ , $D_{\mathrm{ex}}$ , and ADC_PGSE achieved the highest diagnostic accuracy (AUC = 0.92; 95% CI: 0.86-0.99).

MR cytometry noninvasively differentiates high- from low-grade bladder cancer. $v_{\text{in}}$ showed good discriminatory performance, and combining $v_{\text{in}}$ , $D_{\mathrm{ex}}$ , and ADC_PGSE further improves preoperative assessment.

1.

Stage 3: Diagnostic Thinking.