The dynamic changes in quantitative parameters of diffusion-weighted imaging at different b-values in a prostate cancer mouse model and their correlation with histopathology parameters

The aim of this study was to evaluate the dynamic variations in the quantitative parameters of diffusion-weighted imaging (DWI) at different b-value combinations in a prostate cancer (PCa) mouse model for noninvasive monitoring of histopathological changes. Twenty-five male C57BL/6J mice were randomly allocated into a control group (n=5) or an experimental group (n=20). The experimental groups were used to establish the PCa model. On days 9, 12, 15, and 18 post-modeling, 5 mice were randomly selected for MRI, including T1WI, T2WI, T2WI SPIR, and DWI. The b-values were set at 0, 500, 1000, 1500, and 2000 s/mm2. Apparent diffusion coefficient (ADC) and exponential apparent diffusion coefficient (EADC) values from different b-value combinations were measured. Post-MRI, tumors were excised for histopathological analysis. DWI quantitative parameters, tumor nuclear fraction, and Ki-67 area fraction were compared on different days, along with correlation analysis. ADC values gradually decreased as tumor progressed, whereas EADC values gradually increased. Tumor nuclear fraction increased over time. Ki-67 increased first and then decreased. Tumor nuclear fraction was negatively correlated with the ADC value and positively correlated with the EADC value. The Ki-67 was positively correlated with the ADC value and negatively correlated with the EADC value. ADC values at b=1000, 1500 s/mm2 and the EADC values at b=0, 500 s/mm2 demonstrated the strongest correlations with the tumor nuclear fraction; the ADC and EADC values at b=500, 1000 s/mm2 were more strongly correlated with Ki-67, being potential noninvasive imaging biomarkers for monitoring changes in tumor histopathology.