Chemotherapy response of pancreatic cancer by diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) in an orthotopic mouse model

摘要

Purpose To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIMDWI) to assess the chemotherapy response of pancreatic cancer in an orthotopic mouse model. Materials and methods Twenty-four BALB/C nu/nu mice in two groups (n = 12/group) with human pancreatic adenocarcinoma xenografts were dosed intravenously with saline (group 1) and gemcitabine (group 2). DWI with 3 b values (b = 50, 400 and 800 s/mm~2) and IVIM-DWI with multiple b values (b = 0, 25, 50, 80, 100, 300, 500, 800 s/mm~2) were performed on the day before and 1 and 10 days after the treatment. Regions of interest (ROI) were drawn and tumor ADC, Dslow, Dfast and fp values derived from the DWI and IVIM-DWI were compared between the two groups. At the day 28 after the treatment, the tumors were harvested for histologic analyses. Results The values of ADC and Dslow in the entire tumor region were significantly increased in gemcitabine-treated group in contrast to saline-untreated group at day 1 (1.88 ± 0.34 × 10-3 s/mm~2 vs 1.45 ± 0.16 × 10-3 s/mm~2, P = 0.028, and 1.74 ± 0.29 × 10-3 s/mm~2 vs 1.34 ± 0.26 × 10-3 s/mm~2, P =0.030), but Dfast and fp values were not significantly different. Immunohistochemical results showed that cell proliferation was significantly reduced (P < 0.001) and cell apoptosis (P < 0.001) significantly increased in gemcitabine group compared to saline group. MVD was not significantly different. Conclusion Both ADC value and Dslow value can be used as early imaging marker to assess the early chemotherapy response of pancreatic cancer.