Differentiation of prostate cancer from normal prostate tissue in an animal model:: Conventional MRI and dynamic contrast-enhanced MRI

Purpose: To differentiate orthotopically implanted prostate cancer from normal prostate tissue using magnetic resonance imaging (MRI) and Gd-DTPA-BMA-enhanced dynamic MRI in the rat model. Material and Methods: Tumors were induced in 15 rats by orthotopic implantation of G subline Dunning rat prostatic tumor cells. MRI was performed 56 to 60 days after tumor cell implantation using T1-weighted spin-echo, T2-weighted turbo SE sequences, and a 2D FLASH sequence for the contrast medium based dynamic study. The interstitial leakage volume, normalized permeability and the permeability surface area product of tumor and healthy prostate were determined quantitatively using a pharmacokinetic model. The results were confirmed by histologic examination. Results: Axial T2-weighted TSE images depicted low-intensity areas suspicious for tumor in all 15 animals. The mean tumor volume was 46.5 mm3. In the dynamic study, the suspicious areas in all animals displayed faster and more pronounced signal enhancement than surrounding prostate tissue. The interstitial volume and the permeability surface area product of the tumors increased significantly by 420% (p < 0.001) and 424% (p < 0.001), respectively, compared to normal prostate tissue, while no significant difference was seen for normalized permeability alone. Conclusion: The results of the present study demonstrate that quantitative analysis of contrast-enhanced dynamic MRI data enables differentiation of small, slowly growing orthotopic prostate cancer from normal prostate tissue in the rat model.