Virtual in vivo biopsy map of early prostate neoplasm in TRAMP mice by MRI

BACKGROUND The noninvasive, early detection of Prostate Intraepithelial Neoplasia (PIN), a precancerous neoplasia of the prostate, would be highly desirable. In our experiments, we used TRAMP mice to model PIN in the range of grade 1 through grade 4. METHODS Contrast enhanced pixel‐by‐pixel R1 mapping of the prostate was used to detect areas with the different prostate neoplasia grades. After anesthesia, Gd(ABE‐DTTA) was injected I.V. A series of MRI images with varying TI were then acquired to create R1 maps in a 2 mm transversal tomographic slice that included the prostate. After euthanasia and the excision of the prostate, a 2 mm slice, corresponding to the tomographic slice, was selected and prepared for histological analysis. The microscopic sections of this slice were scanned and analyzed along with the R1 maps. The R1 values were normalized to that measured in muscle tissue in each individual mouse to account for possible variations among the mice in contrast agent uptake (R1norm). The R1norm values and the histological grades in the corresponding areas were correlated. RESULTS A significant difference was found between the R1norm values measured in areas with grade 1–2 versus those observed in areas with grades 3–4. Also, a significant correlation was found between the area size of the ROIs differentiated by MRI, and those determined by histology. CONCLUSION This method has the potential for early noninvasive detection of developing prostate cancer. Prostate 69:449–458, 2009. © 2008 Wiley‐Liss, Inc.