Quantitative dynamic contrast-enhanced MRI in tumor-bearing rats and mice with inversion recovery TrueFISP and two contrast agents at 4.7 T.

Purpose To characterize tumor vascularization by dynamic-contrast enhanced (DCE) MRI using low and medium molecular weight paramagnetic contrast agents (CA) and inversion recovery (IR) true fast imaging with steady state precession (TrueFISP) in tumor-bearing rats and mice. Materials and Methods T1 mapping was performed using IR True FISP in phantoms and in vivo at 4.7 T and validated with a segmented IR gradient-echo (IR GE) method. CA concentration in DCE-MRI studies in vivo was calculated from time-series T1 maps using the CAs GdDOTA and P792 (low and medium molecular weight, respectively). Standard vascular input functions (VIFs) were measured in the jugular veins and were used for modeling of the CA kinetics with a two-compartment model. In rat breast tumors, vascular permeability (transfer constant Ktrans), fractional plasma volume vp, and fractional leakage space ve were quantified and parametric maps were generated. Results The IR TrueFISP T1 was slightly underestimated in phantoms and overestimated in vivo (10%) with respect to IR GE. VIFs showed only small interindividual variation. Mean Ktrans values were 0.062 ± 0.017 min–1 for GdDOTA and 0.015 ± 0.005 min–1 for P792 (N = 12). Mean ve and vp values were 0.15 ± 0.04 (0.09 ± 0.03) and 0.04 ± 0.01 (0.03 ± 0.01) for GdDOTA (P792). Conclusion DCE-MRI with IR TrueFISP provided absolute values for Ktrans, vp, and ve. Direct comparison between GdDOTA and P792 revealed significant differences in the VIF, model-fit-quality, permeability, leakage space, and plasma volume. The larger molecular weight CA P792 appears to be better for measuring tumor vascular parameters. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.