摘要
Purpose To quantify the differential plasma flow- (F -) and permeability surface area product per unit mass of tissue- (PS-) weighting in forward volumetric transfer constant (K ) estimates by using a low molecular (Gd-DTPA) versus high molecular (Gadomer) weight contrast agent in dynamic contrast enhanced (DCE) MRI. Materials and methods DCE MRI was performed using a 7T animal scanner in 14 C57BL/6J mice syngeneic for TRAMP tumors, by administering Gd-DTPA (0.9 kD) in eight mice and Gadomer (35 kD) in the remainder. The acquisition time was 10 min with a sampling rate of one image every 2 s. Pharmacokinetic modeling was performed to obtain K by using Extended Tofts model (ETM). In addition, the adiabatic approximation to the tissue homogeneity (AATH) model was employed to obtain the relative contributions of F and PS. Results The K values derived from DCE-MRI with Gd-DTPA showed significant correlations with both PS (r = 0.64, p = 0.009) and F (r = 0.57, p = 0.016), whereas those with Gadomer were found only significantly correlated with PS (r = 0.96, p = 0.0003) but not with F (r = 0.34, p = 0.111). A voxel-based analysis showed that K approximated PS (< 30% difference) in 78.3% of perfused tumor volume for Gadomer, but only 37.3% for Gd-DTPA. Conclusions The differential contributions of F and PS in estimating K values vary with the molecular weight of the contrast agent used. The macromolecular contrast agent resulted in K values that were much less dependent on flow. These findings support the use of macromolecular contrast agents for estimating tumor vessel permeability with DCE-MRI.