A comparison of K-trans measurements obtained with conventional and first pass pharmacokinetic models in human gliomas

Purpose: To compare in a group of patients with cerebral gliomas the estimates of K-trans between a conventionally established pharmacokinetic model and a recently developed first pass method. Materials and Methods: Glioma patients (23) were studied using T-1-weighted dynamic contrast-enhanced magnetic resonance imaging (MRI), and two alternative pharmacokinetic models were used for analysis to derive the volume transfer constant K-trans. These were a modified version of the established model (yielding K-TK) and a recently published method based on first pass leakage profile (FP) of contrast bolus (yielding K-fp). Results: We found a strong correlation between intra-tumoral median K-TK and K-fp (rho = 0.650, P <0.01), but the values from the conventional model were consistently and significantly higher (mean of inter- tumoral K-fp and K-TK medians were 0.018 minute(-1) and 0.284 minute(-1), respectively, P <0.001). The spatial distribution of K-TK and K-fp showed poor correlation in the presence of large vascular structures and good correlation elsewhere. Conclusion: K-TK and K-fp produce similar biologic information within voxels not dominated by vascular tissue. The FP method avoids erroneous overestimation of K-trans in areas of significant intravascular contrast. Findings are in keeping with the predictions of previous mathematical simulations.