Determination of pharmacokinetic parameters in DCE MRI: Consequence of nonlinearity between contrast agent concentration and signal intensity.

Objectives: We sought to compare pharmacokinetic modeling of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data by assuming a linear and nonlinear relationship between signal intensity (SI) and contrast agent (CA) concentration.

Materials And Methods: Data sets were generated by computer-based simulation studies and DCE-MRI examination of 5 tumor-bearing mice using a 1.5 T MR-scanner. Two approaches were investigated: a linear and nonlinear relationship between SI and CA concentration before pharmacokinetic analysis. In a pharmacokinetic 2-compartment model, values of exchange rate constant kep and amplitude A were compared for both assumptions.

Results: In the linear approach, A was as much as 30% less for kep values between 1.0 and 5.0 min, whereas kep was as much as 60% greater, for kep between 0.2 and 5.0 min compared with the nonlinear one, as demonstrated in simulations and animal studies.

Conclusions: Nonlinearity between SI and CA concentration has to be considered for accurate parameter calculation in DCE-MRI studies.