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

Heilmann M, Kiessling F, Enderlin M, Schad LR

Department of Medical Physics in Radiology, German Cancer Research Center (Deutsches Krebsforschungszentrum), Heidelberg, Germany. melanie.heilmann@curie.u-psud.fr

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.

Published 9 June 2006 in Invest Radiol, 41(6): 536-43.
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