Quantification of DCE-MRI: Pharmacokinetic parameter ratio between TOI and RR in reference region model

Abstract

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is performed by obtaining sequential MRI images, before, during, and after the injection of a contrast agent. T(1) weighted MR imaging is used to observe the exchange of contrast agent between the vascular space and extravascular extracellular space (EES), providing information about blood volume and microvascular permeability. Signal intensity is obtained from the sequence of T(1) weighted images and then used to estimate the kinetic parameters in the equation derived from the pharmacokinetic model. In a DCE-MRI study, an accurate knowledge of the arterial input function (AIF) is very important to estimate the kinetic parameters. However, the AIF is usually unknown and it remains very difficult to obtain such information noninvasively. Here we use a reference region model that does not require the information about AIF. Though, this model usually needs literature value for the reference region. In this abstract, without knowledge of AIF, K(trans) in the tissue of interest (TOI) is compared with K(trans) in a reference region (RR). This was done by calculating the ratio K(R) between K(trans) in TOI and RR and the ratio V(R) between v(e) in TOI and RR while the K(trans,RR) was assigned a value ranging from 0.1 to 1.0. It is shown from both simulation and in vivo data set that this ratio is independent of K(trans,RR), implying we are no longer required to get the information about literature value for the reference region.