Simulation studies of impulse response functions for DCEMRI: Comparing a new mathematical model with a single exponential decay function in the two-compartment model

Introduction: Dynamic contrast enhanced MRI (DCEMRI) involves measurement and analysis of contrast media uptake and washout following bolus injection. These studies are critical for detecting and evaluating tumor vasculature and changes during therapy. However, there is no accepted method for analyzing contrast media uptake and washout. The two-compartment model (TCM) [1], though widely used, is not ideal for tumors because of their microscopically heterogeneous anatomy. The TCM treats the contrast concentration curve C(t) as the result of a convolution between the arterial input function (AIF) and the impulse response function (IRF) with a single exponential decay. In this research we introduce a bi-exponentially decaying IRF; results of fitted DCEMRI data were compared with the TCM. Material and Methods: For a causal, linear time-invariant system, C(t) can be considered as convolution between the IRF and the AIF, i.e., C(t) = AIF⊗IRF. The IRF in the TCM has the form: ) v K t exp( K e trans trans ⋅ − , where K(min ) is the volume transfer constant between blood plasma and extravascular, extracellular space (EES), and ve is the volume of the EES per unit volume of tissue. Our new IRF was developed based on the results of a recursive