Error estimation for perfusion parameters obtained using the two-compartment exchange model in dynamic contrast-enhanced MRI: a simulation study

In theory, the application of the two-compartment exchange model (2CXM) to data from a dynamic contrast-enhanced (DCE) MRI exam allows the estimation of the plasma flow, plasma volume, extraction flow and extravascular-extracellular volume. The aim of this paper was to explore whether simulations based on the 2CXM could provide useful information on the trustworthiness of the results. The deviations from the input values of the haemodynamic quantities were estimated for a 'reference tissue' with a clear bi-phasic response and four 'limit tissues' with more challenging 2CXM fitting properties. The impact of the instrumental factors sampling step (T-s), acquisition window (T-acq) and contrast-to-noise ratio (CNR) was investigated. Each factor was varied separately, while keeping the other ones at a value above concern. Measurement guidelines to ensure that all deviations fell within a predefined range (+/- 20%) could not be derived, but simulations for fixed T-s and T-acq were found to provide a practical tool for studying the error behaviour to be expected from a given experimental set-up and for comparing measurement protocols. At the level of an individual DCE exam, a bootstrap version of the simulation approach was shown to lead to a useful estimate of the errors on the fitted parameters.