Dynamic contrast-enhanced QSM for perfusion imaging: a systematic comparison of Δ R 2*- and QSM-based contrast agent concentration time curves in blood and tissue

Objective In dynamic susceptibility contrast MRI (DSC-MRI), an arterial input function (AIF) is required to quantify perfusion. However, estimation of the concentration of contrast agent (CA) from magnitude MRI signal data is challenging. A reasonable alternative would be to quantify CA concentration using quantitative susceptibility mapping (QSM), as the CA alters the magnetic susceptibility in proportion to its concentration. Material and methods AIFs with reasonable appearance, selected on the basis of conventional criteria related to timing, shape, and peak concentration, were registered from both Δ R 2* and QSM images and mutually compared by visual inspection. Both Δ R 2*- and QSM-based AIFs were used for perfusion calculations based on tissue concentration data from Δ R 2*as well as QSM images. Results AIFs based on Δ R 2* and QSM data showed very similar shapes and the estimated cerebral blood flow values and mean transit times were similar. Analysis of corresponding Δ R 2* versus QSM-based concentration estimates yielded a transverse relaxivity estimate of 89 s −1 mM −1 , for voxels identified as useful AIF candidate in Δ R 2* images according to the conventional criteria. Discussion Interestingly, arterial concentration time curves based on Δ R 2* versus QSM data, for a standard DSC-MRI experiment, were generally very similar in shape, and the relaxivity obtained in voxels representing blood was similar to tissue relaxivity obtained in previous studies.