Towards the Absolute Quantitation of DCE-MRI Pharmacokinetic Parameters: Addressing the Assumption of Constant Contrast Reagent Relaxivity and its Effect on Ktrans
Metzger G, Bernardo M, Thomasson D, Choyke P
Philips Medical Systems, University of Minnesota
The assumption of constant relaxivity in the analysis of dynamic contrast enhanced MRI data is demonstrated to lead to an overestimation of Ktrans, the endothelial transfer constant, which characterizes the wash-in of contrast from the blood plasma to the extrvascular-extracellular space. By generating relaxivity correction maps derived from patient dependent magnetization transfer studies, the need for assuming constant relaxivity can be avoided. Average Gd-DTPA concentrations decreased by 22.9% using previous phantom calibration results relating magnetization transfer ratios to changes in relaxivity. This resulted in a decrease in the estimated Ktrans values.