User-defined vascular input function curves: influence on mean perfusion parameter values and signal-to-noise ratio.

The authors reviewed 40 computed tomographic (CT) perfusion studies to determine the effect of arterial and venous input function properties on perfusion parameter values and tissue signal-to-noise ratio (SNR). A 10-subject subset was analyzed to evaluate the effect of varying venous region of interest (ROI) locations. Venous peak enhancement correlated significantly with mean tissue cerebral blood flow (CBF) and cerebral blood volume (CBV); venous and arterial peak enhancement correlated significantly with SNR of perfusion maps. Different ROI locations within the same vein resulted in significantly different CBV and CBF values. Perfusion map parameters are related to peak enhancement within user-selected ROIs. Optimal ROI selection should limit variability and increase quality of CT perfusion images.