Comparison of Partial Volume Effects in Arterial and Venous Contrast Curves in CT Brain Perfusion Imaging

Abstract

PurposeIn brain CT perfusion (CTP), the arterial contrast bolus is scaled to have the same area under the curve (AUC) as the venous outflow to correct for partial volume effects (PVE). This scaling is based on the assumption that large veins are unaffected by PVE. Measurement of the internal carotid artery (ICA), usually unaffected by PVE due to its large diameter, may avoid the need for partial volume correction. The aims of this work are to examine i) the assumptions behind PVE correction and ii) the potential of selecting the ICA obviating correction for PVE.MethodsThe AUC of the ICA and sagittal sinus were measured in CTP datasets from 52 patients. The AUCs were determined by i) using commercial CTP software based on a Gaussian curve-fitting to the time attenuation curve, and ii) by simple integration of the time attenuation curve over a time interval. In addition, frames acquired up to 3 minutes after first bolus passage were used to examine the ratio of arterial and venous enhancement. The impact of selecting the ICA without PVE correction was illustrated by reporting cerebral blood volume (CBV) measurements.ResultsIn 49 of 52 patients, the AUC of the ICA was significantly larger than that of the sagittal sinus (p = 0.017). Measured after the first pass bolus, contrast enhancement remained 50% higher in the ICA just after the first pass bolus, and 30% higher 3 minutes later. CBV measurements were significantly lowered when the ICA was used without PVE correction.ConclusionsContradicting the assumptions underlying PVE correction, contrast in the ICA was significantly higher than in the sagittal sinus, even 3 minutes after the first pass of the contrast bolus. PVE correction might lead to overestimation of CBV if the CBV is calculated using the AUC of the time attenuation curves.

Computed Tomography Perfusion is a Useful Adjunct to Computed Tomography Angiography in the Diagnosis of Brain Death

“…Riordan et al. showed that ICA in patients with normal cerebral circulation is unaffected by PVE [15]; however, in our study mean contrast enhancement in ICA was relatively low −346 HU; therefore, PVE could not be corrected sufficiently. This might result in overestimation of perfusion parameters.…”

Extraction of a vascular function for a fully automated dynamic contrast‐enhanced magnetic resonance brain image processing pipeline

“…In brain imaging, arteries typically are small, making VF selection challenging with respect to avoiding signal contributions from the surrounding non‐vascular tissue. This problem, known as the partial volume effect (PVE), can result in the area under the VF curve being underestimated, possibly compromising the estimation of hemodynamic parameters 9–11 . Cerebral venous structures have the advantage of tending to be larger thus reducing the impact of PVE.…”

“…This problem, known as the partial volume effect (PVE), can result in the area under the VF curve being underestimated, possibly compromising the estimation of hemodynamic parameters. [9][10][11] Cerebral venous structures have the advantage of tending to be larger thus reducing the impact of PVE. In addition, because the blood flow velocity is higher in arteries than in veins, the observed arterial signal intensity can decrease due to signal dephasing.…”