Blood Flow Velocity Pulsatility and Arterial Diameter Pulsatility Measurements of the Intracranial Arteries Using 4D PC-MRI

Abstract

Abstract4D phase contrast magnetic resonance imaging (PC-MRI) allows for the visualization and quantification of the cerebral blood flow. A drawback of software that is used to quantify the cerebral blood flow is that it oftentimes assumes a static arterial luminal area over the cardiac cycle. Quantifying the lumen area pulsatility index (aPI), i.e. the change in lumen area due to an increase in distending pressure over the cardiac cycle, can provide insight in the stiffness of the arteries. Arterial stiffness has received increased attention as a predictor in the development of cerebrovascular disease. In this study, we introduce software that allows for measurement of the aPI as well as the blood flow velocity pulsatility index (vPI) from 4D PC-MRI. The internal carotid arteries of seven volunteers were imaged using 7 T MRI. The aPI and vPI measurements from 4D PC-MRI were validated against measurements from 2D PC-MRI at two levels of the internal carotid arteries (C3 and C7). The aPI and vPI computed from 4D PC-MRI were comparable to those measured from 2D PC-MRI (aPI: mean difference: 0.03 (limits of agreement: −0.14 – 0.23); vPI: 0.03 (−0.17–0.23)). The measured blood flow rate for the C3 and C7 segments was similar, indicating that our proposed software correctly captures the variation in arterial lumen area and blood flow velocity that exists along the distal end of the carotid artery. Our software may potentially aid in identifying changes in arterial stiffness of the intracranial arteries caused by pathological changes to the vessel wall.

Does the Internal Carotid Artery Attenuate Blood‐Flow Pulsatility in Small Vessel Disease? A 7 T 4D‐Flow MRI Study

“…We believe that in practice this effect is very limited for the following reasons. First, we obtain similar observations for 2D and 4D phase‐contrast acquisitions, while both acquisitions are sensitive to different inflow effects 9,34 . Second, we see very consistent variability in area pulsatility along the carotid canal (including lower pulsatility inside the bony carotid canal), which is inversely proportional to the velocity pulsatility.…”

“…First, we obtain similar observations for 2D and 4D phasecontrast acquisitions, while both acquisitions are sensitive to different inflow effects. 9,34 Second, we see very consistent variability in area pulsatility along the carotid canal (including lower pulsatility inside the bony carotid canal), which is inversely proportional to the velocity pulsatility. This is consistent with preservation of flow volume (area  velocity), but not with velocity-induced signal fluctuations.…”

4D flow MRI hemodynamic biomarkers for cerebrovascular diseases

“…4D Flow MRI has been used to describe age‐related increases in pulsatility in distal cerebral vessels in healthy subjects [36] and additional increases in subjects with cerebrovascular disease [49]. Another postprocessing technique that may be used in this context is 4D flow MRI‐based compliance measurements, relating the cyclic distention of cerebral arteries, measured from either the flow rate waveform [26] or from measuring the vessel wall movements directly [50], to the cardiac pulse pressure.…”

Measuring global cerebrovascular pulsatility transmission using 4D flow MRI

“…Pulsatility is typically measured via the pulsatility index ( ) proposed by Gosling et al 17 based on the measured flow traces (standard), the area traces 18 or the velocity traces 19 over the cardiac cycle. Velocity-based is the most popular measurement due to its ability to be measured with conventional transcranial doppler (TCD), as well as 2D- and 3D- phase-contrast MRI (2D-PC and 4D flow, respectively).…”

“…Damping was first identified in the carotid siphon 20 and atlas slope 21 , before being studied in the circle of Willis by Zarrinkoob et al 22 , who analysed damping with age using 2D-PC. Following Zarrinkoob et al, several research works have been produced studying in the circle of Willis using TCD, 2D-PC and 4D flow 4 , 7 , 15 , 16 , 18 , 19 , 23 . What we highlight based on previous research is that damping has always been measured between two vessel locations, for example, a measurement in the internal carotid artery (ICA) or basilar artery (BA), and a measurement in a distal middle, anterior, or posterior cerebral artery (MCA, ACA, PCA, respectively).…”