Middle cerebral artery pressure laterality in patients with symptomatic ICA stenosis

Abstract

An internal carotid artery (ICA) stenosis can potentially decrease the perfusion pressure to the brain. In this study, computational fluid dynamics (CFD) was used to study if there was a hemispheric pressure laterality between the contra- and ipsilateral middle cerebral artery (MCA) in patients with a symptomatic ICA stenosis. We further investigated if this MCA pressure laterality (ΔPMCA) was related to the hemispheric flow laterality (ΔQ) in the anterior circulation, i.e., ICA, proximal MCA and the proximal anterior cerebral artery (ACA). Twenty-eight patients (73±6 years, range 59–80 years, 21 men) with symptomatic ICA stenosis were included. Flow rates were measured using 4D flow MRI data (PC-VIPR) and vessel geometries were obtained from computed tomography angiography. The ΔPMCA was calculated from CFD, where patient-specific flow rates were applied at all input- and output boundaries. The ΔPMCA between the contra- and ipsilateral side was 6.4±8.3 mmHg (p<0.001) (median 3.9 mmHg, range -1.3 to 31.9 mmHg). There was a linear correlation between the ΔPMCA and ΔQICA (r = 0.85, p<0.001) and ΔQACA (r = 0.71, p<0.001), respectively. The correlation to ΔQMCA was weaker (r = 0.47, p = 0.011). In conclusion, the MCA pressure laterality obtained with CFD, is a promising physiological biomarker that can grade the hemodynamic disturbance in patients with a symptomatic ICA stenosis.

Patient-specific brain arteries molded as a flexible phantom model using 3D printed water-soluble resin

“…To recreate the cerebral arteries of a patient as a full-scale flow device in PDMS, we used CTA data from a previous study. This study was conducted on symptomatic carotid stenosis patients with resulting ischemic stroke or transient ischemic attacks 28 . From the CTA images, we segmented the anterior part of the circle of Wills, or more specifically, the primary collateral pathway in the cerebral circulation (see Methods section).…”

“…It also enables flow imaging techniques that require refraction index matching, like particle image velocimetry 29 . This, combined with syringe/peristaltic pumps and integrated pressure sensors, make a complete setup for in vitro experiments of patient-specific arteries, which could be used to verify CFD simulations 28 . In this case, flow conditions could also be advanced beyond what is possible to observe in clinical settings, simulating effects on perfusion pressure of an increased degree of stenosis and helping to find stress points 30 .…”

“…Before segmentation, we used an edge-preserving bilateral filter to reduce background noise from surrounding tissue. We only analysed the anterior part of the circle of Willis, as motivated in the previous study 28 . A coarse segmentation of the cerebral arterial tree was extracted by a threshold filter, from which the software specific gradient-based filter 'Local surface correction' was used for wall detection.…”

“…This process consists of (a) creating a 3D model of the circle of Willis of a patient using CTA scanning techniques, (b) slicing and 3D printing a sacrificial mold using water-soluble resin, (c) casting PDMS around the scaffold before dissolving it, and (d) evaluating the flow device using MRI. In panel (a), we illustrate the internal carotid, anterior and middle cerebral arteries and their position in the human brain (left), as well as show a maximum intensity projection from the 4D flow MRI angiogram of the patient (right)28 , both as axial views. Panel (b) shows overlapping images of the arterial network after it has completed slicing (upper left) and printing (lower right), along with the temporary support structure.…”

4D flow MRI hemodynamic biomarkers for cerebrovascular diseases

“…Another alternative to calculate the pressure drop is to use the Navier-Stokes equations in order to translate a velocity field into a pressure field [40,41]. With computed tomography angiography and 4D flow MRI measurements as input, a computerized approach (computational fluid dynamics) can be used to generate maps of the pressure variations within the visible cerebral arterial tree [42].…”