Optimized analysis of blood flow and wall shear stress in the common carotid artery of rat model by phase-contrast MRI

Abstract

The present study systemically investigated the influence of gated/non-gated sequences, velocity encoding (VENC), and spatial resolution on blood flow, wall shear stress (WSS), and artery area evaluations when scanning the common carotid artery (CCA) in rats using phase-contrast magnetic resonance imaging (PC-MRI). We first tested whether or not non-gated PC-MRI was appropriate for evaluating blood flow and WSS in rats. For both gated and non-gated techniques, VENC values in the range of 60-120 cm/s with an interval of 10 cm/s were also tested. Second, we optimized the inplane resolution of PC-MRI for blood flow and WSS measurements. Results showed the usage of a gated instrument can provide more reproducible assessments, whereas VENC had an insignificant influence on all hemodynamic measurements (all P > 0.05). Lower resolutions, such as 0.63 mm, led to significant overestimations in blood flow and artery area quantifications and to an underestimation in WSS measurements (all P < 0.05). However, a higher resolution of 0.16 mm slightly increased measurement variation. As a tradeoff between accuracy and scan time, we propose a gated PC-MRI sequence with a VENC of 120 cm/s and a resolution of 0.21 mm to be used to extract hemodynamic information about rat CCA.Evaluating local flow profiles in vessels is a useful means to assess cardiovascular function and physiopathological conditions 1, 2 . It is expected to gain increased popularity in both clinical routine and pre-clinical studies. Doppler ultrasound (US) and phase-contrast (PC) MRI are the methods of choice for measuring flow-related parameters. Doppler US has the advantage of better temporal resolution to capture the peak systolic blood flow velocity. However, US measurement requires considerable technical ability, and it is therefore susceptible to the operator dependency 3 . By using phase shifts in moving spins to quantify the velocity information in flowing vessels, PC-MRI enables the noninvasive assessment of blood rheology 4, 5 . Because it is user-independent and allows straightforward flow quantification, PC-MRI has had an immediate impact on various fields.The major use of PC-MRI is to provide insight into the hemodynamic characteristics of blood flow in large vessels, such as cerebral vessels and carotid arteries. By measuring and integrating flow volume from the main feeding arteries of the brain, e.g., the left/right internal carotid arteries (ICA) and the vertebral artery (VA), one can quantify whole brain cerebral blood flow (CBF) 6, 7 . Wall shear stress (WSS) is the frictional force exerted on the endothelium of vessel walls by the circulation. Prior studies have shown that common carotid arteries (CCA) with a relatively low WSS are prone to developing atherosclerosis 8 and are associated with other cerebrovascular diseases 9 . PC-MRI covers a wide range of significant applications and the derived parameters allow comparisons between normal and pathological blood flow. Optimizing the scanning parameters for PC-MRI is therefore nontrivial, and ...

MRI‐based measurements of whole‐brain global cerebral blood flow: Comparison and validation at 1.5T and 3T

“…Therefore, in this study we performed four separate PC‐MRI scans in which each targeted one artery only, which guaranteed that the image slice would be perpendicular to the vessel orientation. Most notably, both lower and higher spatial resolutions have significant effects on flow measurement reliability . In this study we used an optimized spatial resolution of 0.5 mm, which is a compromise between accuracy, repeatability, and time consumption .…”

“…Most notably, both lower and higher spatial resolutions have significant effects on flow measurement reliability. 36 In this study we used an optimized spatial resolution of 0.5 mm, which is a compromise between accuracy, repeatability, and time consumption. 15 Consequently, all of these improved technological considerations enabled better reproducibility in the examinations conducted in the present study.…”

Wall Shear Stress in the Feeding Native Conduit Arteries of Superficial Arteriovenous Malformations of the Lower Face is a Reliable Marker of Disease Progression

“…Oshinski et al reported a spatial-average-time-average WSS of 8.0 ± 4.1 dynes/cm² in the CCA of healthy volunteers measured using MRA imaging [24]. Here, we decided to compute the WSS from Doppler ultrasound data and not from MRA data [25][26][27][28]. Our purpose was to establish a reliable method of WSS calculation based on a noninvasive, low-cost, easily accessible examination with little or no post-processing tasks.…”

Evaluation of Plaque Characteristics and Inflammation Using Magnetic Resonance Imaging

“…First, 2D techniques using triggered radial PC MRI [ 68 ] or Cartesian flow cine MRI [ 71 ] were developed to study WSS in the abdominal aorta of wild-type, ApoE −/− - and Low-density lipoprotein receptor-deficient (Ldlr −/− ) mice. WSS was also assessed in the carotids of mice with unstable plaques using Gd-enhanced 2D flow MRI [ 72 ] and in the carotids of rats [ 73 ]. Furthermore, 2D flow MRI was used to determine WSS at different locations along the vascular tree in arteries and veins in wild-type mice, revealing significant sex- and age-related differences of the WSS and flow values [ 74 ].…”