Velocity and Pulsatility Measures in the Perforating Arteries of the Basal Ganglia at 3T MRI in Reference to 7T MRI

Abstract

Cerebral perforating artery flow velocity and pulsatility can be measured using 7 tesla (T) MRI. Enabling these flow metrics on more widely available 3T systems would make them more employable. It is currently unknown whether these measurements can be performed at 3T MRI due to the lower signal-to-noise ratio (SNR). Therefore, the aim of this study is to investigate if flow velocity and pulsatility in the perforating arteries of the basal ganglia (BG) can be measured at 3T MRI and assess the agreement with 7T MRI measurements as reference. Twenty-nine subjects were included, of which 14 patients with aortic coarctation [median age 29 years (21–72)] and 15 controls [median age 27 years (22–64)]. Using a cardiac-gated 2D phase-contrast MRI sequence BG perforating arteries were imaged at 3T and 7T MRI and perforating artery density (Ndensity, #/cm2), flow velocity (Vmean, cm/s) and pulsatility index (PI) were determined. Agreement between scanner modalities was assessed using correlation and difference plots with linear regression. A p-value ≤ 0.05 indicated statistical significance. It was shown that perforating artery flow velocity and pulsatility can be measured at 3T MRI (Ndensity = 0.21 ± 0.11; Vmean = 6.04 ± 1.27; PI = 0.49 ± 0.19), although values differed from 7T MRI measurements (Ndensity = 0.95 ± 0.21; Vmean = 3.89 ± 0.56; PI = 0.28 ± 0.08). The number of detected arteries was lower at 3T (5 ± 3) than 7T MRI (24 ± 6), indicating that 3T MRI is on average a factor 4.8 less sensitive to detect cerebral perforating arteries. Comparison with 7T MRI as reference showed some agreement in Ndensity, but little to no agreement for Vmean and PI. Equalizing the modalities’ sensitivity by comparing the detected arteries on 7T MRI with the highest velocity with all vessels detected on 3T MRI, showed some improvement in agreement for PI, but not for Vmean. This study shows that it is possible to measure cerebral perforating artery flow velocity and pulsatility at 3T MRI, although an approximately fivefold sample size is needed at 3T relative to 7T MRI for a given effect size, and the measurements should be performed with equal scanner field strength and protocol.

Imaging of the pial arterial vasculature of the human brain in vivo using high-resolution 7T time-of-flight angiography

“…The advantages of imaging the pial arterial vasculature using TOF-MRA without an exogenous contrast agent lie in its non-invasiveness and the potential to combine these data with various other structural and functional image contrasts provided by MRI. One common application is to acquire a velocity-encoded contrast such as phase-contrast MRA ( Arts et al, 2021 ; Bouvy et al, 2016 ). Another interesting approach utilizes the inherent TOF contrast in magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) images acquired at ultra-high field that simultaneously acquires vasculature and structural data, albeit at lower achievable resolution and lower FRE compared to the TOF-MRA data in our study ( Choi et al, 2020 ).…”

Imaging of the pial arterial vasculature of the human brain in vivo using high-resolution 7T time-of-flight angiography

“…The advantages of imaging the pial arterial vasculature using TOF-MRA without an exogenous contrast agent lie in its non-invasiveness and the potential to combine these data with various other structural and functional image contrasts provided by MRI. One common application is to acquire a velocity-encoded contrast such as phase-contrast MRA (Arts et al, 2021; Bouvy et al, 2016). Another interesting approach utilises the inherent time-of-flight contrast in magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) images acquired at ultra-high field that simultaneously acquires vasculature and structural data, albeit at lower achievable resolution and lower FRE compared to the TOF-MRA data in our study (Choi et al, 2020).…”

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

“…All participants gave informed consent for both the first study and using their available data for subsequent research. The current study is a post hoc analysis on a previous 7 T MRI study, 13 which aimed at visualizing the perforating arteries in cSVD patients, for which 7 T MRI indisputably has added value over 3 T MRI 15 . They evaluated pulsatility in penetrating intracranial arteries in 21 patients with cSVD with a lacunar infarction or a spontaneous dICH, attributed to cSVD according to clinical guidelines 16 and 18 age‐ and sex‐matched controls.…”

“…The current study is a post hoc analysis on a previous 7 T MRI study, 13 which aimed at visualizing the perforating arteries in cSVD patients, for which 7 T MRI indisputably has added value over 3 T MRI. 15 They evaluated pulsatility in penetrating intracranial arteries in 21 patients with cSVD with a lacunar infarction or a spontaneous dICH, attributed to cSVD according to clinical guidelines 16 and 18 age-and sex-matched controls. The combination of patients with lacunar infarction and dICH into a single group representative for cSVD for the current study was justified by performing a subgroup analysis, which did not show differences in velocity pulsatility, mean velocity, and arterial distensibility between the subgroups (Supplementary Table S1).…”