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.
Highlights
Cerebral perforating arteries are small branches of the main cerebral arteries that supply blood to the deep gray and white matter brain regions
This study shows that perforating artery flow velocity and pulsatility can be measured at 3T magnetic resonance imaging (MRI) at the level of the basal ganglia (BG), though the values found on 3T MRI differed from those obtained at 7T MRI
When equalizing the modalities’ sensitivity by comparing the detected vessels on 7T MRI with the highest velocities with all vessels detected on 3T MRI, we find an improved agreement for pulsatility index (PI), but not for Vmean
Summary
Cerebral perforating arteries are small branches of the main cerebral arteries that supply blood to the deep gray and white matter brain regions. Dysfunction of these perforating arteries plays a major role in cerebral small vessel disease (Wardlaw et al, 2013, 2019). These perforating arteries can be imaged using 7 tesla (T) magnetic resonance imaging (MRI) with a retrospectively gated 2D phase-contrast sequence (Guralnik et al, 1994; Bouvy et al, 2016; Geurts L. et al, 2018). As a region of interest we chose the level of the basal ganglia (BG), as perforating arteries in this region are relatively large (up to 1 mm in diameter), which increases the likelihood of being detected with 3T MRI
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