Assessment of blood flow velocity and pulsatility in cerebral perforating arteries with 7-T quantitative flow MRI

• Published in: NMR in biomedicine Vol. 29; no. 9; pp. 1295 - 1304
• Main Authors: Bouvy, W. H., Geurts, L. J., Kuijf, H. J., Luijten, P. R., Kappelle, L. J., Biessels, G. J., Zwanenburg, J. J. M.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.09.2016; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Subjects: Adult; blood; Blood Flow Velocity - physiology; brain; Cerebral Angiography - methods; Cerebral Arteries - anatomy & histology; Cerebral Arteries - physiology; Cerebrovascular Circulation - physiology; Female; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Magnetic Fields; Magnetic Resonance Angiography - methods; Male; MRI; Pulsatile Flow - physiology; pulsatility; Qflow; Radiation Dosage; Reproducibility of Results; Sensitivity and Specificity; Special Issue; Special Issue s; velocity; pulsatility; Qflow; velocity; brain; MRI; blood
• ISSN: 0952-3480; 1099-1492; 1099-1492
• DOI: 10.1002/nbm.3306

Thus far, blood flow velocity measurements with MRI have only been feasible in large cerebral blood vessels. High‐field‐strength MRI may now permit velocity measurements in much smaller arteries. The aim of this proof of principle study was to measure the blood flow velocity and pulsatility of cerebral perforating arteries with 7‐T MRI. A two‐dimensional (2D), single‐slice quantitative flow (Qflow) sequence was used to measure blood flow velocities during the cardiac cycle in perforating arteries in the basal ganglia (BG) and semioval centre (CSO), from which a mean normalised pulsatility index (PI) per region was calculated (n = 6 human subjects, aged 23–29 years). The precision of the measurements was determined by repeated imaging and performance of a Bland–Altman analysis, and confounding effects of partial volume and noise on the measurements were simulated. The median number of arteries included was 14 in CSO and 19 in BG. In CSO, the average velocity per volunteer was in the range 0.5–1.0 cm/s and PI was 0.24–0.39. In BG, the average velocity was in the range 3.9–5.1 cm/s and PI was 0.51–0.62. Between repeated scans, the precision of the average, maximum and minimum velocity per vessel decreased with the size of the arteries, and was relatively low in CSO and BG compared with the M1 segment of the middle cerebral artery. The precision of PI per region was comparable with that of M1. The simulations proved that velocities can be measured in vessels with a diameter of more than 80 µm, but are underestimated as a result of partial volume effects, whilst pulsatility is overestimated. Blood flow velocity and pulsatility in cerebral perforating arteries have been measured directly in vivo for the first time, with moderate to good precision. This may be an interesting metric for the study of haemodynamic changes in aging and cerebral small vessel disease. © 2015 The Authors NMR in Biomedicine Published by John Wiley & Sons Ltd. A two‐dimensional, single‐slice, quantitative flow (Qflow) sequence on a 7‐T system yielded the first non‐invasive in vivo measurements of blood flow velocity and pulsatility in cerebral perforating arteries in the basal ganglia (BG) and semioval centre (CSO), with the middle cerebral artery as reference. The precision of the velocity measurements in individual vessels and the pulsatility index per anatomical region was determined using Bland–Altman analysis. This sequence allows the study of the haemodynamics of cerebral perforating arteries and their association with, for example, vascular lesions.