Measurement of vascular water transport in human subjects using time-resolved pulsed arterial spin labelling

• Published in: NMR in biomedicine Vol. 28; no. 8; pp. 1059 - 1068
• Main Authors: Bibic, Adnan, Knutsson, Linda, Schmidt, Anders, Henningsson, Erik, Månsson, Sven, Abul-Kasim, Kasim, Åkeson, Jonas, Gunther, Matthias, Ståhlberg, Freddy, Wirestam, Ronnie
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.08.2015; Wiley Subscription Services, Inc
• Subjects: Adult; Annan fysik; arterial spin labelling; Biological Transport, Active - physiology; blood-brain barrier; Body Water - metabolism; Capillaries - physiology; Capillary Permeability - physiology; capillary transfer time; Cerebrovascular Circulation - physiology; Clinical Medicine; Computer Simulation; Female; Fysik; Humans; Image Interpretation, Computer-Assisted - methods; Klinisk medicin; Langevin modelling; Magnetic Resonance Angiography - methods; Male; Medical and Health Sciences; Medicin och hälsovetenskap; microvasculature; Models, Cardiovascular; Natural Sciences; Naturvetenskap; Other Physics Topics; Physical Sciences; Radiologi och bildbehandling; Radiology and Medical Imaging; Radiology, Nuclear Medicine and Medical Imaging; Reproducibility of Results; Sensitivity and Specificity; Spin Labels; blood-brain barrier; arterial spin labelling; capillary transfer time; Langevin modelling; microvasculature
• ISSN: 0952-3480; 1099-1492; 1099-1492
• DOI: 10.1002/nbm.3344

Most approaches to arterial spin labelling (ASL) data analysis aim to provide a quantitative measure of the cerebral blood flow (CBF). This study, however, focuses on the measurement of the transfer time of blood water through the capillaries to the parenchyma (referred to as the capillary transfer time, CTT) as an alternative parameter to characterise the haemodynamics of the system. The method employed is based on a non‐compartmental model, and no measurements need to be added to a common time‐resolved ASL experiment. Brownian motion of labelled spins in a potential was described by a one‐dimensional general Langevin equation as the starting point, and as a Fokker–Planck differential equation for the averaged distribution of labelled spins at the end point, which takes into account the effects of flow and dispersion of labelled water by the pseudorandom nature of the microvasculature and the transcapillary permeability. Multi‐inversion time (multi‐TI) ASL data were acquired in 14 healthy subjects on two occasions in a test–retest design, using a pulsed ASL sequence and three‐dimensional gradient and spin echo (3D‐GRASE) readout. Based on an error analysis to predict the size of a region of interest (ROI) required to obtain reasonably precise parameter estimates, data were analysed in two relatively large ROIs, i.e. the occipital lobe (OC) and the insular cortex (IC). The average values of CTT in OC were 260 ± 60 ms in the first experiment and 270 ± 60 ms in the second experiment. The corresponding IC values were 460 ± 130 ms and 420 ± 139 ms, respectively. Information related to the water transfer time may be important for diagnostics and follow‐up of cerebral conditions or diseases characterised by a disrupted blood–brain barrier or disturbed capillary blood flow. Copyright © 2015 John Wiley & Sons, Ltd. In the applied model, the Brownian motion of labelled spins was described by a one‐dimensional general Langevin equation as the starting point, and as a Fokker–Planck differential equation for the averaged distribution of labelled spins at the end point. The model allows the measurement of the transfer time of the labelled water as a result of bulk flow in the large vessels and dispersion caused by the pseudo‐random nature of the microvasculature and transcapillary permeability.