Blood–brain barrier water exchange measurements using contrast-enhanced ASL

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A technique for quantifying regional blood–brain barrier (BBB) water exchange rates using contrast-enhanced arterial spin labelling (CE-ASL) is presented and evaluated in simulations and in vivo. The two-compartment ASL model describes the water exchange rate from blood to tissue, (Formula presented.), but to estimate (Formula presented.) in practice it is necessary to separate the intra- and extravascular signals. This is challenging in standard ASL data owing to the small difference in (Formula presented.) values. Here, a gadolinium-based contrast agent is used to increase this (Formula presented.) difference and enable the signal components to be disentangled. The optimal post-contrast blood (Formula presented.) ((Formula presented.)) at 3 T was determined in a sensitivity analysis, and the accuracy and precision of the method quantified using Monte Carlo simulations. Proof-of-concept data were acquired in six healthy volunteers (five female, age range 24–46 years). The sensitivity analysis identified the optimal (Formula presented.) at 3 T as 0.8 s. Simulations showed that (Formula presented.) could be estimated in individual cortical regions with a relative error (Formula presented.) % and coefficient of variation (Formula presented.) %; however, a high dependence on blood (Formula presented.) was also observed. In volunteer data, mean parameter values in grey matter were: arterial transit time (Formula presented.) s, cerebral blood flow (Formula presented.) mL blood/min/100 mL tissue and water exchange rate (Formula presented.) s−1. CE-ASL can provide regional BBB water exchange rate estimates; however, the clinical utility of the technique is dependent on the achievable accuracy of measured (Formula presented.) values.

Original languageEnglish
Article numbere5009
JournalNMR in Biomedicine
Issue number11
Early online date4 Sept 2023
Publication statusPublished - 1 Nov 2023


  • arterial spin labelling
  • blood–brain barrier
  • gadolinium-based contrast agent
  • permeability
  • water exchange


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