Removing the effects of CSF partial voluming on fitted CBF and arterial transit times using FAIR, a pulsed arterial spin labelling technique

• Published in: Magma (New York, N.Y.) Vol. 19; no. 3; pp. 115 - 123
• Main Authors: Wiersma, J, Deichmann, R, Ordidge, R, Turner, R
• Format: Journal Article
• Language: English
• Published: Germany Springer Nature B.V 01.08.2006
• Subjects: Blood Flow Velocity - physiology; Brain - anatomy & histology; Brain - blood supply; Brain - physiology; Cerebral Arteries - anatomy & histology; Cerebral Arteries - physiology; Cerebrospinal Fluid; Cerebrovascular Circulation - physiology; Humans; Image Enhancement - methods; Image Interpretation, Computer-Assisted - methods; Magnetic Resonance Imaging - instrumentation; Magnetic Resonance Imaging - methods; Phantoms, Imaging; Spin Labels; Theoretical analysis
• ISSN: 0968-5243; 1352-8661
• DOI: 10.1007/s10334-006-0034-2

FAIR, an arterial spin labelling technique, provides non-invasive, quantitative CBF values and arterial transit times deltat. This paper focuses on the negative impact of CSF partial voluming on FAIR results. To understand and solve this problem, we performed a theoretical analysis and a range of simulations. We then acquired FAIR data from a volunteer to illustrate our findings. We found that the determinant effect of CSF is a delayed zero-crossing during inversion recovery. The subtraction of magnitude inversion recovery data in FAIR generates erroneous negative data and distorted fit results: we simulated that for CSF percentages of 0-40%, CBF and deltat will be progressively overestimated by up to 50%. For higher CSF percentages the errors were found to increase steeply. We explored a straightforward solution: taking the magnitude of the FAIR data before fitting. This provided a remarkably strong antidote against the effects of CSF partial voluming: for CSF percentages of 0-40%, simulations now gave CBF values accurate within 1%, and deltat within 5%. The fit remained robust for high CSF fractions. Our analysis and simulations demonstrate that using magnitude FAIR data minimises the detrimental effects of CSF partial voluming. Data from a healthy volunteer illustrate these results.