Simultaneous noninvasive measurement of CBF and CBV using double-echo FAIR(DEFAIR)

A new method for measuring cerebral blood flow (CBF) and cerebral blood vol ume (CBV) noninvasively using MRI is presented. The approach is based on th e technique of arterial spin labelling (ASL), in which CBF-based contrast i s generated by controlled modulation of the longitudinal magnetization of t he blood. The proposed method also uses differences in T-2 between tissue a nd blood to differentiate the two compartments and allow assessment of the relative size of each. Two successive EPI images are acquired following spi n preparation using either a slice-selective or global inversion pulse, and the technique is therefore referred to as double-echo FAIR (DEFAIR). DEFAI R is demonstrated in the normal gerbil brain and during hypothermia, where reductions of both CBF and CBV are known to occur. It is also shown theoret ically that this method can be extended to include a measurement of oxygen extraction fraction. The main drawbacks of the technique are the long acqui sition time and relatively low sensitivity to hemodynamic changes compared to conventional qualitative T-2(*)-weighted BOLD contrast, which may limit its applicability and practical use in monitoring functional cerebral activ ation. However, the technique can be used repetitively in longer-term time course studies due to its noninvasive and quantitative nature. (C) 2001 Wil ey-Liss, Inc.