Implementation of quantitative FAIR perfusion imaging with a short repetition time in time-course studies

Flow-sensitive alternating inversion recovery (FAIR) is a pulsed arterial s pin labeling magnetic resonance imaging method for perfusion quantification , In its standard implementation for quantification with full longitudinal relaxation between acquisitions, its use in time-course investigations of r apidly changing flow values is limited. The time efficiency can be improved by decreasing the repetition time but quantification becomes problematic. This situation is further complicated if a whole-body radiofrequency transm it coil is not used since fresh blood spins will flow in from outside the c oil, To alleviate these problems, the use of global pre-saturation is propo sed, The resulting expression for the flow signal depends on the relationsh ip between the imaging parameters and the coil inflow time and can be signi ficantly simplified under certain combinations of these parameters. With th is implementation of FAIR, quantitative flow maps of gerbil brains were obt ained with a 3 minute time resolution in a study of the effects of reperfus ion, The pre-occlusion flow measurements were in good agreement with values obtained by the standard FAIR implementation and by other techniques, but the low values following occlusion were underestimated due to the increased transit times. (C) 1999 Wiley-Liss, Inc.