Separation and quantification of perfusion and BOLD effects by simultaneous acquisition of functional I(0)- and T2(*)-parameter maps.

The nature of the coupling between neuronal activity and the hemodynamic response is the subject of intensive research. As a means to simultaneously measure parametric changes of T2(*), initial intensity (I(0)) and perfusion with high temporal resolution, a multi-image EPI technique with slice-selective inversion recovery (ssIR) for arterial spin labeling was developed and implemented. Comparative measurements with and without the preceding slice-selective inversion pulse were performed. I(0) and R2(*) changes induced by primary visual stimulation were separated. For ssIR-multi-image EPI the average change of I(0) over all 12 subjects was 3.4%, corresponding to a perfusion change of 40 ml/min/100 g, whereas only minor I(0) changes were observed without inversion. On average, the R2(*) of the activated pixels changed by -0.62 sec(-1) without inversion, while a significantly reduced average R2(*) change of -0.46 sec(-1) was calculated for ssIR-multi-image EPI due to a decreased BOLD effect contribution of the intravascular compartment.