Simultaneous MRI acquisition of blood volume, blood flow, and blood oxygenation information during brain activation.
Simultaneous acquisition of complementary functional hemodynamic indices reflecting different aspects of brain activity would be a valuable tool for functional brain-imaging studies offering enhanced detection power and improved data interpretation. As such, a new MRI technique is presented that is able to achieve concurrent acquisition of three hemodynamic images based primarily on the changes of cerebral blood volume, blood flow, and blood oxygenation, respectively, associated with brain activation. Specifically, an inversion recovery pulse sequence has been designed to measure VASO (vascular space occupancy), ASL (arterial spin labeling) perfusion, and BOLD (blood-oxygenation-level-dependent) signals in a single scan. The MR signal characteristics in this sequence were analyzed, and image parameters were optimized for the simultaneous acquisition of these functional images. The feasibility and efficacy of the new technique were assessed by brain activation experiments with visual stimulation paradigms. Experiments on healthy volunteers showed that this technique provided efficient image acquisition, and thus higher contrast-to-noise ratio per unit time, compared with conventional techniques collecting these functional images separately. In addition, it was demonstrated that the proposed technique was able to be utilized in event-related functional MRI experiments, with potential advantages of obtaining accurate transient information of the activation-induced hemodynamic responses.