FUNCTIONAL IMAGING BY I-0-PARAMETER AND T-2-ASTERISK-PARAMETER MAPPING USING MULTIIMAGE EPI

A new functional imaging method has been developed and used to measure T-2- and initial intensity (I-O)-parameter maps of multiple slices d uring activation of the cortex with high temporal resolution. Multiple echo-planar images (EPIs) are read out after a single excitation of t he spin system, leading to several images with increasing effective ec ho times. Changes induced by primary visual stimulation in T-2 and I- O were measured in eight subjects. Although stimulation-induced increa ses in I-O only occurred at short repetition times, T-2 increased fro m 57.3 to 60.9 ms on average. The method combines the high stability o f a single shot EPI experiment with the high information content of a multiecho acquisition. In addition, stimulation-induced changes in inf low can be easily separated from true blood oxygenation level dependen t (BOLD) signal changes.