Simultaneous Acquisition of Cerebral Blood Volume-, Blood Flow-, and Blood Oxygenation-Weighted MRI Signals at Ultra-High Magnetic Field

摘要

Alternative fMRI techniques use single physiological quantities as a marker of neuronal activity rather than a combination of many. Arterial spin labeling (ASL) is a noninvasive technique to measure CBF, and various approaches have been introduced to provide optimal MR signal quality (4-6). ASL uses magnetically labeled blood water as an endogenous tracer; and in contrast with BOLD, it has a strong arteriolar and capillary signal-weighting, which gives this technique an improved spatial specificity (7). The major problem, however, is its low signal-to-noise ratio (SNR). ASL relies on the MR signal coming from the blood, which typically contributes less than 5% to the total signal arising from each voxel (7). Vascular space occupancy (VASO) has been used to measure functionally induced changes in CBV (8). VASO also relies on the inversion of blood water spins, but in contrast with ASL, the MR signals are acquired at the blood nulling time point.