Comparison of Velocity- and Acceleration-Selective Arterial Spin Labeling with [15O]H2O Positron Emission Tomography

In the last decade spatially nonselective arterial spin labeling (SNS-ASL) methods such as velocity-selective ASL (VS-ASL) and acceleration-selective ASL have been introduced, which label spins based on their flow velocity or acceleration rather than spatial localization. Since labeling also occurs within the imaging plane, these methods suffer less from transit delay effects than traditional ASL methods. However, there is a need for validation of these techniques. In this study, a comparison was made between these SNS-ASL techniques with [15O]H2O positron emission tomography (PET), which is regarded as gold standard to measure quantitatively cerebral blood flow (CBF) in humans. In addition, the question of whether these techniques suffered from sensitivity to arterial cerebral blood volume (aCBV), as opposed to producing pure CBF contrast, was investigated. The results show high voxelwise intracranial correlation (0.72 to 0.89) between the spatial distribution of the perfusion signal from the SNS-ASL methods and the PET CBF maps. A similar gray matter (GM) CBF was measured by dual VS-ASL compared with PET (46.7 ± 4.1 versus 47.1 ± 6.5 mL/100 g/min, respectively). Finally, only minor contribution of aCBV patterns in GM to all SNS-ASL methods was found compared with pseudo-continuous ASL. In conclusion, VS-ASL provides a similar quantitative CBF, and all SNS-ASL methods provide qualitatively similar CBF maps as [15O]H2O PET.