Efficient visualization of cortical vascular territories and functional mri by cycled arterial spin labeling mri

Abstract

Regional arterial spin labeling (regASL) speeds up acquisition without sacrificing the signal-to-noise ratio (SNR) of the resulting perfusion images by using the same control image (i.e. acquired without labeling of blood in a vessel) for two or more vascular territory measurements. This regional ASL is accomplished by creating prepared spin magnetization (e.g. inverted or saturated) in a specific blood vessel, instead of preparing spin magnetization in all feeding blood vessels. As in conventional ASL, two data sets are typically acquired in a downstream position: one with (label image) and one without preparation (control image) in one particular vessel. When regASL is extended to repetitive time series of ASL images to identify perfusion changes for functional MRI (fMRI), the speed of the time series of ASL also is increased because only a single C data set can be used redundantly for all time points of ASL measurement, to reduce the amount of data acquired by nearly one half, with no change in the signal to noise ratio in the ASL images. To account for possible movement of the person causing misregistrations in the time series, the C data can be obtained two or more times throughout the time series while still at lower frequency than in prior techniques with alternating L and C data sets.