Qualitative and Quantitative Perfusion Parameters Determined by 3D Single-Shot GRASE ASL MR Imaging

Rationale and Objectives: A particular arterial spin (ASL) labeling technique, called 3D-single-shot GRASE ASL is discussed with respect to the ability and limits of quantifying perfusion parameters. Materials and Methods: The technique enables the acquisition of perfusion weighted signal at multiple delay times (TI) in one scan. The readout part is a gradient and spin-echo combination (GRASE) that uses switched gradient rephrasing of signals to produce several times as many signals as turbo-spin-echo, which translates into faster imaging time and higher signal-to-noise ratio (SNR) per imaging time. The technique provides the possibility for model based quantification of cerebral blood flow and the determination of the bolus arrival information without use of contrast agent and thus the characterization and determination of regions that are supported by collaterals. Results: Whereas for a quantification of the permeability using ASL the SNR is not high enough, at least qualitative permeability maps can be determined, if an optimal homogenous SNR was guaranteed. This was accomplished in brain regions with a high blood supply, typically given in tumors, and by using a correction for coil sensitivity at the highest possible additional scaling. Conclusion: The single-shot 3D GRASE ASL can provide information about the principal blood supply, the transit delay of the blood flow due to a stenosis or collaterals and a qualitative measure of the permeability.