Arterial spin labeling for quantitative functional MRI

BOLD effect imaging is very effective for detection and localization of brain activity, and is the dominant functional imaging technique in cognitive psychology. Despite its efficiency to detect and localize active site, the technique does not lend itself easily to quantifiable measurements. A growingly popular alternative is the use of arterial spin labeling (ASL) to obtain perfusion maps as the indicator of cerebral activation. In this paper, the principles and challenges of arterial spin labeling are discussed and the development of a new fast, two-coil pseudo-continuous labeling scheme is presented. The new scheme permits collection of a multi-slice subtraction pair in less than three seconds, depending on the subject´s arterial transit times. The theoretical basis of the technique, as well as a model for quantification of perfusion from the ASL data, are presented. Experimental data from functional imaging experiments were collected to demonstrate the technique and its characteristics.