Ternary encoded super-selective arterial spin labeling for time-resolved flow territory mapping

Abstract

Arterial spin labeling (ASL) is a non-contrast enhanced method for perfusion measurements. The obtained information is in general a snap-shot of the whole-brain perfusion. Image acquisition is performed after a certain delay time after the labeling of the arterial blood. Time-resolved information alongside flow territory mapping of individual arteries can become useful for the collection of important information such as arterial crossflow, and revascularization. Therefore, a method is presented that combines time-resolved flow territory mapping within a single scan based on encoding of the acquisition cycle using a ternary matrix approach. The super-selective tagging process is divided in individual blocks following a ternary matrix encoding scheme. In each block, the position of the labeling focus changes its position to each of the major brain feeding arteries. Contrary to conventional ASL approaches, no control condition is acquired and the individual flow territories are calculated by combining the label images only. The method was successfully evaluated in healthy volunteers. Each flow territory could be visualized over several post labeling delays within a single scan of approximately five minutes. Comparison of signal intensity (relative perfusion) did not show statistically significant differences between the methods. Encoding super-selective ASL using a ternary matrix allows for the vessel-selective and time-resolved acquisition of perfusion territories within a single scan.