Superselective pseudocontinuous arterial spin labeling

Abstract

A new technique for the imaging of flow territories of individual extra-and intracranial arteries is presented. The method is based on balanced pseudocontinuous arterial spin labeling but employs additional time-varying gradients in between the radiofrequency pulses of the long labeling train. The direction of the additional gradient vector is perpendicular to the selected artery and its azimuthal angle is switched after every radiofrequency pulse. The phases of the radiofrequency pulses are adopted to cancel out the phase accrual of the spins at the center of the target vessel due to the extra applied gradients. This results in efficient inversion at the targeted position, whereas elsewhere time-varying phase changes will result in marginal inversion efficiency. By changing the moment of the added gradients, the size of the labeling focus can be adjusted. Influence of the temporal order of the additional gradients on the labeling efficiency and on the selectivity was investigated by simulations and experimental measurements. In a volunteer study, the acquisition of high signal-to-noise ratio flow territory images of small branches of the anterior cerebral artery distal to the circle of Willis was demonstrated. This shows the method's flexibility for dealing with complicated arterial geometries and its ability to superselectively label small intracranial arteries. Magn Reson Med 64:777-786,

Perfusion territory imaging of intracranial branching arteries – optimization of continuous artery‐selective spin labeling (CASSL)

“…In CASSL, the spatial selectivity can be adjusted to individual wileyonlinelibrary.com/journal/nbm vascular geometries, which allows for the precise planning of the labeling plane to obtain maximum labeling efficiency and the visualization of the flow territory of a single artery. It should be noted that, on the basis of pseudo-CASL, similar methods have been proposed recently that enable the labeling of an individual artery (26,27). In particular, the superselective ASL approach (27) offers similar spatial specificity to the optimized CASSL technique, and may be used as an alternative tagging method, especially at higher field strength.…”

MR Imaging of Individual Perfusion Reorganization Using Superselective Pseudocontinuous Arterial Spin-Labeling in Patients with Complex Extracranial Steno-Occlusive Disease

“…The superselective pseudocontinuous ASL (ss-pCASL) technique with a single circular labeling spot 22,32 works by applying rotating gradients with phase changes of the radiofrequency pulses of the pCASL labeling train, in which the diameter of the labeling focus is controlled by the gradient moments. 22,32 The major advantage of superselective pCASL is its flexibility in positioning: The labeling focus can be individually adapted to different vessel geometries (eg, by tilting).…”

“…22,32 The major advantage of superselective pCASL is its flexibility in positioning: The labeling focus can be individually adapted to different vessel geometries (eg, by tilting). This adaptation can be especially beneficial in patients with altered vasculatures such as tortuous and elongated vessels.…”

“…The labeling duration was 1650 ms, with a postlabeling delay of 1525 ms and background suppression pulses at 1680 and 2830 ms after a saturation pulse preceding the labeling. 22,32 Intracranial perfusion measurements comprised 15 sections covering most perfused brain tissue. Forty averages of label and control images were acquired with an average scan time of 2 minutes 25 seconds per vessel.…”

“…MR imaging-based methods for perfusion imaging with vessel-selective arterial spin-labeling (ASL) have been developed to provide a tool for noninvasive regional perfusion imaging. [18][19][20] The first reports on territorial arterial spin-labeling were presented in 2003, 21 and techniques for vessel-selective labeling have since been improved with respect to vessel selectivity, 22 usability, 23 and data analysis. 24 Initial techniques for vessel-selective labeling required positioning a thick labeling slab in a plane with the aim of selectively labeling only 1 artery.…”