Improved pseudo‐continuous arterial spin labeling for mapping brain perfusion

Abstract

Purpose To investigate arterial spin labeling (ASL) methods for improved brain perfusion mapping. Previously, Pseudo-continuous arterial spin labeling (pCASL) was developed to overcome limitations inherent with conventional continuous arterial spin labeling (CASL), but the control scan (null pulse) in the original method for pCASL perturbs the equilibrium magnetization, diminishing the ASL signal. Here, a new modification of pCASL, termed mpCASL is reported, in which the perturbation caused by the null pulse is reduced and perfusion mapping improved. Materials and Methods Improvements with mpCASL are demonstrated using numerical simulations and experiments. ASL signal intensity as well as contrast and reproducibility of in-vivo brain perfusion images were measured in four volunteers who had MRI scans at 4 Tesla and the data compared across the labeling methods. Results Perfusion maps with mpCASL showed, on average, higher ASL signal intensity and higher image contrast than those from CASL or pCASL. Furthermore, mpCASL yielded better reproducibility in repeat scans than the other methods. Conclusion The experimental results are consistent with the hypothesis that the new null pulse of mpCASL leads to improved brain perfusion images.

Different post label delay cerebral blood flow measurements in patients with Alzheimer's disease using 3D arterial spin labeling

“…The whole-brain 3D PCASL used in this study has several advantages: (1) whole brain coverage, (2) improved signal-to-noise ratio (SNR) in CBF, (3) reduced image distortion [9,10]. Previous studies have shown that PCASL has higher reliability than PASL and CASL [11].…”

Improved quantification of brain perfusion using FAIR with active suppression of superior tagging (FAIR ASST)

“…Although pseudo‐continuous ASL techniques have been proposed that show great promise with respect to high labeling efficiency and SNR (19–21), FAIR ASST, with lower specific absorption rate (SAR), higher temporal resolution, and inherent immunity to off‐resonance effects, can still be a valuable alternative. Further studies comparing FAIR ASST with these or other ASL methods are needed.…”

Interpulse phase corrections for unbalanced pseudo‐continuous arterial spin labeling at high magnetic field

“…Luh et al demonstrated for balanced pCASL on humans at 7 T, that varying the phase during a prescan to measure the optimal phase increment was a robust way to improve the overall perfusion signal while keeping the imaging plane close to the isocenter. Moreover, other studies showed that correcting the control condition separately improves the ASL signal . However, the latter control correction strategies resulted in applying different frequencies for the label and the control conditions, leading to residual magnetization‐transfer effects.…”