Comparison of quantitative perfusion imaging using arterial spin labeling at 1.5 and 4.0 Tesla

TLDR

High‑field arterial spin labeling perfusion MRI is attractive because it offers higher SNR and improved labeling due to longer T1 of labeled blood. The study develops a theoretical model of ASL signal dependence on field strength and experimentally compares multislice PASL at 4 T with PASL and CASL at 1.5 T in rest and motor activation. The authors discuss susceptibility effects and physiological noise as possible explanations for the observed results. Resting‑state data showed that 4 T PASL yielded higher SNR (2.3:1.4:1) and CNR (2.7:1.1:1) than 1.5 T CASL and PASL, but functional 4 T PASL did not improve motor‑cortex activation sensitivity, exhibiting lower perfusion signal change and greater inter‑subject variability. Published in Magn Reson Med 48:242–254 (2002); © 2002 Wiley‑Liss, Inc.

Abstract

Abstract High‐field arterial spin labeling (ASL) perfusion MRI is appealing because it provides not only increased signal‐to‐noise ratio (SNR), but also advantages in terms of labeling due to the increased relaxation time T 1 of labeled blood. In the present study, we provide a theoretical framework for the dependence of the ASL signal on the static field strength, followed by experimental validation in which a multislice pulsed ASL (PASL) technique was carried out at 4T and compared with PASL and continuous ASL (CASL) techniques at 1.5T, both in the resting state and during motor activation. The resting‐state data showed an SNR ratio of 2.3:1.4:1 in the gray matter and a contrast‐to‐noise ratio (CNR) of 2.7:1.1:1 between the gray and white matter for the difference perfusion images acquired using 4T PASL, 1.5T CASL, and 1.5T PASL, respectively. However, the functional data acquired using 4T PASL did not show significantly improved sensitivity to motor cortex activation compared with the 1.5T functional data, with reduced fractional perfusion signal change and increased intersubject variability. Possible reasons for these experimental results, including susceptibility effects and physiological noise, are discussed. Magn Reson Med 48:242–254, 2002. © 2002 Wiley‐Liss, Inc.