Continuous flow‐driven inversion for arterial spin labeling using pulsed radio frequency and gradient fields

TLDR

Continuous labeling by flow‑driven adiabatic inversion is advantageous for ASL perfusion studies, yet implementation inefficiencies, magnetization transfer, and limited clinical scanner support have limited its benefits. The authors propose a new continuous labeling approach using rapidly repeated gradient and RF pulses to achieve high‑efficiency labeling. They describe the theoretical basis, numerical simulations, and in vivo implementation of the pulsed continuous ASL (PCASL) method. In vivo PCASL achieved a 96 % labeling efficiency, far surpassing the 33 % duty cycle of the RF pulses, and enabled 3 T imaging with body‑coil transmission, demonstrating the technique’s potential for clinical use. Magn Reson Med 60:1488–1497, 2008, © 2008 Wiley‑Liss, Inc.

Abstract

Abstract Continuous labeling by flow‐driven adiabatic inversion is advantageous for arterial spin labeling (ASL) perfusion studies, but details of the implementation, including inefficiency, magnetization transfer, and limited support for continuous‐mode operation on clinical scanners, have restricted the benefits of this approach. Here a new approach to continuous labeling that employs rapidly repeated gradient and radio frequency (RF) pulses to achieve continuous labeling with high efficiency is characterized. The theoretical underpinnings, numerical simulations, and in vivo implementation of this pulsed continuous ASL (PCASL) method are described. In vivo PCASL labeling efficiency of 96% relative to continuous labeling with comparable labeling parameters far exceeded the 33% duty cycle of the PCASL RF pulses. Imaging at 3T with body coil transmission was readily achieved. This technique should help to realize the benefits of continuous labeling in clinical imagers. Magn Reson Med 60:1488–1497, 2008. © 2008 Wiley‐Liss, Inc.