Perfusion Imaging using Arterial Spin Labeling (ASL)

Abstract

　Arterial spin labeling (ASL) is a method for evaluating perfusion that uses magnetically labeled arterial blood water as an endogenous tracer. Although research and technical development have been conducted for a long time, introduction of ASL into clinical practice has been delayed because of its low signal-to-noise ratio (SNR). In recent years, advances in the pulse sequence and hardware, such as high static magnetic fields and high-sensitivity phased array coils, have made it possible to obtain high-SNR ASL images in a clinically acceptable time. In this regard, a consensus paper proposed simple and standard usage, including recommended techniques and parameters, to obtain a consistent image quality. Major MR manufacturers offered ASL pulse sequences based on this study. Hence, ASL has been used in clinical practice, and the effectiveness in measuring perfusion using ASL has been reported for the diagnosis of various neurological disorders. This article will review the technique for perfusion measurement and quantification and the recent technical progress in ASL.