Examination of Tissue Perfusion by Arterial Spin Labeling (ASL)

Abstract

Arterial spin labeling (ASL) is a non-invasive magnetic resonance technique for tissue perfusion quantification working without contrast media application. The method uses magnetically labeled blood protons as intrinsic tracer. Perfusion-weighted images are obtained by the signal difference between an image with proximal labeling of the arterial water protons and a control image. Initially designed for cerebral perfusion measurement, the ASL technique is increasingly being used for the evaluation of extracranial organs which might be attributed to the improvements in scanner, coil and sequence technology but also to the elaboration of postprocessing tools. In this review, the basic principles of ASL are explained. Technical difficulties in ASL sequence design are discussed. To illustrate the potential role of ASL in clinical research and diagnostics, comparison of ASL with other methods currently applied for perfusion assessment is performed. Finally, a variety of clinical applications of ASL is presented with respect to the current literature.