Arterial spin labeling (ASL) perfusion: techniques and clinical use.

Arterial spin labeling (ASL) perfusion is a MRI technique to quantify tissue blood flow. ASL is a non-invasive technique that labels the protons in the arterial blood by radiofrequency pulses, without the exogenous injection of contrast media. This article has three goals: 1) present the principles of ASL perfusion, the types of labeling and the ways to obtain the mapping; 2) specify and the quality criteria for the mapping obtained, while emphasizing the artifacts; and 3) describe the main encephalic and renal applications.