Introduction to Perfusion Quantification using Arterial Spin Labelling

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) is unique in being a completely non-invasive method for imaging perfusion in the brain. Relying upon a blood-borne tracer that is created by the MRI scanner itself, ASL is becoming a popular tool to study cerebral perfusion, as well as how this perfusion changes in response to neuronal activity or in disease. This primer provides an introduction to perfusion quantification using ASL MRI, focusing both on the methods needed to extract perfusion-weighted images and on how to quantify perfusion and other hemodynamic parameters. Starting with the simplest implementation of ASL, the primer details all the common acquisition methods, as well as the subsequent analysis steps required to quantify perfusion in an individual, detect changes in perfusion in response to neural activity or pharmacological intervention, and examine perfusion variations across groups of individuals. This is supported with examples from real data illustrating all the major steps in the analysis process, linked to online material where the reader can undertake the same analysis for themselves.