Arterial Spin Labelling

Arterial spin labelling (ASL) is a functional magnetic resonance imaging (fMRI) technique for measuring cerebral blood flow (CBF). This technique uses endogenous arterial blood water as a flow tracer instead of an exogenous contrast agent. As such, the technique is completely non-invasive and infinitely repeatable, making ASL ideal for monitoring changes in cerebral blood flow associated with brain function. Unlike conventional fMRI that detects signal differences associated with immediate changes in brain activity, ASL can be used to study long-term changes since it measures cerebral blood flow directly.

Our group was the first to use ASL to map changes in regional CBF associated with pain perception (Owen, Pain 2010; Owen J Magn Reson Imag 2012). Through CIHR funding, we are currently using ASL to investigate the functional changes caused by chronic pain (fibromyalgia & complex regional pain syndrome) and how these changes are affected by treatment efficacy.

Because ASL is a non-contrast-enhanced perfusion method, it can be easily incorporated with other MRI methods to investigate the relationship between cerebrovascular health and changes in brain morphometry and connectivity. We are currently applying this approach to investigate neurological changes associated with cardiovascular disease (Anazodo Neuroimage Clin 2013).

We are also combining ASL with PET on a 3T MRI/PET system. This hybrid imaging platform provides the unique ability to provide simultaneous structural (MRI), functional (ASL) and molecular (PET) imaging. An example of whole-brain imaging of cerebral glucose and blood flow are shown to the right. This approach is current being used to investigate the metabolic and perfusion changes associated with frontotemporal dementia. Future goals are to use this hybrid system to investigate the relationship between pain perception and alterations in the opioid receptor system due to chronic pain, and to combine ASL, BOLD-fMRI and PET to image cerebral oxidative metabolism at rest and during functional activation.

Collin Clarke, Anesthesiology
Elizabeth Finger, Neurology
Frank Prato, Medical Physics
Patricia Morley-Forester, Anesthesiology
Dwight Moulin, Neurology
Kevin Shoemaker, Kinesiology
Keith St. Lawrence, Medical Biophysics

Karen Davis, U of Toronto