New brain imaging technique seeks to improve stroke outcomes

Stroke is the fourth leading cause of death in North America and the most common cause of neurological disability worldwide. Thanks to new funding from the Canadian Institutes of Health Research, doctors Bijoy Menon and Mayank Goyal and colleagues from the University of Calgary and the Hotchkiss Brain Institute are working on a new imaging technique that could mean improved treatment for stroke patients. 

Their technique, called multi-phase CTA, measures collaterals – small vessels in the brain that redirect blood flow when an artery becomes blocked. The procedure allows for quick and reliable stroke imaging, faster decision-making and the potential for uniform imaging across various stroke centers.

As Menon explains, “Collaterals are the body’s natural way of compensating when there is a blockage, or stroke. When an artery is obstructed, collaterals work to redirect blood flow around the blocked artery and to the normal vessels.”

Understanding why some people have better collaterals

This is particularly important in the brain, where reduced blood flow results in the irreversible death of brain cells within minutes. “With stroke, time is the most important factor,” explains Menon. “What the collaterals do is re-route blood flow and keep brain tissue alive until the physician can intervene with drugs or surgery to remove the blockage.” 

This study will look at the correlation between collateral quality and patient outcome, in an attempt to determine which stroke patients might benefit most from therapies aimed at opening up blocked arteries.

• Above: Multi-phase CTA scans showing patients with stroke (blockage indicated by the arrow) and examples of patients with good collaterals (top) and poor collaterals (bottom). Patients with good collaterals tend to have better outcomes following stroke, because brain blood flow is preserved.

Menon’s team will perform multi-phase CTA scanning on 600 subjects over the next three years who suffer from a major stroke. The technique is quick, available 24-7 and is safe, since it doesn’t require any additional dye or significant radiation exposure. The researchers will also collect demographic and lifestyle information from these patients in an attempt to determine why some people seem to have better collaterals than others – something that Menon finds particularly interesting.

As he explains, “We hope to find physical, demographic, or lifestyle factors that can be correlated with the health of collaterals. To date, no research has been able to definitively tell us why some people seem to have better collaterals than others.”

Seeking to identify ways to improve collateral health

This kind of information would open the door to customized therapeutics and the development of valuable preventive strategies. In a study he published in the journal Annals of Neurology in 2013, Menon discovered that patients with disorders such as metabolic syndrome (characterized by symptoms including obesity and high blood pressure) tend to have poor collaterals. 

“This makes me hopeful that our research could identify modifiable variables that impact collateral health,” says Menon. “It would be amazing if we could one day use this information to not only customize treatment for stroke patients, but also to educate the public on the best ways to maintain and improve their brain health.”

Dr. Bijoy Menon is a stroke neurologist and assistant professor in the departments of Clinical Neurosciences and Radiology at the University of Calgary. Dr. Mayank Goyal, an interventional neuroradiologist, is professor of radiology and clinical neurosciences at the University of Calgary and medical director of the Seaman Family MR Centre. Their study, "Precise and rapid assessment of collaterals using multi-phase CTA in the triage of patients with acute ischemic stroke for IV or IA Therapy (PRoVe-IT)," was one of six HBI projects funded through the most recent CIHR funding competition.