Scientists: Aaron Fenster, PhD, FCCPM, David Holdsworth, PhD, Grace Parraga, PhD, J. David Spence, BA, MD, MBA, FRCP(C), FAHA , James Lacefield, PhD, P.Eng & Ting-Yim Lee, PhD, FCCPM
Stroke accounts for 7% of all deaths, and is the fourth leading cause of death in Canada. Each year, 40,000 to 50,000 Canadians will succumb to stroke and only 10% of victims will recover sufficiently to return to normal living. The cost of treatment, rehabilitation, loss of productivity from disability and premature death totals $2.7 billion a year. The Stroke Imaging Research Program at Robarts strives to provide accurate diagnosis of stroke risk and severity, to guide selection of appropriate treatment and prevent secondary complications such as bleeding within the brain following treatment. This program is strengthened by collaborations with other leading stroke research centres in Canada and the US.
Extending the Stroke Treatment Window
Stroke is caused by an abrupt interruption of blood flow to the brain by a blood clot. The only approved drug for stroke is the clot dissolving drug (rtPA). For rtPA to be effective, it must be determined before the drug is given whether there is surviving (viable) brain tissue, and currently, there is no reliable diagnostic method for such a determination. Emergency physicians rely on an empirical rule, albeit well tested, based on time since onset of symptoms to decide if rtPA can be given; and this time window is only 3 to 4.5 hours. Due to this very narrow treatment window, only 5% of stroke patients benefit from this treatment. The stroke imaging research team has developed a CT scanning method that can accurately identify surviving brain tissue in stroke patients, but before this method can be widely adopted, a multi-centre trial is required to prove its validity.
Enhancing the Safety of rtPA
Although rtPA is effective in dissolving the blood clots that cause stroke, it also can damage blood vessels already affected by stroke, resulting in bleeding in some patients. To enhance the safety of rtPA, a method to assess stroke damage to blood vessels is urgently required. With support from the Ontario Research Fund, our researchers have developed a CT scanning method to assess vessel damage in the brain, and have identified the key limits beyond which the likelihood of bleeding is much greater, putting the patient at risk. They are now validating this vessel damage assessment method in a larger sample of stroke patients to be recruited in London, Toronto, and Ottawa.
Predicting Stroke Risk - Imaging of Carotid Atherosclerosis
The pioneering research of Dr. Barnett at Robarts identified that atherosclerosis in the carotid artery is the main source of the blood clots that cause stroke. Our researchers are focused on direct imaging using ultrasound and MRI of the patient's carotid artery, plaque, and the arterial wall components, to better understand the difference between patients with stable disease and those who are deemed vulnerable or at risk of imminent stroke. This can provide new direct measurements (as compared to blood levels of cholesterol) to help better guide patient management and treatment before stroke occurs.
Improving Stroke Prevention Treatment
To provide an enhanced understanding of the local changes in the carotid artery that occur over time and after treatment, this team has invented a new imaging method that provides 3D images of the carotid arteries. These images are analyzed to allow them to determine the blood vessel and atherosclerosis plaque changes over time. This method will elucidate how and when treatments such as those related to drug, lifestyle, or dietary interventions affect stroke prevention and risk.