Why I Became a Scientist
I have always been fascinated by the ways things work. At the beginning I was drawn to mathematics and physics because of the simplicity and elegance of the methods employed and explanations of how matter interact. Later on, in graduate school, I realized that biology is more exciting because the applications are more varied and have direct bearing on the well being of ourselves and society. I have transitioned from being a theoretician to an experimentalist and am very satisfied with this change. One privilege of being a scientist is that we never know what lies ahead at the next turn of the road. There will always be a fresh start everyday when we come to work.
My research program focuses on the use of imaging to study physiological processes in diseases. My lab has pioneered a method of using x-ray dye and CT scanning to measure blood flow in various tissues including the brain, tumors, and the heart. The method has found applications in stroke for selecting patients for thrombolytic treatment, in cancer for monitoring anti-angiogenesis therapy, and in heart attack for identifying patients who would benefit from revascularization. The software implementing the method has been licensed to GE Healthcare and is distributed worldwide for use with their CT scanners.
Can measurement of blood flow and blood-brain barrier permeability Identify ischemic penumbra (viable tissue) and assess risk of hemorrhagic transformation in acute stroke patients?
Current thrombolytic treatment of embolic stroke is hampered by the lack of diagnostic methods to ascertain the extent of penumbra and risk of intracerebral hemorrhage (hemorrhagic transformation). As a result, thrombolytic treatment is limited to less than 4.5 hours after symptom onset based on empirical rules established by clinical trials. Knowledge of the size of the penumbra as well as the risk of hemorrhage in individual patients could push the treatment window further back to 6-9 hours post symptom onset resulting in more patients treated with thrombolysis, which is the only effective medical treatment for acute stroke.
Can perfusion measurement reflect the efficacy of anti-angiogenesis treatment of cancer?
Cancer induces proliferation of endothelial cells which leads to the formation of an interconnecting vascular network that would support perfusion. This is the basis of the hypervascularity seen in most cancers. As such, measurement of tumor perfusion can be a good imaging biomarker for monitoring the effect of angiogenesis inhibitors. A caveat of such treatment is that angiogenesis inhibitors are not cytotoxic and therefore the traditional RECIST criteria based on tumor size shrinkage may not accurately reflect the effect of the treatment.
Is the blood-brain barrier compromised in vascular cognitive impairment and Alzheimer disease?
One of the pathological hallmarks of Alzheimer disease is the deposition of amyloid plaque in the brain. An abundant source of amyloid beta protein, which is the main constituent of Alzheimer plaques, is the blood. In addition, microbleed detected by MR imaging is a risk factor for cognitive decline in stroke patients. Lastly, the accompanying inflammatory response to ischemia would induce opening of the blood-brain barrier. Taken together, these disparate evidences point to the connection between blood-brain barrier disruption and cognitive impairment and that normalization of the blood-brain barrier could be a new treatment.
- PhD (London University)
- MSc (London University)
- BSc (Hong Kong University)
- CIHR-GE Healthcare Chair in Functional Imaging
- May 2010, Schulich School of Medicine & Dentistry Dean’s Award of Excellence ($500), The University of Western Ontario
BoffE.E. Stewart, H. Sun, X. Chen, P.H. Schafer, Y. Chen, B.M. Garcia, and T.-Y. Lee. Effect of an angiogenesis inhibitor on hepatic tumor perfusion and the implications for adjuvant cytotoxic therapy. Radiology: In Press, March 12, 2012.
So, J. Hsieh, J. Kramer, K. Procknow, Y. Imai, S. Dutta, and T.-Y. Lee. Prospectively ECG triggered rapid kV switching dual energy CT for quantitative imaging of myocardial perfusion. Journal of the American College of Cardiology Cardiovascular Imaging: Accepted January 9, 2012.
So, J. Hsieh, J.-Y. Li, J. Hadway, H.F. Kong, and T.-Y. Lee. Quantitative myocardial perfusion measurement using CT Perfusion: A validation study in a porcine model of reperfused acute myocardial infarction. International Journal of Cardiovascular Imaging: Epub ahead of print, July 29, 2011.
So, G. Wisenberg, A. Islam, J. Amann, W. Romano, J. Brown, D. Humen, G. Jablonsky, J.-Y. Li, J. Hsieh, and T.-Y. Lee. Non-invasive assessment of functionally relevant coronary artery stenoses with quantitative CT perfusion: Preliminary clinical experiences. European Radiology 22(1): 39-50, January 2012.
T.-Y. Lee and R.K. Chhem. Impact of new technologies on dose reduction in CT. European Journal of Radiology 76(1): 28-35, October 2010.
J.H. Tai, J. Tessier, A.J. Ryan, L. Hoffman, X. Chen, and T.-Y. Lee. Assessment of acute anti-vascular effects of Vandetanib with high-resolution dynamic contrast-enhanced computed tomographic imaging in a human colon tumour xenograft model in the nude rat. Neoplasia 12(9): 697-707, September 2010.
Contact InfoPhone: 519-931-5272 (Assistant)
Phone: 519-931-5777 ext. 24131 (Office)