Giles Santyr, Robarts Scientist
Why I Became a Scientist
The ability to understand complex physical systems and unlock mysteries in nature by the scientific method is the main reasons I became a scientist. I am particularly motivated to solve problems involving human health which can make a difference in our society. As a medical imaging scientist I have the opportunity to create new ways of visualizing and quantifying disease. Imaging can help bridge the gap between basic discoveries and clinical practice.
Dr. Giles Santyr ‘s work involves development of new and improved approaches for measurement and understanding of tissue relaxation times. Relaxation times are the basis for the rich soft tissue contrast available in Magnetic Resonance Imaging (MR Imaging). The general goal of my research is to use knowledge of tissue relaxation to optimize conventional MR imaging as well as develop innovative methods for improved detection and treatment of disease, particularly cancer and lung disease. My current projects involve the use of novel contrast agents called hyperpolarized noble gases (HNG’s), specifically helium-3 and xenon-129, which permit gas phase imaging (ie. lungs) as well as blood pool imaging with exquisite spatial (mm) and temporal resolution (s). My group has been investigating HNG’s with a focus on obstructive pulmonary diseases, primarily COPD, asthma and lung injury. We have developed quantitative HNG imaging techniques for the purpose of measuring dynamic ventilation, alveolar oxygen concentration, apparent diffusion coefficient (ADC) and xenon diffusing capacity.
Research Questions and Disease Implications
What can quantitative regional measures of lung anatomy and function, obtained using MR and CT imaging, provide in terms of improved detection and characterization of obstructive lung disease?
Current methods for diagnosing COPD based on spirometry can have low sensitivity and are effort dependent. Quantitative imaging approaches based on MRI and CT have the potential to improve early detection of disease. In particular, MRI of the lung with hyperpolarized nobles gases offers a wide palette of anatomical and functional measures. One promising approach will be to combine measures of helium-3 ventilation and ADC to stratify COPD subjects into primarily airways disease vsersus parenchymal disease (ie. emphysema) for improved patient management. This could have a significant impact on the use of inhaled corticosteroids in emphysema patients.
Given the high cost and limited availability of helium-3 gas, can hyperpolarized xenon-129 provide equivalent, if not better, information?
The scarcity of helium-3 will likely limit the use of this very promising MRI approach to major research centres only. Xenon-129 is infinitely abundant and inexpensive. To the extent that it can provide similar information as helium-3, xenon-129 provides a logical pathway for routine clinical application. Wide-spread availability of this methodology will lead to break-throughs in COPD and asthma management and eventual cure.
Can novel low field MRI geometries, possible using the very high signal available from HNG’s, provide improved lung imaging, functional insight and reduced complexity and cost?
Current approaches to MRI of the lung with HNG’s involved supine subjects in an expensive and restrictive magnet using awkward breathing protocols. This can limit the technique to relatively healthy, cooperative and adult subjects. Furthermore, it is desirable to perform spirometry at the time of imaging for proper validation, ideally accounting for the patient positioning and posture. The above limitations can largely be surmounted by performing MRI in a novel ‘open’ magnet possible at low magnetic field strength. This could revolutionize the manner in which lung imaging is currently performed, allowing critically-ill subjects as well as children to be scanned.
• F.C.C.P.M. 2004 Fellow, Canadian College of Physicists in Medicine
• Ph.D. 1990 Medical Biophysics, University of Toronto.
• B.Sc. (Honours) 1985 Physics Queen's University
• Assistant Scientist 1994 Medical Physics, University of Wisconsin
• Professor 2004 Physics, Carleton University
• 1981-83 Queen's Tricolor Scholarship Queen's University
• 1984 NSERC Summer Research Award McMaster University
• 1985 NMR Summer School Education Stipend University of Waterloo
• 1985 Ontario Cancer Institute Studentship University of Toronto
• 1986-87 University of Toronto Open Fellowship University of Toronto
• 1987-88 Ontario Graduate Scholarship University of Toronto
• 1987-89 Truman Brown Education Stipend University of Toronto
• 1988-90 National Cancer Institute Studentship University of Toronto
• 1993-99 National Cancer Institute FIRST Award University of Wisconsin
• 1998 CFI New Opportunities Award Carleton University
• 2001 Teaching Achievement Award Carleton University
• 2002 Research Achievement Award Carleton University
• 2005 Industry-Partnered Research Chair Award CIHR
1. Boudreau M., X. Xu and G. E. Santyr, Measurement of 129Xe Apparent Diffusion Coefficient Anisotropy in an Elastase-instilled Rat Model of Emphysema, Magn. Reson. Med. (in press).
2. Couch M., A.V. Ouriadov and G. E. Santyr, Regional Ventilation Mapping of the Rat Lung using Hyperpolarized 129Xe Magnetic Resonance Imaging, Magn. Reson. Med. (in press).
3. Xu X., M. Boudreau, A. Ouriadov and G.E. Santyr, Mapping of 3He Apparent Diffusion Coefficient Anisotropy at Sub-millisecond Diffusion Times in an Elastase-instilled Rat Model of Emphysema, Magn. Reson. Med. (E-pub ahead of print).
4. Mathew L., M. Kirby, D. Farquahar, C. Licskai, G. Santyr, R. Etemad-Rezai, G. Parraga and D.G. McCormack, Hyperpolarized 3He Magnetic Resonance Imaging of Bronchoscopic Airway Bypass in Chronic Obstructive Pulmonary Disease Can Resp J 19: 41-43 (2012).
5. Carias M., W. Dominguez-Viqueira and G.E. Santyr, Improving SNR of Hyperpolarized Noble Gas MRI at 73.5 mT using Multi-turn Litz Wire Radiofrequency Receive Coils, Concepts in MR Part B MR Engineering 39B: 37-42 (2011).
6. W. Dominguez-Viqueira, A. Ouriadov, R. O?Halloran, S. Fain and G.E. Santyr, Signal-to-Noise Ratio for Hyperpolarized 3He MR Imaging of Human Lungs: A 1.5 T and 3 T Comparison, Magn. Reson. Med. 66: 1400-1404 (2011).
7. Olding T., O. Holmes, P. DeJean, K. McAuley, K. Nkongchu, G.E. Santyr and L. J. Schreiner, Small Field Dose Delivery Evaluations Using Cone Beam Optical Computed Tomography-Based Polymer Gel Dosimetry, J. of Medical Physics 36: 3-14 (2011).
8. Santyr G.E., M.J. Couch, W.W. Lam, A. Ouriadov, M. Drangova, D.G. McCormack and D.W. Holdsworth, Comparison of Hyperpolarized 3He MR with Xe-enhanced CT Imaging for Ventilation Mapping of the Rat Lung, NMR in Biomedicine. 24, 1073-1080 (2011).
9. Kraayvanger R., C. Bidinosti, W. Dominguez-Viqueira, J. Parra-Robles, M. Fox, W.W. Lam and G.E. Santyr, Measurement of Alveolar Oxygen Partial Pressure in the Rat Lung Using Spin-Spin Relaxation Times of Hyperpolarized 3He and 129Xe at 74 mT, Magn. Reson. Med. 64: 1484-1490 (2010).
10. Kirby M., L. Mathew, A. Wheatley, G.E. Santyr, D.G. McCormack and G. Parraga, Chronic Obstructive Pulmonary Disease: Longitudinal Hyperpolarized 3He Magnetic Resonance Imaging, Radiology 256: 280-289 (2010).
11. Dominguez-Viqueira W., W. Berger, J. Parra-Robles, G.E. Santyr, Litz Wire Radiofrequency Receive Coils for Hyperpolarized Noble Gas MR Imaging of Rodent Lungs at 74 mT, Concepts in MR Part B MR Engineering 37B: 75-85 (2010).
12. Akhavan Sharif M.R., W.W. Lam, A.V. Ouriadov, D.W. Holdsworth and G.E. Santyr, Comparison of Hyperpolarized 3He MRI Rat Lung Volume Measurement with Micro-Computed Tomography, NMR in Biomedicine 23: 359-367 (2010).