PhD, University of Toronto
Dr. Graham is a medical physicist and biomedical engineer with diverse interests in the development of MRI technology for clinical applications involving the brain. In the past, he has conducted numerous studies aimed at improving the understanding of the biophysical properties of biological tissue that affect MRI signal contrast; improving the method and application of functional Magnetic Resonance Imaging (fMRI) of brain activity in healthy individuals as well as patients suffering from stroke, Alzheimer's Disease, mild cognitive impairment, brain cancer, and traumatic brain injury; general development and optimization of MRI methods; and detailed numerical simulations, computational methods, and MRI hardware development towards improved use of MRI and associated medical devices (e.g. deep brain stimulators). He has a lengthy track record of successfully leading collaborative research grants and projects. Several ongoing research projects are described below.
Parallel Radiofrequency Transmission for Safe MRI of Patients with Deep Brain Stimulators
The neural equivalent of the cardiac pacemaker for treating heart disease, implanted devices for deep brain stimulation (DBS) are increasingly used to treat various neurologic and psychiatric conditions when other treatment options fail. Pre-implantation, MRI is important to identify and localize the DBS treatment targets, enabling neurosurgeons to position DBS electrodes correctly for the delivery of electric current to alleviate symptoms. Post-implantation, MRI is useful to verify correct implantation and evaluate potential surgical side-effects, such as hemorrhage. In the years after implantation, most DBS patients would benefit from follow-up MRI to monitor the course of their disease and evaluate any other brain conditions that may arise. However, at present MRI of DBS patients is severely limited due to possible risk of injury – especially on 3 Tesla MRI systems, even though they are particularly well suited to evaluate the central nervous system. Although considerable work has been done to improve the MRI safety of DBS devices, concerns persist that the MRI procedure may cause the tip of DBS electrodes to become heated, damaging neural tissue.
This localized heating is caused by the transmission of radiofrequency (RF) energy during MRI, which concentrates the electric field at the tip of the DBS lead, forcing current to flow and power to be deposited in tissue. To correct this problem, Dr. Graham is developing a method called “parallel radiofrequency transmission (pTX)” that uses multiple transmitters to control the electric and magnetic RF fields very precisely over the imaging volume. Using the pTX method, it is possible to force the RF electric field to zero at the DBS lead tip while maintaining useful image quality. Projects in the laboratory include a) hardware development to link pTX equipment to hospital-grade MRI systems; b) optimization of pTX methods for imaging DBS patients as well as other patient applications; c) electromagnetic simulations of the interactions of RF fields with DBS devices and biological tissues; d) investigation of pTX methods in tissue-equivalent, anthropomorphic “phantom” test objects mimicking the brain. More information about this research program can be found here.
Neuroimaging of Long-haul COVID-19
Coronavirus disease 2019 (COVID-19) is having a major impact on the health and well-being of Canadians. In approximately 10-20 % of those infected, persistent, lingering symptoms can last for months, including fatigue, brain fog, shortness of breath, as well as cognitive and psychiatric impairments. Many of these symptoms suggest that COVID-19 is directly or indirectly impacting the brain. To study these symptoms in detail and to provide key scientific data to inform clinicians as they develop and implement strategies to rehabilitate those with long-haul symptoms, Dr. Graham is leading the NeuroCOVID19 project. NeuroCOVID19 is a longitudinal observational study involving MRI of brain structure and function, electroencephalography of brain electrical signals, sensory and behavioural assessments, and symptom self-reports. The study involves COVID-19 survivors who were hospitalized or self-isolated when they were infectious, as well as control participants. Recently, Dr. Graham has received CIHR funding to focus the study principally on the elderly in the Greater Toronto Area who are living in our communities. These individuals are at elevated risk of serious COVID19 infection, which may exacerbate existing health complaints and contribute to physical or cognitive decline, and reduced quality of life. Recruitment into the study is ongoing, for example through email at email@example.com. Multiple opportunities exist for NeuroCOVID19-related graduate student research projects.
Functional Magnetic Resonance Imaging of Behavioural Tasks in Virtual Reality
Another aspect of research in the Graham lab involves pushing the boundaries of recording brain activity using fMRI. Most “task-based” fMRI studies investigate brain activity associated with simple sensory stimuli (e.g. images shown on a display) and simple behavioural responses (e.g. pressing a button). However, many aspects of human behaviour cannot be studied well by this approach, including those that require complex manipulation of tools (such as communication by writing/drawing with a pen or pencil), or body-centred interactions with the world around us in three spatial dimensions (such as walking or driving to find a certain store within the city). As research participants must lie on a patient table in a magnet bore during fMRI experiments, Dr. Graham has taken the approach to develop unique technology that permits brain activity to be recorded during fMRI while participants interact in virtual reality. Current work in this area involves fMRI studies of driving automobiles, to characterize the brain / behaviour relationships associated with multi-tasking and distractions, in healthy adults as well as those with cognitive impairment. In addition, Dr. Graham has developed novel tablet technology that enables participants to engage in realistic writing and drawing behaviour in an augmented reality environment. Projects ongoing with the tablet technology include study of the brain activity that supports writing abilities, and various neuropsychological assessments that are administered to patients as pen-and-paper tests in the real world.
Collaborative Neuroimaging Studies
Dr. Graham also has numerous collaborations in neuroimaging studies that do not fit within the above categories. For example, in collaboration with Dr. Tom Schweizer and colleagues at St. Michael’s Hospital in Toronto, Dr. Graham is studying biomarkers that reflect recovery from sport-related concussion, through use of neuroimaging and behavioural assessment. (The NeuroCOVID19 and Virtual Reality projects are also undertaken in collaboration with Dr. Schweizer.) Dr. Graham is also working with Dr. Sanjay Kalra at the University of Alberta, in the Canadian Amyotrophic Lateral Sclerosis NeuroImaging Consortium (CALSNIC) to develop neuroimaging biomarkers that may be used in future drug development to treat ALS.
- M. Arianpouya, B. Yang, F. Tam, B. Davidson, C. Hamani, N. Lipsman, S.J. Graham. Safe MRI of Deep Brain Stimulation Implants: A Review of the Promises and Challenges. Frontiers in Neurology and Neuroscience Research. 2021 May 31;2:1-23. DOI: 10.51956/FNNR.100012
- B. Davidson, F. Tam, B. Yang, Y. Meng, C. Hamani, S.J. Graham, N. Lipsman. 3-Tesla Magnetic Resonance Imaging of Patients With Deep Brain Stimulators: Results From a Phantom Study and a Pilot Study in Patients. Neurosurgery. 2021 Jan 13;88(2):349-355.
- Z. Lin, F. Tam, N. Churchill, T. Schweizer, S.J. Graham. Tablet Technology for Writing and Drawing during Functional Magnetic Resonance Imaging: A Review. Sensors (Basel). 2021 Jan 8;21(2):401.
- Z. Lin, F. Tam, N.W. Churchill, F-H. Lin, B.J. MacIntosh, T.A. Schweizer, S.J. Graham. Trail Making Test Performance using a Touch-sensitive Tablet: Behavioural Kinematics and Electroencephalography. Front Hum Neurosci. 2021 Jul 1;15:663463.
- N.H. Yuen, F. Tam, N. Churchill, T.A. Schweizer, S.J. Graham. Driving with distraction: measuring brain activity and oculomotor behavior using fMRI and eye-tracking. Front Hum Neurosci. 2021;15:413.
- S. Kalra, H.-P. Muller, A. Ishaque, L. Zinman, L. Korngut, A.L. Genge, C. Beaulieu, R. Frayne, S. J. Graham, J. Kassubek. A prospective harmonized multicentre DTI study of cerebral white matter degeneration in ALS. Neurology. 2020 Aug 25;98(8)e943-e952.
- Y.Yang, F. Tam, S.J. Graham, J.J. Li, C.Y. Gu, T. Ran, N. Wang, H.Y. Bi, Z.T. Zuo. Men and women differ in the neural basis of handwriting. Hum Brain Mapp. 2020 Jul;41(10):2642-55.
- S. Kalra, M. Khan, L. Barlow, C. Beaulieu, M. Benatar, H. Briemberg, S. Chenji, M.G. Clua, S. Das, A. Dionne, N. Dupré, D. Emery, D. Eurich, R. Frayne, A. Genge, S. Gibson, S.J. Graham, C. Hanstock, A. Ishaque, J.T. Joseph, J. Keith, L. Korngut, D. Krebs, C.R. McCreary, P. Pattany, P. Seres, C. Shoesmith, T. Szekeres, F. Tam, R. Welsh, A. Wilman, Y.H. Yang, Y. Yunusova, L. Zinman, for the Canadian ALS Neuroimaging Consortium. The Canadian ALS Neuroimaging Consortium (CALSNIC) – a multicenter platform for standardized imaging and clinical studies in ALS. medRxiv. doi: https://doi.org/10.1101/2020.07.10.20142679
- N.W. Churchill, M. Hutchison, S.J. Graham, T.A. Schweizer. Mapping brain recovery after concussion: From acute injury to one year after medical clearance. Neurology. 2019 Nov 19;93(21):e1980-e1992.
- S. Maknojia, N.W. Churchill, T.A. Schweizer, S.J. Graham. Resting State fMRI: Going Through the Motions. Front Neurosci. 2019 Aug 13;13:825.
- C.E. McElcheran, L. Golestanirad, M.I. Iacono, P-S. Wei, B. Yang, K.J.T. Anderson, G. Bonmassar, S.J. Graham. Numerical simulations of realistic lead trajectories and an experimental verification support the efficacy of parallel radiofrequency transmission to reduce heating of deep brain stimulation implants during MRI. Sci Rep. 2019 Feb 14;9(1):2124.
- M. Karimpoor, N. Churchill, F. Tam, C. Fischer, T. Schweizer, S.J. Graham. Functional MRI of Handwriting Tasks: a Study of Healthy Young Adults Interacting with a Novel Touch-Sensitive Tablet. Front Hum Neurosci. 2018 Feb 13;12:30.
- K. Landheer, R. Schulte, B. Geraghty, C. Hanstock, A.P. Chen, C.H. Cunningham, S.J. Graham. Diffusion-Weighted J-Resolved Spectroscopy. Magn Reson Med. 2017 Oct;78(4):1235-45.
- N.W. Churchill, M. Hutchison, D. Richards, G. Leung, S.J. Graham, T.A. Schweizer. Neuroimaging of sport concussion: persistent alterations in brain structure and function at medical clearance. Sci Rep. 2017 Aug 24;7(1):8297.
- M. Morrison, F. Tam, M. Garavaglia, G. Hare, M. Cusimano, T. Schweizer, S. Das, S.J. Graham. Sources of variation influencing concordance between functional MRI and direct cortical stimulation in brain tumor surgery. Front Neurosci. 2016 Oct 18;10:461.
- Z. Faraji-Dana, F. Tam, J. J. Chen, S. J. Graham. A Robust Method for Suppressing Motion-induced Coil Sensitivity Variations during Prospective Correction of Head Motion in fMRI. Magn Reson Imaging. 2016 Oct;34(8):1206-19.
- M. Morrison, N. Churchill, M. Cusimano, T. Schweizer, S. Das, S Graham. Reliability of task-based fMRI for preoperative planning: a test-retest study in brain tumor patients and healthy controls. PLoS One. 2016 Feb 19;11(2):e0149547.