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About Sickkids
About SickKids

John Sled, PhD

Research Institute
Senior Scientist
Translational Medicine

Principal Investigator
Mouse Imaging Centre

University of Toronto
Professor and Vice-Chair, Medical Biophysics
Institute of Biomaterials & Biomedical Engineering

Adjunct Professor
Institute of Biomaterials & Biomedical Engineering, Dept. of Obstetrics & Gynaecology

Phone: 416-813-7654 ext. 309557
Fax: 647-837-5832
Email: john.sled@utoronto.ca
Alternate Contact: Katie Polanic
Alternate Phone: 416-813-7654 ext. 309536
Alternate Fax: 647-837-5832
Alternate Email: katie.polanic@sickkids.ca

For more information, visit:

Mouse Imaging Centre, The Hospital for Sick Children
Department of Medical Biophysics, University of Toronto
The Centre for Phenogenomics

Brief Biography

Dr. John G. Sled (PhD, MEng) is a Senior Scientist in the Program of Translational Medicine who joined the Mouse Imaging Centre at The Hospital for Sick Children in 2003. He is a Professor and vice-Chair in the Department of Medical Biophysics at the University of Toronto. Dr. Sled is widely recognized for his contributions to the development of MRI technologies. He was the first to describe comprehensive quantitative magnetization transfer imaging in humans and is the author of the widely used neuroimaging software N3. He has also made contributions in the areas of MR relaxometry, tissue microstructure / diffusion, perfusion, and morphometric techniques. His recent work has focused on applications of MRI, ultrasound, and X-ray CT in experimental mice to understand gene / environment / phenotype relationships in disease.  A particular area of interest is formal methods for describing the patterning differences that characterize a phenotype.

Dr. Sled received an MEng in 1997 from the Department of Biomedical Engineering at McGill University for his work on the causes and remedies of intensity non-uniformity artifacts in MRI. He received his PhD from the department of electrical engineering at McGill University in 2001. For his PhD, he developed an MRI technique for imaging the human brain called quantitative magnetization transfer imaging. This technique, of particular interest in the study of white matter diseases such as multiple sclerosis, shows the concentration and rigidity of the semisolid components of tissue that are normally invisible to MRI. From 2001-2003, he was a postdoctoral fellow in Imaging Research at Sunnybrook and Women’s College Health Sciences Centre with Dr. R. Mark Henkelman. During that period, he investigated the use of micro-computed tomography for characterizing the microvasculature of whole organs. In 2003, Dr. Sled joined the Mouse Imaging Centre at The Hospital for Sick Children. This state-of-the-art imaging facility has undergone continuous development and refinement since its inception, making it one of the best known and most prolific centres worldwide working on mouse imaging.

Research Interests

Dr. Sled’s research program at the Mouse Imaging Centre of The Hospital for Sick Children seeks, through the development and application of advanced imaging technologies in mice, to understand human disease, to answer basic questions about the function of genes, and to understand complex biological systems. One focus of his research has been to understand the adaptations and malformations that occur in the vascular system. This interest has led him to create a number of technologies based on MRI, X-ray computed tomography, ultrasound, and optical techniques to better identify functional and structural changes in the vasculature of experimental mice. An application where this has proven particularly interesting is in describing patterning defects in the placental circulation that occur with mutations or experimental challenges.

Another exciting application has been to study the adaptations that occur in the adult brain with disease or experimental challenges such as exercise. The multidisciplinary nature of this work and the natural translation of many of the imaging techniques for use in humans, fetal imaging technologies for instance, has led him to work closely with clinical collaborators on many of these projects.  


Neonatal and fetal imaging

  • A. Rahman, Y.-Q. Zhou, Y. Yee, J. Dazai, L. Cahill, J. Kingdom, C.K. Macgowan, J.G. Sled. “Ultrasound detection of altered placental vascular morphology based on hemodynamic pulse wave reflection.” American Journal of Physiology-Heart and Circulatory Physiology. 312(5):H1021-H1029, 2017. PMID 28364018 DOI 10.1152/ajpheart.00791.2016
  • L.S. Cahill, Y-Q. Zhou, M. Seed, C.K. Macgowan, J.G. Sled.  “Brain Sparing in Fetal Mice: BOLD MRI and Doppler Ultrasound Demonstrate Blood Redistribtuion during Hypoxia.”  Journal of Cerebral Blood Flow and Metabolism.  vol. 34, issue 6, pp. 1082-1088, 2014
  • R. Nossin-Manor, D. Card, D. Morris, S. Noormohamed, M.M. Shroff, H.E. Whyte, M. Taylor, J.G. Sled.  “Quantitative MRI in the Very Preterm Brain: Assessing Tissue Organization and Myelination using MTR, DTI, and T1 Relaxometry.”  NeuroImage.  vol. 64, pp. 505-516, 2013 (Cover Illustration).

Patterning of the microcirculation

  • M.Y. Rennie, J. Detmar, K.J. Whiteley, A. Jurisicova, S.L. Adamson, J.G. Sled.  “Expansion of the Fetoplacental Vasculature in Late Gestation is Strain Dependant in Mice.”  American Journal of Physiology-Heart and Circulatory Physiology.  vol. 302, issue 6, pp. H1261-1273, 2012.
  • S. Ghanavati, J.P. Lerch, J.G. Sled.  “Automatic Anatomical Labelling of the Complete Cerebral Vasculature in Mouse Models.”  NeuroImage.  vol. 95, pp. 117-128, 2014. (Cover Illustration).

Brain morphology and function

  • J.P. Lerch, A.P. Yiu, A. Martinez-Canabal, T. Pekar, V.D. Bohbot, P.W. Frankland, R.M. Henkelman, S.A. Josselyn, J.G. Sled.  “Maze training in mice induces MRI detectable brain shape changes specific to the type of learning.” NeuroImage. vol. 54, pp: 2086-95, 2011.
  • Badhwar, J.P. Lerch, E. Hamel, J.G. Sled. “Impaired Structural Correlates of Memory in Alzheimer’s Disease Mice.” NeuroImage Clinical. Vol. 3, pp. 290-300, 2013. DOI 10.1016/j.nicl.2013.08.017 PMID 24273714
  • B.P. Chugh, J. Bishop, Y-Q. Zhou, J. Wu, R.M. Henkelman, J.G. Sled.  “Robust Method for 3D Arterial Spin Labeling in Mice.”  Magnetic Resonance in Medicine.  Vol. 68, issue 1, pp. 98-106, 2012.  DOI 10.1002/mrm.23209  PMID 22102489

View more publications by Dr. Sled.