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About Sickkids
About SickKids

Karen Thomas, MB BCh, MA, MRCP, FRCR, FRCP(C)

The Hospital for Sick Children
Diagnostic Imaging

University of Toronto
Assistant Professor
Medical Imaging

Other Positions

The Hospital for Sick Children
Diagnostic Imaging
Modality Lead, Body CT

Phone: 416-813-8457
Fax: 416-813-7591
Email: karen.thomas@sickkids.ca
Alternate Contact: Katherine McLaren
Alternate Phone: 416-813-5823
Alternate Email: katherine.mclaren@sickkids.ca

Brief Biography

Dr. Karen Thomas graduated from the University of Oxford Medical School, England and obtained the Membership of the Royal College of Physicians (Paediatric) in 1993. She entered radiological training at St. Mary’s Hospital, London and completed her paediatric radiology fellowship at The Hospital for Sick Children in 2000. After a short interval at Great Ormond Street Hospital and St. Mary’s Hospital, London, UK, she returned to take up a staff position in the body imaging group. 

Academic Background

Projects/ Initiatives: 

  1. Improving our knowledge of the radiation dose used in CT, Fluoroscopy (GIGU), X-ray and Nuclear Medicine examinations.
  2. Promoting and developing new dose reduction methods to ensure that studies which involve radiation are adapted to a child's age and the reason for the study so that radiation doses are kept as low as possible while still keeping diagnostic quality.
  3. Joint projects with clinical services studying the most important imaging studies.
  4. Speaker on paediatric radiation safety at national and international medical meetings, including the International Paediatric Radiology conference, Radiological Society of north America, Canadian and Ontario Associations of Radiology.

Research Interests

Radiation safety in children- practical, strategic and educational aspects of radiation safety and dose reduction in children's imaging.

She has developed a wide-ranging research interest in the practical, strategic and educational aspects of radiation safety and dose reduction in pediatric imaging with clinical impact on dose reduction and optimisation of practice within the diagnostic imaging department at Sickkids in addition to contributing towards current international efforts to improve physician, manufacturer and public awareness.

Her research activities have included various direct and indirect dosimetry studies, patient cohort cumulative dose estimation, innovation of new MDCT body scanning protocols and intravenous contrast regimes, CT image quality analysis with iterative reconstruction, and physician and caregiver radiation dose awareness surveys.  Her work has involved a collaborative multi-disciplinary approach with medical physicist Christopher Gordon, radiologist and medical imaging technologist colleagues, physician groups, and medical physics students from McMaster and Ryerson Universities.


Dr Thomas has received several Caffey awards from the Society for Pediatric Radiology for her work. She has been an invited speaker on various aspects of pediatric radiation safety, including participation in the ‘Image Gently’ 2011 ALARA CT Dose Reduction Conference, keynote radiation safety speaker at the 2011 International Pediatric Radiology Congress, and presentations to the Ontario Hospitals Association, Ontario Association of Radiologists and Radiological Society of North America. She was a member of the MOHLTC Ontario CT Safety Committee and has sat on the GE medical advisory board for pediatric CT.


Major Publications:

Comparative dose in pediatric radiology: uncertainty, estimates and ballparks
Karen E Thomas
Pediatr Radiol (2011) 41(Suppl 1): S212-214

Cumulative effective doses from diagnostic and interventional radiological procedures in pediatric oncology patients.
B A Ahmed, BL Connolly, P Shroff, A Lee Chong, CL Gordon, ML Greenberg, KE Thomas
Pediatrics (2010) 126(4) e851-8 Epub 2010 Sep27

Age-specific effective doses for Pediatric MSCT examinations at a large children’s hospital using DLP conversion coefficients; a simple estimation method.
Karen Thomas and Bo Wang
Pediatric Radiology (2008) 38: 645-56