Plenary Talks

Prof. David W. Townsend

Prof. David W. Townsend

Founding Director, Singapore Clinical Imaging Research Centre Fellow, IEEE

Radiation phobia : Fake news and alternative facts


For the past two decades there has been growing concern about the use of ionizing radiation for medical imaging. This concern is based on the perception that any exposure to ionizing radiation carries with it an increased risk of cancer. For over 50 years, such risks have been estimated based on the Linear No Threshold (LNT) model. This model assumes that there is a risk associated with any radiation exposure, however small, and that the risks of low-level exposure can be estimated by extrapolating to zero from high, often lethal, levels of radiation. Hence the concern that even the very low levels of radiation associated with medical imaging may cause cancer. However, there are no reliable data from which to estimate the cancer risk from such low radiation levels, and specifically, no data to unequivocally support the LNT model. Unfortunately, the perception that all radiation causes cancer has been extensively hyped through the media, creating radiation phobia and unnecessary concern among the patient population even though it is unsupported by scientific data. Such media reports have even been endorsed by members of the medical imaging profession even though the evidence increasingly supports an alternative to the LNT model whereby low levels of radiation may even be beneficial (hormesis model). Over the past few years, significant technological progress has resulted in imaging systems that require very low levels of ionizing radiation to acquire an image. This presentation will summarize the recent advances in medical imaging devices and review the data available to assess the corresponding radiation risk and, by identifying a few alternative facts, attempt to put into perspective the real concerns associated with medical imaging using ionizing radiation.


David W. Townsend obtained his B.Sc in Physics and his Ph.D. in Particle Physics and was a staff member for eight years at the European Centre for Nuclear Research (CERN) in Geneva, Switzerland. In 1980, Dr Townsend joined the faculty of Geneva University Hospital. In 1993, he moved to the University of Pittsburgh as an Associate Professor of Radiology and Senior PET Physicist. He was Co-Director of the Pittsburgh PET Facility from 1996-2002, and became Professor of Radiology in 2000. The PET/CT scanner, developed by Dr Townsend and Dr Ronald Nutt, was named by TIME Magazine as the medical invention of the year 2000. Dr Townsend received the 2004 Distinguished Clinical Scientist Award from the Academy of Molecular Imaging, and the 2008 Austrian Nuclear Medicine Pioneer Award. In 2006, he was elected a Fellow of the IEEE. He shared with Dr Ronald Nutt the 2010 IEEE Medal for Innovations in Healthcare Technology. From 2003 to 2009, Dr Townsend was Director of the Molecular Imaging and Translational Research Program at the University of Tennessee, Knoxville. In July 2009, he became Head of PET and SPECT Development for the Singapore Bioimaging Consortium, Professor of Radiology at the National University of Singapore and was appointed Director of the A*STAR-NUS Clinical Imaging Research Centre in December 2010, a position from which he retired in 2018. He has received Honorary Doctorates from the University of the Mediterranean in Marseille, France and the University of Bristol in the UK. He was elected an Honorary Fellow of the Royal College of Radiologists in London. Dr Townsend has co-authored over 175 peer-reviewed publications and book chapters, is a reviewer for a number of scientific journals and has served as an Associate Editor for the Journal of Nuclear Medicine. More recently, he received the prestigious Paul C. Aebersold Award from the Society of Nuclear Medicine and Molecular Imaging, and the Edward J Hoffman Medical Imaging Scientist Award from the IEEE NSS-MIC and shared the Rotblat Medal for co-authoring the 2016 most-cited paper in Physics in Medicine and Biology.