Professor David Townsend

Doctor of Science Professor David Townsend

Friday 12 July 2013 at 4.45 pm - Orator: Professor Nick Brook

Mr Pro Vice-Chancellor,

Physics is at the core of science - underpinning advances in chemistry and biology through to engineering and medicine. It allows us to design solutions to real life problems and to revolutionise the world we live in. It stretches from fundamental research at places like CERN to the very foundations of today’s society. It provided the fuel for the industrial revolution, through to electricity, to electronics, to computers, to quantum technologies.  Often the solutions physicists find have unexpected impacts in new areas of activity: new biomedical imaging techniques and cancer treatments, broadband communication, solar cells, green energy and power, organic photovoltaics, nanotechnology and advanced materials. David Townsend, whom we are honouring today, has played his role in that revolutionary Physics.

Physics and science graduates move into many professions. Those such as research in universities and government laboratories, and drivers of high technology industries, require discipline-specific knowledge. However, science graduates are also keenly sought for their ability to think critically, analyse data and solve abstract problems. Bristol scientists can be found in academic institutions, laboratories and industries around the globe. I am proud to say David is one of you – a Bristol graduate.

The use of fundamental discoveries in Physics has a rich history in medical diagnostics. Soon after the discovery of X-rays, in 1895, they were being used for investigating bones or teeth within the body and hence “radiography” was born.  Half a century later the concept of radioactive tracers was invented. The idea is that small doses of radioactive material are administered to patients allowing the study of organs such as the kidneys or thyroid gland. The need for a supply of suitable radioactive isotopes means some hospitals have their very own particle accelerator.

Physicist around the world are leading the fight against cancer, whether that is through developing detectors and novel imaging techniques to detect cancerous cells or applying accelerator technology to destroy them. In fact, there are six of these accelerators in the basement of the hospital just across the road from where I work. The latest UK figures show there were nearly 160,000 deaths per annum from cancer and that is predicted to grow to 190,000 by 2030. It is estimated that cancer costs the UK economy nearly £16 billion every year, half of which is due to premature deaths and lost working days.  And that is not to mention the personal emotional turmoil and anguish this disease causes.

The creation of the hybrid positron emission tomography/computed tomography (or PET-CT) scanner by David Townsend and his collaborators transformed diagnostic medical imaging. It enabled earlier detection of cancer and better monitoring of the effectiveness of treatment. PET scanners make use of that stock in trade of Star Trek and other science fiction literature – antimatter. A positron (an anti-electron), once produced from a radioisotope injected in the body, is quickly annihilated by matter, usually an electron. This annihilation of the positron and the electron produces a characteristic signal - two gamma rays travelling back-to-back. From this it is possible to extract where in the body these annihilations occurred. The beauty of the PET scanner is that it allows non-invasive detailed diagnostic measurements of the physiological and biochemical processes within the body whilst the anatomic (structural) changes are detected via (X-ray) CT technology that helps determine whether a cancer is benign or malignant.

It is by no means an exaggeration to say PET-CT detectors really did radically transform approaches to medical imaging. The first prototype PET-CT detector only became operational in 1998 whilst the first commercial PET-CT scanner came on the market 3 years later, in 2001. Just 5 years further on, the previous PET-only scanners were no longer commercially obtainable. The better diagnostics from the PET-CT approach had made them obsolete. At the time PET-CT was one of the fastest growing medical imaging technologies, rivaling the growth of Magnetic Resonance imaging during the 1980s and 1990s. This is even more impressive when you realise one of these scanners is likely to set you back by well over a million pounds.  Within the NHS in England there are approximately 50,000 PET_CT scans every year.

It is not only the University of Bristol that has recognised David’s significant achievement. His success has been recognised around the globe. TIME magazine awarded the scanner the accolade of the medical invention of the year in 2000. In recognition of his work on PET-CT, he received the 2004 Distinguished Clinical Scientist Award from the Academy of Molecular Imaging, and the 2008 Nuclear Medicine Pioneer Award from the Austrian Society of Nuclear Medicine. In 2006, he was elected a Fellow of the Institute of Electrical and Electronic Engineers (IEEE). In 2009 the IEEE created a new award for innovations in healthcare technology. This award was created to celebrate outstanding contributions and/or innovations in engineering within the fields of medicine, biology and healthcare technology. A year later David became the first recipient of that medal. Last, and by no means least, in 1999 he received the Image of the Year Award from the Society of Nuclear Medicine in the US, for an image from the very first prototype scanner combining state-of-the art PET with diagnostic-quality CT. Another measure of the impact of David’s work is that his initial academic paper on the PET-CT scanner, in the Journal of Nuclear Medicine, has been cited nearly 800 times.

Of course all of these things alone are excellent reasons for honouring David here today.  But to top it all, David was a Physics graduate of the University of Bristol. After graduating from Bristol, David obtained a doctorate in experimental high-energy physics (as Particle Physics used to be known) before moving to work at CERN in 1970’s. Even in the 1970’s technology and scientific advancement went hand-in-hand at CERN. During his time in Geneva David also worked closely with the 1992 Physics Nobel laureate, George Charpak, on medical applications of Charpak’s multi-wire chambers. At the time David was working at CERN, weak neutral currents were discovered there which were a significant step towards unifying the fundamental forces of electromagnetism and the weak force, which govern radioactive decays. The very same radioactive decays used in the radioactive tracer used in the PET technique. In 1979 David moved to the University Hospital of Geneva. The concept of the PET-CT developed from the early work on the PET scanner that David was undertaking in Geneva. It was during this time David and co-workers developed a rotating bank of scintillator detectors for use as a PET detector. It was then the suggestion was made to fill the gaps between the banks of these detectors with the CT technology.  Easier said then done! The crucial problem that had to be overcome was how to find the space to mount both CT and PET components.

But it was only after David moved to Pittsburgh in 1993, that his group in the US overcame the earlier problems and helped to develop the first combined PET-CT scanner. From 2003 to 2009, he was Professor of Medicine and Radiology, and Director of the Molecular Imaging and Translational Research Program at the University of Tennessee. He is currently the Director of the Clinical Imaging Research Centre at the National University of Singapore.

Mr Pro Vice Chancellor, I present to you David William Townsend as eminently worthy of the degree of Doctor of Science honoris causa.


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