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SINGAPORE-BASED physicist David Townsend is in the vanguard of what promises to be a revolutionary breakthrough in biomedical imaging.
 The British-born scientist is one of the two inventors of the original PET/CT scanner – Time magazine’s medical science invention of the year in 2000 – and is working here to push the frontiers of diagnostics further by combining positron emission tomography (PET) with magnetic resonance imaging (MRI).
The combination promises a quantum leap in cancer diagnostics, and the head of the Singapore Bioimaging Consortium is racing against other research bodies to bring out the first fully functioning PET/MRI scanner for hospitals.
Professor Townsend, 65, explains that while a PET/CT scanner can spot an abnormal growth in the body as well as its growth rate, a PET/MRI system would provide better structural detail, especially of soft tissue, and expose the patient to less radiation.
Doctors could see anatomical changes, such as a tumour hidden in tissue, by MRI, and get functional information, such as whether it is malignant, by PET.
As well as helping to diagnose and treat disease, such a powerful combination could find out whether drugs are working by watching them travel through the body. But there are many challenges to overcome in developing such a machine before it can be used on humans.
Prof Townsend admitted the PET/MRI combination is much more technically challenging. “While PET and CT don’t interfere with each other, unfortunately inside a magnetic field, PET detectors don’t work at all.”
He is upbeat about overcoming this and other issues though, and predicts
that PET/MRI scanners could be working in hospitals “in another 10 years or so”.
“It is something we are working out in Singapore because we have an outstanding institute here and we are collaborating with Siemens to come up with a combined PET/MRI system,” he said.
He sees the new technology working alongside PET/CT scanners.
When the first magnetic resonance systems appeared in 1982, pundits said CT would be finished in five years, given the radiation produced, he said. “CT today is better than it’s ever been – faster, higher resolution, lower doses. Any prediction that PET/MRI would replace PET/CT would go the same way, I feel.”
Prof Townsend’s background and research pedigree suggest he and his team stand a good chance of beating the technical challenges. He was trained in nuclear physics and has a PhD in particle physics from the University of London.
He worked for eight years at the European Centre for Nuclear Research in Geneva, Switzerland, before joining Geneva University Hospital as a physicist in the Department of Nuclear Medicine in 1980.
His tenacity and belief in the PET/CT scanner – combining the best of PET and CT technologies to identify and localise a tumour at an early stage in a single swoop – won him and his co-inventor, electrical engineer Ronald Nutt, the prestigious 2010 Institute of Electrical and Electronics Engineers Medal for Innovations in Health-care Technology.
The idea came in 1992 when a surgeon walking by made a remark to the two on the ample space in the shell of a rotating PET scanner.
“So we came up with the idea of putting CT into this little rotating PET scanner and we started asking people what they thought,” he recalled.
The duo battled naysayers who felt the fledgling device would never work, be too expensive or fail to make a difference.
Three years of refining the concept and shuttling between Knoxville, Tennessee, where Dr Nutt’s company was located, and Geneva took a toll.
But winning US$3 million from the National Cancer Institute (NCI) to work with Siemens Molecular Imaging to design and build the next generation of PET/CT scanners was a key milestone.
Prof Townsend and his colleague never felt like throwing in the towel, even when NCI rejected their first application.
“Two reviewers missed the point of what we were trying to do. So we decided we had just not explained our idea clearly.”
Even when engineers at Siemens, the conglomerate that helped to develop the PET/CT scanner, said the inclusion of PET would do nothing to boost sales, they did not lose heart.
It was no comfort to Prof Townsend that Siemens was later pipped at the post by General Electric, which shipped the first PET/CT scanner to Zurich in 2001.
The sprightly professor is looking forward with zest to developing the PET/MRI. He has no thoughts of retiring on royalties earned from his previous invention, as some peers have suggested.
“I’ve never really looked on these activities much as a job. It was more of something I just like doing,” he said. “Retiring is certainly not the reason I moved to Singapore. It’s the opportunity.”
Prof Townsend has lived in Europe and the United States, and had always thought of spending time in Asia. So, when he heard Singapore wanted to expand into the PET field, he jumped at the chance of moving here last year.
“It was just a neat fit, with me reaching a point in my career where I wanted to do the same thing but somewhere different, rather than wanting to do something different.”
A drying up of research and development funds in the US, in a weaker economy, helped him make up his mind.
“Singapore offers tremendous opportunities for translational research in the medical imaging field,” he said, referring to research that could be translated into treatment for patients in hospitals.
“The environment and resources available are actually making it happen.”
Taking a look inside
w POSITRON EMISSION TOMOGRAPHY SCAN (PET SCAN)
A nuclear medicine imaging procedure using radioactive isotopes or atoms that are bound to a dye injected into the patient’s body. This allows the doctor to study the rate of growth of abnormal tissues, especially in cancers.
w COMPUTED TOMOGRAPHY SCAN (CT SCAN)
A computerised X-ray procedure that gives cross-sectional images of the body. These images are more detailed than conventional X-ray films, and can reveal disease or abnormalities in tissue and bone. The procedure is usually non-invasive.
w POSITRON EMISSION TOMOGRAPHYCOMPUTED TOMOGRAPHY SCAN (PET-CT SCAN)
The combination provides images that pinpoint the location of abnormal growth within the body and the rate at which it is growing. The combined scans have been shown to provide more accurate diagnoses than the two scans done separately.
w MAGNETIC RESONANCE IMAGING (MRI)
A non-invasive medical imaging technique used to look at detailed internal structure and limited function of the body. It uses a powerful magnetic field to provide a greater contrast between the different soft tissues of the
body, making it especially useful in scanning the brain, the central nervous system and the heart.
w POSITRON EMISSION TOMOGRAPHYMAGNETIC RESONANCE IMAGING (PET-MRI)
It provides better structural detail than CT scans, especially of soft tissue, and gives off less radiation. But this combination is difficult because the two systems interfere with each other. The MRI scanner relies on very strong magnetic fields that can easily be disturbed by metallic objects inside the scanner. At the same time, magnetic fields can seriously affect the detectors and electronics needed in PET scanning.
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