CentreMeet for Probe Development McMaster
John Valliant ‘93, ‘97, leads the Centre for Probe Development and Commercialization, one solution to Canada’s innovation gap.
When John Valliant was young, his mother, a physiotherapist, used to bring home copies of Scientific American given to her by a retired doctor. As mother and son pored over the magazines together, Valliant’s fascination with science began to take root. Today, it is bearing fruit. As an associate professor of chemistry and medical physics and CEO and Scientific Director of the Centre for Probe Development and Commercialization, he is helping to change the face of medical imaging. He is also positioning McMaster as a leader in the growing field of molecular medicine. Valliant was born in Montreal and grew up in Kingston. In high school he fell in love with chemistry, a subject that brought together his interest in physics, mathematics and biology. He arrived at McMaster as an undergraduate in 1989, and got his first taste of hands-on lab work when Dr. Ed Hileman hired him as a summer student. “That changed my life,” he says. “You never know what doing research is like until you get the real experience. I knew immediately that I wanted to do research.”
When it came time for grad school, Valliant ended up working with two McMaster professors, Russell Bell and the late Colin Lock, on an early project to turn radioactive isotopes into imaging probes. “It combined all my different interests and sounded like an incredible field,” says Valliant. And so it has proved. Medical imaging lies at the heart of modern medicine, allowing physicians to detect disease, diagnose it correctly and monitor treatment, all without opening up patients. It began in the early 20th century with the invention of X-ray technology. Imaging has become increasingly sophisticated over the years, but until the past decade, most technologies imaged anatomical structures, such as bones, organs, and tumours. Valliant and his team are working on the new frontier – functional or molecular imaging. This rapidly advancing technology detects the biochemical changes that lead to disease and helps physicians diagnose disease long before conventional imaging can show anatomical changes. Molecular imaging uses chemical probes or biomarkers in combination with imaging
techniques like positron emission tomography (PET) scanners. The probes are drugs that are designed to carry radioactive isotopes to the disease sites, bind to target receptors on the diseased cells, and then emit a signal that a PET scanner uses to create an accurate image of the biochemistry at the site. For example, tumours generally grow rapidly and consume more glucose than normal cells. Radioactive isotopes attached to a probe made from glucose will accumulate in diseased cells at much higher concentrations than in healthy cells and alert physicians to the presence of a tumour. The next generation of probes that Valliant and his team are developing will be used to indicate the aggressiveness of a tumour and the likelihood of a tumour spreading — important information that physicians can use to personalize patient care. Molecular imaging can also be used to monitor treatment. The probes can indicate declining biochemical activity of a tumour within just a few days of starting treatment, quickly providing doctors with an accurate idea of how each individual patient is responding to Left: John Valliant and Karin Stephenson of the Centre for Probe Development and Commercializaton Above: Lead-lined container used to ship Glucovision to a PET imaging centre. McMaster Times - Fall 2010
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