Credit: Elizabeth Roberts
"Forty percent of cancer patients in Australia receive radiation therapy to cure or manage their disease. My job involves developing new imaging and treatment approaches specifically for these patients," says medical physicist Paul Keall.
Keall has spent much of his career finding ways to accurately hit a moving target. He is a specialist in radiation oncology, where high energy X-rays produced by a linear accelerator are used to kill cancer cells. The target in question is the tumour, an extreme example of which is lung cancer. Lung tumours can move up to centimetres and even rotate as a patient breathes. The disease is the leading cause of cancer deaths worldwide and has a very low five-year survival rate of 16%.
Traditional strategies for getting sufficient radiation into the tumour target include adding a beam margin around it to compensate for motion. However, this means healthy tissue surrounding the tumour receives a significant radiation dose too. This can result in toxic side effects, ranging from mild to severe, that can reduce a patient's quality of life. Keall's research has included the ongoing development of a smart beam aperture for the linear accelerator that tracks the tumour as it moves, reducing the amount of healthy tissue irradiated.
Intelligent imaging for cancer
Keall and his team have also started to develop an intelligent imaging system specifically for lung cancer patients. The new scanner will be integrated with a linear accelerator and enable more accurate positioning of the patient on the treatment couch prior to therapy.
Keall finds medical physics particularly rewarding given the opportunities to tangibly benefit individuals' lives. "I really enjoy the ability to go from idea creation to clinical translation that is offered by medical physics research. It's incredibly satisfying to have ideas that start in the laboratory, follow them with experiments in the clinic and then see these new technologies for patients being adopted around the world."
Keall and his peers have a vision for the future of radiation therapy. "We would like to target the radiation beam to the moving tumour anatomy. In the clinic, if a tumour moves out of the radiation beam, we have no way of correcting for that," he says. "Beyond that, we'd like to customise the radiation beam to account for variations in tumour physiology. For example, we know hypoxic regions in a tumour - which contain low amounts of oxygen - can be the most aggressive and resistant to the effects of radiation. If we can selectively boost radiation to these regions, it's anticipated we'll have greater clinical success."
