Weighing in on 60 combined years of ionizing radiation

- Ottawa, Ontario

Cancer refers to a large group of diseases involving abnormal cell growth, with the potential to invade or spread to other parts of the body. At some point, cancer will affect everyone, either directly or through a loved one. It is the leading cause of death in Canada, accounting for 30% of all mortalities. During their lifetime, 1 in 2 Canadians will be diagnosed with cancer and 1 in 4 will die from the disease.

For years, radiation therapy has been one of the primary methods for treating cancer. As a full cure or to relieve pain, radiation therapy can be used alone or alongside other techniques, including surgery or chemotherapy. The purpose of radiation therapy is to use ionizing radiation to destroy tumors and cancer cells while saving healthy tissues at the same time. Ionizing radiation dosimetry is the measurement or calculation of energy deposited by the interaction of ionizing radiation with matter per unit mass, also known as the absorbed dose.

Since the 1950s, the National Research Council of Canada (NRC) has been finding ways to support and improve cancer-related research. Now, in 2021, 3 researchers from the Metrology Research Centre are each celebrating 20 years of working to advance knowledge and skills in ionizing radiation, helping in the fight against cancer. Researchers Ernesto Mainegra‑Hing, Hong Shen, and Stewart Walker from the Ionizing Radiation Standards (IRS) team spend each day exploring and designing new, more reliable ways to measure and control ionizing radiation.

Calibrating excellence

Low- and medium-energy X-rays are widely used for imaging, such as computed tomography (CT) scanning and radiation therapy. There is a narrow window in which the application of ionizing radiation is intense enough to have a diagnostic or therapeutic effect, while minimizing collateral damage to healthy tissue. In order to achieve this, the energy per unit mass delivered during patient treatments must be estimated and monitored precisely; this optimizes the effectiveness of a radiation treatment and safeguards patients during imaging. Having calibrated instruments for this task is a crucial requirement at any cancer centre or hospital. It is a life-saving service the NRC provides to the public.

All the instruments used to measure the output of radiation-producing devices should be traceable to a primary calibration laboratory—the NRC is one of many around the world, but the only one in Canada. Developing the equipment and techniques to provide accurate measurements and traceability has required much work to be done over many years, and has not been an easy feat.

"X-rays have been used for imaging and therapy almost since the day they were discovered by Willhelm Roentgen in 1895. The safe use of these radiation beams requires accurate measurements, performed by medical physicists in cancer centres and hospitals all across Canada. Those measurements depend on the standards and calibrations provided by this experienced trio of scientists," says Malcolm McEwen, Director of Research and Development at the Metrology Research Centre.

Behind the science

Ernesto Mainegra-Hing is a research officer responsible for low-energy photon beam calibrations including X-rays, brachytherapy and irradiators. He provides scientific support to calibration services such as improving the accuracy of existing standards, developing new standards, and supervising client calibrations, in addition to providing maintenance and development of calibration service software. His favourite part of the job is finding new and different ways to speed up computer simulation to reach desired results in record time.

Stewart Walker is a technical officer and takes care of the equipment for the entire workgroup. He is the electronics specialist in charge of helping his colleagues deal with technical problems, checking data from the server for irregularities, and designing and assembling new devices. He considers long‑term solutions, thinks about how one solution can address multiple potential liabilities, and evaluates what could possibly go wrong with a system so he can pre-emptively fix it. When something does go wrong with any of the equipment, he analyzes the problem and works out a solution.

Hong Shen, Technical Officer, spends a lot of his time providing low- and medium-energy X-ray calibration services to clients. However, he also works on research projects and is currently developing a national primary standard to measure the radioactive strength of brachytherapy seeds, which are used to treat cancer. Brachytherapy is a type of internal radiation therapy that involves implanting multiple small, encapsulated, radioactive sources inside, or close to, the cancer tumor. He began the project in 2014 and the first calibrations for Canadian cancer centres were carried out in 2020.

In addition to the research work the team does to advance ionizing radiation, for the past 8 years the group has been growing their moustaches in November to raise money for the Movember Foundation to increase the awareness of men's health issues.

Moving forward

"The important part of the work being done is to be innovatively conservative: to make improvements to long-term reliability and accuracy while not making disruptive changes, to double-check to avoid single points of failure," shares Stewart Walker. "Perfection is important in standards work; innovation is important in research work. Team cohesion is very important in maintaining quality even though we all work fairly independently on our particular aspects of the job."

These researchers are certainly not sitting on their laurels. Every facet of the operation is looked at to see where improvements can be made. The team has 2 new X-ray tubes that should be commissioned soon, which will replace the older machines currently in use. They are working on a full overhaul of the calibration software which will make delivering the service more flexible. Increased integration of the X-ray laboratory with the other facilities operated by the IRS team is also part of the plan, and the application of high‑performance computing to the analysis is part of a wider research plan to leverage data science techniques to increase the accuracy of the measurements and calibrations that the team provides.

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