National Research Council Canada
Symbol of the Government of Canada

Physics Finds a Better Way to Target Cancer

Warning Information found on this page has been archived and is for reference, research or recordkeeping purposes. Please visit NRC's new site for the most recent information.

Archived Content

Information identified as archived on the Web is for reference, research or recordkeeping purposes. It has not been altered or updated after the date of archiving. Web pages that are archived on the Web are not subject to the Government of Canada Web Standards. As per the Communications Policy of the Government of Canada, you can request alternate formats by contacting us.

These days, a cancer diagnosis is not automatically seen as a death sentence. Over the years, successful treatments have allowed cancer patients to carry on longer and more productive lives.

One such treatment is radiation therapy, which attacks cancerous tissue using ionizing radiation. Before doctors can use radiation treatments, however, they must first figure out the right dosage – and that's no easy task.

A careful balance of power and protection

Transferring the technology to treatment centres

NRC's dose calculation system was licensed for commercial use in 2000. NRC established a licensing partnership with MDS Nordion, a Canadian company specializing in radiation and other cancer diagnosis and treatment methods. The technology won approval from both Health Canada and the U.S. Food and Drug Administration. Since 2002, it has been used in cancer clinics around the world.


Doctors must ensure they are delivering just the right amount of radiation during cancer treatments – it must be enough to kill the cancer cells but not too much which could harm the patient by destroying healthy tissue. Figuring out how much radiation is required involves meticulous and complex calculations based on the patient's anatomy, the size and depth of the cancer, the characteristics of the radiation beam and the body's radiation allowance, among other factors.

For years, medical physicists have used simplified models for the interaction of radiation with matter to figure out radiation dosages. Although often adequate, there are some situations where these models introduce significant errors. That all changed when physicists from the NRC Institute for National Measurement Standards devised software based on the Monte Carlo technique that lets cancer treatment centres accurately calculate radiation dosages in mere minutes for even the most complicated geometries.

More convenient calculations

The Monte Carlo technique uses statistical methods to follow the path of each ionizing particle from the radiation source until it is absorbed in the material of interest. NRC has been developing and using the Monte Carlo method since 1980, and it remains a leader in the field. NRC's Iwan Kawarakow created the new software program specifically optimized for calculating the radiation dose to patients. His new method was based on the Monte Carlo technique but ran at 100 times the speed of earlier Monte Carlo codes.

Perfecting the calculations and precise mathematical steps required to speed up the process of determining radiation dosages took years, but NRC eventually developed the necessary techniques.The software package it developed can be easily integrated into the sophisticated treatment planning systems medical professionals already use to visualize anatomy, see tumors and make decisions about how to treat them. The addition of the NRC software helps them accurately predict the radiation that will be delivered to the tumour and healthy tissue.

Cutaway view of a mannequin subject to electron beam radiotherapy treatment planning.
Cutaway view of a mannequin subject to electron beam radiotherapy treatment planning.

NRC's research activities have helped improve radiation treatment, providing cancer specialists with a speedy and highly-accurate means of helping their patients. Today, NRC continues to host medical physicists from around the world at training courses about radiation dose calculations.