Medical Physics

The Medical Physics Department within the Cancer Centre has an active research program with goals to improve the quality and safety of radiation therapy both locally and around the world.  The program has three principal areas of research:  

 New tools for measuring radiation dose

Gel Dosimetry
Modern radiation therapy involves focusing radiation on the cancer cells in a patient while limiting the radiation received by healthy organs.  To do this the radiation dose delivered must have a complex three dimensional (3D) pattern.  However, traditional dose measurement tools can only measure the radiation dose to one point in space at a time.  As a result, radiation measurements to check the accuracy of treatments are time-consuming and challenging.   

Researchers John Schreiner, Tim Olding and Greg Salomons in the Medical Physics department and their graduate students are working on 3D gel dosimeters capable of measuring these complex 3D dose distributions.  Their work involves collaborations with Dr. Kim McAuley, Queen’s Chemical Engineering, to study the fundamental behavior of these dosimeters; with Dr. Gabor Fichtinger from the PERK Lab at Queen’s School of Computing to improve the computational environment to analyze the complex dose data inherent with 3D measurements; and Modus Medical, a company working on providing clinical tools to extract the 3D dose measurements from the gels.  Dr. John Schreiner has developed an international reputation for his work on these dosimeters. 

Film Dosimetry
Medical Physicists have been using radiation-sensitive film to check radiation patterns for a long time, but extracting quantitative information from the film continues to be a challenge.  To address this challenge, Dr. John Schreiner, Dr. Tim Olding and Dr. Greg Salomons and their students are working in partnership with Modus Medical, to develop a new device to obtain accurate quantitative dose measurements from modern radiation sensitive film.  

Improved Patient Safety

More accurate Brachytherapy Treatments
Brachytherapy is a specialized radiation therapy technique that involves placing one or more radioactive sources next to or within a tumour.  The advantage of this technique is that radiation doses to the rest of the patient are greatly reduced so that higher doses of radiation can be safely given to the tumour.  However, accurate placement of the radiation sources is key to effective treatment.  

Dr. Chandra Joshi, Dr. John Schreiner and Dr. Conrad Falkson, (a Radiation Oncologist at KHSC) are teaming up with Drs. Gabor Fichtinger and Andras Lasso of the  Lab for Percutaneous Surgery (PERK) at Queen’s School of Computing to tackle this challenge.  They are working to combine modern imaging techniques with 3D printing to generate custom templates which can be used to precisely and reproducibly guide the placement of the radioactive sources for a patient’s treatment.

Pacemaker safety
The use of pacemakers and other cardiac implantable electronic devices (CIEDs) has been steadily increasing.  As a result it is increasingly common for patients requiring radiation treatments to be using one of these devices.  Unfortunately, there is a chance that these devices might fail if they receive too much radiation.  To keep these patients safe, it is important to be able to accurately measure the radiation dose received by a CIED and to track that dose over the lifetime of the device.
Dr Chandra Joshi has performed several studies aimed at improving our accuracy in estimating radiation doses being received by a CIED.  Dr. Andrew Kerr is tackling the problem from a different angle but working on a solid state dosimeter which could be incorporated into the CIED at the same time of manufacture.  This dosimeter would then provide a means tracking the actual radiation dose received by the pacemaker from all sources.  

Software safety
As the use of technology in healthcare expands, so too has the reliance on software, to the point where software failure is no longer just an inconvenience, but has the potential to be life-threatening. Dr. Greg Salomons, a medical physicist at KHSC, has teamed up with Dr. Diane Kelley, a software engineer at the Royal Military College of Canada, to develop methods to ensure that software being used in a hospital will always be safe for patient care 

New uses for old technology

Modern radiation therapy units are complex robotic systems that require an extremely stable electrical supply system and a clean, reliable water supply for cooling. In many parts of the world this infrastructure is not always available.  A team of medical physicists, graduate students and other trainees at KHSC have joined forces with Best Theratronics to develop treatment technology which is capable of performing modern radiation therapy techniques, and yet do not require the robust infrastructure needed by other therapy units.

Modern treatments with Equinox 
The very first high energy radiation therapy machines were invented in Canada in the 1950s and used Cobalt-60 as their radiation source.  The Cobalt-60 unit was a workhorse of many clinics until the 1980s, but since that time little work was done to improve the Cobalt-60 unit and machines using linear accelerator technology replaced them.  The result has been that hospitals in regions with less reliable infrastructures have difficulty maintaining the operation of modern radiation devices and lose valuable treatment time. The alternative is often the robust Cobalt-60 unit, which can perform only very basic treatment techniques.

Best Theratronics is going back to the Canadian roots, taking that original Cobalt-60 technology and working to make it capable of modern radiation therapy techniques.  The company has recently upgraded our circa 1970 model into the newest Cobalt-60 machine, the Equinox, giving it the functionality of a modern unit.  Dr. John Schreiner and Dr. Chandra Joshi are performing extensive tests on this machine, along with additional accessories being donated by Best Theratronics, to compare its ability to deliver modern radiation therapy with that typical of linear accelerator based units now used in modern clinics.

Flattening filter design for a Cobalt-60 Total Body Irradiation Unit
Total body irradiation (TBI) is an important modality in the treatment of certain types of blood-based cancers. A Cobalt-60 teletherapy unit is particularly suitable for TBI, as it can be made to produce a large, uniform radiation field, so that the patient can be in a comfortable stationary position during the whole treatment. Best Theratronics is currently developing a Cobalt-60 TBI unit in collaboration with Drs. Schreiner and Joshi. In particular students ate KHSC are designing accessories for the unit to optimize beam parameters using Monte Carlo simulations, as well as other radiation dose calculation techniques.