Dr. Magdalena Bazalova-Carter lives life big — big mountains, big climbing walls, big bike rides. But when she’s not climbing 6,964 m to the highest peak of the Americas or biking 2,297 km across Western Canada, she has her sights set on much smaller things in life; things that can’t be seen with the naked eye: atoms, x-rays and cancer cells.
Bazalova-Carter, a Czech Republic native with a background in engineering physics, left the world of high energy physics, as well as her position at the Institute of Physics of the Czech Academy of Sciences, to pursue her interest in medical physics back in 2005.
“I wanted to switch to medical physics because it’s much more satisfying to be helping people,” says Bazalova-Carter. “I wanted to make an impact.”
In addition to becoming a certified clinical medical physicist, Bazalova-Carter is now an assistant professor with the University of Victoria’s Department of Physics & Astronomy and a recipient of the Canada Research Chair in Medical Physics. Her home base is the X-ray Cancer Imaging and Therapy Experimental (XCITE) Laboratory, where she conducts research on innovative x-ray imaging techniques and radiation therapy.
X-ray fluorescence computed tomography (XFCT). One of Bazalova-Carter’s objectives is to improve cancer detection by conducting research into combination imaging techniques that are capable of generating standard x-ray-based anatomical images, along with novel PET-like physiological images. She is particularly interested in diagnostic x-ray fluorescence computed tomography (XFCT).
“It’s like CT,” says Bazalova-Carter, “only better.”
A traditional CT scan produces a 3D anatomical image by capturing the direct emerging beam of x-rays as it passes through the human body. X-rays interact more with particular types of human tissues (bones for example), while they pass almost straight through other types of tissue (such as lung). An x-ray image is much like the shadow produced on the wall when a hand is placed in front of a flashlight.
XFCT has the added benefit of also capturing a secondary scattered x-ray beam that is produced when an atom absorbs the x-ray’s energy and displaces one of its electrons. This phenomenon allows for the production of an additional high contrast image that pinpoints high atomic number elements within the scanned structure.
This is important because another one of Bazalova-Carter’s research areas is selective nanoparticle (aka extremely small particles) uptake by tumor cells. Because these nanoparticles tend to be composed of high atomic number elements, such as gold, XFCT could play an important role in refining tumor location and imaging.
Dose-enhanced radiation therapy (DERT) with nanoparticles. Bazalova-Carter hopes that by studying the effects of various nanoparticles in conjunction with traditional radiotherapy, cancer radiation treatment outcomes will improve.
The overall concept, in a nutshell, is that nanoparticles can be modified — often by tagging them with antibodies that seek out specific antigens found on cancerous cells — so that they are taken up exclusively by the tumor.
These tumor-bound nanoparticles, when irradiated with kilovoltage x-rays, have the capacity to act as radio sensitizers, “meaning that the dose deposited in the vicinity of the nanoparticles will be much higher than it would normally.” This means that clinicians could selectively deliver the radiation to the nanoparticle-tumor-complex in higher doses, while decreasing the dose to healthy tissues caught in the periphery of the radiation beam. Ultimately, this means less potential for negative side effects.
Working in collaboration with UVic colleague, Dr. Frank Van Veggel, Bazalova-Carter will be experimenting with a host of nanoparticles — from gold to lanthanides — and variables that include: nanoparticle type, concentration and size (is it small enough to cross the blood brain barrier if desired?), as well as optimal energy dosages for distinct tumor sites (shallow versus deep).
Kilovoltage arc therapy (KVAT). Another one of Bazalova-Carter’s goals is to design and develop a more economical radiotherapy source that can treat a broad range of cancers. She is currently looking at the feasibility of using kilovoltage x-rays, rather than the megavoltage x-rays predominantly used in radiation therapy. Kilovoltage-based machines would also allow clinicians to tap into the additional benefits of nanoparticle-dose enhancement.
Megavoltage machines require a linear accelerator and, thus, carry a hefty price tag, upwards of $5 million per machine. “We are hoping to make a kilovoltage machine for about $200,000,” says Bazalova-Carter, “because we don’t need linear accelerators and it would be our own technology.”
While kilovoltage machines aren’t novel (they are routinely used in treatments of superficial lesions and in small animal radiotherapy machines), designing one that is capable of successfully delivering effective doses of radiation to deep-seated cancers within the human body will require a substantial amount of work.
Along with graduate student and Vanier Scholarship-recipient, Dylan Breitkreutz, Bazalova-Carter will conduct Monte Carlo simulations in order to calculate the optimal geometric design for a KVAT machine. She hopes to have a prototype completed within the next 5 years.
Small animal radiotherapy. In collaboration with Dr. Julian Lum and the BC Cancer Agency’s Deeley Research Centre, Bazalova-Carter intends to test out the research she is conducting at XCITE Lab. She hopes to mount her XFCT system onto the Centre’s small animal radiotherapy kilovoltage machine and irradiate mice injected with nanoparticles in order to study the outcomes and side effects of the experimental procedure.
Very high-energy electron (VHEE) beam therapy. Bazalova-Carter also has a “small side project” she is working on. Having already completed a substantial amount of the ground work for therapy with very high-energy electron (VHEE) beams during her instructorship at Stanford, Bazalova-Carter continues to have an interest in the potential of successfully employing VHEE in cancer treatment modalities. She is currently looking at collaborating with TRIUMPH at the University of British Columbia.
VHEE is of great interest because it allows a much faster radiation dose delivery rate. This is advantageous because it means that squirmy, pediatric patients and those with difficult-to-immobilize tumors (ie lung tumors) won’t have to remain still for treatments that currently take between 3 to 90 minutes long. Shortened treatment times could also mean a reduction in nasty side effects.
There are only so many hours in a day and, in her own words, “only so much space in my brain”, but Bazalova-Carter is still always able to find time for her students.
“I think it’s really satisfying to be training students and helping with their future careers,” says Bazalova-Carter. “I think that’s really just as important as research.”