Can Photoacoustic Imaging Be Useful in Cancer Treatment Monitoring?
By Connie Jeske Crane
Whenever a particular cancer treatment is tested, doctors and patients alike have a similar question – is it working? With both novel and traditional cancer therapies, accurate imaging tools are key in being able to monitor effectiveness.
At Ryerson, Eno Hysi, a Biomedical Physics PhD candidate, wants to investigate this clinical problem of how early on physicians can determine if a particular treatment is having an effect. At the moment, traditional methods come with a couple of barriers. The first is timeliness. “Typically, patients undergo their entire prescribed treatment before the oncologist can determine whether the treatment was effective,” explains Hysi. “This is of course not ideal and often times a second treatment is required.”
Cost is another factor, he adds. “Currently, most traditional techniques such as MRI or CT scans are too expensive and burdensome on the patient to be implemented routinely. There is a need for a cheap, non-invasive and reliable technique that can provide sufficient structural and functional information on tumors as they undergo treatment.”
Here, supervised by Dr. Michael Kolios, Hysi and fellow researchers have been conducting innovative research involving the use of photoacoustic (PA) imaging to monitor cancer treatment response in a small animal, in-vivo tumor model. “PA imaging is a hybrid modality which relies on the detection of ultrasound waves from the absorption of laser light into tissue.”
As for the team’s methodology, the first step in the Ryerson team’s project, was to innoculate test mice with breast cancer tumors. (Hysi says an animal experiment was a first for him.) Next, mice were treated with a thermosensitive liposome which releases a chemotherapy drug called doxorubicin when the tumor and its blood vessels are heated to 42◦C. (This novel approach minimizes overall toxicity of chemotherapeutic drugs.) Post-treatment, Hysi and fellow researchers Lauren Wirtzfeld, Jonathan May, Elijus Undzys, Shyh-Dar Li, and Kolios, performed PA imaging at very short intervals – after 30 minutes, two hours, five hours, 24 hours and seven days post-treatment. Using PA imaging, the Ryerson team estimated the oxygen saturation (sO2) of the tumor blood vessels using at each interval. The frequency content of the PA signals was also analyzed to monitor the changes in the size of the tumor blood vessels.
Interestingly, Hysi says the team noted significant changes right away. “We found that combining the sO2 estimates with the frequency analysis allowed us to differentiate treatment responders from non-responders as early as 30 minutes after the administration of treatment.”
Among other duties, Hysi, the paper’s first author, designed the experimental methodologies of the project, devised and implemented an imaging sequence and developed signal processing techniques for extracting the frequency response from the tumors.
As a Ryerson student for 11 years (six as a graduate student), Hysi says, “I have made countless memories over the years but I would have to say that winning the Vanier Canada Graduate Scholarship definitely stands out for me. I felt extremely humbled and privileged that Ryerson’s research is being recognized in the national stage.”
Hysi also adds that says choosing Ryerson was the best decision he ever made. “At Ryerson’s Biomedical Physics program I found the perfect niche where I was exposed to cutting-edge research and a group of faculty and students who truly wanted to see me succeed.”
Hysi’s research was supported through a Vanier Canada Graduate Scholarship, NSERC, CIHR, the Terry Fox Foundation and the Ontario Institute for Cancer Research.