Cancer Research

New electromagnet guidance for brachytherapy aims to improve targeting

Ananth Ravi and Eric Leung

When Debbie Vaz heard about a research trial testing a new navigation system for brachytherapy, she says the decision to participate was a “no brainer.”

“Anything I could do to help with a medical advancement, I’d do it,” said Debbie, of Oakville.

Initially diagnosed with uterine cancer in 2017, Debbie underwent a radical hysterectomy as well as chemotherapy and external beam radiation. At a check-up earlier this year, Debbie learned that cancer had returned to her gynecological area. She was referred to radiation oncologist Dr. Eric Leung at Sunnybrook, who recommended brachytherapy treatment.

Brachytherapy is a type of radiation therapy where a radiation source is placed directly in the tumour. For interstitial brachytherapy, a cylinder and applicators that look like needles are inserted in or around the vagina, cervix or uterus near to the tumour. The applicators are attached to treatment unit that move a radiation source precisely through the applicators to treat the tumour.

Currently, for gynecological interstitial brachytherapy, an MR image is taken about a week prior to the procedure. The radiation oncology team uses the MRI to plan the placement of the needles in relation to the cylinder that is placed into the vagina.

“Placing the needles is like driving on a street at night with no lights: it’s difficult,” said medical physicist Ananth Ravi, PhD. “So we do use ultrasound imaging while placing the needles, but that image is very much like using dim headlights: it’s still very difficult to see.”

The radiation oncologist studies the MRI and relies on the ultrasound image to place the needles as near to the tumour as possible. Once placed, the patient gets an MRI to check the needle placements and often needles have to be repositioned, removed or pulled out.

Ananth and research engineer Mark Semple, and their team, wanted to give the radiation oncologists a better way. Because of Sunnybrook’s high volume of brachytherapy cases, the team is well positioned to determine challenges and motivated to invent solutions.

“We wanted to turn the high beams on, so to speak,” he said.

The team repurposed existing electromagnet tracking technology combined with other made-in-Sunnybrook parts to create an active guidance system for gynecological interstitial brachytherapy. A device is attached to the cylinder, which tracks the needle placement. The system is connected to a nearby computer, so the clinicians can see where the needles have been placed with respect to the tumour.

A trial is underway to test the system’s safety and begin to compare its efficacy with the current way of placing needles. This March, Debbie was the first person to undergo brachytherapy using this electromagnet navigation as part of this trial.

“The radiation oncologist will use this new system for one insertion procedure and the current standard for the other,” explained Ananth.

Dr. Leung says the first few treatments using the new guidance system have shown promise, with the system providing clear visualization of the applicator and the needle implantation.

“It made the procedure smooth and extremely precise,” he said. “We were able to decrease the number of adjustments during the procedure, which may be able to decrease risks of complications.

The team hopes that with improved and more accurate targeting, they will be able to improve the outcomes for patients with gynecological cancers.

“Ultimately, the radiation is getting to the same spots, and in the same doses,” Ananth said. “But what we really want to do is improve the patient experience and the time it takes to get that placement right. It can be very stressful for a patient who has to have needles repositioned or removed at an already stressful time. We want to make this experience better and faster for patients and for the healthcare team.”

For Debbie, knowing that the new system could potentially help target her tumour with unprecedented precision comforted her during this latest step in her treatment journey.

“I’ve had a follow-up appointment, and Dr. Leung said that the tumour has shrunk,” she said. “I’m feeling great.”

Learn more about Sunnybrook's Cancer Ablation Therapy program

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Alexis Dobranowski

Alexis Dobranowski is a Communications Advisor at Sunnybrook.

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