Upgrading HDR Brachytherapy

High-dose-rate (HDR) brachytherapy is a procedure where the patient receives a dose from a powerful radioactive source for a few minutes per treatment session, after which the source is removed. The radioactive source, stored in an afterloader unit, travels through special applicators that then deliver the dose to the site of the tumor.

Led by Kevin Albuquerque, M.D., FACR, Professor of Radiation Oncology, Director of Radiation Oncology Accreditation, and Chief of Gynecological Radiation Oncology Service, the Department of Radiation Oncology’s gynecological disease-oriented team is among the few in North Texas treating patients with this method, particularly patients with vaginal, cervical, and recurrent endometrial cancers. While the treatment is highly effective, the department has been seeking upgraded technology that benefits both the patient and care team. The Elekta Flexitron® HDR afterloader, acquired in July 2023, allows for multiple benefits.

“These applicators are more beneficial for hybrid implants where you are doing standard tandem and ovoid and tandem and ring type implants, plus interstitial,” says Brian Hrycushko, Ph.D., Associate Professor of Radiation Oncology. “Overall, there are many benefits of this new HDR afterloader and applicator system, from improved needle placement to more accurate MRI guidance.”

According to Dr. Albuquerque, the Flexitron brings improvement to four key components of the treatment process: accuracy, reproducibility, customization, and adaptability.

In the previous model, needles were placed freehand during treatment and could go in many directions, risking damage to nearby tissue and suboptimal treatment to the tumor site. The Flexitron allows for treatment to be preplanned with the needles. The applicators also have predetermined needle positions and angles, so the physician does not have to spend extra time determining coordinates.

“You can imagine the challenge of placing many needles by hand and trying to create a plan off each individual needle,” Dr. Albuquerque says. “With the fixed geometries on these applicators, not only can we plan beforehand which needles will completely cover the tumor, but we can also place many more needles than before and replicate the positioning at each recurring treatment.”

Another significant difference is the material of the upgraded technology. While the previous model’s titanium applicators could possibly interfere with the MR simulator and images, the Flexitron’s applicators are plastic and thus more MR-friendly, allowing for clearer images when determining tumor size and shape.

The new treatment planning system has several features that make creating plans faster, including applicator modeling and different optimization algorithms to distribute the dose where needed. The Department of Radiation Oncology also has an initiative to implement artificial intelligence-(AI) based techniques throughout different areas, one of which is a model for brachytherapy procedures. In this model, created by Weiguo Lu, Ph.D., Professor of Radiation Oncology, AI-generated contours speed up and even remove steps from the process.

At the same time, physicist Zohaib Iqbal, Ph.D., Assistant Professor of Radiation Oncology, is, among others, creating a treatment plan whereby the AI contours can be created and then brought into the Flexitron system, increasing both the ease and efficiency of the entire process.

“We have a lot more control outside to help guide the physician when implanting devices inside the operating room,” Dr. Iqbal says. “It’s wonderful getting to work directly alongside the physician and to get that real-time feedback to improve the patient’s plan. That side-by-side aspect is rewarding and a unique part of the HDR process.”