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Johns Hopkins Pediatric

Precision Brachytherapy, Using Real-Time X-Rays

January 01, 2017

The key to killing prostate cancer with brachytherapy, or seed implantation, is precisely placed seeds, says Danny Song, M.D. He should know; he’s one of the best in the world at this – and he is always working to make the procedure even better. As precisely as the seeds are placed, he notes, “due to multiple factors, it is not unusual for the final seed distribution to be different from what was intended.”

To address this, Song and a team of collaborators from the Whiting School of Engineering and Acoustic MedSystems developed and tested a prototype system that uses ultrasound and x-ray imaging during the procedure, with excellent results. They have nearly completed a Phase II trial testing a more refined, advanced version of this system.

In their study of 45 patients, “we start the implants using standard ultrasound-guided seed localization, but near the end of the procedure, we take a set of x-rays and run a custom set of computer algorithms” to see whether the seeds are where they’re supposed to be. “This provides a ‘real-time’ image of the seed positions, and many patients were found to have gaps in their prostate seed coverage which otherwise would have been missed.”

Based on the x-rays, Song added an average of four seeds per procedure. Afterward, when he confirmed the seed placement with MRI and CT imaging, “all 45 patients had excellent levels of prostate dose and gland coverage,” with minimal levels of radiation exposure to the rectum and urethra. When compared to an earlier group of more than 150 men treated with the traditional approach, “prostate gland coverage was significantly better in the x-ray imaging group, and there was an encouraging trend toward lower doses to the rectum as well.” In a few months, the team plans to combine this system with “newer imaging methods which can show where cancer is located within the gland. This will allow for precision, ‘focal’ brachytherapy.”

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