Brachytherapy Gets More Precise with 3-D Technology
Radiation oncologist Danny Y. Song, M.D., is aiming for utmost precision — making brachytherapy (implanting radioactive seeds to treat prostate cancer) as accurate and effective as possible. Some of the challenges during the procedure itself include tissue swelling and slight movement of the prostate, as the seeds are placed and the needle used to place them is removed. “Unfortunately, current brachytherapy techniques do not allow us to identify these slight but important variations until after the procedure, and this gives us little opportunity to take corrective action,” he says.
To address this, Song and colleagues have developed a “real-time” system of registered ultrasound and fluoroscopy that allows the seeds to be seen inside the prostate, in 3-D, during the procedure. Using standard x-ray images taken from multiple directions, the computer system makes a three-dimensional map showing where the seeds are, Song explains. “Then we can modify our treatment plan, or add seeds before the procedure is completed.” So far, Song and colleagues have tested the new system on six patients in a pilot study. “We took x-ray images and calculated seed positions three times during each treatment, and modified subsequent seed positions as needed. The x-ray system identified areas of underdosing, and we added extra seeds (between three and 10) to the original treatment plan.
Afterward, CT scans showed excellent coverage of the prostate, as well as good sparing of the urethra and rectum.” After the pilot study is completed, Song plans to begin a Phase II clinical trial to compare the results of this three-dimensional system with standard brachytherapy.