Prostate seed implants are a type of internal radiation therapy, also known as brachytherapy. A doctor or clinician implants radioactive seeds (containing either iodine-125 or palladium-103) into specific parts of the prostate gland using ultrasound guidance. The number of seeds and where they are placed is determined by a treatment plan tailored for each patient. Anywhere from 40 to 160 seeds are commonly implanted.
The implants remain in place permanently, and the radioactivity of the seeds slowly decays over several weeks to months. This technique allows a high dose of radiation to be delivered to the prostate with limited exposure to nearby organs.