Prostate seed implantation is the placement of tiny radioactive pellets, or seeds, directly into the prostate using needles guided by a medical imaging device such as ultrasound. The seeds are about the size of a grain of rice and are deposited uniformly throughout the prostate so that the radiation can cover the entire gland. Depending on the radioactive material used, the seeds release radiation gradually over a 6-12 month period, after which they completely lose their strength. Since they lose their radioactivity, the seeds do not have to be removed and can safely remain in the prostate for the rest of your life