It refers to the placement of tiny radioactive pellets ("seeds") in prostate gland, that is performed since 1985 in USA and since 1996 in Greece. It is applied in patients diagnosed with prostate adenocarcinoma in one session, under constant transrectal ultrasound guidance and without the need of any surgical incision.

The material used has the size of 1/3 of a grain of rice and is composed of radioactive Iodine-125. The "seeds" are surrounded by titanium capsule and measure 4.5mm in length and 0.8mm in diameter. They are placed permanently in the prostate, becoming totally inactive in around 6 months and they are harmless to humans and their environment.