Radioactive seeds are sometimes placed in diseased tissue on an outpatient basis or during an operation. They may be used to keep the radiation dose focused on a specific organ or they may be placed in areas where it is difficult or impossible to assure complete surgical removal of all the diseased tissue during an operation. One type of low dose rate brachytherapy is a prostate seed implant or PSI. During this intraoperative procedure, radioactive seeds are placed within the prostate gland to treat prostate cancer. This is one of the most effective options for many men whose cancer is in an early stage. Seeds are placed using ultrasound guided implantation techniques and deliver a dose of radiation to the prostate gland, with real time dose optimization, while sparing the normal surrounding tissues. These tiny seeds contain a radioactive material, such as Iodine-125, Palladium-103 or Cesium-131 and are permanently implanted in the prostate gland where they give off low-level radiation for weeks or months and then become inert.