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Patrick Maguire, MD, Oncology, answeredIf the patient with prostate cancer is deemed a good candidate for brachytherapy after the planning transrectal ultrasound (TRUS; multiple images of the prostate obtained from the anus), then the radiation oncologist and physicist create a plan to treat the entire prostate with a small margin around it, based on the particular size and shape of the patient's gland. At the time of the brachytherapy procedure in the operating room, a team approach is generally employed that includes the patient's urologist, radiation oncologist, and medical physicist. The low dose rate (LDR) procedure is most often performed under general anesthesia on an outpatient basis and takes roughly one hour. The most common radioisotope used is iodine-125 (I-125), though some doctors use palladium or cesium in certain cases. For treatment of an average size prostate of about 30 grams with average strength I-125 seeds, about 70 to 90 seeds would be implanted. Each seed is about the size of a grain of rice. The seeds stay permanently, but the I-125 in the seeds decays or dissipates by 50% about every two months. So, after about 10-12 months, there's very little radiation left.