High dose rate, or HDR brachytherapy is a revolutionary new form of internal radiation which temporarily exposes abnormal tissue to a high amount of radiation. Under CT and fluoroscopy guidance, a bronchoscope is used to deliver a catheter into a position at the site of the bronchial tumor. The other end of this catheter is connected to a computerized machine. This machine passes a small radioactive metal pellet, or seed, through the catheter. The catheter guides the seed to the tumor site. The duration and positioning of the seed can be used to control the radiation dose in different regions of the tumor. The overall effect of HDR brachytherapy is to deliver short and precise amounts of high-dose radiation to a tumor while minimizing healthy tissue exposure. After a series of treatments, the catheter is removed leaving no radioactive seeds in the body. Brachytherapy can also be used to treat prostate cancer and breast cancer.