The higher the energy, the deeper the x-rays can penetrate, therefore the radiation can be delivered to cancers deep in the body. Internal radiotherapy, also called brachytherapy , involves the use of radioactive elements in pellet or other form that are placed directly in a body cavity or implanted in the tumor itself. In this type of therapy, the radiation dose is concentrated in a small area, and might require a short hospital stay. Simply put, radiation in high doses kills cells and keeps them from growing and dividing. Cancer cells are abnormal and usually grow and divide at a faster rate than the healthy cells around them.
Radiation is more effective on rapidly dividing cells than normal cells that divide more slowly.
Normal cells are affected by radiation, but unlike cancer cells, they can recover from those effects. Your physician and their treatment staff will carefully limit doses of radiation to healthy tissue while delivering a high dose to the tumor itself. External beam radiation treatments are painless, like having an x-ray taken. External beam radiation does not cause you to become radioactive. Most of the time, external beam radiation is delivered in daily treatments, or fractions over a period of weeks.