More than half of the people who are diagnosed with cancer get radiation treatment for their disease, which means most of us know someone going through this experience.

When his mother-in-law was diagnosed with cancer, David Jennings quickly realized he didn't understand what was really happening during her treatment sessions. "My mother-in-law was treated with radiation when she had cancer, I don't think most people realize how radiation actually works."

Radiologist Dr. Keith Miller says that external radiation uses x-ray beams to treat several different forms of cancer; it works by destroying the cancer cells' ability to reproduce. "Radiation therapy works by its effect on the DNA of cancer cells, it injures the cancer cell's DNA so that they are no longer able to reproduce."

Dr. Miller says there are important elements of this treatment option for patients to understand. "I think the biggest thing is for them to know that there's no discomfort, there's no pain, typically there's no nausea, no vomiting. The side effects are related to where we put the beam."

Physicians like Dr. Miller plan out the total dose of radiation needed, which is divided into the smaller doses the patient receives over several weeks. "A patient may get anywhere from four to eight weeks of radiation treatments once a day, Monday through Friday."

Radiation can be external, through beam radiation, or it can be internal, coming from a small implant placed directly into or near the tumor.

Radiation therapy may be used alone or in combination with other cancer treatments, such as chemotherapy or surgery. In some cases, a patient may receive more than one type of radiation therapy.