Dictionary

radius The smaller of the two bones of the forearm, located on the thumb’s side. (The larger bone in the forearm is the ulna.)

radon A radioactive element that is formed, as a gas, during the breakdown of radium. Radon exposure is the second leading cause of lung cancer deaths in the United States, after smoking. Radon gas continuously seeps into the air from uraniumand radium-bearing soil and rock. Well water can be contaminated with radon and may carry…

Raeder syndrome See cluster headache.

ragweed Any of several weedy composite herbs that produce a pollen to which many people are allergic. Of all allergy sufferers in the US, 75 percent are allergic to ragweed.

RAI Radioactive iodine.

rale An abnormal lung sound that can be heard through a stethoscope. Rales may be sibilant (whistling), dry (crackling), or wet (sloshy), depending on the amount and density of fluid refluxing back and forth in the air passages.

radiation 1 Rays of energy. Gamma rays and Xrays are two types of radiation that are often used in medicine. 2 The use of energy waves to diagnose or treat disease.

radiation, seed See radiation therapy, interstitial.

radiation oncologist A physician whose specialty is the use of radiation therapy as a treatment for cancer.

radiation oncology The medical specialty that is involved in the use of radiation (X-rays, gamma rays, or electrons) to treat cancer.

radiation pneumonitis See pneumonitis, radiation.

radiation therapy The use of high-energy rays to damage cancer cells, stopping them from growing and dividing. Like surgery, radiation therapy is a local treatment that affects cancer cells only in the treated area. Radiation can come from a machine (external radiation) or from a small container of radioactive material implanted directly into or near…