reactive arthritis A chronic form of inflammatory arthritis that features arthritis, inflammation of the eyes (conjunctivitis), and inflammation of the genital, urinary, or gastrointestinal systems. Reactive arthritis is the preferred name for what was formerly called Reiter syndrome. Reactive arthritis seems to involve an immune system that is “reacting” to the presence of a bacterial…
radioimmunoassay A very sensitive, specific laboratory test (assay) that uses radiolabeled and unlabeled substances in an immunological (antibody-antigen) reaction.
radioinsensitive Not sensitive to X-rays and other forms of radiant energy. For example, if a tumor is radioinsensitive, it cannot be successfully attacked by using radiation therapy. The opposite of radioinsensitive is radiosensitive.
radioisotope A version of a chemical element that has an unstable nucleus and emits radiation during its decay to a stable form. Radioisotopes have important uses in medical diagnosis, treatment, and research.
radiologic Having to do with radiology.
radiologist A physician who specializes in radiology, the branch of medicine that uses radiation for the diagnosis and treatment of disease. A radiologist can subspecialize and become, for example, a radiation oncologist or an interventional radiologist. See also radiation oncologist; radiologist, interventional.
radiologist, interventional A radiologic subspecialist who uses fluoroscopy, computerized axial tomography (CT), and ultrasound to guide wires and catheters for performing procedures such as biopsies, draining fluids, inserting catheters, and dilating or stenting narrowed ducts or vessels. See also radiology, interventional.
radiology The medical specialty concerned with radiation for the diagnosis and treatment of disease, including both ionizing radiation such as X-rays and nonionizing radiation such as ultrasound. Also known as roentgenology.
radiology, interventional The use of image guidance methods to gain access to the deepest interior of most organs and organ systems. Interventional radiology includes the use of balloons, catheters, microcatheters, stents, therapeutic embolization (deliberately clogging up a blood vessel), and more. The specialty of interventional radiology overlaps with other surgical arenas, including interventional cardiology, vascular…
radiolucent Permeable to one or another form of radiation, such as X-rays. Radiolucent objects do not block radiation but let it pass. Plastic is usually radiolucent. The opposite of radiolucent is radiopaque.
radionuclide scan An exam that produces pictures (scans) of internal parts of the body based upon the presence of radioactive material. The patient is administered a small amount of radioactive material. A machine called a scanner then measures the radioactivity in certain organs.
radiopaque Opaque to one or another form of radiation, such as X-rays. Radiopaque objects block radiation rather than allow it to pass through. Metal, for instance, is radiopaque, so metal objects that a patient may have swallowed are visible on X-rays. Radiopaque dyes are used in radiology to enhance X-ray pictures of internal anatomic structures….