RADIOLOGY

  RADIOLOGY

The branch of medicine that deals with the use of radioactive substances in diagnosis and treatment of disease.

Branch of medicine that uses radiation for diagnosis (diagnostic imaging) and treatment (radiation therapy) of disease. Originally, it involved X rays for diagnosis and X rays, gamma rays, and other ionizing radiation for treatment. Diagnostic methods now include isotope scanning ( nuclear medicine), use of nonionizing radiation, as in ultrasound and magnetic resonance imaging, and radioimmunoassay (in which radioactive isotopes in antibodies against hormones detect minute amounts of hormones for diagnosis of endocrine disorders). Radiotherapy now includes, in cancer treatment, radioactive hormones and chemotherapeutic drugs.

The medical science concerned with x-rays, radioactive materials, and other ionizing radiations, and the application of the principles of this science to diagnosis and treatment of disease. Nonionizing radiations of infrared and ultrasound are also used for diagnosis.
Diagnostic radiology uses radiation, usually x-rays, to study the configuration of anatomical structures or the function of body organ systems. See also Radiography.
Radioactive isotopes are used to obtain images of organ systems and functions. The accumulation of isotope in a tumor or an organ such as the thyroid is recorded by a suitable γ-ray detector attached to an electronic amplifier and recording equipment. The image of the radioactivity concentrated in an organ is viewed on a television-type screen and recorded on a photographic print. See also Radioactive tracer.
Sound waves of 1–10 MHz are transmitted from a crystal transducer, and after amplification are displayed on an oscilloscope and recorded on a photographic print. The ultrasound pulses demonstrate organ structures such as the heart, liver, and spleen. Although the resolution is less fine than that obtained with x-ray, there is an advantage in that the ultrasound is nonionizing radiation. Ultrasound is particularly useful, therefore, in determining the size and degree of development of the human fetus. See also Ultrasonics.
Infrared radiation from the human body is used to detect tumors such as breast tumors, which are near the body surface. The technique, thermography, is based on the idea that tumors are warmer than the surrounding normal tissue. This increase in temperature is detected by an infrared device, and the “hot spot” scan is displayed on a television-type screen, with permanent records kept on photographic prints.
Radiation therapy deals with the treatment of disease with ionizing radiation. The diseases most commonly treated are cancer and allied diseases. Radiation therapy has been found useful in the management of some diseases such as ringworm of the scalp and bursitis, but because of possible serious complications occurring many years later, the use of ionizing radiation is generally avoided if alternative methods of treatment are available.
In cancer therapy the objective is to destroy a tumor without causing irreparable radiation damage in normal body tissues that must of necessity be irradiated in the process of delivering a lethal dose to the tumor. This applies particularly to important normal structures in the vicinity of the tumor. The relative radiosensitivity of the tumor with respect to these normal structures is the chief factor determining the success of the treatment.

This medical specialty originally involved the use of X-rays in the diagnosis and treatment of disease. Improved technology over the years with computer analysis of images has led to many sophisticated developments. Computed tomography (CT scans), developed by Sir Godfrey Hounsfield in 1972, was probably the most spectacular advance in radiology, using X-rays to provide three-dimensional information. Along with a progressive increase in the use of X-rays in diagnosis, other methods such as those utilizing gamma rays from radioactive isotopes (isotope scans), and positron emission tomography (PET scans), became incorporated into the modern practice of radiology. More recently radiologists have become involved also in ultrasound and magnetic resonance imaging (MRI) which do not involve ionizing radiation. Further sophistication has led to Doppler ultrasound, duplex scanning, and MRI angiography. These diagnostic methods are all known as organ imaging or imaging techniques and are described more fully elsewhere. They display in superb detail various organs or blood vessels and are very much a part of a modern radiologist's activities.

When one reflects that X-rays were only discovered in 1895, the developments have been quite staggering and expensive. Who could have foreseen, a hundred years ago, that putting patients inside magnets (MRI) could produce images? We are in the Golden Age of radiology with not enough gold to do all that is possible. Present day radiologists must be aware of the potential of these imaging methods, ensuring that optimal diagnostic pathways are followed. Radiologists now tend to subspecialize: neuroradiologists work solely within the nervous system, while others develop expertise in chest, bone, or gastrointestinal investigations.

Interventional radiology — dealing not with diagnosis but with treatment — is now a special field where various procedures are carried out using radiology for a visual display. Thus, under X-ray control, a catheter or needle may be positioned for various purposes; narrowed blood vessels in the leg or heart can be dilated (angioplasty) ; stents can be placed to widen arteries, bronchial airways, or ducts in the urinary or biliary tracts; tumours can be embolized (injected with material to block their blood vessels) to reduce their size; and abscesses can be drained.

— J. K. Davidson

radiology, branch of medicine specializing in the use of X rays, gamma rays, radioactive isotopes, and other forms of radiation in the diagnosis and treatment of disease. X ray machines and fluoroscopes are essential in diagnosing bone fractures, tumors, and other abnormalities of the internal organs. The computerized axial tomography (CAT) scan uses computer technology to focus X rays on precise sections of the body. Magnetic resonance imaging (MRI) utilizes supercooled magnets to concentrate and focus radiation in very small areas of the body, rendering sharp detail. Radioactive isotopes are also employed in diagnosis, e.g. iodine-131 is used to confirm cases of suspected thyroid disorder. In radiotherapy, X rays, gamma rays, and other radiation sources are used in the treatment of cancer and related diseases.

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