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radiotherapy

radiotherapy refers to the use of ionizing radiation in the treatment of disease — mainly cancer.

Radiation — exposure to X-rays or gamma rays — can kill cells or stop their growth. It can be effective in the treatment of cancerous growths, because malignant cells are more sensitive than normal body cells: the radiation can be applied to a particular area, whilst the rest of the body is shielded from it.

Historically, radiotherapy dates back to the discovery of X-rays by Röntgen in 1895, and of the radioactivity of substances such as uranium by Becquerel in 1896, leading to that of radium, identified in 1898 by Marie and Pierre Curie.

The first use of X-rays as a treatment, for breast cancer, occurred in the USA within two to three months of their discovery. More followed within a year in Germany, France, and Austria. The loss of hair which followed exposure in these early cases alerted the medical profession to potentially harmful effects on normal tissues. The first report of successful treatment by X-ray was of a skin cancer in 1899. The use of radium in treatment was explored after Becquerel had been burnt by carrying a tube of radium in his pocket. The first accredited success, again for skin cancer, was in 1903. Radium tubes could be inserted, for example for treatment of uterine cancer (the standard method in the 1930s), or rays from a radium source could be directed at the lesion. Radium ‘needles’ were also inserted into tumours such as breast cancers. ‘Teletherapy’ — directing beams of radiation at the appropriate part — was thus a method applicable to either X-rays or radium. The two continued to be the mainstay of cancer treatment for the first half of the twentieth century.

Despite early realization of danger, protection of personnel involved in radiotherapy was not taken seriously before the mid 1930s nor implemented adequately until considerably later than that. In the late 1920s it was even recommended that the physician should use the redness produced on his own skin to determine the appropriate X-ray dose for a patient.

The discovery of plutonium-239 in 1941 led to the therapeutic use of artificially produced radioactive isotopes (as well as to nuclear weapons). The gamma rays which these emit can be directed at a tumour through a tube or needle. They are safer than X-rays both for patients and attendants; they have a much shorter half life than radium and emit gamma rays of lower energy. Thus cobalt-60 for example mainly supplanted radium for cancer of the uterus, and other radioisotopes, such as caesium-137 and iridium-192, have been developed for particular uses. These treatments, along with the diagnostic imaging techniques which employ radioisotopes have become the province of the specialty of nuclear medicine.

X-rays, however, have not been supplanted. In recent years radiologists involved in radiotherapy have expanded their activities to include the use of radioisotopes and also the combination of radiotherapy with a variety of chemotherapeutic drugs or with hormones in the treatment of cancer. This specialty is now termed, ‘radiation oncology’.

J. K. Davidson


See also cancer; chemotherapy; imaging techniques; radiation, ionizing; radioactivity; radiology; X-rays.

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Radiotherapy

Radiotherapy

Radiotherapy is the treatment of disease with radiation. Doctors use radiotherapy most often to treat certain kinds of cancers. The method of radiotherapy familiar to most people is X-ray treatment. X-ray radiation, however, can only show dense materials such as bone. A better way of diagnosing internal disorders is through the use of radionuclides, or radioactive tracers (isotopes).

Radioactive Isotopes

Radioactive tracers that are introduced into the body by injection are called radiopharmaceuticals. According to the type of radionuclide, the tracer will collect in one or more areas of the body. Since the tracer emits radiation, it is easily tracked by a Geiger counter (a device that measures radioactive levels) or scanning device. Because the tracer sends out information for a long time, doctors can follow its path through the body and check to see if organs are working properly.

Radioactive trace elements are a favorite diagnostic tool because they can be used to target individual organs, like the kidney. The trace elements also give off less radiation than a standard x-ray, so they are generally safer to use.

Beta and Isotope Injection Therapy

Once a radiotherapy diagnosis has been made, the doctor has a choice of treatments. For cancers near the skin surface, a stream of beta particles is used to kill cancerous cells. For cancers in a body organ, an isotope such as radioactive iodine is injected into the patient. The doctor will leave the isotope in the body until it has killed the cancer cells. The tracer is then flushed from the body before it can do permanent damage.

Edith Quimby

The person most responsible for the use of nuclear medical procedures is Edith Quimby, an American radiologist. Quimby was the first researcher to accurately measure the amount of radiation necessary to allow body traces. She later determined the exact dosages needed to use radiation as a diagnostic tool.

Other Uses

In addition to diagnostic applications, radiotherapy is used to sterilize medical instruments. Because it can be applied at very low temperatures, radiation can be used to sterilize plastic instruments that might be destroyed by steam. In addition, the radiation can reach all areas of an instrument, including small cervices, that traditional steam treatments often misses.

[See also X-ray machine ]

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radiotherapy

radiotherapy In medicine, the use of radiation to treat tumours or other pathological conditions. It may be done either by implanting a pellet of a radioactive source in the part to be treated, or by dosing the patient with a radioactive isotope or by exposing the patient to precisely focused beams of radiation from a machine such as an X-ray machine or a particle accelerator. Cobalt-60 is often used as it produces highly penetrating gamma radiation. In the treatment of cancers, the radiation slows down the proliferation of the cancerous cells.

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radiotherapy

radiotherapy (ray-di-oh-th'e-răpi) n. therapeutic radiology: the treatment of disease with penetrating radiation, such as X-rays, beta rays, or gamma rays. Beams of radiation may be directed at a diseased part from a distance (see teletherapy), or radioactive material, in the form of needles, wires, or pellets, may be implanted in the body. See also brachytherapy.
http://info.cancerresearchuk.org/cancerandresearch/learnaboutcancer/treatment/radiotherapy Explanation of radiotherapy from Cancer Research UK

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radiotherapy

ra·di·o·ther·a·py / ˌrādēōˈ[unvoicedth]erəpē/ • n. another term for radiation therapy. DERIVATIVES: ra·di·o·ther·a·peu·tic / -ˌ[unvoicedth]erəˈpyoōtik/ adj. ra·di·o·ther·a·pist / -pist/ n.

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radiotherapy

radiotherapy See radiology.

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radiotherapy

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"radiotherapy." Oxford Dictionary of Rhymes. . Encyclopedia.com. 19 Aug. 2017 <http://www.encyclopedia.com>.

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