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radiation therapy

the treatment of disease, usually cancer, by ionizing radiation in order to deliver an optimal dose of either particulate or electromagnetic radiation to a particular area of the body with minimal damage to normal tissues. The source of radiation may be outside the body of the patient (external beam irradiation) or it may be an isotope that has been implanted or instilled into abnormal tissue or a body cavity. Called also radiotherapy and irradiation. 

Because of improvements in tumor localization, beam direction, planning and prescribing the field to be irradiated, and determining the precise dosage needed, radiation therapy is far more effective and less harmful now than when it was first introduced.
External Beam Irradiation. Modern radiation therapy primarily uses high-energy x-rays or gamma rays with peak photon energies above 1 megavolt; this is called megavoltage therapy. These high voltages are produced by linear accelerators or by cobalt-60 teletherapy units. Megavoltage radiation is more penetrating than lower energy radiation. It produces less damage to the skin at the entry port, is absorbed less in bone, and is scattered less, thus reducing the exposure to tissues outside the x-ray beam. Low-energy x-rays that do not penetrate are used for treatment of superficial skin lesions.
Internal Radiation Therapy (brachytherapy). This can involve the implantation of sealed radiation sources in or near cancerous tissue. Isotopes, such as radium-226, cesium-137, iridium-192, and iodine-125, are introduced either temporarily or permanently into body tissues (interstitial radiation therapy) or body cavities (intracavitary radiation therapy). Permanent sources have a short half-life so that the dose received by the patient is limited. 

Another form of internal radiation therapy is the administration of radioactive materials into the bloodstream or a body cavity. Iodine-131 is given orally in certain cases of hyperthyroidism and cancer of the thyroid; it is absorbed by the digestive system and concentrated in the thyroid. Phosphorus-32, a pure beta emitter, is injected intravenously for the treatment of various myeloproliferative diseases, leukemias, and lymphomas.
Protection from Radiation. Hospital personnel concerned with the care of patients receiving radiation therapy must be aware of the hazards of radiation and the protective policies and procedures established to reduce these hazards. Most institutions and clinics provide a safety program under the leadership of a radiation physicist or radiation safety officer. Since radiation cannot be seen or felt, it is extremely important to observe all rules outlined in the program. 

Sources of radiation that may be of particular concern to health care personnel include: radioactive substances such as radium and cobalt-60 that are used as implants and serve as internal sources of radiation; external sources of radiation such as x-ray machines and cobalt-60 therapy units; and liquid radioisotopes such as iodine-131 and suspensions of radioactive gold or phosphorus.

Generally speaking, the degree of exposure to radiation depends on three factors: (1) the distance between the source of radiation and the individual, (2) the amount of time an individual is exposed to radiation, and (3) the type of shielding provided. (See discussion at radiation.)

When a patient receives radiation therapy from an external source, therapists must be aware of, and observe carefully, the policies and procedures established for personnel in and around x-ray rooms and the rooms that house teletherapy units. After the treatment is finished, the patient will not serve as a hazard of radiation. This type of radiation therapy is often done on an outpatient basis.

Internal implants can present certain hazards for persons in contact with the patient for as long as the implant is in place. Visitors should sit at least six feet away from the patient and stay no longer than a total of one hour each day. Pregnant staff members and visitors should avoid all contact with the patient.

When administering direct patient care, staff members should plan interventions so that each task can be accomplished as quickly as possible. Since distance is a factor in protection, it is advisable to position oneself as far as is feasible from the source of radiation. For example, if the radioactive implant is in the pelvis, the caregiver might stand at the head or foot, rather than the side, of the bed. Protective lead aprons or portable shields may or may not be recommended by hospital protocol. Whatever the policies, every person caring for the patient should know and follow the recommended policies and procedures.

A film badge is worn on the outside of any protective devices worn by caregivers. The badge records the cumulative dose of radiation received by each person, and is used to monitor exposure over a period of time. It should be sent for monthly testing to be sure that no one is receiving more than the maximum allowable exposure. This amount should not exceed five rem per year. One should never lend one's badge to another staff member or borrow another staff member's badge.

Another factor to be considered is accidental removal or dislodgment of a radioactive implant. Most patients are confined to bed and refused bathroom privileges, but it is still possible for a radium needle or radon seeds, for example, to be accidentally removed from the body. Should an implant become dislodged the physician or radiation safety officer must be notified immediately. Under no circumstances should a radioactive substance be handled with the bare hands. A lead container and long-handled forceps should be kept at the patient's bedside in the event an implant should become dislodged. It can then be picked up immediately and placed in the container. Dressings, bed linen, bedpans, and emesis basins should be checked with a radiation detection instrument after each use or before disposal.

Liquid radioactive substances require additional precautions since these substances can enter the body of a worker through the skin, or by ingestion or inhalation. Not all types of radioactive materials require the same precautions. For example, iodine-131 is excreted in the urine for several days after it has been administered to the patient. In addition it appears in the patient's sweat, tears and saliva; thus all articles such as bed linens and toothbrush used by the patient must be considered a possible radiation hazard. Phosphorus-32 acts in the same way. Colloidal gold-98 usually is instilled into a body cavity and is not absorbed as are iodine and phosphorus. However, the radioactive gold emits gamma rays that penetrate beyond the patient's body and present a radiation hazard.
Patient Care. Specific goals for the care of a patient receiving radiation thearapy will depend on the location of the irradiated site, the patient's medical diagnosis, and the source of radiation, i.e., whether it is internal or external. Special precautions in regard to handling radioactive material have been presented above. In addition to the goal of protecting patients and caregivers from unnecessary exposure, goals of patient care include familiarizing patients and significant others with the purpose and therapeutic effects of radiation therapy and helping them recognize and deal with its expected side effects. 

Most people have a limited knowledge of radiation and how it affects cells, both normal and malignant. This lack of knowledge can add to the anxiety and stress already being felt by patients and significant others. The kinds of information they will need include how radiation works, whether or not patients present a hazard to others while undergoing treatment, when they will begin to experience its effects, and how long it will be before they begin to recover from the effects.

Before treatment is initiated, the patient is told the expected therapeutic effects, what it is like to have a treatment, and what might be expected of the patient during the course of therapy. Most patients will receive external radiation therapy on an outpatient basis; hence, they will need to keep scheduled appointments or notify the clinic if they are unable to come when expected. They should be assured that the source of radiation is outside their bodies (if it is) and that they cannot serve as a source of radiation.

Teaching patients and significant others how to recognize expected side effects and participate in their management is especially important when patients are not hospitalized. Written information that is easily comprehended should be available to them, as well as sufficient time and personnel to answer any questions they may have after reading the instructions and attempting to follow them at home. They should be encouraged to write down questions that have arisen between visits and to bring these questions with them on their next visit.

In general, most side effects will not begin before a week to ten days after the first treatment. This allows time for patients to assimilate information given to them and to adjust to whatever changes they might experience. They can be told that side effects typically continue throughout the course of treatment and for several weeks after the last treatment. However, individual reactions can and do vary.

Although all body systems can be affected by radiation, the skin is the system most at risk for injury. The reaction results from an inflammatory process caused by breakdown of cells in the epidermis and is similar to a sunburn. In preparation for radiation therapy the physician will mark the target area with indelible ink.

Daily assessment of the skin for degree of reaction can be done by the patient or some other knowledgeable person. First-degree reactions resemble a sunburn and can destroy hair roots, causing the hair to fall out. Second-degree reactions, also called dry desquamation, produce bright red erythema. Sweat glands and hair follicles are damaged and the hair falls out. This change can be irreversible. Third-degree reactions, also called moist desquamation, are characterized by a dark purple color and possibly formation of blisters and ulcers. If the area is exposed to air, scabbing over the exposed area can occur. Fourth-degree reactions are very rare and are the result of radiation overdose. They are characterized by tissue necrosis.

Effects of radiation on major systems of the body, healing time, and appropriate nursing interventions are summarized in the table at radiation.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

ra·di·a·tion on·col·o·gy

1. the medical specialty concerned with the use of ionizing radiation in the treatment of disease;
2. the medical specialty of radiation therapy;
3. the use of radiation in the treatment of neoplasms.
Farlex Partner Medical Dictionary © Farlex 2012


n. pl. radiothera·pies
Treatment of disease with radiation, especially by selective irradiation with x-rays or other ionizing radiation and by ingestion of radioisotopes. Also called radiation therapy.

ra′di·o·ther′a·pist n.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

radiography episode

A regionally popular UK term for the treatment provided to a patient by a radiotherapist at a specific NHS site, which is usually comprised of a series of external beam therapy sessions. The episode is initiated by a clinician who prescribes a course of treatment and decides when to end the episode.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


The medical specialty concerned with the use of electromagnetic or particulate radiation in the treatment of disease.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


The medical specialty concerned with the treatment, almost exclusively of cancer, by ionizing radiation. Radiation affects cancerous cells more than normal cells and can be directed accurately by shielding, collimation and other means. The size and timing of the dosage is calculated to cause maximal damage to the tumour and the minimal damage to the patient. Radiotherapy sources include high voltage X-ray machines, linear accelerators and powerful radioactive isotopes such as cobalt 60. Isotopes may be inserted directly into tumours in tubes or needles or may be placed in close proximity.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


The use of ionizing radiation, either as x rays or radioactive isotopes, to treat disease.
Mentioned in: Goiter
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


The medical specialty concerned with the use of electromagnetic or particulate radiation in the treatment of disease.
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about radiotherapy

Q. What is radiotherapy? My Grandfather had a surgery to remove a cancerous tumor on his cheek. He now needs to undergo radiotherapy. What is this? what are its side effects?

A. Generally, radiotherapy causes tiredness and sore, red skin in the area being treated. This is a bit like sunburn. Radiotherapy to the neck can damage the thyroid gland. Other side effects include: a sore throat- due to mouth ulcers, pain on swallowing,
a dry mouth- due to damage caused to the salivary glands (which are in charge of making the saliva), taste changes, a hoarse voice and effect on the sense of smell.

Q. What problems my sister may face if radiation therapy is not given to her? My sister will have her radiation therapy by next week. Two weeks before she had her chemotherapy treatment. She is feeling good if not great. After her diagnosis of breast cancer she had her mastectomy and soon she was given chemotherapy treatment. I was wondering whether the radiation therapy has many serious side effects associated with it. So can we avoid this treatment? What problems my sister may face if radiation therapy is not given to her?

A. Radiation therapy is used to clear the surgical area with any leftover cancer cells. These cancer cells can again return with the cancer if left inside the body. This can also pass through the blood to other areas of the body and can develop into a cancer in other areas of the body. To stop the chances of cancer reoccurrence this radiation therapy is helpful. Avoiding this treatment may be harmful as the future occurrence may be more serious. Hence it is better to go with the treatment.

Q. I am pregnant and my mother is having radiotherapy for breast cancer, Will it affect me or my unborn child? I married my close relative last month and there is a 8-year difference in our. I am healthy enough to take care of my family. Now I am pregnant and my mother is having radiotherapy for breast cancer, can I be around her? Will it affect me or my unborn child?

A. Congrats! There is definitely no problem with radiotherapy for breast cancer. This is to with external high energy x-rays which pass straight through. People need to be careful with radioactive iodine for thyroid problems or treatment for similar diseases... hope this helps you. Take care of your mom. Have a healthy baby soon and let me know.

More discussions about radiotherapy
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