radiation therapy (redirected from 3-dimensional radiation therapy)

Radiation Therapy 

Definition

Radiation therapy, sometimes called radiotherapy, x-ray therapy radiation treatment, cobalt therapy, electron beam therapy, or irradiation uses high energy, penetrating waves or particles such as x rays, gamma rays, proton rays, or neutron rays to destroy cancer cells or keep them from reproducing.

Purpose

The purpose of radiation therapy is to kill or damage cancer cells. Radiation therapy is a common form of cancer therapy. It is used in more than half of all cancer cases. Radiation therapy can be used:

• alone to kill cancer
• before surgery to shrink a tumor and make it easier to remove
• during surgery to kill cancer cells that may remain in surrounding tissue after the surgery (called intraoperative radiation)
• after surgery to kill cancer cells remaining in the body
• to shrink an inoperable tumor in order to and reduce pain and improve quality of life.
• in combination with chemotherapy

For some kinds of cancers such as early-stage Hodgkin's disease, non-Hodgkin's lymphoma, and certain types of prostate, or brain cancer, radiation therapy alone may cure the disease. In other cases, radiation therapy used in conjunction with surgery, chemotherapy, or both, increases survival rates over any of these therapies used alone.

Precautions

Radiation therapy does not make the person having the treatments radioactive. In almost all cases, the benefits of this therapy outweigh the risks. However radiation therapy can have has serious consequences, so anyone contemplating it should be sure understand why the treatment team believes it is the best possible treatment option for their cancer. Radiation therapy is often not appropriate for pregnant women, because the radiation can damage the cells of the developing baby. Women who think they might be pregnant should discuss this with their doctor.

Description

Radiation therapy is a local treatment. It is painless. The radiation acts only on the part of the body that is exposed to the radiation. This is very different from chemotherapy in which drugs circulate throughout the whole body. There are two main types of radiation therapy. In external radiation therapy a beam of radiation is directed from outside the body at the cancer. In internal radiation therapy, called brachytherapy or implant therapy, where a source of radioactivity is surgically placed inside the body near the cancer.

How radiation therapy works

The protein that carries the code controlling most activities in the cell is called deoxyribonucleic acid or DNA. When a cell divides, its DNA must also double and divide. High-energy radiation kills cells by damaging their DNA, thus blocking their ability to grow and increase in number.

One of the characteristics of cancer cells is that they grow and divide faster than normal cells. This makes them particularly vulnerable to radiation. Radiation also damages normal cells, but because normal cells are growing more slowly, they are better able to repair radiation damage than are cancer cells. In order to give normal cells time to heal and reduce side effects, radiation treatments are often given in small doses over a six or seven week period.

External radiation therapy

External radiation therapy is the most common kind of radiation therapy. It is usually done during outpatient visits to a hospital clinic and is usually covered by insurance.

Once a doctor, called a radiation oncologist, determines the proper dose of radiation for a particular cancer, the dose is divided into smaller doses called fractions. One fraction is usually given each day, five days a week for six to seven weeks. However, each radiation plan is individualized depending on the type and location of the cancer and what other treatments are also being used. The actual administration of the therapy usually takes about half an hour daily, although radiation is administered for only from one to five minutes at each session. It is important to attend every scheduled treatment to get the most benefit from radiation therapy.

Recently, trials have begun to determine if there are ways to deliver radiation fractions so that they kill more cancer cells or have fewer side effects. Some trials use smaller doses given more often. Up-to-date information on voluntary participation in clinical trials and where they are being held is available by entering the search term "radiation therapy" at the following web sites:

• National Cancer Institute. 〈http://cancertrials.nci.nih.gov〉 or (800) 4-CANCER.
• National Institutes of Health Clinical Trials. 〈http://clinicaltrials.gov〉
• Center Watch: A Clinical Trials Listing. 〈http://www.centerwatch.com〉.

The type of machines used to administer external radiation therapy and the material that provides the radiation vary depending on the type and location of the cancer. Generally, the patient puts on a hospital gown and lies down or sits in a special chair. Parts of the body not receiving radiation are covered with special shields that block the rays. A technician then directs a beam of radiation to a pre-determined spot on the body where the cancer is located. The patient must stay still during the administration of the radiation so that no other parts of the body are affected. As an extra precaution in some treatments, special molds are made to make sure the body is in the same position for each treatment. However, the treatment itself is painless, like having a bone x-rayed.

Internal radiation therapy

Internal radiation therapy is called brachytherapy, implant therapy, interstitial radiation, or intracavitary radiation. With internal radiation therapy, a bit of radioactive material is sealed in an implant (sometimes called a seed or capsule). The implant is then placed very close to the cancer. The advantage of internal radiation therapy is that it concentrates the radiation near the cancer and lessens the chance of damage to normal cells. Many different types of radioactive materials can be used in the implant, including cesium, iridium, iodine, phosphorus, and palladium.

How the implant is put near the cancer depends on the size and location of the cancer. Internal radiation therapy is used for some cancers of the head, neck, thyroid, breast, female reproductive system, and prostate. Most people will have the radioactive capsule implanted by a surgeon while under either general or local anesthesia at a hospital or surgical clinic.

Patients receiving internal radiation therapy do become temporarily radioactive. They must remain in the hospital during the time that the implant stays in place. The length of time is determined by the type of cancer and the dose of radioactivity to be delivered. During the time the implant is in place, the patient will have to stay in bed and remain reasonably still.

While the implant is in place, the patient's contact with other people will be limited. Healthcare workers will make their visits as brief as possible to avoid exposure to radiation, and visitors, especially children and pregnant women, will be limited.

The implant usually can be removed in a simple procedure without an anesthetic. As soon as the implant is out of the body, the patient is no longer radioactive, and restrictions on being with other people are lifted. Generally people can return to a level of activity that feels comfortable to them as soon as the implant is removed. Occasionally the site of the implant is sore for some time afterwards. This discomfort may limit specific activities.

In some cases, an implant is left permanently inside the body. People who have permanent implants need to stay in the hospital and away from other people for the first few days. Gradually the radioactivity of the implant decreases, and it is safe to be around other people.

Radioimmunotherapy

Radioimmunotherapy is a promising way to treat cancer that has spread (metastasized) to multiple locations throughout the body. Antibodies are immune system proteins that specifically recognize and bind to only one type of cell. They can be designed to bind only with a certain type of cancer cell. To carry out radioimmunotherapy, antibodies with the ability to bind specifically to a patient's cancer cells are attached to radioactive material and injected into the patient's bloodstream. When these man-made antibodies find a cancer cell, they bind to it. Then the radiation kills the cancer cell. This process is still experimental, but because it can be used to selectively attack only cancer cells, it holds promise for eliminating cancers that have spread beyond the primary tumor.

Radiation used to treat cancer

PHOTON RADIATION. Early radiation therapy used x rays like those used to take pictures of bones, or gamma rays. X rays and gamma rays are high energy rays composed of massless particles of energy (like light) called photons. The distinction between the two is that gamma rays originate from the decay of radioacive substances (like radium and cobalt-60), while x rays are generated by devices that excite electrons (such as cathode ray tubes and linear accelerators). These high energy rays act on cells by disrupting the electrons of atoms within the molecules inside cells, disrupting cell functions, and most importantly stop their ability to divide and make new cells.

PARTICLE RADIATION. Particle radiation is radiation delivered by particles that have mass. Proton therapy has been used since the early 1990s. Proton rays consist of protons, a type of positively charged atomic particle, rather than photons, which have neither mass nor charge. Like x rays and gamma rays, proton rays disrupt cellular activity. The advantage of using proton rays is that they can be shaped to conform to the irregular shape of the tumor more precisely than x rays and gamma rays. They allow delivery of higher radiation doses to tumors without increasing damage to the surrounding tissue.

Neutron therapy is another type of particle radiation. Neutron rays are very high-energy rays. They are composed of neutrons, which are particles with mass but no charge. The type of damage they cause to cells is much less likely to be repaired than that caused by x rays, gamma rays, or proton rays.

Neutron therapy can treat larger tumors than conventional radiation therapy. Conventional radiation therapy depends on the presence of oxygen to work. The center of large tumors lack sufficient oxygen to be susceptible to damage from conventional radiation. Neutron radiation works in the absence of oxygen, making it especially effective for the treatment of inoperable salivary gland tumors, bone cancers, and some kinds of advanced cancers of the pancreas, bladder, lung, prostate, and uterus.

Recent advances in radiation therapy

A newer mode of treating brain cancers with radiation therapy is known as stereotactic radiosurgery. As of the early 2000s, this approach is limited to treating cancers of the head and neck because only these parts of the body can be held completely still throughout the procedure. Stereotactic radiosurgery allows the doctor to deliver a single high-level dose of precisely directed radiation to the tumor without damaging nearby healthy brain tissue. The treatment is planned with the help of three-dimensional computer-aided analysis of CT and MRI scans. The patient's head and neck are held steady in a skeletal fixation device during the actual treatment. Stereotactic radiosurgery can be used in addition to standard surgery to treat a recurrent brain tumor, or in place of surgery if the tumor cannot be reached by standard surgical techniques.

Two major forms of stereotactic radiosurgery are in use as of 2003. The gamma knife is a stationary machine that is most useful for small tumors, blood vessels, or similar targets. Because it does not move, it can deliver a small, highly localized and precise beam of radiation. Gamma knife treatment is done all at once in a single hospital stay. The second type of radiosurgery uses a movable linear accelerator-based machine that is preferred for larger tumors. This treatment is delivered in several small doses given over several weeks. Radiosurgery that is performed with divided doses is known as fractionated radiosurgery. The total dose of radiation is higher with a linear accelerator-based machine than with gamma knife treatment.

Another advance in intraoperative radiotherapy (IORT) is the introduction of mobile devices that allow the surgeon to use radiotherapy in early-stage disease and to operate in locations where it would be difficult to transport the patient during surgery for radiation treatment. Mobile IORT units have been used successfully as of 2003 in treating early-stage breast cancer and rectal cancer.

Radiation sensitizers are another recent innovation in radiation therapy. Sensitizers are medications that are given to make cancer cells easier to kill by radiation than normal calls. Gemcitabine (Gemzar) is one of the drugs most commonly used for this purpose.

Preparation

Before radiation therapy, the size and location of the patient's tumor are determined very precisely using magnetic resonance imaging (MRI) and/or computed tomography scans (CT scans). The correct radiation dose, the number of sessions, the interval between sessions, and the method of application are calculated by a radiation oncologist based on the tumor type, its size, and the sensitivity of the nearby tissues.

The patient's skin is be marked with a semipermanent ink to help the radiation technologist achieve correct positioning for each treatment. Molds may be built to hold tissues in exactly the right place each time.

Aftercare

Many patients experience skin burn, fatigue, nausea, and vomiting after radiation therapy regardless of the where radiation is applied. After treatment, the skin around the site of the treatment may also become sore. Affected skin should be kept clean and can be treated like sunburn, with skin lotion or vitamin A and D ointment. Patients should avoid perfume and scented skin products and protect affected areas from the sun.

Nausea and vomiting are most likely to occur when the radiation dose is high or if the abdomen or another part of the digestive tract is irradiated. Sometimes nausea and vomiting occur after radiation to other regions, but in these cases the symptoms usually disappear within a few hours after treatment. Nausea and vomiting can be treated with antacids, Compazine, Tigan, or Zofran.

Fatigue frequently starts after the second week of therapy and may continue until about two weeks after the therapy is finished. Patients may need to limit their activities, take naps, and get extra sleep at night.

Patients should see their oncologist (cancer doctor) at least once within the first few weeks after their final radiation treatment. They should also see an oncologist every six to twelve months for the rest of their lives so they can be checked to see if the tumor has reappeared or spread.

Key terms

Anemia — Insufficient red blood cells in the body.

Antibody — Protein molecule that recognizes and binds specifically to a foreign substance in the body in order to eliminate it.

Chemotherapy — Injecting drugs into the body where they circulate and kill cancer cells.

Computed tomography (CT or CAT) scan — —Using x rays taken from many angles and computer modeling, CT scans help locate and size tumors and provide information on whether they can be surgically removed.

Fractionation — A procedure for dividing a dose of radiation into smaller treatment doses.

Gamma rays — Short wavelength, high energy electromagnetic radiation emitted by radioactive substances.

Hodgkin's disease — Cancer of the lymphatic system, characterized by lymph node enlargement and the presence of a large polyploid cells called Reed-Sternberg cells.

Magnetic resonance imaging (MRI) — MRI uses magnets and radio waves to create detailed crosssectional pictures of the interior of the body.

Stereotactic — Characterized by precise positioning in space. When applied to radiosurgery, stereotactic refers to a system of three-dimensional coordinates for locating the target site.

Risks

Radiation therapy can cause anemia, nausea, vomiting, diarrhea, hair loss, skin burn, sterility, and rarely death. However, the benefits of radiation therapy almost always exceed the risks. Patients should discuss the risks with their doctor and get a second opinion about their treatment plan.

Normal results

The outcome of radiation treatment varies depending on the type, location, and stage of the cancer. For some cancers such as Hodgkin's disease, about 75% of the patients are cured. Prostate cancer also responds well to radiation therapy. Radiation to painful bony metastases is usually a dramatically effective form of pain control. Other cancers may be less sensitive to the benefits of radiation.

Resources

Periodicals

Goer, D. A., C. W. Musslewhite, and D. M. Jablons. "Potential of Mobile Intraoperative Radiotherapy Technology." Surgical Oncology Clinics of North America 12 (October 2003): 943-954.

Lawrence, T. S. "Radiation Sensitizers and Targeted Therapies." Oncology (Huntington) 17 (December 2003): 23-28.

Merrick, H. W. IIIrd, L. L. Gunderson, and F. A. Calvo. "Future Directions in Intraoperative Radiation Therapy." Surgical Oncology Clinics of North America 12 (October 2003): 1099-1105.

Nag, S., and K. S. Hu. "Intraoperative High-Dose-Rate Brachytherapy." Surgical Oncology Clinics of North America 12 (October 2003): 1079-1097.

Witt, M. E., M. Haas, M. A. Marrinan, and C. N. Brown. "Understanding Stereotactic Radiosurgery for Intracranial Tumors, Seed Implants for Prostate Cancer, and Intravascular Brachytherapy for Cardiac Restenosis" Cancer Nursing 26 (December 2003): 494-502.

Organizations

American Cancer Society. 1599 Clifton Rd. NE, Atlanta GA 30329-4251. (800) ACS-2345. http://www.cancer.org.

International Radiosurgery Support Association (IRSA). 3005 Hoffman Street, Harrisburg, PA 17110. (717) 260-9808. http://www.irsa.org.

National Association for Proton Therapy. 7910 Woodmont Ave., Suite 1303, Bethesda, MD 20814. (301) 913-9360. 〈http://www.proton-therapy.org/Default.htm〉.

Other

Radiation Therapy and You. A Guide to Self-Help During Treatment. National Cancer Institute CancerNet Information Service. http://cancernet.nci.nih.gov.

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therapy /ther·a·py/ (-pe) the treatment of disease; see also treatment.

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ablation therapy  the destruction of small areas of myocardial tissue, usually by application of electrical or chemical energy, in the treatment of some tachyarrhythmias.

adjuvant therapy  the use of chemotherapy or radiotherapy in addition to surgical resection in the treatment of cancer.

antiplatelet therapy  the use of platelet-modifying agents to inhibit platelet adhesion or aggregation and so prevent thrombosis, alter the course of atherosclerosis, or prolong vascular graft patency.

art therapy  the use of art, the creative process, and patient response to the products created for the treatment of psychiatric and psychologic conditions and for rehabilitation.

aversion therapy , aversive therapy that using aversive conditioning to reduce or eliminate undesirable behavior or symptoms; sometimes used synonymously with aversive conditioning.

behavior therapy  a therapeutic approach that focuses on modifying the patient's observable behavior, rather than on the conflicts and unconscious processes presumed to underlie the behavior.

biological therapy  treatment of disease by injection of substances that produce a biological reaction in the organism.

chelation therapy  the use of a chelating agent to remove toxic metals from the body, used in the treatment of heavy metal poisoning. In complementary medicine, also used for the treatment of atherosclerosis and other disorders.

cognitive therapy , cognitive-behavioral therapy that based on the theory that emotional problems result from distorted attitudes and ways of thinking that can be corrected, the therapist guiding the patient to do so.

convulsive therapy  treatment of mental disorders, primarily depression, by induction of convulsions; now it is virtually always by electric shock (electroconvulsive t.) .

couples therapy  marital t.

dance therapy  the therapeutic use of movement to further the emotional, social, cognitive, and physical integration of the individual in the treatment of a variety of social, emotional, cognitive, and physical disorders.

electroconvulsive therapy  (ECT) a treatment for mental disorders, primarily depression, in which convulsions and loss of consciousness are induced by application of brief pulses of low-voltage alternating current to the brain via scalp electrodes.

electroshock therapy  (EST) electroconvulsive t.

endocrine therapy  treatment of disease by the use of hormones.

estrogen replacement therapy  administration of an estrogen to treat estrogen deficiency, as that following menopause; in women with a uterus, a progestational agent is usually included to prevent endometrial hyperplasia.

enzyme therapy  in complementary medicine, the oral administration of proteolytic enzymes to improve immune system function; used for a wide variety of disorders and as adjunctive therapy in cancer treatment.

family therapy  group therapy of the members of a family, exploring and improving family relationships and processes and thus the mental health of the collective unit and of individual members.

fibrinolytic therapy  the use of fibrinolytic agents (e.g., prourokinase) to lyse thrombi in patients with acute peripheral arterial occlusion, deep venous thrombosis, pulmonary embolism, or acute myocardial infarction.

gene therapy  manipulation of the genome of an individual to prevent, mask, or lessen the effects of a genetic disorder.

group therapy  psychotherapy carried out regularly with a group of patients under the guidance of a group leader, usually a therapist.

highly active antiretroviral therapy  (HAART) the aggressive use of extremely potent antiretroviral agents in the treatment of human immunodeficiency virus infection.

hormonal therapy , hormone therapy endocrine t.

hormone replacement therapy  the administration of hormones to correct a deficiency, such as postmenopausal estrogen replacement ttherapy.

immunosuppressive therapy  treatment with agents, such as x-rays, corticosteroids, or cytotoxic chemicals, that suppress the immune response to antigen(s); used in conditions such as organ transplantation, autoimmune disease, allergy, multiple myeloma, and chronic nephritis.

inhalation therapy  former name for respiratory care (2).

light therapy 

1. phototherapy (def. 1).

2. photodynamic t.

marital therapy  a type of family therapy aimed at understanding and treating one or both members of a couple in the context of a distressed relationship, but not necessarily addressing the discordant relationship itself; sometimes used more restrictively as a synonym of marriage therapy .

marriage therapy  a subset of marital therapy (q.v.) that focuses specifically on the bond of marriage between two people, enhancing and preserving it.

massage therapy  the manipulation of the soft tissues of the body for the purpose of normalizing them, thereby enhancing health and healing.

milieu therapy  treatment, usually in a psychiatric hospital, that emphasizes the provision of an environment and activities appropriate to the patient's emotional and interpersonal needs.

music therapy  the use of music to effect positive changes in the psychological, physical, cognitive, or social functioning of individuals with health or educational problems.

occupational therapy  the therapeutic use of self-care, work, and play activities to increase function, enhance development, and prevent disabilities.

oral rehydration therapy  (ORT) oral administration of a solution of electrolytes and carbohydrates in the treatment of dehydration.

orthomolecular therapy  treatment of disease based on the theory that restoration of optimal concentrations of substances normally present in the body, such as vitamins, trace elements, and amino acids, will effect a cure.

photodynamic therapy  intravenous administration of hematoporphyrin derivative, which concentrates selectively in metabolically active tumor tissue, followed by exposure of the tumor tissue to red laser light to produce cytotoxic free radicals that destroy hematoporphyrin-containing tissue.

physical therapy 

1. treatment by physical means.

2. the health profession concerned with the promotion of health, the prevention of disability, and the evaluation and rehabilitation of patients disabled by pain, disease, or injury, and with treatment by physical therapeutic measures as opposed to medical, surgical, or radiologic measures.

poetry therapy  a form of bibliotherapy in which a selected poem, which may be created by the patient, is used to evoke feelings and responses for discussion in a therapeutic setting.

PUVA therapy  a form of photochemotherapy for skin disorders such as psoriasis and vitiligo; oral psoralen administration is followed two hours later by exposure to ultraviolet light.

radiation therapy  radiotherapy.

relaxation therapy  any of a number of techniques for inducing the relaxation response, used for the reduction of stress; useful in the management of a wide variety of chronic illnesses caused or exacerbated by stress.

replacement therapy 

1. treatment to replace deficiencies in body products by administration of natural or synthetic substitutes.

2. treatment that replaces or compensates for a nonfunctioning organ, e.g., hemodialysis.

respiratory therapy  see under care.

substitution therapy  the administration of a hormone to compensate for glandular deficiency.

thrombolytic therapy  fibrinolytic t.

thyroid replacement therapy  treatment with a preparation of a thyroid hormone.

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radiation therapy

n.

Radiotherapy.

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radiation therapy.

See radiotherapy.

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radiation (rā´dēā´shn),

n 1. the process of emitting radiant energy in the form of waves or particles.
n 2. the combined processes of emission, transmission, and absorption of radiant energy.

radiation, actinic,

n radiation capable of producing chemical change (e.g., effect of light and roentgen rays on photographic emulsions).

radiation, background,

n radiation arising from radioactive material other than the one directly under consideration. Background radiation resulting from cosmic rays and natural radioactivity is always present. Background radiation may also exist because of radioactive substances in other parts of a building (e.g., building material).

Radiation.

radiation, backscatter,

n radiation that deflects off its target at an angle of deflection greater than 90°, possibly affecting those who may be off to the side of or behind the main beam. See also radiation, scattered.

radiation, biologic effectiveness of,

n the ability of a particular type of ionizing radiation to produce biologic effects on an organism with small absorbed doses. See relative biologic effectiveness.

radiation, bremsstrahlung

n (white), describes the distribution of roentgen rays from extremely low energy photons to roentgen rays originating from the highest kilovoltage applied to a radiographic tube.
Bremsstrahlung translates to “braking radiation,” referring to the sudden slowing of electrons that occurs when they encounter nuclei with a high positive charge.

radiation caries,

n a type of tooth decay caused by the reduction in saliva that may result from the use of ionizing radiation in the treatment of oral and facial malignancies. Radiation caries is an unfortunate side effect of a necessary radical procedure to cure or prevent the spread of cancer.

radiation cataract,

n a cataract that is caused by extended exposure of the eye to ionizing radiation in the course of treating facial cancers.

radiation, characteristic,

n radiation that originates from an atom after removal of an electron or excitation of the nucleus. The wavelength of the emitted radiation is specific, depending only on the element concerned and on the particular energy levels involved. Also refers to the specific type of secondary radiation resulting when rays from a radio ray tube strike another substance, such as copper.

radiation, coherent scattering,

n See coherent scattering.

radiation, Compton scatter,

n See Compton scatter radiation.

radiation, corpuscular

n subatomic particles, such as electrons, protons, neutrons, or alpha particles, that travel in streams at various velocities. All the particles have definite masses and travel at various speeds. The properties are in opposition to electromagnetic radiations, which have no mass and travel in wave forms at the speed of light. See also radiation, electromagnetic.

radiation, cosmic,

n See ray, cosmic.

radiation, cumulative effect of

n reactions vary depending on the dosage; if the radiation received is in several smaller doses, the reaction is not as severe as if the same amount of radiation is received all at once. Unless a tissue is completely destroyed by the radiation, some or all of it will be repaired, although cumulative damage may cause some irreparable conditions.

radiation, dermatitis,

n See dermatitis, radiation.

radiation detector,

n a device for converting radiant energy to a form more suitable for observation and recording. Examples include radiograph films and radiometers.

radiation, direct,

n (primary radiation), radiation emanating from a tube aperture and comprising the useful beam, as compared with any stray radiation, such as that which comes from the tube container.

radiation, electromagnetic,

n forms of energy propagated by wave motion, such as photons or discrete quanta. The radiations have no matter associated with them, as opposed to corpuscular radiations, which have definite masses. They differ widely in wavelength, frequency, and photon energy and have strikingly different properties. Covering an enormous range of wavelengths (from 10⁻⁶ to 10¹⁷ Å), they include radio waves, infrared waves, visible light, ultraviolet radiation, gamma rays, and cosmic radiation. See also radiation, corpuscular.

radiation exposure,

n a measure of the ionization produced in air by roentgen rays or gamma rays. It is the sum of the electric charges on all ions of one sign that are produced when all electrons liberated by photons in a volume of air are completely stopped, divided by the mass of air in the volume element. The unit of exposure is the roentgen.

radiation field,

n See radiographic beam, field size.

radiation, gamma,

n See ray, gamma.

radiation, genetic effects of,

n See genetic effects of radiation.

radiation, grenz,

n See ray, grenz.

radiation, hard,

radiation consisting of the short wavelengths (higher kilovolt peak equals greater penetration).

radiation hazard,

n See hazard, radiation.

radiation, heterogeneous

n a beam or “bundle” of radiation containing photons of many wavelengths.

radiation, homogeneous,

n a beam of radiation consisting of photons that all have the same wavelength.

radiation hygiene,

n See hygiene, radiation.

radiation intensity,

n See intensity, radiation.

radiation, ionizing,

n electomagnetic radiation such as roentgen rays and gamma rays; particulate radiation such as alpha particles, beta particles, protons, and neutrons; all other types of radiations that produce ionization directly or indirectly.

radiation leakage,

n (stray radiation), the escape of radiation through the protective shielding of the radiography unit tube head. This radiation is detected at the sides, top, bottom, or back of the tube head; it does not include the useful beam.

radiation, monochromatic,

n See radiation, homogeneous.

radiation necrosis,

n See necrosis, radiation.

radiation, neutron,

n See ray, neutron.

radiation oncology,

n the study of the treatment of cancer using ionizing radiation

radiation osteomyelitis/osteonecrosis

n an infection of the bone that occurs after exposure to radiation. Most commonly seen in cancer patients when radiation therapy damages healthy tissue surrounding the targeted tumor.

radiation, primary,

n all radiation produced directly from the target in a radiographic tube. See also radiation, direct.

radiation protection,

n provision designed to reduce exposure to radiation. For external radiation, this provision consists of using protective barriers of radiation-absorbing material, ensuring adequate distances from the radiation sources, reducing exposure time, and combinations of these measures. For internal radiation, it involves measures to restrict inhalation, ingestion, or other modes of entry of radioactive material into the body.

radiation quality,

n the ability of a beam of radiographs to allow the production of diagnostically useful radiographs. Usually measured in half-value layers of aluminum and controlled by the kilovolt peak.

radiation quantity,

n amount of radiation. The amount of exposure is expressed in roentgens (R), whereas quantity of dose is expressed in rads.

radiation, relative biologic effectiveness of (RBE),

n a comparison between various types of ionizing radiation with respect to the ability to produce biologic effects with small doses.

radiation, remnant,

n the radiation passing through an object or part being examined that is available either for recording on a radiographic film or for measurement.

radiation, scattered,

n (backscatter radiation), radiation whose direction has been altered. It may include secondary and stray radiation.

radiation, secondary,

n the new radiation created by primary radiation acting on or passing through matter.

radiation shield,

n See shield, radiation.

radiation sickness,

n a self-limited syndrome characterized by varying degrees of nausea, vomiting, diarrhea, and psychic depression after exposure to very large doses of ionizing radiation, particularly doses to the abdominal region. Its mechanism is not completely understood. It usually occurs a few hours after treatment and may subside within a day. It may be sufficiently severe to necessitate interrupting the treatment series, or it may incapacitate the patient.

radiation, soft,

n radiation consisting of the long wavelengths (lower kilovolt peak results in less penetration).

radiation, speed of,

n the speed of light, or approximately 186,000 miles per second.

radiation, stray,

n See radiation leakage.

radiation survey,

n See survey, radiation.

radiation therapy,

n See therapy, radiation.

radiation, total body,

n the exposure of the entire body to penetrating radiation. In theory, all cells in the body receive the same overall dose.

radiation treatment,

n a cancer treatment method that uses roentgen rays to modify or destroy cancer cells; dental patients who are undergoing radiation therapy may exhibit an increased need for certain nutrients. See also therapy, radiation.

radiation, useful,

n the part of the primary radiation that is permitted to pass from the tube housing through the tube head port, aperture, or collimating device. See beam, useful.

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therapy (ther´pē),

n the treatment of disease, injury, or illness.

therapy, antibiotic,

n the treatment of disease states by the local or systemic administration of antibodies.

therapy, antimicrobial,

n a treatment modality that attacks the microorganisms responsible for a specific disease or condition.

therapy, chlorhexidine chip,

n controlled delivery of the antimicrobial agent chlorhexidine in which a tiny, biodegradable dose of the drug is inserted into the periodontal pocket, where it continues to slowly release medication for approximately 7 to 10 days before disintegrating. This therapy is a means of attacking periodontal infection at its source without systemic involvement.

therapy, compromise periodontal maintenance,

n a program of continuing periodontal treatment designed to slow disease progression in patients for whom surgery is not an option because of specific health concerns or economic restrictions.

therapy, doxycycline polymer,

n delivery via syringe and cannula of a biodegradable liquid form of the antimicrobial agent doxycycline polymer directly into a periodontal pocket. The medication hardens upon contact with moisture, thus sealing the pocket and allowing the agent to destroy periodontal pathogens as it dissolves.

therapy, growth modification,

n a treatment employed to modify the growth of the jaw or other bones as they are still developing, usually to treat cases of malocclusion.

therapy, hormonal replacement,

n the administration of synthetic female hormones in order to ease the negative impacts of losing these hormones due to menopause, hysterectomy, or disease.

therapy, indirect pulpal,

n the application of a drug that heals the pulpal cells beneath a layer of sound or carious dentin, as in a moderately deep preparation for a restoration.

therapy, megavoltage radiation,

n a form of radiation therapy used in the treatment of oral cancer. It delivers a more precise point of contact than other forms.

therapy, myofunctional (myotherapeutic exercises),

n the use of muscle exercises as an adjunct to mechanical correction of malocclusion.

therapy, oxygen,

n the providing of additional oxygen for patients who need it.

therapy, periodontal,

n the treatment of the periodontal lesion. Such therapy has two principal objectives: the eradication or arrest of the periodontal lesion with correction or cure of the deformity created by it, and the alteration in the oral cavity of the periodontal climate that was conducive or contributory to the periodontal breakdown.

therapy, periodontal, maintenance phase,

n the part of periodontal therapy that is necessary for the preservation of the results obtained during active therapy and for the prevention of further periodontal disease; an extension of active periodontal therapy, requiring the combined efforts of both the periodontist and the patient.

therapy, pharmacotherapeutic nonsurgical pocket

n the use of both systemic and topical antibiotic compounds to fight bacterial infections in periodontal pockets.

therapy, pocket,

n the debridement or removal of deposits and endotoxins from the periodontal pocket in order to begin the healing process.

therapy, pulp canal,

n See endodontology.

therapy putty,

n a malleable, doughlike substance used in hand exercises to enhance the force and control of the hand muscles.

therapy, radiation (radiotherapy),

n the treatment of disease with a type of radiation.

therapy, radiation, external beam,

n a treatment for cancer in which a beam of high- or low-yield radiation is directed from outside the body at the site of the cancerous tumor or lesion; may cause unnecessary radiation to normal tissues.

therapy, radiation, internal,

n a treatment for cancer in which the radiation source takes the form of an interstitial implant. It is placed in the body among the affected tissues to provide a directed dose of radiation that is not possible using external methods.

therapy, radiation, orthovoltage,

n a form of cancer treatment in which a beam of low-yield radiation is directed from outside the body at a superficial lesion, such as those found in the oral cavity or on the lips.

therapy, radiation, supervoltage,

n See therapy, radiation, megavoltage.

therapy, replacement,

n the administration, as a therapeutic agent, of an essential constituent in which the body is deficient (e.g., insulin in diabetes mellitus).

therapy, root canal,

n See endodontology.

therapy, speech,

n the science that deals with the use of procedures, training, and remedies for the cure, alleviation, or prevention of speech disorders.

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radiation

1. divergence from a common center.

2. a structure made up of diverging elements, especially a tract of the central nervous system made up of diverging fibers.

3. energy carried by waves or a stream of particles. One type is electromagnetic radiation, which consists of wave motion of electric and magnetic fields. The quantum theory is based on the fact that electromagnetic waves consist of discrete particles, called photons, that have an energy inversely proportional to the wavelength of the wave. In order of increasing photon energy and decreasing wavelength, the electromagnetic spectrum is divided into radio waves, infrared light, visible light, ultraviolet light and x-rays.

Another type is the radiation emitted by radioactive materials. Alpha particles are high-energy helium-4 nuclei consisting of two protons and two neutrons, which are emitted by radioisotopes of heavy elements, such as uranium. Beta particles are high-energy electrons, which are emitted by radioisotopes of lighter elements. Gamma rays are high-energy photons, which are emitted along with alpha and beta particles and are also emitted alone by metastable radionuclides, such as technetium-99m. Gamma rays have energies in the x-ray region of the spectrum and differ from x-rays only in that they are produced by radioactive decay rather than by x-ray machines.

Radiation with enough energy to knock electrons out of atoms and produce ions is called ionizing radiation. This includes alpha and beta particles and x-rays and gamma rays.

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radiation biology

study of the effects of ionizing radiation on living tissues.

corpuscular radiation

particles emitted in nuclear disintegration, including alpha and beta particles, protons, neutrons, positrons and deuterons.

radiation detection

special equipment, including Geiger-Müller tubes and a scintillation crystal, is available to detect radiation which may be accidental, or detect small amounts where this is expected but it needs to be measured in terms of accumulated dose.

electromagnetic radiation

energy, unassociated with matter, that is transmitted through space by means of waves (electromagnetic waves) traveling in all instances at 3 × 10¹⁰ cm or 186,284 miles per second, but ranging in length from 10¹¹ cm (electrical waves) to 10⁻¹² cm (cosmic rays) and including radio waves, infrared, visible light and ultraviolet, x-rays and gamma rays.

radiation exposure

means more than the patient being exposed intentionally to an x-ray beam. Technical persons in the vicinity will also be exposed to a much less dangerous but perniciously cumulative load of radiation.

infrared radiation

the portion of the spectrum of electromagnetic radiation of wavelengths ranging between 0.75 and 1000 μm. See also infrared.

radiation injury

is caused by exposure to radioactive material. High doses cause intense diarrhea and dehydration and extensive skin necrosis. Median doses cause initial anorexia, lethargy and vomiting then normality for several weeks followed by vomiting, nasal discharge, dysentery, recumbency, septicemia and a profound pancytopenia. Death is the most common outcome. Chronic doses cause cataract in a few. Congenital defects occur rarely.

interstitial radiation

energy emitted by radium or radon inserted directly into the tissue.

ionizing radiation

corpuscular or electromagnetic radiation that is capable of producing ions, directly or indirectly, in its passage through matter. Used in treatment of radiosensitive cancer, in sterilization of animal products and food for experimental use.

radiation necrosis

see radionecrosis.

radiation physicist

the person responsible for the administration of radiation therapy including estimating the dose required for a treatment, arranging for the dose to be delivered and making arrangements for safety of the patient and staff, and disposing of any residual radioactive material. Technical aspects of the work include computer estimations, preparation of isodose curves, preparation of wedge and compensating filters, and calibration of teletherapy equipment.

primary radiation

radiation emanating from the x-ray tube which is absorbed by the subject or passes on through the subject without any change in photon energy.

radiation protection

includes proper control of emissions from the x-ray machines, proper protective clothing for staff, keeping unnecessary people out of the way while the tube is actually generating its beam, the wearing and regular examination of a dosimeter and the proper storage of radioactive materials or residues.

pyramidal radiation

fibers extending from the pyramidal tract to the cortex.

radiation sensitivity

tissues vary in their sensitivity to the damaging effects of irradiation. The rapidly growing tissues are most susceptible, e.g. the embryo, rapidly growing cancer, gonads, alimentary tract, skin and blood-forming organs.

radiation sickness

see radiation injury (above).

solar radiation

see solar.

radiation striothalamica

a fiber system joining the thalamus and the hypothalamic region.

tegmental radiation

fibers radiating laterally from the nucleus ruber.

thalamic radiation

fibers streaming out through the lateral surface of the thalamus, through the internal capsule to the cerebral cortex.

radiation therapist

a person skilled in radiotherapy. See also radiation therapy (below).

radiation therapy

see radiotherapy.

ultraviolet radiation

the portion of the spectrum of electromagnetic radiation of wavelengths ranging between 0.39 and 0.18 μm. See also ultraviolet rays.

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therapy

the treatment of disease; therapeutics. See also treatment.

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animal-assisted therapy

the treatment of humans, usually for mental or psychological illness, which incorporates familiarization with a companion or pleasure animal. Called also pet-facilitated or pet-assisted therapy. See also animal facilitated therapy.

anticoagulant therapy

the use of drugs to render the blood sufficiently incoagulable to discourage thrombosis.

heat therapy

see hyperthermia (2).

immunosuppressive therapy

treatment with agents, such as x-rays, corticosteroids and cytotoxic chemicals, which suppress the immune response to antigen(s); used in organ transplantation, autoimmune disease, allergy, multiple myeloma, etc.

inhalation therapy

see aerosol.

neoadjuvant therapy

given before the primary treatment, such as chemotherapy, hormone therapy, radiation therapy.

oxygen therapy

the administration of supplemental oxygen to relieve hypoxemia and prevent damage to the tissue cells as a result of oxygen lack (hypoxia). See also oxygen therapy.

physical therapy

use of physical agents and methods in rehabilitation and restoration of normal bodily function after illness or injury; it includes massage and manipulation, therapeutic exercises, hydrotherapy, and various forms of energy (electrotherapy, actinotherapy and ultrasound). See also physical therapist.

radiation therapy

treatment of disease by means of ionizing radiation. See also radiotherapy.

replacement therapy

treatment to replace deficient formation or loss of body products by administration of the natural body products or synthetic substitutes.

serum therapy

serotherapy; treatment of disease by injection of serum from immune animals.

substitution therapy

the administration of a hormone to compensate for glandular deficiency.

vaporization therapy

see aerosol.

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radiation therapy

Radiotherapy Administration of ionizing radiation to treat disease, usually malignant Types Local low energy radiation–brachytherapy or radioisotopes placed at or near the tumor or cancer cells–internal RT, implant radiation; high energy radiation delivered at a distance–teletherapy; most RT uses high-energy radiation from x-rays, neutrons, etc to kill CA and shrink tumors delivered as external-beam radiation; systemic RT includes use of radiolabeled monoclonal antibodies that circulate in the body, binding target cells, effecting therapy. See Conformal radiotherapy, Intracoronary radiotherapy, Intraoperative radiotherapy, Plaque radiotherapy, Radiation oncology, Stereotactic radiotherapy.

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Patient discussion about 3-dimensional radiation therapy.

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.
http://www.youtube.com/watch?v=8mDWk0KV6jI&eurl=http://www.imedix.com/health_community/v8mDWk0KV6jI_breast_cancer_treatment_alternative_hyperthermia?q=radiation%20thera&feature=player_embedded

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.
http://www.youtube.com/watch?v=JW6TDaotL_o&eurl=http://www.imedix.com/health_community/vJW6TDaotL%5Eo_breast_cancer?q=breast%20cancer&feature=player_embedded