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Encyclopedia > Radiation therapy
Varian Clinac 2100C Linear Accelerator
Varian Clinac 2100C Linear Accelerator

Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiotherapy may be used for curative or adjuvant cancer treatment. It is used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit but is not curative) Total body irradiation (TBI) is a radiotherapy technique used to prepare the body to receive a bone marrow transplant. Radiotherapy has a few applications in non-malignant conditions, such as the treatment of trigeminal neuralgia, severe thyroid eye disease, pterygium, prevention of keloid scar growth, and prevention of heterotopic ossification. The use of radiotherapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers. Image File history File linksMetadata Download high resolution version (1600x1200, 443 KB) Description fr: Accélérateur de particules Clinac 2100 C à la polyclinique de Courlancy à Reims, France. ... Image File history File linksMetadata Download high resolution version (1600x1200, 443 KB) Description fr: Accélérateur de particules Clinac 2100 C à la polyclinique de Courlancy à Reims, France. ... For the chemical substances known as medicines, see medication. ... Radiation hazard symbol. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... See cancer for the biology of the disease, as well as a list of malignant diseases. ... In medicine, malignant is a clinical term that means to be severe and become progressively worse, as in malignant hypertension. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Image A: A normal chest X-ray. ... Medical imaging designates the ensemble of techniques and processes used to create images of the human body (or parts thereof) for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). ... In general, diagnosis (plural diagnoses) has two distinct dictionary definitions. ... In medicine, adjuvants are agents which modify the effect of other agents while having few if any direct effects when given by themselves. ... Palliative care is any form of medical care or treatment that concentrates on reducing the severity of the symptoms of a disease or slows its progress rather than providing a cure. ... Total Body Irradiation (TBI) is a radiotherapy technique used to ablate the bone marrow and immune system prior to bone marrow transplantation or peripheral blood stem cell transplantation. ... Bone marrow transplantation or hematopoietic stem cell transplantation (HSCT) is a medical procedure in the field of hematology and oncology that involves transplantation of hematopoietic stem cells (HSC). ... Trigeminal neuralgia, or Tic Douloureux, is a neuropathic disorder of the trigeminal nerve that causes episodes of intense pain in the eyes, lips, nose, scalp, forehead, and jaw. ... Graves-Basedow disease or known simply as Graves disease is a medical disorder that may manifest several different conditions including goitre and hyperthyroidism (over-activity of thyroid hormone production), infiltrative exophthalmos (protruberance of one or both eyes and associated problems) and infiltrative dermopathy (a skin condition usually of the lower... A pterygium, meaning wing, is a benign growth of the conjunctiva. ... A keloid is a special type of scar which results in an overgrowth of tissue at the site of a healed skin injury. ... Wikipedia does not have an article with this exact name. ...


Radiotherapy is commonly used for the treatment of malignant tumors (cancer), and may be used as the primary therapy. It is also common to combine radiotherapy with surgery, chemotherapy, hormone therapy or some mixture of the three. Most common cancer types can be treated with radiotherapy in some way. The precise treatment intent (curative, adjuvant, neoadjuvant, therapeutic, or palliative) will depend on the tumour type, location, and stage, as well as the general health of the patient. For malignant tumors specifically, see cancer. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... “Surgeon” redirects here. ... Chemotherapy is the use of chemical substances to treat disease. ... In medicine, hormone therapy is the use of hormones in medical treatment and covers various types of hormones including growth hormones and sex hormones. ... In medicine, adjuvants are agents which modify the effect of other agents while having few if any direct effects when given by themselves. ... In medicine, adjuvants are agents which modify the effect of other agents while having few if any direct effects when given by themselves. ... Palliative care is any form of medical care or treatment that concentrates on reducing the severity of the symptoms of a disease or slows its progress rather than providing a cure. ...


Radiation therapy is commonly applied to the tumour. The radiation fields may also include the draining lymph nodes if they are clinically or radiologically involved with tumour, or if there is thought to be a risk of subclinical malignant spread. It is necessary to include a margin of normal tissue around the tumour to allow for uncertainties in daily set-up and internal tumor motion. These uncertainties can be caused by internal movement (for example, respiration and bladder filling) and movement of external skin marks relative to the tumour position.


To spare normal tissues (such as skin or organs which radiation must pass through in order to treat the tumour), shaped radiation beams are aimed from several angles of exposure to intersect at the tumour, providing a much larger absorbed dose there than in the surrounding, healthy tissue. Absorbed dose is a measure of the energy deposited in a medium by ionising radiation. ...

Contents

Side effects

Radiation Therapy is in itself painless. Many low-dose palliative treatments (for example, radiotherapy to bony metastases) cause minimal or no side effects. Treatment to higher doses causes varying side effects during treatment (acute side effects), in the months or years following treatment (long-term side effects), or after re-treatment (cumulative side effects). The nature, severity, and longevity of side effects depends on the organs that receive the radiation, the treatment itself (type of radiation, dose, fractionation, concurrent chemotherapy), and the patient. Palliative care is any form of medical care or treatment that concentrates on reducing the severity of the symptoms of a disease or slows its progress rather than providing a cure. ... Metastasis (Greek: change of the state) is the spread of cancer from its primary site to other places in the body. ...


Most side effects are predictable and expected. One of the aims of modern radiotherapy is to reduce side effects to a minimum, and to help the patient to understand and to deal with those side effects which are unavoidable.


Acute side effects

Damage, possibly severe, to epithelial surfaces (skin, oral, pharyngeal and bowel mucosa, urothelium)
The rates of onset and of recovery depend on the rate of turnover of the epithelial cells. Typically the skin starts to become pink and sore several weeks into treatment. The reaction may become more severe during the treatment and for up to about one week following the end of radiotherapy, and the skin may break down. Although this moist desquamation is uncomfortable, recovery is usually quick. Skin reactions tend to be worse in areas where there are natural folds in the skin, such as underneath the female breast, behind the ear, and in the groin.
Similarly, the lining of the mouth, throat, esophagus, and bowel may be damaged by radiation. If the head and neck area is treated, temporary soreness and ulceration commonly occur in the mouth and throat. If severe, this can affect swallowing, and the patient may need painkillers and nutritional support. The esophagus can also become sore if it is treated directly, or if, as commonly occurs, it receives a dose of collateral radiation during treatment of lung cancer.
The lower bowel may be treated directly with radiation (treatment of rectal or anal cancer) or be exposed by radiotherapy to other pelvic structures (prostate, bladder, female genital tract). Typical symptoms are soreness, diarrhoea, and nausea.
Swelling (edema or Oedema)
As part of the general inflammation that occurs, swelling of soft tissues may cause problems during radiotherapy. This is a concern during treatment of brain tumours and brain metastases, especially where there is pre-existing raised intracranial pressure or where the tumour is causing near-total obstruction of a lumen (e.g., trachea or main bronchus). Surgical intervention may be considered prior to treatment with radiation. If surgery is deemed unnecessary or inappropriate, the patient may receive steroids during radiotherapy to reduce swelling.
Infertility
The gonads (ovaries and testicles) are very sensitive to radiation. They may be unable to produce gametes following direct exposure to most normal treatment doses of radiation. Treatment planning for all body sites is designed to minimize, if not completely exclude dose to the gonads if they are not the primary area of treatment.
Generalized fatigue

The urothelium is the lining of the ureters, urethra, and urinary bladder. ... In zootomy, epithelium is a tissue composed of a layer of cells. ... Moist desquamation is a description of the clinical pattern seen in radiotherapy where the skin thins and then starts to weep because of loss of integrity of the epithelial barrier. ... Intracranial pressure, (ICP), is the pressure exerted by the cranium on the brain tissue, cerebrospinal fluid (CSF), and the brains circulating blood volume. ... Lumen can mean: Lumen (unit), the SI unit of luminous flux Lumen (anatomy), the cavity or channel within a tubular structure Thylakoid lumen, the inner membrane space of the chloroplast 141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875 Lumen (band), an American post-rock band... Windpipe redirects here. ... A bronchus (plural bronchi, adjective bronchial) is a caliber of airway in the respiratory tract that conducts air into the lungs. ... In chemistry and biology, Steroids are a type of lipid, characterized by a carbon skeleton with four fused rings. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis... Gametes (in Greek: γαμέτες) —also known as sex cells, germ cells, or spores—are the specialized cells that come together during fertilization (conception) in organisms that reproduce sexually. ...

Medium and long-term side effects

These depend on the tissue that received the treatment; they may be minimal.

Fibrosis
Tissues which have been irradiated tend to become less elastic over time due to a diffuse scarring process.
Hair loss
This may be most pronounced in patients who have received radiotherapy to the brain. Unlike the hair loss seen with chemotherapy, radiation-induced hair loss is more likely to be permanent, but is also more likely to be limited to the area treated by the radiation.
Dryness
The salivary glands and tear glands have a radiation tolerance of about 30 Gy in 2 Gy fractions, a dose which is exceeded by most radical head and neck cancer treatments. Dry mouth (xerostomia) and dry eyes (xerophthalmia) can become irritating long-term problems and severely reduce the patient's quality of life. Similarly, sweat glands in treated skin (such as the armpit) tend to stop working, and the naturally moist vaginal mucosa is often dry following pelvic irradiation.
Cancer
Radiation is a potential cause of cancer, and secondary malignancies are seen in a very small minority of patients, generally many years after they have received a course of radiation treatment. In the vast majority of cases, this risk is greatly outweighed by the reduction in risk conferred by treating the primary cancer.

Fibrosis is the formation or development of excess fibrous connective tissue in an organ or tissue as a reparative or reactive process, as opposed to a formation of fibrous tissue as a normal constituent of an organ or tissue. ... The gray (symbol: Gy) is the SI unit of absorbed dose. ... Xerostomia is the medical term for a dry mouth due to a lack of saliva. ... Xerophthalmia (Greek for dry eyes) is a medical condition in which the eye doesnt produce tears. ... Sweating (also called perspiration or sometimes transpiration) is the loss of a watery fluid, consisting mainly of sodium chloride and urea in solution, that is secreted by the sweat glands in the skin of mammals. ... The armpit (or axilla) is the area on the human body directly under the joint where the arm connects to the shoulder. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ...

Cumulative side effects

Cumulative effects from reirradiation should not be confused with long-term effects—when short-term effects have disappeared and long-term effects are subclinical, reirradiation can still be problematic [1].


Best Results

Radiation therapy as cancer treatment should be used in conjunction with anti-aging strategies such as immunotherepy for best results in prolonged life. Observations suggest these tools may convert "anecdotal" remissions or cures to a more comprehensible and more rational causal basis. A hypothesis that anomalously superior survival may correlate meaningfully with an increase in natural killer (NK) cells, and that SB and NK% determinations contribute to an objective basis for a science of clinical immunotherapy applicable to individual patients. If unusual remissions in carcinoma patients are more often found to be associated with extraordinarily high NK%, it is believed that elevated NK% will prove to be useful as prognostic indicator. Several case histories which show a correlation between a rise in natural killer cells with the use of individually tailored regimens of immunotherapy. [2]


Dose

The amount of radiation used in radiation therapy is measured in gray (Gy), and varies depending on the type and stage of cancer being treated. For curative (radical) cases, the typical dose for a solid epithelial tumor ranges from 60 to 80 Gy, while lymphoma tumors are treated with 20 to 40 Gy. Preventative (adjuvant) doses are typically around 45 - 60 Gy in 1.8 - 2 Gy fractions (for Breast, Head and Neck cancers respectively.) Many other factors are considered by radiation oncologists when selecting a dose, including whether the patient is receiving chemotherapy, whether radiation therapy is being administered before or after surgery, and the degree of success of surgery. The gray (symbol: Gy) is the SI unit of absorbed dose. ... A radiation oncologist is a doctor who specialises in the treatment of cancer patients, using radiation as the main modality of treatment as opposed to a medical oncologist who is a doctor who uses chemotherapy as the preferred modality of treatment. ...


Fractionation

The total dose is fractionated (spread out over time) in order to give normal cells time to recover. In the USA, Australia, and Europe, the typical fractionation schedule for adults is 1.8 to 2 Gy per day, five days a week. In the northern United Kingdom, fractions are more commonly 2.67 to 2.75 Gy per day, which eases the burden on thinly spread resources in the National Health Service. For children, a typical fraction is 1.5 to 1.7 Gy per day, reducing the chance and severity of late-onset side effects. NHS redirects here. ...


In some cases, two fractions per day are used near the end of a course of treatment. This schedule, known as a concomitant boost regimen and/or hyperfractionation, is used on tumors that regenerate more quickly when they are smaller. In particular, tumors in the head and neck demonstrate this behavior.


One of the best-known alternative fractionation schedules is Continuous Hyperfractionated Accelerated Radiotherapy (CHART). CHART, used to treat lung cancer, consists of three smaller fractions per day. Although reasonably successful, CHART can be a strain on radiation therapy departments.


Implants can be fractionated over minutes or hours, or they can be permanent seeds which slowly deliver radiation until they become inactive.


Mechanism of action

Radiation therapy works by damaging the DNA of cells. The damage is caused by a photon, electron, proton, neutron, or ion beam directly or indirectly ionizing the atoms which make up the DNA chain. Indirect ionization happens as a result of the ionization of water, forming free radicals, notably hydroxyl radicals, which then damage the DNA. In the most common forms of radiation therapy, most of the radiation effect is through free radicals. Because cells have mechanisms for repairing DNA damage, breaking the DNA on both strands proves to be the most significant technique in modifying cell characteristics. Because cancer cells generally are undifferentiated and stem cell-like, they reproduce more, and have a diminished ability to repair sub-lethal damage compared to most healthy differentiated cells. The DNA damage is inherited through cell division, accumulating damage to the cancer cells, causing them to die or reproduce more slowly. Proton radiotherapy works by sending protons with varying kinetic energy to precisely stop at the tumor. The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... For other uses, see Electron (disambiguation). ... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... This article is about the electrically charged particle. ... ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... Ionization is the physical process of converting an atom or molecule into an ion by changing the difference between the number of protons and electrons. ... In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... Mouse embryonic stem cells with fluorescent marker. ... Embryonic stem cells differentiate into cells in various body organs. ... The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. ...


One of the major limitations of radiotherapy is that the cells of solid tumors become deficient in oxygen. This is because solid tumours usually outgrow their blood supply, causing a low-oxygen state known as hypoxia. The more hypoxic the tumours are the more resistant they are to the effects of radiation because oxygen makes the radiation damage to DNA permanent. Much research has been devoted to overcoming this problem including the use of high pressure oxygen tanks, blood substitutes that carry increased oxygen, hypoxic cell radiosensitizers such as misonidazole and metronidazole, and hypoxic cytotoxins, such as tirapazamine. There is also interest in the fact that high LET particles such as carbon or neon ions may have an antitumour effect which is independent of tumour hypoxia. Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. ... Metronidazole (INN) (IPA: ) is a nitroimidazole anti-infective drug used mainly in the treatment of infections caused by susceptible organisms, particularly anaerobic bacteria and protozoa. ... Chemical structure of tirapazamine. ...


History of radiation therapy

Radiation therapy has been in use as a cancer treatment for more than 100 years, with its earliest roots traced from the discovery of x-rays in 1895.[3] The concept of therapeutic radiation was invented by German physicist Wilhelm Conrad Rontgen when he discovered that the x-ray was a powerful and effective tool with which to treat cancer. Wilhelm Conrad Röntgen Wilhelm Conrad Röntgen (in English: William Conrad Roentgen) (March 27, 1845 – February 10, 1923) was a German physicist, of the University of Würzburg, who, on November 8, 1895, produced and detected electromagnetic radiation in a wavelength range today known as x-rays or R...


The field of radiation therapy began to grow in the early 1900s largely due to the groundbreaking work of Nobel Prize-winning scientist Marie Curie, who discovered the radioactive elements polonium and radium. This began a new era in medical treatment and research.[3]. Radium was used in various forms until the mid-1900s when cobalt and caesium units came into use. Medical linear accelerators have been developed since the late 1940s. The Nobel Prize (Swedish: ), as designated in Alfred Nobels will in 1895, is awarded in Physics, Chemistry, Physiology or Medicine, Literature, and Peace. ... This article is about the chemist and physicist. ... General Name, Symbol, Number polonium, Po, 84 Chemical series metalloids Group, Period, Block 16, 6, p Appearance silvery Standard atomic weight (209) g·mol−1 Electron configuration [Xe] 4f14 5d10 6s2 6p4 Electrons per shell 2, 8, 18, 32, 18, 6 Physical properties Phase solid Density (near r. ... General Name, Symbol, Number radium, Ra, 88 Chemical series alkaline earth metals Group, Period, Block 2, 7, s Appearance silvery white metallic Standard atomic weight (226) g·mol−1 Electron configuration [Rn] 7s2 Electrons per shell 2, 8, 18, 32, 18, 8, 2 Physical properties Phase solid Density (near r. ... For other uses, see Cobalt (disambiguation). ... General Name, Symbol, Number caesium, Cs, 55 Chemical series alkali metals Group, Period, Block 1, 6, s Appearance silvery gold Standard atomic weight 132. ... Linear accelerator (LINAC) used for medical radiation therapy; example made by Siemens AG. A linear particle accelerator (also called a LINAC) is an electrical device for the acceleration of subatomic particles. ...


With Godfrey Hounsfield’s discovery of computed tomography (CT), three-dimensional planning became a possibility and created a shift from 2-D to 3-D radiation delivery; physicians and physics were no longer limited because CT-based planning allowed physicians to directly measure the dose delivered to the patient's anatomy based on axial tomographical images. Orthovoltage and cobalt units have largely been replaced by megavoltage linear accelerators, useful for their penetrating energies and lack of physical radiation source. Sir Godfrey Newbold Hounsfield (28 August 1919 - 12 August 2004) was an English electrical engineer who shared the 1979 Nobel Prize for Physiology or Medicine with Allan McLeod Cormack for his part in developing the diagnostic technique of computerized axial tomography (CAT). ... negron305 Cat scan redirects here. ...


In the last few decades, the advent of new imaging technologies, e.g., magnetic resonance imaging (MRI) in the 1970s and positron emission tomography (PET) in the 1980s, as well as new radiation delivery and visualization products, e.g., digital linear accelerator, image fusion has moved radiation therapy from 3-D conformal to IMRT and eventually to IGRT (4-D) in the near future. These advances have resulted in better treatment outcomes and less side effects. Now 70% of cancer patients receive radiation therapy as part of their cancer treatment. “MRI” redirects here. ... Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three-dimensional image or map of functional processes in the body. ... In computer vision, Multisensor Image Fusion is the process of combining relevant information from two or more images into a single image. ...


Types of radiation therapy

Historically, the three main divisions of radiotherapy are external beam radiotherapy (EBRT or XBRT) or teletherapy, brachytherapy or sealed source radiotherapy and unsealed source radiotherapy. The differences relate to the position of the radiation source; external is outside the body, while sealed and unsealed source radiotherapy has radioactive material delivered internally. Brachytherapy sealed sources are usually extracted later, while unsealed sources may be administered by injection or ingestion. Proton therapy is a special case of external beam radiotherapy where the particles are protons. Introperative radiotherapy[4] is a special type of radiotherapy that is delivered immediately after surgical removal of the cancer. This method has been employed in breast cancer (TARGeted Introperative radioTherapy), brain tumours and rectal cancers. External beam radiotherapy otherwise known as teletherapy, is the most frequently used form of radiotherapy. ... External beam radiotherapy is the most common form of radiotherapy where a patient lies on a couch and an external source of X-rays is pointed at a particular part of the body. ... Brachytherapy for prostate cancer is administered using seeds, small radioactive rods implanted directly into the tumour. ... Sealed source radiotherapy or brachytherapy or endocurietherapy is the application of radiation from close range and is used for techniques where the radioactive source is placed inside the area requiring treatment. ... Unsealed source radiotherapy relates to the use of soluble forms of radioactive substances which are injected into the body. ... Proton therapy is a kind of external beam radiotherapy where protons are directed to a tumor site. ... For other uses, see Proton (disambiguation). ...


Roughly half of the 2500 worldwide radiotherapy clinics are in the US (as of 2001).


Conventional external beam radiotherapy

Conventional external beam radiotherapy (2DXRT) is delivered via two-dimensional beams using linear accelerator machines. 2DXRT mainly consists of a single beam of radiation delivered to the patient from several directions: often front or back, and both sides. Conventional refers to the way the treatment is planned or simulated on a specially calibrated diagnostic x-ray machine known as a simulator because it recreates the linear accelerator actions (or sometimes by eye), and to the usually well established arrangements of the radiation beams to achieve a desired plan. The aim of simulation is to accurately target or localize the volume which is to be treated. This technique is well established and is generally quick and reliable. The worry is that some high-dose treatments may be limited by the radiation toxicity capacity of healthy tissues which lay close to the target tumor volume. An example of this problem is seen in radiation of the prostate gland, where the sensitivity of the adjacent rectum limits the dose which can be safely prescribed to such an extent that tumor control may not be easily achievable. Previous to the invention of the CT, physicians and physicists had limited knowledge about the true radiation dosage delivered to both cancerous and healthy tissue. For this reason, 3-dimensional conformal radiotherapy is becoming the standard treatment for a number of tumor sites.


Virtual simulation, 3-dimensional conformal radiotherapy, and intensity-modulated radiotherapy

The planning of radiotherapy treatment has been revolutionized by the ability to delineate tumors and adjacent normal structures in three dimensions using specialized CT and/or MRI scanners and planning software.[5] Virtual simulation, the most basic form of planning, allows more accurate placement of radiation beams than is possible using conventional X-rays, where soft-tissue structures are often difficult to assess and normal tissues difficult to protect.


An enhancement of virtual simulation is 3-Dimensional Conformal Radiotherapy (3DCRT), in which the profile of each radiation beam is shaped to fit the profile of the target from a beam's eye view (BEV) using a multileaf collimator (MLC) and a variable number of beams. When the treatment volume conforms to the shape of the tumour, the relative toxicity of radiation to the surrounding normal tissues is reduced, allowing a higher dose of radiation to be delivered to the tumor than conventional techniques would allow. Beams Eye View Beams Eye View (or BEV) is an imaging technique used in Radiation therapy for the quality assurance and planning of External Beam Radiation Therapy treatments. ...


Intensity-Modulated Radiation Therapy (IMRT) is an advanced type of high-precision radiation that is the next generation of 3DCRT.(Galvin et al 2004) Computer-controlled x-ray accelerators distribute precise radiation doses to malignant tumors or specific areas within the tumor. The pattern of radiation delivery is determined using highly-tailored computing applications to perform optimization and treatment simulation (Treatment Planning). The radiation dose is consistent with the 3-D shape of the tumor by controlling, or modulating, the radiation beam’s intensity. IMRT also improves the ability to conform the treatment volume to concave tumor shapes, for example when the tumor is wrapped around a vulnerable structure such as the spinal cord or a major organ or blood vessel. The radiation dose intensity is elevated near the gross tumor volume while radiation among the neighboring normal tissue is decreased or avoided completely. The customized radiation dose is intended to maximize tumor dose while simultaneously protecting the surrounding normal tissue. Because of this, IMRT allows for higher radiation doses to be delivered to the tumor while sparing healthy tissue as compared with conventional radiation therapy techniques (2DXRT and 3DCRT). This in turn results in better tumor targeting, lessened side effects, and improved treatment outcomes than even 3DCRT. In mathematics, the term optimization, or mathematical programming, refers to the study of problems in which one seeks to minimize or maximize a real function by systematically choosing the values of real or integer variables from within an allowed set. ... In Radiotherapy, Treatment Planning is the process in which a team consisting of radiation oncologists, medical radiation physicists and dosimetrists plan the appropriate external beam radiotherapy treatment technique for a patient with cancer. ...


3DCRT is still used extensively for many body sites but the use of IMRT is growing in more complicated body sites such as CNS, head and neck, prostate, breast and lung. Unfortunately, IMRT is limited by its need for additional time from experienced medical personnel. This is because physicians must manually delineate the tumors one CT image at a time through the entire disease site which can take much longer than 3DCRT preparation. Then, medical physicists and dosimetrists must be engaged to create a viable treatment plan. Also, the IMRT technology has only been used commercially since the late 1990s even at the most advanced cancer centers, so radiation oncologists who did not learn it as part of their residency program must find additional sources of education before implementing IMRT.


Proof of improved survival benefit from either of these two techniques over conventional radiotherapy (2DXRT) is growing for many tumor sites, but the ability to reduce toxicity is generally accepted. Both techniques enable dose escalation, potentially increasing usefulness. There has been some concern, particularly with 3DCRT, about increased exposure of normal tissue to radiation and the consequent potential for secondary malignancy. Overconfidence in the accuracy of imaging may increase the chance of missing lesions that are invisible on the planning scans (and therefore not included in the treatment plan) or that move between or during a treatment (for example, due to respiration or inadequate patient immobilization). New techniques are being developed to better control this uncertainty—for example, real-time imaging combined with real-time adjustment of the therapeutic beams. This new technology is called image-guided radiation therapy (IGRT) or four-dimensional radiotherapy. Image-guided radiation therapy (IGRT) is the process of frequent two and three-dimensional imaging, during a course of radiation treatment, used to direct radiation therapy utilizing the imaging coordinates of the actual radiation treatment plan. ... Image-guided radiation therapy (IGRT) is the process of frequent two and three-dimensional imaging, during a course of radiation treatment, used to direct radiation therapy utilizing the imaging coordinates of the actual radiation treatment plan. ...


Radioisotope Therapy (RIT)

Radiotherapy can also be delivered through infusion (into the bloodstream) or ingestion. Examples are the infusion of metaiodobenzylguanidine (MIBG) to treat neuroblastoma, of oral iodine-131 to treat thyroid cancer or thyrotoxicosis, and of hormone-bound lutetium-177 and yttrium-90 to treat neuroendocrine tumors (peptide receptor radionuclide therapy). Another example is the injection of radioactive glass or resin microspheres into the hepatic artery to radioembolize liver tumors or liver metastases. In pharmacology and toxicology, a route of administration is the path by which a drug, fluid, poison or other substance is brought into contact with the body. ... Neuroblastoma is the most common extracranial solid cancer in infancy and childhood. ... Iodine-131 (131I), also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. ... Thyroid cancer is malignant growth of the thyroid gland. ... Hyperthyroidism (thyrotoxicosis or fast thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) and free triiodothyronine (T3), or both. ... General Name, Symbol, Number lutetium, Lu, 71 Chemical series lanthanides Group, Period, Block n/a, 6, d Appearance silvery white Standard atomic weight 174. ... General Name, Symbol, Number yttrium, Y, 39 Chemical series transition metals Group, Period, Block 3, 5, d Appearance silvery white Standard atomic weight 88. ... Neuroendocrine tumors, or more properly gastro-entero-pancreatic or gastroenteropancreatic neuroendocrine tumors (GEP-NETs), are cancers of the interface between the endocrine (hormonal) system and the nervous system. ... Hepatic artery is an artery that distributes blood to the liver, pancreas and gallbladder as well as to the stomach and duodenal portion of the small intestine. ...


In 2002, the United States Food and Drug Administration (FDA) approved Ibritumomab tiuxetan (Zevalin), which is a monoclonal antibody anti-CD20 conjugated to a molecule of Yttrium-90. [6] In 2003, the FDA approved Tositumomab Iodine-131 (Bexxar), which conjugates a molecule of Iodine-131 to the monoclonal antibody anti-CD20. [7] These medications were the first agents of what is known as radioimmunotherapy, and they were approved for the treatment of refractory non-Hodgkins lymphoma.Uranium-235 is also used in radiotherapy recently to treat some diseases. The United States Food and Drug Administration is the government agency responsible for regulating food, dietary supplements, drugs, cosmetics, medical devices, biologics and blood products in the United States. ... Ibritumomab tiuxetan, also sold under the trade name Zevalin® is a monoclonal antibody radioimmunotherapy treatment for some forms of non-Hodgkins lymphoma, a myeloproliferative disorder of the lymphatic system. ... Monoclonal antibodies (mAb) are antibodies that are identical because they were produced by one type of immune cell, all clones of a single parent cell. ... CD20 is a non-glycosylated phosphoprotein expressed on the surface of all mature B-cells. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... The United States Food and Drug Administration is the government agency responsible for regulating food, dietary supplements, drugs, cosmetics, medical devices, biologics and blood products in the United States. ... Tositumomab is a monoclonal antibody. ... Iodine-131 (131I), also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... Iodine-131 (131I), also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. ... Monoclonal antibodies (mAb) are antibodies that are identical because they were produced by one type of immune cell, all clones of a single parent cell. ... CD20 is a non-glycosylated phosphoprotein expressed on the surface of all mature B-cells. ... Radioimmunotherapy (RIT) utilizes an antibody labeled with a radionuclide to deliver cytotoxic radiation to a target cell (1). ... Non-Hodgkins lymphoma is a type of cancer. ...


References

  • Galvin, JM; Ezzel, G & Eisbrauch, A et al. (2004), "Implementing IMRT in clinical practice: a joint document of the American Society for Therapeutic Radiology and Oncology and the American Association of Physicists in Medicine.", Int J Radiat Oncol Biol Phys. 58 (5): 1616-34

General references

  • Practical Radiotherapy Planning, Dobbs J, Barrett A, Ash D (1999) Arnold ISBN 0-340-70631-7
  1. ^ Nieder C, Milas L, Ang KK (2000). "Tissue tolerance to reirradiation.". Semin Radiat Oncol 10 (3): 200-9. PMID 11034631. 
  2. ^ Smith, R. Arnold. North Central Regional Cancer Center. [1]
  3. ^ a b University of Alabama at Birmingham Comprehensive Cancer Center, History of Radiation Oncology.
  4. ^ Vaidya J. TARGIT (TARGeted Intraoperative radioTherapy). Retrieved on 2007-03-11.
  5. ^ Bucci M, Bevan A, Roach M (2005). "Advances in radiation therapy: conventional to 3D, to IMRT, to 4D, and beyond.". CA Cancer J Clin 55 (2): 117-34. PMID 15761080. Full text
  6. ^ [2]
  7. ^ [3]

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 70th day of the year (71st in leap years) in the Gregorian calendar. ...

External links

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  Results from FactBites:
 
Radiation Therapy for Cancer: Q & A - National Cancer Institute (3920 words)
Radiation therapy may be used to treat almost every type of solid tumor, including cancers of the brain, breast, cervix, larynx, lung, pancreas, prostate, skin, spine, stomach, uterus, or soft tissue sarcomas.
Radiation may come from a machine outside the body (external radiation), may be placed inside the body (internal radiation), or may use unsealed radioactive materials that go throughout the body (systemic radiation therapy).
Proton beam therapy is also being used in clinical trials for intraocular melanoma (melanoma that begins in the eye), retinoblastoma (an eye cancer that most often occurs in children under age 5), rhabdomyosarcoma (a tumor of the muscle tissue), some cancers of the head and neck, and cancers of the prostate, brain, and lung.
Radiation Therapy - Cancer information (cancers, symptoms, treatment) on MedicineNet.com (511 words)
In radiation therapy (also called radiotherapy), high-energy rays are used to damage cancer cells and stop them from growing and dividing.
External radiation therapy is usually given on an outpatient basis in a hospital or clinic 5 days a week for a number of weeks.
With radiation therapy, the side effects depend on the treatment dose and the part of the body that is treated.
  More results at FactBites »

 
 

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