Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is therapyusing ionizing radiation, generally as part of cancer treatment to control or killmalignant cells. Radiation therapy may be curative in a number of types of cancer if they are localized to one area of the body. It may also be used as part of adjuvant therapy, to prevent tumor recurrence after surgery to remove a primary malignant tumor (for example, early stages of breast cancer). Radiation therapy is synergistic withchemotherapy, and has been used before, during, and after chemotherapy in susceptible cancers. The subspecialty of oncology that focuses on radiotherapy is called radiation oncology.
Radiation therapy is commonly applied to the cancerous tumor because of its ability to control cell growth. Ionizing radiation works by damaging the DNA of cancerous tissue leading to cellular death. To spare normal tissues (such as skin or organs which radiation must pass through to treat the tumor), shaped radiation beams are aimed from several angles of exposure to intersect at the tumor, providing a much larger absorbed dose there than in the surrounding, healthy tissue. Besides the tumour itself, the radiation fields may also include the draining lymph nodes if they are clinically or radiologically involved with tumor, 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 tumor 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 tumor position.
Radiation oncology is the medical specialty concerned with prescribing radiation, and is distinct from radiology, the use of radiation in medical imagingand diagnosis. Radiation may be prescribed by a radiation oncologist with intent to cure ("curative") or for adjuvanttherapy. It may also be 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 and it can be curative). It is also common to combine radiation therapy with surgery, chemotherapy,hormone therapy, immunotherapy or some mixture of the four. Most common cancer types can be treated with radiation therapy in some way.
The precise treatment intent (curative, adjuvant, neoadjuvant, therapeutic, orpalliative) will depend on the tumor type, location, and stage, as well as the general health of the patient. Total body irradiation (TBI) is a radiation therapy technique used to prepare the body to receive a bone marrow transplant.Brachytherapy, in which a radiation source is placed inside or next to the area requiring treatment, is another form of radiation therapy that minimizes exposure to healthy tissue during procedures to treat cancers of the breast, prostate and other organs.
Radiation therapy has several applications in non-malignant conditions, such as the treatment oftrigeminal neuralgia, acoustic neuromas, severe thyroid eye disease, pterygium,pigmented villonodular synovitis, and prevention of keloid scar growth, vascular restenosis, and heterotopic ossification. The use of radiation therapy in non-malignant conditions is limited partly by worries about the risk of radiation-induced cancers.
Classification and external resourcesSpecialtyCardiology, nephrologyICD-10R60.9DiseasesDB9148MedlinePlus003103MeSHD004487
Edema (also oedema, dropsy, andhydropsy) (/ᵻˈdimə/; Greek οἴδημαoídēma, "swelling")[1] is an abnormal accumulation of fluid in the interstitium, located beneath the skin and in the cavities of the body which cause severe pain. Clinically, edema manifests asswelling; the amount of interstitial fluidis determined by the balance of fluidhomeostasis, and the increased secretion of fluid into the interstitium, or the impaired removal of the fluid can cause edema.
Classifications
Cutaneous edema is referred to as "pitting" when, after pressure is applied to a small area, the indentation persists after the release of the pressure.Peripheral pitting edema, as shown in the illustration, is the more common type, resulting from water retention. It can be caused by systemic diseases, pregnancy in some women, either directly or as a result of heart failure, or local conditions such as varicose veins,thrombophlebitis, insect bites, anddermatitis.
Non-pitting edema is observed when the indentation does not persist. It is associated with such conditions aslymphedema, lipedema, and myxedema.
Edema caused by malnutrition defineskwashiorkor, an acute form of childhood protein-energy malnutrition characterized by edema, irritability, anorexia, ulcerating dermatoses, and an enlarged liver with fatty infiltrates. The insufficient protein consumption, but with sufficient calorie intake, distinguishes it from marasmus. Kwashiorkor cases occur in areas of famine or poor food supply. Cases in the developed world are rare.
Generalized
Grading of edema[2]GradeDefinition"Absent"AbsentGrade +Mild: Both feet / anklesGrade ++Moderate: Both feet,
plus lower legs,
hands or lower armsGrade +++Severe: Generalised
bilateral pitting edema,
including both feet,
legs, arms and face
A rise in hydrostatic pressure occurs incardiac failure. A fall in osmotic pressure occurs in nephrotic syndromeand liver failure.[3]
Causes of edema which are generalized to the whole body can cause edema in multiple organs and peripherally. For example, severe heart failure can causepulmonary edema, pleural effusions,ascites and peripheral edema. In rare cases, a Parvovirus B19 infection may cause generalized edemas.[4]
Although a low plasma oncotic pressureis widely cited for the edema of nephrotic syndrome, most physicians note that the edema may occur before there is any significant protein in the urine (proteinuria) or fall in plasma protein level. Most forms of nephrotic syndrome are due to biochemical and structural changes in the basement membrane of capillaries in the kidney glomeruli, and these changes occur, if to a lesser degree, in the vessels of most other tissues of the body. Thus the resulting increase in permeability that leads to protein in the urine can explain the edema if all other vessels are more permeable as well.[5]
As well as the previously mentioned conditions, edemas often occur during the late stages of pregnancy in some women. This is more common with those of a history of pulmonary problems or poor circulation also being intensified if arthritis is already present in that particular woman. Women that already have arthritic problems most often have to seek medical help for pain caused from over-reactive swelling. Edemas that occur during pregnancy are usually found in the lower part of the leg, usually from the calf down.
Organ-specific
An edema will occur in specific organs as part of inflammations, tendonitis or pancreatitis, for instance. Certain organs develop edema through tissue specific mechanisms.
Examples of edema in specific organs:
Cerebral edema is extracellular fluid accumulation in the brain. It can occur in toxic or abnormal metabolic states and conditions such as systemic lupus or reduced oxygen at high altitudes. It causes drowsiness or loss of consciousness.Pulmonary edema occurs when the pressure in blood vessels in the lung is raised because of obstruction to the removal of blood via the pulmonary veins. This is usually due to failure of the left ventricle of the heart. It can also occur in altitude sickness or on inhalation of toxic chemicals. Pulmonary edema produces shortness of breath. Pleural effusions may occur when fluid also accumulates in the pleural cavity.Edema may also be found in the cornea of the eye with glaucoma, severe conjunctivitis or keratitis or after surgery. Sufferers may perceive coloured haloes around bright lights.Edema surrounding the eyes is called periorbital edema or eye puffiness. The periorbital tissues are most noticeably swollen immediately after waking, perhaps as a result of the gravitational redistribution of fluid in the horizontal position.Common appearances ofcutaneous edema are observed withmosquito bites, spider bites, bee stings (wheal and flare), and skin contact with certain plants such asPoison Ivy or Western Poison Oak,[6]the latter of which are termed contact dermatitis.Another cutaneous form of edema is myxedema, which is caused by increased deposition of connective tissue. In myxedema (and a variety of other rarer conditions) edema is caused by an increased tendency of the tissue to hold water within its extracellular space. In myxedema this is because of an increase in hydrophilic carbohydrate-rich molecules (perhaps mostly hyaluronan) deposited in the tissue matrix. Edema forms more easily in dependent areas in the elderly (sitting in chairs at home or on aeroplanes) and this is not well understood. Estrogens alter body weight in part through changes in tissue water content. There may be a variety of poorly understood situations in which transfer of water from tissue matrix to lymphatics is impaired because of changes in the hydrophilicity of the tissue or failure of the 'wicking' function of terminal lymphatic capillaries.In lymphedema abnormal removal of interstitial fluid is caused by failure of the lymphatic system. This may be due to obstruction from, for example, pressure from a cancer or enlargedlymph nodes, destruction of lymph vessels by radiotherapy, or infiltration of the lymphatics by infection (such as elephantiasis). It is most commonly due to a failure of the pumping action of muscles due to immobility, most strikingly in conditions such as multiple sclerosis, or paraplegia. It has been suggested that the edema that occurs in some people following use of aspirin-like cyclo-oxygenase inhibitors such as ibuprofen or indomethacin may be due to inhibition of lymph heart action.Hydrops fetalis is a condition of the fetus characterized by an accumulation of fluid, or edema, in at least two fetal compartments.
No comments:
Post a Comment