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Rad (unit)
The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue or silicon microchips or any other medium (for example, air, water, lead shielding, etc.). It has been replaced by the gray (Gy) in SI derived units, but is still used in the United States, although this is "strongly discouraged" in Chapter 5.2 of the ''Guide to the SI'', which was written and published by the U.S. National Institute of Standards and Technology. However, the numerically equivalent SI unit, the centigray, is widely used to report absorbed doses within radiotherapy. The roentgen, used to quantify the radiation exposure, may be related to the corresponding absorbed dose by use of the F-factor. Health effects A dose of under 100 rad will typically produce no immediate symptoms other than blood ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absorbed Dose
Absorbed dose is a dose quantity which is the measure of the energy deposited in matter by ionizing radiation per unit mass. Absorbed dose is used in the calculation of dose uptake in living tissue in both radiation protection (reduction of harmful effects), and radiology (potential beneficial effects for example in cancer treatment). It is also used to directly compare the effect of radiation on inanimate matter such as in radiation hardening. The SI unit of measure is the gray (Gy), which is defined as one Joule of energy absorbed per kilogram of matter. The older, non-SI CGS unit rad, is sometimes also used, predominantly in the USA. Deterministic effects Conventionally, in radiation protection, unmodified absorbed dose is only used for indicating the immediate health effects due to high levels of acute dose. These are tissue effects, such as in acute radiation syndrome, which are also known as deterministic effects. These are effects which are certain to happen in a short ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Commission On Radiological Protection
The International Commission on Radiological Protection (ICRP) is an independent, international, non-governmental organization, with the mission to protect people, animals, and the environment from the harmful effects of ionising radiation. Its recommendations form the basis of radiological protection policy, regulations, guidelines and practice worldwide. The ICRP was effectively founded in 1928 at the second International Congress of Radiology in Stockholm, Sweden but was then called the International X-ray and Radium Protection Committee (IXRPC). In 1950 it was restructured to take account of new uses of radiation outside the medical area and re-named as the ICRP. The ICRP is a sister organisation to the International Commission on Radiation Units and Measurements (ICRU). In general terms ICRU defines the units, and ICRP recommends, develops and maintains the International system of radiological protection which uses these units. Operation The ICRP is a not-for-profit organ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milligray
The gray (symbol: Gy) is the unit of ionizing radiation dose in the International System of Units (SI), defined as the absorption of one joule of radiation energy per kilogram of matter. It is used as a unit of the radiation quantity absorbed dose that measures the energy deposited by ionizing radiation in a unit mass of matter being irradiated, and is used for measuring the delivered dose in radiotherapy, food irradiation and radiation sterilization. It is important in predicting likely acute health effects, such as acute radiation syndrome and is used to calculate equivalent dose using the sievert, which is a measure of the stochastic health effect on the human body. The gray is also used in radiation metrology as a unit of the radiation quantity kerma; defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation in a sample of matter per unit mass. The gray is an important unit in ionising radiation measurement ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relative Biological Effectiveness
In radiobiology, the relative biological effectiveness (often abbreviated as RBE) is the ratio of biological effectiveness of one type of ionizing radiation relative to another, given the same absorbed dose, amount of absorbed energy. The RBE is an empirical value that varies depending on the type of ionizing radiation, the energies involved, the biological effects being considered such as cell death, and the oxygen tension of the tissues or so-called oxygen effect. Application The absorbed dose can be a poor indicator of the biological effect of radiation, as the biological effect can depend on many other factors, including the type of radiation, energy, and type of tissue. The relative biological effectiveness can help give a better measure of the biological effect of radiation. The relative biological effectiveness for radiation of type ''R'' on a tissue is defined as the ratio :RBE= \frac where ''D''''X'' is a reference absorbed dose of radiation of a standard type ''X'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbert Parker (scientist)
Herbert M. Parker (13 April 1910, Accrington – 5 March 1984, Richland, Washington) was an English, and American immigrant, medical physicist. He was a pioneer of medical radiation therapy and radiation safety, known for introducing the roentgen equivalent physical (rep), the forerunner of the gray and the rad, and also the roentgen equivalent biological (reb), the forerunner of the rem and the sievert. Career After receiving an M.S. in physics from the University of Manchester in 1931, Parker became a medical physicist at the Christie Hospital and the Holt Radium Institute in Manchester. With James R. Paterson, he developed in 1932 the Paterson-Parker method, or Manchester System, for radiation therapy. The method allows physicians to use radium needles or tubes to maximize the radiation dose delivered to a cancerous tumour whilst minimizing the dose to healthy tissue. In 1938 Parker immigrated to the U.S.A. to begin work at the Swedish Hospital in Seattle, where he worked wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Valentine Mayneord
William Valentine Mayneord, CBE FRS (14 February 1902 – 10 August 1988) was a British physicist and pioneer in the field of medical physics. Early life and education He was born in Redditch, Worcestershire to Walter and Elizabeth Mayneord but after the early death of his mother was adopted by an aunt in Evesham. He was educated at Prince Henry's School, Evesham and gained a Bachelor of Science at the University of Birmingham Career He entered the field of medical physics in 1924 at St Bart's Hospital in London. In 1927 he moved to the Cancer Hospital, now the Royal Marsden Hospital. There he was involved in pioneering work with Izrael Hieger. During World War II he was seconded by the government to work in Canada on the radiological aspects of atomic energy development. It has been said that such was his renown, especially for bringing in the use of the radiological unit the rad, that the SI unit may well have been called the mayneord instead of the gray (2). It was dur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Harold Gray
Louis Harold Gray FRS (10 November 1905 – 9 July 1965) was an English physicist who worked mainly on the effects of radiation on biological systems. He was one of the earliest contributors of the field of radiobiology. A summary of his work is given below. Amongst many other achievements, he defined a unit of radiation dosage which was later named after him as an SI unit, the gray. Career * 1933 - Hospital physicist at Mount Vernon Hospital, London * 1936 - Developed the Bragg–Gray equation, the basis for the cavity ionization method of measuring gamma-ray energy absorption by materials * 1937 - Built an early neutron generator at Mount Vernon Hospital * 1938 - Studied biological effects of neutrons using the generator * 1940 - Developed concept of RBE (Relative Biological Effectiveness) of doses of neutrons * 1952 - Initiated research into cells in hypoxic tumors and hyperbaric oxygen * 1953 - Established the British Empire Cancer Campaign Research Unit in Radiobiolo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wood River Junction, Rhode Island
Wood River Junction is a small village in the town of Richmond, Rhode Island, Washington County, Rhode Island, in the United States. It is home to the Chariho school district's main campus and is otherwise largely Sod, turf farms. Geography Wood River Junction is commonly considered by locals to be one of the coldest locations in the state of Rhode Island, due to its low-lying and flat geography. It is the home of Meadowbrook Pond, also known as Wood River Pond, a popular fishing area. It is surrounded by two rivers: the Wood River (Pawcatuck River), Wood River and Pawcatuck River. History Overview The village was the site of Wood River Junction station, originally known as Richmond Switch. The Wood River Branch Railroad was chartered in 1872 and completed in 1874. The name was changed in April 1874. The six-mile branch line was built to provide service from the Hope Valley to the main line of the New York, Providence and Boston Railroad and was only six miles long. The New York ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiotherapy
Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. 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 with chemotherapy, and has been used before, during, and after chemotherapy in susceptible cancers. The subspecialty of oncology concerned with radiotherapy is called radiation oncology. A physician who practices in this subspecialty is a radiation oncologist. 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 l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erythema
Erythema (from the Greek , meaning red) is redness of the skin or mucous membranes, caused by hyperemia (increased blood flow) in superficial capillaries. It occurs with any skin injury, infection, or inflammation. Examples of erythema not associated with pathology include nervous blushes. Types * Erythema ab igne * Erythema chronicum migrans * Erythema induratum * Erythema infectiosum (or fifth disease) * Erythema marginatum * Erythema migrans * Erythema multiforme (EM) * Erythema nodosum * Erythema toxicum * Erythema elevatum diutinum * Erythema gyratum repens * Keratolytic winter erythema * Palmar erythema Causes It can be caused by infection, massage, electrical treatment, acne medication, allergies, exercise, solar radiation (sunburn), photosensitization, acute radiation syndrome, mercury toxicity, blister agents, niacin administration, or waxing and tweezing of the hairs—any of which can cause the capillaries to dilate, resulting in redness. Erythema is a common sid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamma Ray
A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays. With frequencies above 30 exahertz (), it imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation ''gamma rays'' based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power. Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts (keV) to approximately 8 megaelectronvolts (MeV), corresponding to the typical energy levels in nuclei with reasonably long lif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz ( to ) and energies in the range 145 eV to 124 keV. X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays. In many languages, X-radiation is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it on November 8, 1895. He named it ''X-radiation'' to signify an unknown type of radiation.Novelline, Robert (1997). ''Squire's Fundamentals of Radiology''. Harvard University Press. 5th edition. . Spellings of ''X-ray(s)'' in English include the variants ''x-ray(s)'', ''xray(s)'', and ''X ray(s)''. The most familiar use of X-rays is checking for fractures (broken bones), but X-rays are also used in other ways. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
