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Gel Dosimetry
Gel dosimeters, also called Fricke gel dosimeters, are manufactured from radiation sensitive chemicals that, upon irradiation with ionising radiation, undergo a fundamental change in their properties as a function of the absorbed radiation dose. Over many years individuals have endeavoured to measure absorbed radiation dose distributions using gels. As long ago as 1950, the radiation-induced colour change in dyes was used to investigate radiation doses in gels. Further, in 1957 depth doses of photons and electrons in agar gels were investigated using spectrophotometry. Gel dosimetry today however, is founded mainly on the work of Gore ''et al'' who in 1984 demonstrated that changes due to ionising radiation in Fricke dosimetry solutions, developed in the 1920s, could be measured using nuclear magnetic resonance (NMR). Gel dosimeters generally consist of two types; Fricke and polymer gel dosimeters and are usually evaluated or 'read-out' using magnetic resonance imaging (MRI), optica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Magnetic Resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. High-resolution nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crysta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves to form images of the organs in the body. MRI does not involve X-rays or the use of ionizing radiation, which distinguishes it from computed tomography (CT) and positron emission tomography (PET) scans. MRI is a medical application of nuclear magnetic resonance (NMR) which can also be used for imaging in other NMR applications, such as NMR spectroscopy. MRI is widely used in hospitals and clinics for medical diagnosis, staging and follow-up of disease. Compared to CT, MRI provides better contrast in images of soft tissues, e.g. in the brain or abdomen. However, it may be perceived as less comfortable by patients, due to the usually longer and louder measurements with the subject in a long, confining tube, although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Tomography
A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists. CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry to measure X-ray attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is contraindicated. Since its development in the 1970s, CT scanning has proven to be a versatile imaging technique. While CT is most prominently used in medical diagnosis, it can also be used to form images of non-living objects. The 1979 Nobel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultrasound
Ultrasound is sound with frequency, frequencies greater than 20 Hertz, kilohertz. This frequency is the approximate upper audible hearing range, limit of human hearing in healthy young adults. The physical principles of acoustic waves apply to any frequency range, including ultrasound. Ultrasonic devices operate with frequencies from 20 kHz up to several gigahertz. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is often used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws. Industrially, ultrasound is used for cleaning, mixing, and accelerating chemical processes. Animals such as bats and porpoises use ultrasound for locating prey and obstacles. History Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of String instrument ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xylenol Orange
Xylenol orange is an organic reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ..., most commonly used as a tetrasodium salt as an indicator for metal titrations. When used for metal titrations, it will appear red in the titrand and become yellow once it reaches its endpoint. Historically, commercial preparations of it have been notoriously impure, sometimes consisting of as little as 20% xylenol orange, and containing large amounts of semi-xylenol orange and iminodiacetic acid. Purities as high as 90% are now available. It is fluorescent, and has excitation maximums of 440 & 570 nm and an emission maximum of 610 nm. References Analytical reagents Triarylmethane dyes Benzoxathioles Acetic acids {{OrganicAcid-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acrylamide
Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary amide (CONH2). It is produced industrially mainly as a precursor to polyacrylamides, which find many uses as water-soluble thickeners and flocculation agents. Acrylamide forms in burnt areas of food, particularly starchy foods like potatoes, when cooked with high heat, above . Despite health scares following this discovery in 2002, and its classification as a probable carcinogen, acrylamide from diet is thought unlikely to cause cancer in humans; Cancer Research UK categorized the idea that eating burnt food causes cancer as a "myth". Production Acrylamide can be prepared by the hydration of acrylonitrile, which is catalyzed enzymatically: :CH2=CHCN + H2O → CH2=CHC(O)NH2 This reaction also is catalyzed by sulfuric acid as wel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrous Oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an Nitrogen oxide, oxide of nitrogen with the Chemical formula, formula . At room temperature, it is a colourless Flammability#Definitions, non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful Oxidising agent, oxidiser similar to molecular oxygen. Nitrous oxide has significant Nitrous oxide (medication), medical uses, especially in surgery and dentistry, for its Anesthesia, anaesthetic and Analgesic, pain-reducing effects, and it is on the WHO Model List of Essential Medicines, World Health Organization's List of Essential Medicines. Its colloquial name, "laughing gas", coined by Humphry Davy, describes the Euphoria, euphoric effects upon inhaling it, which cause it to be used as a recreational drug inducing a brief "Dissociative, high". When abused chronically ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clive Baldock
Clive Baldock is a British-born Australian professor. He graduated with a BSc (hons) in Physics from the University of Sussex, an MSc in Radiation Physics from St Bartholomew's Hospital Medical College, University of London, a PhD in Medical Physics from King's College London and a Masters of Tertiary Education Management from the University of Melbourne. He also graduated from the University of Oxford Saïd Business School Executive Leadership Programme. He is Honorary Professor at the University of Wollongong and Adjunct Professor at Western Sydney University. His previous roles included Head of the School of Physics at the University of Sydney, Executive Dean of Science at Macquarie University, Executive Director for Physical Sciences, Engineering, Mathematics and Information Sciences at the Australian Research Council (ARC), Dean of Graduate Research and Pro Vice-Chancellor for Researcher Development at the University of Tasmania, Dean of Graduate Research at the University ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Association Of Physicists In Medicine
The American Association of Physicists in Medicine (AAPM) is a scientific, educational, and professional organization of Medical Physicists. In 2011, it absorbed the American College of Medical Physics. Their headquarters are located at 1631 Prince Street, Alexandria, Virginia. Publications include two scientific journals: ''Medical Physics'' and the '' Journal of Applied Clinical Medical Physics'' (JACMP), as well as technical reports, and symposium proceedings. The purposes of the American Association of Physicists in Medicine are to promote the application of physics to medicine and biology and to encourage interest and training in medical physics and related fields. AAPM has established ''Medical Physics'' as its primary scientific and informational journal. AAPM is a Member of the American Institute of Physics The American Institute of Physics (AIP) promotes science and the profession of physics, publishes physics journals, and produces publications for scientific an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cancer
Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible Signs and symptoms of cancer, signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in defecation, bowel movements. While these symptoms may indicate cancer, they can also have other causes. List of cancer types, Over 100 types of cancers affect humans. Tobacco use is the cause of about 22% of cancer deaths. Another 10% are due to obesity, poor Diet (nutrition), diet, sedentary lifestyle, lack of physical activity or Alcohol abuse, excessive alcohol consumption. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. infectious causes of cancer, Infection with specific viruses, bacteria and parasites is an environmental factor cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hugo Fricke
Hugo Fricke (August 15, 1892, in Aarhus, Denmark – April 5, 1972, in Huntington, New York, US) was a Danish-American physicist who studied the chemical (radiolysis) and biological (radiation biology) effects of X-ray and electron beams and who also invented the Fricke dosimeter named after him. He also made important contributions to the theory of impedance measurements. Early life, education and career Hugo Fricke was born on August 15, 1892, in Aarhus, Denmark, to Hedevig (''née'' Kämpfner) and Gunnar Fricke, the oldest of four siblings. Fricke relocated to Copenhagen in 1910, where he studied at the University of Copenhagen from 1910 to 1916, where he also worked as an assistant to Niels Bohr. In 1918, he moved to Lund University where he worked with Manne Siegbahn on X-ray spectroscopy. In 1919 he emigrated to the US, working at Columbia University and at Harvard University with Theodore Lyman until 1921. He moved to Cleveland Clinic by invitation of George Crile to h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
