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Multileaf Collimator
A multileaf collimator (MLC) is a collimator or beam-limiting device that is made of individual "leaves" of a high atomic numbered material, usually tungsten, that can move independently in and out of the path of a radiotherapy beam in order to shape it and vary its intensity. MLCs are used in external beam radiotherapy to provide conformal shaping of beams. Specifically, conformal radiotherapy and Intensity Modulated Radiation Therapy (IMRT) can be delivered using MLCs. The MLC has improved rapidly since its inception and the first use of leaves to shape structures in 1965 to modern day operation and use. MLCs are now widely used and have become an integral part of any radiotherapy department. MLCs were primarily used for conformal radiotherapy, and have allowed the cost-effective implementation of conformal treatment with significant time saving, and also have been adapted for use for IMRT treatments. For conformal radiotherapy the MLC allows conformal shaping of the beam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Collimator
A collimator is a device which narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spatial cross section of the beam to become smaller (beam limiting device). History The English physicist Henry Kater was the inventor of the floating collimator, which rendered a great service to practical astronomy. He reported about his invention in January 1825. In his report, Kater mentioned previous work in this area by Carl Friedrich Gauss and Friedrich Bessel. Optical collimators In optics, a collimator may consist of a curved mirror or lens with some type of light source and/or an image at its focus. This can be used to replicate a target focused at infinity with little or no parallax. In lighting, collimators are typically designed using the principles of nonimaging optics. Optical collimators can be used to calibrate other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every atom of that element. The atomic number can be used to uniquely identify ordinary chemical elements. In an ordinary uncharged atom, the atomic number is also equal to the number of electrons. For an ordinary atom which contains protons, neutrons and electrons, the sum of the atomic number ''Z'' and the neutron number ''N'' gives the atom's atomic mass number ''A''. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) and the mass defect of the nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in daltons (making a quantity called the " relative isotopic mass"), is within 1% ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tungsten
Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first isolated as a metal in 1783. Its important ores include scheelite and wolframite, the latter lending the element its alternative name. The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all known elements, melting at . It also has the highest boiling point, at . Its density is 19.254 g/cm3, comparable with that of uranium and gold, and much higher (about 1.7 times) than that of lead. Polycrystalline tungsten is an intrinsically brittle and hard material (under standard conditions, when uncombined), making it difficult to work into metal. However, pure single-crystalline tungsten is more ductile and can be cut with a hard-steel hacksaw. Tungsten occurs in many alloys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
External Beam Radiotherapy
External beam radiation therapy (EBRT) is a form of radiotherapy that utilizes a high-energy collimated beam of ionizing radiation, from a source outside the body, to target and kill cancer cells. The radiotherapy beam is composed of particles, which are focussed in a particular direction of travel using collimators. Each radiotherapy beam consists of one type of particle intended for use in treatment, though most beams contain some contamination by other particle types. Radiotherapy beams are classified by the particle they are intended to deliver, such as photons (as x-rays or gamma rays), electrons, and heavy ions; x-rays and electron beams are by far the most widely used sources for external beam radiotherapy. Orthovoltage ("superficial") X-rays are used for treating skin cancer and superficial structures. Megavoltage X-rays are used to treat deep-seated tumors (e.g. bladder, bowel, prostate, lung, or brain), whereas megavoltage electron beams are typically used to tre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation Therapy
Radiation therapy or radiotherapy (RT, RTx, or XRT) is a therapy, treatment using ionizing radiation, generally provided as part of treatment of cancer, cancer therapy to either kill or control the growth of malignancy, malignant cell (biology), cells. It is normally delivered by a linear particle accelerator. Radiation therapy may be cure, curative in a number of types of cancer if they are localized to one area of the body, and have not metastasis, spread to other parts. 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 canc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intensity Modulated Radiation Therapy
Radiation therapy or radiotherapy (RT, RTx, or XRT) is a treatment using ionizing radiation, generally provided as part of cancer therapy to either kill or control the growth of malignant cells. It is normally delivered by a linear particle accelerator. Radiation therapy may be curative in a number of types of cancer if they are localized to one area of the body, and have not spread to other parts. 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 radia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluence
In radiometry, radiant exposure or fluence is the radiant energy ''received'' by a ''surface'' per unit area, or equivalently the irradiance of a ''surface,'' integrated over time of irradiation, and spectral exposure is the radiant exposure per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of radiant exposure is the joule per square metre (), while that of spectral exposure in frequency is the joule per square metre per hertz () and that of spectral exposure in wavelength is the joule per square metre per metre ()—commonly the joule per square metre per nanometre (). Mathematical definitions Radiant exposure Radiant exposure of a ''surface'', denoted ''H''e ("e" for "energetic", to avoid confusion with photometric quantities), is defined as H_\mathrm = \frac = \int_0^T E_\mathrm(t)\, \mathrmt, where *∂ is the partial derivative symbol; *''Q''e is the radiant energy; *''A'' is the area; *''T'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treatment Planning
In radiation therapy, radiotherapy, radiation treatment planning (RTP) is the process in which a team consisting of radiation oncologists, radiation therapist, Medical physics, medical physicists and Dosimetrist, medical dosimetrists plan the appropriate external beam radiotherapy or internal brachytherapy treatment technique for a patient with cancer. History In the early days of radiotherapy planning was performed on 2D Radiography, x-ray images, often by hand and with manual calculations. Computerised treatment planning systems began to be used in the 1970s to improve the accuracy and speed of dose calculations. By the 1990s CT scans, more powerful computers, improved dose calculation algorithms and Multileaf collimators (MLCs) lead to 3D conformal planning (3DCRT), categorised as a Level 2 technique by the European Dynarad consortium. 3DCRT uses MLCs to shape the radiotherapy beam to closely match the shape of a target tumour, reducing the dose to healthy surrounding tissue. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medical Equipment
A medical device is any device intended to be used for medical purposes. Significant potential for hazards are inherent when using a device for medical purposes and thus medical devices must be proved safe and effective with reasonable assurance before regulating governments allow marketing of the device in their country. As a general rule, as the associated risk of the device increases the amount of testing required to establish safety and efficacy also increases. Further, as associated risk increases the potential benefit to the patient must also increase. Discovery of what would be considered a medical device by modern standards dates as far back as in Baluchistan where Neolithic dentists used flint-tipped drills and bowstrings. Study of Archaeology, archeology and Roman medical literature also indicate that many types of medical devices were in widespread use during the time of ancient Rome. In the United States it was not until the Federal Food, Drug, and Cosmetic Act ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medical Physics
Medical physics deals with the application of the concepts and methods of physics to the prevention, diagnosis and treatment of human diseases with a specific goal of improving human health and well-being. Since 2008, medical physics has been included as a health profession according to International Standard Classification of Occupations, International Standard Classification of Occupation of the International Labour Organization. Although medical physics may sometimes also be referred to as ''biomedical physics'', ''medical biophysics'', ''applied physics in medicine'', ''physics applications in medical science'', ''radiological physics'' or ''hospital radio-physics'', a "medical physicist" is specifically a health professional with specialist education and training in the concepts and techniques of applying physics in medicine and competent to practice independently in one or more of the subfields of medical physics. Traditionally, medical physicists are found in the following ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
