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Dual-energy X-ray Absorptiometry
Dual-energy X-ray absorptiometry (DXA, or DEXA) is a means of measuring bone mineral density (BMD) using spectral imaging. Two X-ray beams, with different energy levels, are aimed at the patient's bones. When soft tissue absorption is subtracted out, the bone mineral density (BMD) can be determined from the absorption of each beam by bone. Dual-energy X-ray absorptiometry is the most widely used and most thoroughly studied bone density measurement technology. The DXA scan is typically used to diagnose and follow osteoporosis, as contrasted to the nuclear bone scan, which is sensitive to certain metabolic diseases of bones in which bones are attempting to heal from infections, fractures, or tumors. It is also sometimes used to assess body composition. Physics Soft tissue and bone have different attenuation coefficients to X-rays. A single X-ray beam passing through the body will be attenuated by both soft tissue and bone, and it is not possible to determine, from a single beam, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bone Mineral Density
Bone density, or bone mineral density, is the amount of bone mineral in bone tissue. The concept is of mass of mineral per volume of bone (relating to density in the physics sense), although clinically it is measured by proxy according to optical density per square centimetre of bone surface upon imaging. Bone density measurement is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk. It is measured by a procedure called densitometry, often performed in the radiology or nuclear medicine departments of hospitals or clinics. The measurement is painless and non-invasive and involves low radiation exposure. Measurements are most commonly made over the lumbar spine and over the upper part of the hip. The forearm may be scanned if the hip and lumbar spine are not accessible. There is a statistical association between poor bone density and higher probability of fracture. Fractures of the legs and pelvis due to falls are a significant public health pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dual X-ray Absorptiometry And Laser
Dual X-ray absorptiometry and laser technique (DXL) in the area of bone density studies for osteoporosis assessment is an improvement to the DXA Technique, adding an exact laser measurement of the thickness of the region scanned. The addition of object thickness adds a third input to the two x-ray energies used by DXA, better solving the equation for bone and excluding more efficiently these soft tissues components. Background The body consists of three main components: bone mineral, lean soft tissue (skin, blood, water and skeletal muscle) and adipose tissue (fat and yellow bone marrow). These different components have different x-ray attenuating properties. The standard in bone mineral density scanning developed in the 1980s is called Dual X-ray Absorptiometry, known as DXA. The DXA technique uses two different x-ray energy levels to estimate bone density. DXA scans assume a constant relationship between the amounts of lean soft tissue and adipose tissue. This assumption lead ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ratio
In mathematics, a ratio shows how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lemons is eight to six (that is, 8:6, which is equivalent to the ratio 4:3). Similarly, the ratio of lemons to oranges is 6:8 (or 3:4) and the ratio of oranges to the total amount of fruit is 8:14 (or 4:7). The numbers in a ratio may be quantities of any kind, such as counts of people or objects, or such as measurements of lengths, weights, time, etc. In most contexts, both numbers are restricted to be Positive integer, positive. A ratio may be specified either by giving both constituting numbers, written as "''a'' to ''b''" or "''a'':''b''", or by giving just the value of their quotient Equal quotients correspond to equal ratios. Consequently, a ratio may be considered as an ordered pair of numbers, a Fraction (mathematics), fraction with the first number in the numerator and the second in the denom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volumetric
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The definition of length (cubed) is interrelated with volume. The volume of a container is generally understood to be the capacity of the container; i.e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. In ancient times, volume is measured using similar-shaped natural containers and later on, standardized containers. Some simple three-dimensional shapes can have its volume easily calculated using arithmetic formulas. Volumes of more complicated shapes can be calculated with integral calculus if a formula exists for the shape's boundary. Zero-, one- and two-dimensional objects have no volume; in fourth and higher dimensions, an analogous concept to the normal volu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volume
Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The definition of length (cubed) is interrelated with volume. The volume of a container is generally understood to be the capacity of the container; i.e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. In ancient times, volume is measured using similar-shaped natural containers and later on, standardized containers. Some simple three-dimensional shapes can have its volume easily calculated using arithmetic formulas. Volumes of more complicated shapes can be calculated with integral calculus if a formula exists for the shape's boundary. Zero-, one- and two-dimensional objects have no volume; in fourth and higher dimensions, an analogous concept to the normal vo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mass
Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementary particles, theoretically with the same amount of matter, have nonetheless different masses. Mass in modern physics has multiple definitions which are conceptually distinct, but physically equivalent. Mass can be experimentally defined as a measure of the body's inertia, meaning the resistance to acceleration (change of velocity) when a net force is applied. The object's mass also determines the strength of its gravitational attraction to other bodies. The SI base unit of mass is the kilogram (kg). In physics, mass is not the same as weight, even though mass is often determined by measuring the object's weight using a spring scale, rather than balance scale comparing it directly with known masses. An object on the Moon would weigh le ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Z-score
In statistics, the standard score is the number of standard deviations by which the value of a raw score (i.e., an observed value or data point) is above or below the mean value of what is being observed or measured. Raw scores above the mean have positive standard scores, while those below the mean have negative standard scores. It is calculated by subtracting the population mean from an individual raw score and then dividing the difference by the population standard deviation. This process of converting a raw score into a standard score is called standardizing or normalizing (however, "normalizing" can refer to many types of ratios; see normalization for more). Standard scores are most commonly called ''z''-scores; the two terms may be used interchangeably, as they are in this article. Other equivalent terms in use include z-values, normal scores, standardized variables and pull in high energy physics. Computing a z-score requires knowledge of the mean and standard devi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteopenia
Osteopenia, known as "low bone mass" or "low bone density", is a condition in which bone mineral density is low. Because their bones are weaker, people with osteopenia may have a higher risk of fractures, and some people may go on to develop osteoporosis. In 2010, 43 million older adults in the US had osteopenia. Unlike osteoporosis, osteopenia does not usually cause symptoms, and losing bone density in itself does not cause pain. There is no single cause for osteopenia, although there are several risk factors, including modifiable (behavioral, including dietary and use of certain drugs) and non-modifiable (for instance, loss of bone mass with age). For people with risk factors, screening via a DXA scanner may help to detect the development and progression of low bone density. Prevention of low bone density may begin early in life and includes a healthy diet and weight-bearing exercise, as well as avoidance of tobacco and alcohol. The treatment of osteopenia is controversial: non-p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morbus Fabry DXA 01
''Teenage Mutant Ninja Turtles'' is an American media franchise created by the comic book artists Kevin Eastman and Peter Laird. It follows Leonardo, Michelangelo, Donatello and Raphael, four anthropomorphic turtle brothers (named after Italian Renaissance artists) trained in ninjutsu who fight evil in New York City. Supporting characters include the turtles' rat sensei Splinter, their human friends April O'Neil and Casey Jones, and enemies such as Baxter Stockman, Krang, and their archenemy, the Shredder. The franchise began as a comic book, ''Teenage Mutant Ninja Turtles'', which Eastman and Laird conceived as a parody of elements popular in superhero comics at the time. The first issue was published in 1984 by Eastman and Laird's company Mirage Studios and was a surprise success. In 1987, Eastman and Laird licensed the characters to Playmates Toys, which developed a line of ''Turtles'' action figures. About US$1.1 billion of ''Turtles'' toys were sold between 1988 and 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glucocorticoids
Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebrate animal cell. The name "glucocorticoid" is a portmanteau (glucose + cortex + steroid) and is composed from its role in regulation of glucose metabolism, synthesis in the adrenal cortex, and its steroidal structure (see structure below). Glucocorticoids are part of the feedback mechanism in the immune system, which reduces certain aspects of immune function, such as inflammation. They are therefore used in medicine to treat diseases caused by an overactive immune system, such as allergies, asthma, autoimmune diseases, and sepsis. Glucocorticoids have many diverse (pleiotropic) effects, including potentially harmful side effects. They also interfere with some of the abnormal mechanisms in cancer cells, so they are used in high doses to tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FRAX
FRAX (Fracture Risk Assessment Tool) is a diagnostic tool used to evaluate the 10-year probability of bone fracture risk. It was developed by the University of Sheffield. FRAX integrates clinical risk factors and bone mineral density at the femoral neck to calculate the 10-year probability of hip fracture and the 10-year probability of a major osteoporotic fracture (clinical spine, forearm, hip or shoulder fracture). The models used to develop the FRAX diagnostic tool were derived from studying patient populations in North America, Europe, Latin America, Asia and Australia. Components The parameters included in a FRAX assessment are: *Country *Age *Sex *Weight *Height *Previous fracture *Hip fracture in the subject's mother or father *Smoking *Glucocorticoid treatment *Rheumatoid arthritis *Disease strongly associated with osteoporosis *Alcohol intake of 3 or more standard drinks per day *Bone mineral density (BMD) of the femoral neck *Trabecular bone score (optional) Availabilit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ABIM Foundation
Choosing Wisely is a United States-based health educational campaign, led by the ABIM Foundation (American Board of Internal Medicine), about unnecessary health care. The campaign identifies over 500 tests and procedures and encourages doctors and patients to discuss, research, and possibly get second opinions, before proceeding with them. To conduct the campaign, the ABIM Foundation asks medical specialty societies to make five to ten recommendations for preventing overuse of a treatment in their field. The foundation then publicizes this information, and the medical specialty societies disseminate it to their members. The campaign has garnered both praise and criticism, and some of its ideas have spread to other countries. It does not include evaluation of its effects on costs, on discussions or on medical outcomes. Some doctors have said they lack time for the recommended discussions. History In 2002 the ABIM Foundation published ''Medical professionalism in the new millenni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
