document_title: X-ray

question_text: when were x rays first used in medicine

question_tokens: when were x rays first used in medicine

text: X-ray

text: History[edit]

text: Discovery[edit]

text: German physicist Wilhelm Röntgen is usually credited as the discoverer of X-rays in 1895, because he was the first to systematically study them, though he is not the first to have observed their effects. He is also the one who gave them the name "X-rays" (signifying an unknown quantity[4]) though many others referred to these as "Röntgen rays" (and the associated X-ray radiograms as, "Röntgenograms") for several decades after their discovery and even to this day in some languages, including Röntgen's native German.

text: X-rays were found emanating from Crookes tubes, experimental discharge tubes invented around 1875, by scientists investigating the cathode rays, which are energetic electron beams that were first created in the tubes. Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube. Many of the early Crookes tubes undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below. Wilhelm Röntgen was the first to systematically study them, in 1895.[7]

text: The discovery of X-rays stimulated a veritable sensation. Röntgen's biographer Otto Glasser estimated that, in 1896 alone, as many as 49 essays and 1044 articles about the new rays were published.[8] This was probably a conservative estimate, if one considers that nearly every paper around the world extensively reported about the new discovery, with a magazine such as Science dedicating as many as 23 articles to it in that year alone.[9] Sensationalist reactions to the new discovery included publications linking the new kind of rays to occult and paranormal theories, such as telepathy.[10][11]

text: Early research[edit]

text: The earliest experimenter thought to have (unknowingly) produced X-rays was actuary William Morgan. In 1785 he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a partially evacuated glass tube, producing a glow created by X-rays.[12] This work was further explored by Humphry Davy and his assistant Michael Faraday.

text: In 1877 Ukrainian-born Ivan Pulyui, a lecturer in experimental physics at the University of Vienna, constructed various designs of vacuum discharge tube to investigate their properties.[13] He continued his investigations when appointed professor at the Prague Polytechnic and in 1886 he found that sealed photographic plates became dark when exposed to the emanations from the tubes. Early in 1896, just a few weeks after Röntgen published his first X-ray photograph, Pulyui published high-quality X-ray images in journals in Paris and London.[13] Although Pulyui had studied with Röntgen at the University of Strasbourg in the years 1873–75, his biographer Gaida (1997) asserts that his subsequent research was conducted independently.[13]

text: X-rays were generated and detected by Fernando Sanford (1854–1948), the foundation Professor of Physics at Stanford University, in 1891. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as previously studied by Heinrich Hertz and Philipp Lenard. His letter of January 6, 1893 (describing his discovery as "electric photography") to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner.[14]

text: Starting in 1888, Philipp Lenard, a student of Heinrich Hertz, conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air. He built a Crookes tube (later called a "Lenard tube") with a "window" in the end made of thin aluminum, facing the cathode so the cathode rays would strike it. He found that something came through, that would expose photographic plates and cause fluorescence. He measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were actually X-rays.[15]

text: Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his discovery and announcement. It was formed on the basis of the electromagnetic theory of light.[16] However, he did not work with actual X-rays.

text: In 1894 Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this radiant energy of "invisible" kinds.[17][18] After Röntgen identified the X-ray Tesla began making X-ray images of his own using high voltages and tubes of his own design,[19] as well as Crookes tubes.

text: In November 1896, the inventor Dr. Robert D'Unger proposed a X-Ray telephot, supposed able to make transmission of pictures by telegraph wire.[20]

text: Wilhelm Röntgen[edit]

text: On November 8, 1895, German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard and Crookes tubes and began studying them. He wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to Würzburg's Physical-Medical Society journal.[21] This was the first paper written on X-rays. Röntgen referred to the radiation as "X", to indicate that it was an unknown type of radiation. The name stuck, although (over Röntgen's great objections) many of his colleagues suggested calling them Röntgen rays. They are still referred to as such in many languages, including German, Hungarian, Danish, Polish, Swedish, Finnish, Estonian, Russian, Japanese, Dutch, Georgian and Norwegian. Röntgen received the first Nobel Prize in Physics for his discovery.[22]

text: There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a likely reconstruction by his biographers:[23][24] Röntgen was investigating cathode rays from a Crookes tube which he had wrapped in black cardboard so that the visible light from the tube would not interfere, using a fluorescent screen painted with barium platinocyanide. He noticed a faint green glow from the screen, about 1 meter away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow. He found they could also pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper.[citation needed]

text: Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays. The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death."[25]

text: Advances in radiology[edit]

text: There was immediate interest from researchers for the X-ray. A. A. Campbell-Swinton and Nikola Tesla were amongst the firsts to test the new discovery. In 1896, Thomas Edison investigated materials' ability to fluoresce when exposed to X-rays, and found that calcium tungstate was the most effective substance. Around March 1896, the fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903, even before the death of Clarence Madison Dally, one of his glassblowers. Dally had a habit of testing X-ray tubes on his hands, and acquired a cancer in them so tenacious that both arms were amputated in a futile attempt to save his life.

text: The first use of X-rays under clinical conditions was by John Hall-Edwards in Birmingham, England on 11 January 1896, when he radiographed a needle stuck in the hand of an associate.[26] On February 14, 1896 Hall-Edwards was also the first to use X-rays in a surgical operation.[27] In early 1896, several weeks after Röntgen's discovery, Ivan Romanovich Tarkhanov irradiated frogs and insects with X-rays, concluding that the rays "not only photograph, but also affect the living function".[28]

text: The first medical X-ray made in the United States was obtained using a discharge tube of Pulyui's design. In January 1896, on reading of Röntgen's discovery, Frank Austin of Dartmouth College tested all of the discharge tubes in the physics laboratory and found that only the Pulyui tube produced X-rays. This was a result of Pulyui's inclusion of an oblique "target" of mica, used for holding samples of fluorescent material, within the tube. On 3 February 1896 Gilman Frost, professor of medicine at the college, and his brother Edwin Frost, professor of physics, exposed the wrist of Eddie McCarthy, whom Gilman had treated some weeks earlier for a fracture, to the X-rays and collected the resulting image of the broken bone on gelatin photographic plates obtained from Howard Langill, a local photographer also interested in Röntgen's work.[29]

text: In 1901, U.S. President William McKinley was shot twice in an assassination attempt. While one bullet only grazed his sternum, another had lodged somewhere deep inside his abdomen and could not be found. A worried McKinley aide sent word to inventor Thomas Edison to rush an X-ray machine to Buffalo to find the stray bullet. It arrived but wasn't used. While the shooting itself had not been lethal, gangrene had developed along the path of the bullet, and McKinley died of septic shock due to bacterial infection six days later.[30]

text: Hazards discovered[edit]

text: With the widespread experimentation with x‑rays after their discovery in 1895 by scientists, physicians, and inventors came many stories of burns, hair loss, and worse in technical journals of the time. In February 1896, Professor John Daniel and Dr. William Lofland Dudley of Vanderbilt University reported hair loss after Dr. Dudley was X-rayed. A child who had been shot in the head was brought to the Vanderbilt laboratory in 1896. Before trying to find the bullet an experiment was attempted, for which Dudley "with his characteristic devotion to science"[31][32][33] volunteered. Daniel reported that 21 days after taking a picture of Dudley's skull (with an exposure time of one hour), he noticed a bald spot 2 inches (5.1 cm) in diameter on the part of his head nearest the X-ray tube: "A plate holder with the plates towards the side of the skull was fastened and a coin placed between the skull and the head. The tube was fastened at the other side at a distance of one-half inch from the hair."[34]

text:
In August 1896 Dr. HD. Hawks, a graduate of Columbia College, suffered severe hand and chest burns from an x-ray demonstration. It was reported in Electrical Review and led to many other reports of problems associated with x-rays being sent in to the publication.[35] Many experimenters including Elihu Thomson at Edison's lab, William J. Morton, and Nikola Tesla also reported burns. Elihu Thomson deliberately exposed a finger to an x-ray tube over a period of time and suffered pain, swelling, and blistering.[36] Other effects were sometimes blamed for the damage including ultraviolet rays and (according to Tesla) ozone.[37] Many physicians claimed there were no effects from X-ray exposure at all.[36]
On August 3, 1905 at San Francisco, California, Elizabeth Fleischman, American woman X-ray pioneer, died from complications as a result of her work with X-rays.[38][39][40]

text: 20th century and beyond[edit]

text: The many applications of X-rays immediately generated enormous interest. Workshops began making specialized versions of Crookes tubes for generating X-rays and these first-generation cold cathode or Crookes X-ray tubes were used until about 1920.

text: Crookes tubes were unreliable. They had to contain a small quantity of gas (invariably air) as a current will not flow in such a tube if they are fully evacuated. However, as time passed, the X-rays caused the glass to absorb the gas, causing the tube to generate "harder" X-rays until it soon stopped operating. Larger and more frequently used tubes were provided with devices for restoring the air, known as "softeners". These often took the form of a small side tube which contained a small piece of mica, a mineral that traps relatively large quantities of air within its structure. A small electrical heater heated the mica, causing it to release a small amount of air, thus restoring the tube's efficiency. However, the mica had a limited life, and the restoration process was difficult to control.

text: In 1904, John Ambrose Fleming invented the thermionic diode, the first kind of vacuum tube. This used a hot cathode that caused an electric current to flow in a vacuum. This idea was quickly applied to X-ray tubes, and hence heated-cathode X-ray tubes, called "Coolidge tubes", completely replaced the troublesome cold cathode tubes by about 1920.

text: In about 1906, the physicist Charles Barkla discovered that X-rays could be scattered by gases, and that each element had a characteristic X-ray spectrum. He won the 1917 Nobel Prize in Physics for this discovery.

text: In 1912, Max von Laue, Paul Knipping, and Walter Friedrich first observed the diffraction of X-rays by crystals. This discovery, along with the early work of Paul Peter Ewald, William Henry Bragg, and William Lawrence Bragg, gave birth to the field of X-ray crystallography.

text: The Coolidge X-ray tube was invented during the following year by William D. Coolidge. It made possible the continuous emissions of X-rays. X-ray tubes similar to this are still in use in 2012.

text: The use of X-rays for medical purposes (which developed into the field of radiation therapy) was pioneered by Major John Hall-Edwards in Birmingham, England. Then in 1908, he had to have his left arm amputated because of the spread of X-ray dermatitis on his arm.[41]

text: In 1914 Marie Curie developed radiological cars to support soldiers injured in World War I. The cars would allow for rapid X-ray imaging of wounded soldiers so battlefield surgeons could quickly and more accurately operate.[42]

text: From the 1920s through to the 1950s, x-ray machines were developed to assist in the fitting of shoes and were sold to commercial shoe stores.[43][44][45] Concerns regarding the impact of frequent or poorly controlled use were expressed in the 1950s,[46][47] leading to the practise's eventual end that decade.[48]

text: The X-ray microscope was developed during the 1950s.

text: The Chandra X-ray Observatory, launched on July 23, 1999, has been allowing the exploration of the very violent processes in the universe which produce X-rays. Unlike visible light, which gives a relatively stable view of the universe, the X-ray universe is unstable. It features stars being torn apart by black holes, galactic collisions, and novae, and neutron stars that build up layers of plasma that then explode into space.

text: An X-ray laser device was proposed as part of the Reagan Administration's Strategic Defense Initiative in the 1980s, but the only test of the device (a sort of laser "blaster" or death ray, powered by a thermonuclear explosion) gave inconclusive results. For technical and political reasons, the overall project (including the X-ray laser) was de-funded (though was later revived by the second Bush Administration as National Missile Defense using different technologies).

text: Phase-contrast X-ray imaging refers to a variety of techniques that use phase information of a coherent x-ray beam to image soft tissues. It has become an important method for visualizing cellular and histological structures in a wide range of biological and medical studies. There are several technologies being used for x-ray phase-contrast imaging, all utilizing different principles to convert phase variations in the x-rays emerging from an object into intensity variations.[49][50] These include propagation-based phase contrast,[51] talbot interferometry,[50] refraction-enhanced imaging,[52] and x-ray interferometry.[53] These methods provide higher contrast compared to normal absorption-contrast x-ray imaging, making it possible to see smaller details. A disadvantage is that these methods require more sophisticated equipment, such as synchrotron or microfocus x-ray sources, X-ray optics, and high resolution x-ray detectors.

text: Energy ranges[edit]

text: Soft and hard X-rays[edit]

text: X-rays with high photon energies (above 5–10 keV, below 0.2–0.1 nm wavelength) are called hard X-rays, while those with lower energy (and longer wavelength) are called soft X-rays.[54] Due to their penetrating ability, hard X-rays are widely used to image the inside of objects, e.g., in medical radiography and airport security. The term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. Since the wavelengths of hard X-rays are similar to the size of atoms, they are also useful for determining crystal structures by X-ray crystallography. By contrast, soft X-rays are easily absorbed in air; the attenuation length of 600 eV (~2 nm) X-rays in water is less than 1 micrometer.[55]

text: Gamma rays[edit]

text:
There is no consensus for a definition distinguishing between X-rays and gamma rays. One common practice is to distinguish between the two types of radiation based on their source: X-rays are emitted by electrons, while gamma rays are emitted by the atomic nucleus.[56][57][58][59] This definition has several problems: other processes also can generate these high-energy photons, or sometimes the method of generation is not known. One common alternative is to distinguish X- and gamma radiation on the basis of wavelength (or, equivalently, frequency or photon energy), with radiation shorter than some arbitrary wavelength, such as 10−11 m (0.1 Å), defined as gamma radiation.[60]
This criterion assigns a photon to an unambiguous category, but is only possible if wavelength is known. (Some measurement techniques do not distinguish between detected wavelengths.) However, these two definitions often coincide since the electromagnetic radiation emitted by X-ray tubes generally has a longer wavelength and lower photon energy than the radiation emitted by radioactive nuclei.[56]
Occasionally, one term or the other is used in specific contexts due to historical precedent, based on measurement (detection) technique, or based on their intended use rather than their wavelength or source.
Thus, gamma-rays generated for medical and industrial uses, for example radiotherapy, in the ranges of 6–20 MeV, can in this context also be referred to as X-rays.[citation needed]

text: Properties[edit]

text: X-ray photons carry enough energy to ionize atoms and disrupt molecular bonds. This makes it a type of ionizing radiation, and therefore harmful to living tissue. A very high radiation dose over a short period of time causes radiation sickness, while lower doses can give an increased risk of radiation-induced cancer. In medical imaging this increased cancer risk is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be utilized in cancer treatment to kill malignant cells using radiation therapy. It is also used for material characterization using X-ray spectroscopy.

text: Hard X-rays can traverse relatively thick objects without being much absorbed or scattered. For this reason, X-rays are widely used to image the inside of visually opaque objects. The most often seen applications are in medical radiography and airport security scanners, but similar techniques are also important in industry (e.g. industrial radiography and industrial CT scanning) and research (e.g. small animal CT). The penetration depth varies with several orders of magnitude over the X-ray spectrum. This allows the photon energy to be adjusted for the application so as to give sufficient transmission through the object and at the same time provide good contrast in the image.

text: X-rays have much shorter wavelengths than visible light, which makes it possible to probe structures much smaller than can be seen using a normal microscope. This property is used in X-ray microscopy to acquire high resolution images, and also in X-ray crystallography to determine the positions of atoms in crystals.

text: Interaction with matter[edit]

text: X-rays interact with matter in three main ways, through photoabsorption, Compton scattering, and Rayleigh scattering. The strength of these interactions depends on the energy of the X-rays and the elemental composition of the material, but not much on chemical properties, since the X-ray photon energy is much higher than chemical binding energies. Photoabsorption or photoelectric absorption is the dominant interaction mechanism in the soft X-ray regime and for the lower hard X-ray energies. At higher energies, Compton scattering dominates.

text: Photoelectric absorption[edit]

text: The probability of a photoelectric absorption per unit mass is approximately proportional to Z3/E3, where Z is the atomic number and E is the energy of the incident photon.[61] This rule is not valid close to inner shell electron binding energies where there are abrupt changes in interaction probability, so called absorption edges. However, the general trend of high absorption coefficients and thus short penetration depths for low photon energies and high atomic numbers is very strong. For soft tissue, photoabsorption dominates up to about 26 keV photon energy where Compton scattering takes over. For higher atomic number substances this limit is higher. The high amount of calcium (Z=20) in bones together with their high density is what makes them show up so clearly on medical radiographs.

text: A photoabsorbed photon transfers all its energy to the electron with which it interacts, thus ionizing the atom to which the electron was bound and producing a photoelectron that is likely to ionize more atoms in its path. An outer electron will fill the vacant electron position and produce either a characteristic photon[clarification needed] or an Auger electron. These effects can be used for elemental detection through X-ray spectroscopy or Auger electron spectroscopy.

text: Compton scattering[edit]

text: Compton scattering is the predominant interaction between X-rays and soft tissue in medical imaging.[62] Compton scattering is an inelastic scattering of the X-ray photon by an outer shell electron. Part of the energy of the photon is transferred to the scattering electron, thereby ionizing the atom and increasing the wavelength of the X-ray. The scattered photon can go in any direction, but a direction similar to the original direction is more likely, especially for high-energy X-rays. The probability for different scattering angles are described by the Klein–Nishina formula. The transferred energy can be directly obtained from the scattering angle from the conservation of energy and momentum.

text: Rayleigh scattering[edit]

text: Rayleigh scattering is the dominant elastic scattering mechanism in the X-ray regime.[63] Inelastic forward scattering gives rise to the refractive index, which for X-rays is only slightly below 1.[64]

text: Production[edit]

text: Whenever charged particles (electrons or ions) of sufficient energy hit a material, X-rays are produced.

text: Production by electrons[edit]

text:
Characteristic X-ray emission lines for some common anode materials.[65][66]

Anodematerial
Atomicnumber
Photon energy [keV]
Wavelength [nm]

Kα1
Kβ1
Kα1
Kβ1

W

74
59.3
67.2
0.0209
0.0184

Mo

42
17.5
19.6
0.0709
0.0632

Cu

29
8.05
8.91
0.154
0.139

Ag

47
22.2
24.9
0.0559
0.0497

Ga

31
9.25
10.26
0.134
0.121

In

49
24.2
27.3
0.0512
0.455

tag: table

text: X-rays can be generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate the electrons released by a hot cathode to a high velocity. The high velocity electrons collide with a metal target, the anode, creating the X-rays.[67] In medical X-ray tubes the target is usually tungsten or a more crack-resistant alloy of rhenium (5%) and tungsten (95%), but sometimes molybdenum for more specialized applications, such as when softer X-rays are needed as in mammography. In crystallography, a copper target is most common, with cobalt often being used when fluorescence from iron content in the sample might otherwise present a problem.

text: The maximum energy of the produced X-ray photon is limited by the energy of the incident electron, which is equal to the voltage on the tube times the electron charge, so an 80 kV tube cannot create X-rays with an energy greater than 80 keV. When the electrons hit the target, X-rays are created by two different atomic processes:

text:
Characteristic X-ray emission (X-ray fluorescence): If the electron has enough energy it can knock an orbital electron out of the inner electron shell of a metal atom, and as a result electrons from higher energy levels then fill up the vacancy and X-ray photons are emitted. This process produces an emission spectrum of X-rays at a few discrete frequencies, sometimes referred to as the spectral lines. The spectral lines generated depend on the target (anode) element used and thus are called characteristic lines. Usually these are transitions from upper shells into K shell (called K lines), into L shell (called L lines) and so on.
Bremsstrahlung: This is radiation given off by the electrons as they are scattered by the strong electric field near the high-Z (proton number) nuclei. These X-rays have a continuous spectrum. The intensity of the X-rays increases linearly with decreasing frequency, from zero at the energy of the incident electrons, the voltage on the X-ray tube.

tag: ol

text: So the resulting output of a tube consists of a continuous bremsstrahlung spectrum falling off to zero at the tube voltage, plus several spikes at the characteristic lines. The voltages used in diagnostic X-ray tubes range from roughly 20 kV to 150 kV and thus the highest energies of the X-ray photons range from roughly 20 keV to 150 keV.[68]

text: Both of these X-ray production processes are inefficient, with a production efficiency of only about one percent, and thus most of the electric power consumed by the tube is released as waste heat. When producing a usable flux of X-rays, the X-ray tube must be designed to dissipate the excess heat.

text: Short nanosecond bursts of X-rays peaking at 15-keV in energy may be reliably produced by peeling pressure-sensitive adhesive tape from its backing in a moderate vacuum. This is likely to be the result of recombination of electrical charges produced by triboelectric charging. The intensity of X-ray triboluminescence is sufficient for it to be used as a source for X-ray imaging.[69]

text: A specialized source of X-rays which is becoming widely used in research is synchrotron radiation, which is generated by particle accelerators. Its unique features are X-ray outputs many orders of magnitude greater than those of X-ray tubes, wide X-ray spectra, excellent collimation, and linear polarization.[70]

text: Production by fast positive ions[edit]

text:
X-rays can also be produced by fast protons or other positive ions. The proton-induced X-ray emission or particle-induced X-ray emission is widely used as an analytical procedure. For high energies, the production cross section is proportional to Z12Z2−4, where Z1 refers to the atomic number of the ion, Z2 to that of the target atom.[71]
An overview of these cross sections is given in the same reference.

text: Production in lightning and laboratory discharges[edit]

text: X-rays are also produced in lightning accompanying terrestrial gamma-ray flashes. The underlying mechanism is the acceleration of electrons in lightning related electric fields and the subsequent production of photons through Bremsstrahlung.[72] This produces photons with energies of some few keV and several tens of MeV.[73] In laboratory discharges with a gap size of approximately 1 meter length and a peak voltage of 1 MV, X-rays with a characteristic energy of 160 keV are observed.[74] A possible explanation is the encounter of two streamers and the production of high-energy run-away electrons;[75] however, microscopic simulations have shown that the duration of electric field enhancement between two streamers is too short to produce a significantly number of run-away electrons.[76]Recently, it has been proposed that air perturbations in the vicinity of streamers can facilitate the production of run-away electrons and hence of X-rays from discharges.[77] [78]

text: Detectors[edit]

text: X-ray detectors vary in shape and function depending on their purpose. Imaging detectors such as those used for radiography were originally based on photographic plates and later photographic film, but are now mostly replaced by various digital detector types such as image plates and flat panel detectors. For radiation protection direct exposure hazard is often evaluated using ionization chambers, while dosimeters are used to measure the radiation dose a person has been exposed to. X-ray spectra can be measured either by energy dispersive or wavelength dispersive spectrometers.

text: Medical uses[edit]

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text: Since Röntgen's discovery that X-rays can identify bone structures, X-rays have been used for medical imaging. The first medical use was less than a month after his paper on the subject.[29] Up to 2010, 5 billion medical imaging examinations had been conducted worldwide.[79] Radiation exposure from medical imaging in 2006 made up about 50% of total ionizing radiation exposure in the United States.[80]

text: Projectional radiographs[edit]

text: Projectional radiography is the practice of producing two-dimensional images using x-ray radiation. Bones contain much calcium, which due to its relatively high atomic number absorbs x-rays efficiently. This reduces the amount of X-rays reaching the detector in the shadow of the bones, making them clearly visible on the radiograph. The lungs and trapped gas also show up clearly because of lower absorption compared to tissue, while differences between tissue types are harder to see.

text: Projectional radiographs are useful in the detection of pathology of the skeletal system as well as for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer, or pulmonary edema, and the abdominal x-ray, which can detect bowel (or intestinal) obstruction, free air (from visceral perforations) and free fluid (in ascites). X-rays may also be used to detect pathology such as gallstones (which are rarely radiopaque) or kidney stones which are often (but not always) visible. Traditional plain X-rays are less useful in the imaging of soft tissues such as the brain or muscle. One area where projectional radiographs are used extensively is in evaluating how an orthopedic implant, such as a knee, hip or shoulder replacement, is situated in the body with respect to the surrounding bone. This can be assessed in two dimensions from plain radiographs, or it can be assessed in three dimensions if a technique called '2D to 3D registration' is used. This technique purportedly negates projection errors associated with evaluating implant position from plain radiographs.[81][82]

text: Dental radiography is commonly used in the diagnoses of common oral problems, such as cavities.

text: In medical diagnostic applications, the low energy (soft) X-rays are unwanted, since they are totally absorbed by the body, increasing the radiation dose without contributing to the image. Hence, a thin metal sheet, often of aluminium, called an X-ray filter, is usually placed over the window of the X-ray tube, absorbing the low energy part in the spectrum. This is called hardening the beam since it shifts the center of the spectrum towards higher energy (or harder) x-rays.

text: To generate an image of the cardiovascular system, including the arteries and veins (angiography) an initial image is taken of the anatomical region of interest. A second image is then taken of the same region after an iodinated contrast agent has been injected into the blood vessels within this area. These two images are then digitally subtracted, leaving an image of only the iodinated contrast outlining the blood vessels. The radiologist or surgeon then compares the image obtained to normal anatomical images to determine whether there is any damage or blockage of the vessel.

text: Computed tomography[edit]

text: Computed tomography (CT scanning) is a medical imaging modality where tomographic images or slices of specific areas of the body are obtained from a large series of two-dimensional X-ray images taken in different directions.[83] These cross-sectional images can be combined into a three-dimensional image of the inside of the body and used for diagnostic and therapeutic purposes in various medical disciplines.

text: Fluoroscopy[edit]

text: Fluoroscopy is an imaging technique commonly used by physicians or radiation therapists to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope. In its simplest form, a fluoroscope consists of an X-ray source and a fluorescent screen, between which a patient is placed. However, modern fluoroscopes couple the screen to an X-ray image intensifier and CCD video camera allowing the images to be recorded and played on a monitor. This method may use a contrast material. Examples include cardiac catheterization (to examine for coronary artery blockages) and barium swallow (to examine for esophageal disorders and swallowing disorders).

text: Radiotherapy[edit]

text: The use of X-rays as a treatment is known as radiation therapy and is largely used for the management (including palliation) of cancer; it requires higher radiation doses than those received for imaging alone. X-rays beams are used for treating skin cancers using lower energy x-ray beams while higher energy beams are used for treating cancers within the body such as brain, lung, prostate, and breast.[84][85]

text: Adverse effects[edit]

text: Diagnostic X-rays (primarily from CT scans due to the large dose used) increase the risk of developmental problems and cancer in those exposed.[86][87][88] X-rays are classified as a carcinogen by both the World Health Organization's International Agency for Research on Cancer and the U.S. government.[79][89] It is estimated that 0.4% of current cancers in the United States are due to computed tomography (CT scans) performed in the past and that this may increase to as high as 1.5-2% with 2007 rates of CT usage.[90]

text: Experimental and epidemiological data currently do not support the proposition that there is a threshold dose of radiation below which there is no increased risk of cancer.[91] However, this is under increasing doubt.[92] It is estimated that the additional radiation will increase a person's cumulative risk of getting cancer by age 75 by 0.6–1.8%.[93] The amount of absorbed radiation depends upon the type of X-ray test and the body part involved.[94] CT and fluoroscopy entail higher doses of radiation than do plain X-rays.

text: To place the increased risk in perspective, a plain chest X-ray will expose a person to the same amount from background radiation that people are exposed to (depending upon location) every day over 10 days, while exposure from a dental X-ray is approximately equivalent to 1 day of environmental background radiation.[95] Each such X-ray would add less than 1 per 1,000,000 to the lifetime cancer risk. An abdominal or chest CT would be the equivalent to 2–3 years of background radiation to the whole body, or 4–5 years to the abdomen or chest, increasing the lifetime cancer risk between 1 per 1,000 to 1 per 10,000.[95] This is compared to the roughly 40% chance of a US citizen developing cancer during their lifetime.[96] For instance, the effective dose to the torso from a CT scan of the chest is about 5 mSv, and the absorbed dose is about 14 mGy.[97] A head CT scan (1.5mSv, 64mGy)[98] that is performed once with and once without contrast agent, would be equivalent to 40 years of background radiation to the head. Accurate estimation of effective doses due to CT is difficult with the estimation uncertainty range of about ±19% to ±32% for adult head scans depending upon the method used.[99]

text: The risk of radiation is greater to a fetus, so in pregnant patients, the benefits of the investigation (X-ray) should be balanced with the potential hazards to the fetus.[100][101] In the US, there are an estimated 62 million CT scans performed annually, including more than 4 million on children.[94] Avoiding unnecessary X-rays (especially CT scans) reduces radiation dose and any associated cancer risk.[102]

text: Medical X-rays are a significant source of man-made radiation exposure. In 1987, they accounted for 58% of exposure from man-made sources in the United States. Since man-made sources accounted for only 18% of the total radiation exposure, most of which came from natural sources (82%), medical X-rays only accounted for 10% of total American radiation exposure; medical procedures as a whole (including nuclear medicine) accounted for 14% of total radiation exposure. By 2006, however, medical procedures in the United States were contributing much more ionizing radiation than was the case in the early 1980s. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources. The increase is traceable to the growth in the use of medical imaging procedures, in particular computed tomography (CT), and to the growth in the use of nuclear medicine.[80][103]

text: Dosage due to dental X-rays varies significantly depending on the procedure and the technology (film or digital). Depending on the procedure and the technology, a single dental X-ray of a human results in an exposure of 0.5 to 4 mrem. A full mouth series of X-rays may result in an exposure of up to 6 (digital) to 18 (film) mrem, for a yearly average of up to 40 mrem.[104][105][106][107][108][109][110]

text: Financial incentives have been shown to have a significant impact on X-ray use with doctors who are paid a separate fee for each X-ray providing more X-rays.[111]

text: Other uses[edit]

text: Other notable uses of X-rays include

text:
X-ray crystallography in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analysed to reveal the nature of that lattice. In the early 1990s, experiments were done in which layers a few atoms thick of two different materials were deposited in a Thue-Morse sequence. The resulting object was found to yield X-ray diffraction patterns.[112] A related technique, fiber diffraction, was used by Rosalind Franklin to discover the double helical structure of DNA.[113]
X-ray astronomy, which is an observational branch of astronomy, which deals with the study of X-ray emission from celestial objects.
X-ray microscopic analysis, which uses electromagnetic radiation in the soft X-ray band to produce images of very small objects.
X-ray fluorescence, a technique in which X-rays are generated within a specimen and detected. The outgoing energy of the X-ray can be used to identify the composition of the sample.
Industrial radiography uses X-rays for inspection of industrial parts, particularly welds.

tag: ul

text:
Authentication and quality control, X-ray is used for authentication and quality control of packaged items.
Industrial CT (computed tomography) is a process which uses X-ray equipment to produce three-dimensional representations of components both externally and internally. This is accomplished through computer processing of projection images of the scanned object in many directions.
Paintings are often X-rayed to reveal underdrawings and pentimenti, alterations in the course of painting or by later restorers. Many pigments such as lead white show well in radiographs.
X-ray spectromicroscopy has been used to analyse the reactions of pigments in paintings. For example, in analysing colour degradation in the paintings of van Gogh[115]
Airport security luggage scanners use X-rays for inspecting the interior of luggage for security threats before loading on aircraft.
Border control truck scanners use X-rays for inspecting the interior of trucks.

text:
X-ray art and fine art photography, artistic use of X-rays, for example the works by Stane Jagodič
X-ray hair removal, a method popular in the 1920s but now banned by the FDA.[116]
Shoe-fitting fluoroscopes were popularized in the 1920s, banned in the US in the 1960s, banned in the UK in the 1970s, and even later in continental Europe.
Roentgen stereophotogrammetry is used to track movement of bones based on the implantation of markers
X-ray photoelectron spectroscopy is a chemical analysis technique relying on the photoelectric effect, usually employed in surface science.
Radiation implosion is the use of high energy X-rays generated from a fission explosion (an A-bomb) to compress nuclear fuel to the point of fusion ignition (an H-bomb).

text: Visibility[edit]

text: While generally considered invisible to the human eye, in special circumstances X-rays can be visible. Brandes, in an experiment a short time after Röntgen's landmark 1895 paper, reported after dark adaptation and placing his eye close to an X-ray tube, seeing a faint "blue-gray" glow which seemed to originate within the eye itself.[117] Upon hearing this, Röntgen reviewed his record books and found he too had seen the effect. When placing an X-ray tube on the opposite side of a wooden door Röntgen had noted the same blue glow, seeming to emanate from the eye itself, but thought his observations to be spurious because he only saw the effect when he used one type of tube. Later he realized that the tube which had created the effect was the only one powerful enough to make the glow plainly visible and the experiment was thereafter readily repeatable. The knowledge that X-rays are actually faintly visible to the dark-adapted naked eye has largely been forgotten today; this is probably due to the desire not to repeat what would now be seen as a recklessly dangerous and potentially harmful experiment with ionizing radiation. It is not known what exact mechanism in the eye produces the visibility: it could be due to conventional detection (excitation of rhodopsin molecules in the retina), direct excitation of retinal nerve cells, or secondary detection via, for instance, X-ray induction of phosphorescence in the eyeball with conventional retinal detection of the secondarily produced visible light.

text: Though X-rays are otherwise invisible, it is possible to see the ionization of the air molecules if the intensity of the X-ray beam is high enough. The beamline from the wiggler at the ID11 at the European Synchrotron Radiation Facility is one example of such high intensity.[118]

text: Units of measure and exposure[edit]

text: The measure of X-rays ionizing ability is called the exposure:

text:
The coulomb per kilogram (C/kg) is the SI unit of ionizing radiation exposure, and it is the amount of radiation required to create one coulomb of charge of each polarity in one kilogram of matter.
The roentgen (R) is an obsolete traditional unit of exposure, which represented the amount of radiation required to create one electrostatic unit of charge of each polarity in one cubic centimeter of dry air. 1 roentgen= 2.58×10−4 C/kg.

text: However, the effect of ionizing radiation on matter (especially living tissue) is more closely related to the amount of energy deposited into them rather than the charge generated. This measure of energy absorbed is called the absorbed dose:

text:
The gray (Gy), which has units of (joules/kilogram), is the SI unit of absorbed dose, and it is the amount of radiation required to deposit one joule of energy in one kilogram of any kind of matter.
The rad is the (obsolete) corresponding traditional unit, equal to 10 millijoules of energy deposited per kilogram. 100 rad= 1 gray.

text: The equivalent dose is the measure of the biological effect of radiation on human tissue. For X-rays it is equal to the absorbed dose.

text:
The Roentgen equivalent man (rem) is the traditional unit of equivalent dose. For X-rays it is equal to the rad, or, in other words, 10 millijoules of energy deposited per kilogram. 100 rem = 1 Sv.
The sievert (Sv) is the SI unit of equivalent dose, and also of effective dose. For X-rays the "equivalent dose" is numerically equal to a Gray (Gy). 1 Sv= 1 Gy. For the "effective dose" of X-rays, it is usually not equal to the Gray (Gy).

text:
Radiation related quantities view ‧ talk ‧ edit

Quantity
Unit
Symbol
Derivation
Year
SI equivalence

Activity (A)

curie

Ci

3.7 × 1010 s−1

1953

3.7×1010 Bq

becquerel

Bq

s−1

1974

SI

rutherford

Rd

106 s−1

1946

1,000,000 Bq

Exposure (X)

röntgen

R

esu / 0.001293 g of air

1928

2.58 × 10−4 C/kg

Fluence (Φ)

(reciprocal area)

m−2

1962

SI

Absorbed dose (D)

erg

erg⋅g−1

1950

1.0 × 10−4 Gy

rad

rad

100 erg⋅g−1

1953

0.010 Gy

gray

Gy

J⋅kg−1

1974

SI

Dose equivalent (H)

röntgen equivalent man

rem

100 erg⋅g−1

1971

0.010 Sv

sievert

Sv

J⋅kg−1 × WR

1977

SI


document_title: Promissory note

question_text: what's the difference between a loan agreement and a promissory note

question_tokens: what 's the difference between a loan agreement and a promissory note

root

text: Promissory note

text: Overview[edit]

text: Promissory notes are a common financial instrument in many jurisdictions, employed principally for short time financing of companies. Often, the seller or provider of a service is not paid upfront by the buyer (usually, another company), but within a period of time, the length of which has been agreed upon by both the seller and the buyer. The reasons for this may vary; historically, many companies used to balance their books and execute payments and debts at the end of each week or tax month; any product bought before that time would be paid only then. Depending on the jurisdiction, this deferred payment period can be regulated by law; in countries like France, Italy or Spain, it usually ranges between 30 and 90 days after the purchase.[2]

tag: p

text: When a company engages in many of such transactions, for instance by having provided services to many customers all of whom then deferred their payment, it is possible that the company may be owed enough money that its own liquidity position (i.e., the amount of cash it holds) is hampered, and finds itself unable to honour their own debts, despite the fact that by the books, the company remains solvent. In those cases, the company has the option of asking the bank for a short term loan, or using any other such short term financial arrangements to avoid insolvency. However, in jurisdictions where promissory notes are commonplace, the company (called the payee or lender) can ask one of its debtors (called the maker, borrower or payor) to accept a promissory note, whereby the maker signs a legally binding agreement to honour the amount established in the promissory note (usually, part or all its debt) within the agreed period of time.[3] The lender can then take the promissory note to a financial institution (usually a bank, albeit this could also be a private person, or another company), that will exchange the promissory note for cash; usually, the promissory note is cashed in for the amount established in the promissory note, less a small discount. Once the promissory note reaches its maturity date, its current holder (the bank) can execute it over the emitter of the note (the debtor), who would have to pay the bank the amount promised in the note. If the maker fails to pay, however, the bank retains the right to go to the company that cashed the promissory note in, and demand payment. In the case of unsecured promissory notes, the lender accepts the promissory note based solely on the maker's ability to repay; if the maker fails to pay, the lender must honour the debt to the bank. In the case of a secured promissory note, the lender accepts the promissory note based on the maker's ability to repay, but the note is secured by a thing of value; if the maker fails to pay and the bank reclaims payment, the lender has the right to execute the security.[4]

text: Thus, promissory notes can work as a form of private money. In the past, particularly during the 19th century, their widespread and unregulated use was a source of great risk for banks and private financiers, who would often face the insolvency of both debtors, or simply be scammed by both.

text: The terms of a note usually include the principal amount, the interest rate if any, the parties, the date, the terms of repayment (which could include interest) and the maturity date. Sometimes, provisions are included concerning the payee's rights in the event of a default, which may include foreclosure of the maker's assets. Demand promissory notes are notes that do not carry a specific maturity date, but are due on demand of the lender. Usually the lender will only give the borrower a few days' notice before the payment is due. For loans between individuals, writing and signing a promissory note are often instrumental for tax and record keeping. A promissory note alone is typically unsecured,[5] but these may be used in combination with security agreements such as mortgage, in which case they are called mortgage notes.

text: International law[edit]

text: Definition and usage of promissory notes are internationally established by the Convention providing a uniform law for bills of exchange and promissory notes, signed in Geneva in 1930.[6] Article 75 of the treaty stated that a promissory note shall contain:

text:
the term "promissory note" inserted in the body of the instrument and expressed in the language employed in drawing up the instrument
an unconditional promise to pay a determinate sum of money;
a statement of the time of payment;
a statement of the place where payment is to be made;
the name of the person to whom or to whose order payment is to be made;
a statement of the date and of the place where the promissory note is issued;
the signature of the person who issues the instrument (maker).

text: United States law[edit]

text: In the United States, a promissory note that meets certain conditions is a negotiable instrument regulated by article 3 of the Uniform Commercial Code. Negotiable promissory notes called mortgage notes are used extensively in combination with mortgages in the financing of real estate transactions. One prominent example is the Fannie Mae model standard form contract Multistate Fixed-Rate Note 3200, which is publicly available.[7] Promissory notes, or commercial papers, are also issued to provide capital to businesses. However, Promissory Notes act as a source of Finance to the company's creditors.

text: The various State law enactments of the Uniform Commercial Code define what is and what is not a promissory note, in section 3-104(d):

text:
“
§ 3-104. NEGOTIABLE INSTRUMENT.
...
(d) A promise or order other than a check is not an instrument if, at the time it is issued or first comes into possession of a holder, it contains a conspicuous statement, however expressed, to the effect that the promise or order is not negotiable or is not an instrument governed by this Article.

”

text: Thus, a writing containing such a disclaimer removes such a writing from the definition of negotiable instrument, instead simply memorializing a contract.

text: British law[edit]

text:
“
§ 83. BILLS OF EXCHANGE ACT 1882. Part IV.[8]
...
Promissory note defined
(1) A promissory note is an unconditional promise in writing made by one person to another signed by the maker, engaging to pay, on demand or at a fixed or determinable future time, a sum certain in money, to, or to the order of, a specified person or to bearer.
(2) An instrument in the form of a note payable to maker’s order is not a note within the meaning of this section unless and until it is indorsed by the maker.
(3) A note is not invalid by reason only that it contains also a pledge of collateral security with authority to sell or dispose thereof.
(4) A note which is, or on the face of it purports to be, both made and payable within the British Islands is an inland note. Any other note is a foreign note.

”

text: History[edit]

text: Historically, promissory notes have acted as a form of privately issued currency. Flying cash or feiqian was a promissory note used during the Tang dynasty (618 – 907). Flying cash was regularly used by Chinese tea merchants, and could be exchanged for hard currency at provincial capitals.[10] The Chinese concept of promissory notes was introduced by Marco Polo to Europe.[11] According to tradition, in 1325 a promissory note was signed in Milan. However, according to a travelogue of a visit to Prague in 960 by Ibrahim ibn Yaqub, small pieces of cloth were used as a means of trade, with these cloths having a set exchange rate versus silver.[12] There is evidence of promissory notes being issued in 1384 between Genoa and Barcelona, although the letters themselves are lost. The same happens for the ones issued in Valencia in 1371 by Bernat de Codinachs for Manuel d'Entença, a merchant from Huesca (then part of the Crown of Aragon), amounting a total of 100 florins.[13] In all these cases, the promissory notes were used as a rudimentary system of paper money, for the amounts issued could not be easily transported in metal coins between the cities involved. Ginaldo Giovanni Battista Strozzi issued an early form of promissory note in Medina del Campo (Spain), against the city of Besançon in 1553.[14] However, there exists notice of promissory notes being in used in Mediterranean commerce well before that date.

text: Difference from IOU[edit]

text: Promissory notes differ from IOUs in that they contain a specific promise to pay along with the steps and timeline for repayment as well as consequences if repayment fails.[15] IOUs only acknowledge that a debt exists.[16][17] In common speech, other terms, such as "loan", "loan agreement", and "loan contract" may be used interchangeably with "promissory note" but a loan agreement or contract will typically be more detailed than a promissory note.[18]

text: Difference from loan contract[edit]

text: A promissory note is very similar to a loan. Each is a legally binding contract to unconditionally repay a specified amount within a defined time frame. However, a promissory note is generally less detailed and rigid than a loan contract.[19] For one thing, loan agreements often require repayment in installments, while promissory notes typically do not. Furthermore, a loan agreement usually includes the terms for recourse in the case of default, such as establishing the right to foreclose, while a promissory note does not. Also, while a loan agreement requires signatures from both the borrower and the lender, a promissory note only requires the signature of the borrower.[20]

text: Negotiability[edit]

text: Negotiable instruments are unconditional and impose few to no duties on the issuer or payee other than payment. In the United States, whether a promissory note is a negotiable instrument can have significant legal impacts, as only negotiable instruments are subject to Article 3 of the Uniform Commercial Code and the application of the holder in due course rule.[1] The negotiability of mortgage notes has been debated, particularly due to the obligations and "baggage" associated with mortgages; however, in mortgages notes are often determined to be negotiable instruments.[1]

text: In the United States, the Non-Negotiable Long Form Promissory Note is not required.[21]


question_text: the specialized agency that serves as the public health division of the united nations is

text: Food and Agriculture Organization (FAO)[edit]

text: The Food and Agriculture Organization of the United Nations leads international efforts to defeat hunger. Serving both developed and developing countries, FAO acts as a neutral forum where all nations meet as equals to negotiate agreements and debate policy. FAO's mandate is to raise levels of nutrition, improve agricultural productivity, better the lives of rural populations and contribute to the growth of the world economy. FAO is the largest of the UN agencies. It was established in 1945 and its headquarters is in Rome, Italy.

text: International Civil Aviation Organization (ICAO)[edit]

text: The International Civil Aviation Organization (ICAO) was founded in 1947. It codifies the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. Its headquarters are located in the Quartier international de Montréal of Montreal, Quebec, Canada.

text: The ICAO Council adopts standards and recommended practices concerning air navigation, prevention of unlawful interference, and facilitation of border-crossing procedures for international civil aviation. In addition, ICAO defines the protocols for air accident investigation followed by transport safety authorities in countries signatory to the Convention on International Civil Aviation, commonly known as the Chicago Convention.

text: It also solves disputes between two countries.[citation needed]

text: International Fund for Agricultural Development (IFAD)[edit]

text: The International Fund for Agricultural Development (IFAD) was established as an international financial institution in 1977, as one of the major outcomes of the 1974 World Food Conference and a response to the situation in the Sahel. It is dedicated to eradicating rural poverty in developing countries. Its headquarters are in Rome, Italy.

text: International Labour Organization (ILO)[edit]

text: The International Labour Organization (ILO) deals with labour issues. Its headquarters are in Geneva, Switzerland. Founded in 1919, it was formed through the negotiations of the Treaty of Versailles and was initially an agency of the League of Nations. It became a member of the UN system after the demise of the League and the formation of the UN at the end of World War II. Its Constitution, as amended to date, includes the Declaration of Philadelphia on the aims and purposes of the Organization. Its secretariat is known as the International Labor Office.

text: International Maritime Organization (IMO)[edit]

text: The International Maritime Organization (IMO), formerly known as the Inter-Governmental Maritime Consultative Organization (IMCO), was established in 1948 through the United Nations to coordinate international maritime safety and related practices. However the IMO did not enter into full force until 1958.

text: Headquartered in London, United Kingdom, the IMO promotes cooperation among government and the shipping industry to improve maritime safety and to prevent marine pollution. IMO is governed by an Assembly of members and is financially administered by a Council of members elected from the Assembly. The work of IMO is conducted through five committees and these are supported by technical sub-committees. Member organizations of the UN organizational family may observe the proceedings of the IMO. Observer status may be granted to qualified non-governmental organizations.

text: The IMO is supported by a permanent secretariat of employees who are representative of its members. The secretariat is composed of a Secretary-General who is periodically elected by the Assembly, and various divisions including, inter alia, marine safety, environmental protection, and a conference section.And also promotes international cooperation in education, science and culture

text: International Monetary Fund (IMF)[edit]

text: International Monetary Fund (IMF) is part of the United Nations system and has a formal relationship agreement with the UN, but retains its independence.[6] The IMF provides monetary cooperation and financial stability and acts as a forum for advice, negotiation and assistance on financial issues. It is headquartered in Washington, D.C., United States of America.

text: International Telecommunication Union (ITU)[edit]

text: The International Telecommunication Union (ITU) was established to standardize and regulate international radio and telecommunications. It was founded as the International Telegraph Union in Paris on 17 May 1865. Its main tasks include standardization, allocation of the radio spectrum, and organizing interconnection arrangements between different countries to allow international phone calls — in which regard it performs for telecommunications a similar function to what the UPU performs for postal services. It has its headquarters in Geneva, Switzerland, next to the main United Nations campus.

text: United Nations Educational, Scientific and Cultural Organization (UNESCO)[edit]

text: The United Nations Educational, Scientific and Cultural Organization (UNESCO) is a specialized agency of the United Nations established in 1946 with its headquarters in Paris, France. Its stated purpose is to contribute to peace and security by promoting international collaboration through education, science, and culture in order to further universal respect for justice, the rule of law, and the human rights and fundamental freedoms proclaimed in the UN Charter.

text: United Nations Industrial Development Organization (UNIDO)[edit]

text: United Nations Industrial Development Organization (UNIDO) is the specialized agency of the United Nations, which promotes inclusive and sustainable industrial development(ISID), headquartered in Vienna, Austria. The Organization addresses some of the most pressing issues of our time, and works to accelerate economic growth in order to bring prosperity to all while at the same time safeguarding the environment. UNIDO’s mandate is fully aligned with the global development agenda, which underlines the central role of industrialization and its importance as a key enabler for all 17 Global Goals, and especially for SDG9. The Director General is Li Yong.

text: Universal Postal Union (UPU)[edit]

text: The Universal Postal Union (UPU), headquartered in Berne, Switzerland, coordinates postal policies between member nations, and hence the worldwide postal system. Each member country agrees to the same set of terms for conducting international postal duties.

text: World Bank Group (WBG)[edit]

text: The World Bank Group is part of the United Nations system and has a formal relationship agreement with the UN, but retains its independence.[6] The WBG comprises a group of five legally separate but affiliated institutions: the International Bank for Reconstruction and Development (IBRD), the International Finance Corporation (IFC), the International Development Association (IDA), the Multilateral Investment Guarantee Agency (MIGA), and the International Centre for Settlement of Investment Disputes (ICSID). It is a vital source of financial and technical assistance to developing countries around the world. Its mission is to fight poverty with passion and professionalism for lasting results and to help people help themselves and their environment by providing resources, sharing knowledge, building capacity and forging partnerships in the public and private sectors. The WBG headquarters are located in Washington, D.C., United States of America.

text: International Bank for Reconstruction and Development (IBRD)[edit]

text: The IBRD makes loans to developing countries for development programmes with the stated goal of reducing poverty. It is part of the World Bank Group (WBG).

text: International Finance Corporation (IFC)[edit]

text: The IFC is the largest multilateral source of loan and equity financing for private sector projects in the developing world. It is part of the World Bank Group (WBG).

text: International Development Association (IDA)[edit]

text: The IDA's mandate is close to that of IBRD, with the focus on the poorest countries. It is part of the World Bank Group (WBG).

text: World Health Organization (WHO)[edit]

text: The World Health Organization (WHO) acts as a coordinating authority on international public health and deals with health and sanitation and diseases and sends medical teams to help combat epidemics. Established on 7 April 1948, the agency inherited the mandate and resources of its predecessor, the Health Organization, which had been an agency of the League of Nations. It was established in April 7, 1948 when 26 members of the United Nations ratified its Constitution. April 7 is celebrated as the World Health Day every year. The WHO is governed by 194 Member States through the World Health Assembly. Its headquarters are at Geneva in Switzerland.

text: World Intellectual Property Organization (WIPO)[edit]

text: The World Intellectual Property Organization (WIPO) is a specialized agency of the United Nations created in 1967 and headquartered in Geneva, Switzerland. Its purpose is to encourage creative activity and to promote the protection of intellectual property throughout the world. The organization administers several treaties concerning the protection of intellectual property rights.

text: World Meteorological Organization (WMO)[edit]

text: The World Meteorological Organization (WMO) originated from the International Meteorological Organization (IMO), which was founded in 1873. Established in 1950, WMO became the specialized agency of the United Nations for modern meteorology (weather and climate), operational hydrology and related geophysical sciences. It has its headquarters in Geneva, Switzerland.

text: World Tourism Organization (UNWTO)[edit]

text: The World Tourism Organization (UNWTO) was established in 1974 in Madrid, Spain, to replace the International Union of Official Tourist Publicity Organizations (IUOTPO). UNWTO has 160 member states and 350 affiliated members representing private organizations, educational institutions and others. It is headquartered in Madrid, Spain. The World Tourism Organization serves as a forum for tourism policies and acts as a practical source for tourism know-how.

text: Former specialized agencies[edit]

text: The only UN specialized agency to go out of existence is the International Refugee Organization, which existed from 1946 to 1952. In 1952, it was replaced by the Office of the United Nations High Commissioner for Refugees (headquartered in Geneva, Switzerland), which is a subsidiary organ of the United Nations General Assembly.

text: Related organizations[edit]

text: This section's factual accuracy is disputed. Relevant discussion may be found on Talk:List of specialized agencies of the United Nations. Please help to ensure that disputed statements are reliably sourced. (January 2013) (Learn how and when to remove this template message)

text: There are many other intergovernmental organizations that have concluded cooperation agreements with the United Nations such as, IOM, UNIDO, WFP, IMSO (International Mobile Satellite Organization) and many more. In terms of cooperation structures, some agreements come very close to the relationship agreements concluded under articles 57 and 63 of the UN Charter with the specialized agencies, but due to Charter requirements that the agencies deal with "economic, social, cultural, educational, health, and related fields", organizations with such agreements are not formally specialized agencies of the United Nations.[7][8][9][10][11][12] The IAEA established such an agreement with the UN in 1957, and the OPCW and the CTBTO used this model for agreements of their own with the UN.[11][12][13]

text: Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission[edit]

text: The Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission preparatory commission is tasked with preparing the activities of the nuclear non-proliferation organization.

text: International Atomic Energy Agency (IAEA)[edit]

text: The International Atomic Energy Agency (IAEA) is an intergovernmental organization for scientific and technical cooperation in the field of nuclear technology. It seeks to promote the peaceful use of nuclear energy and to inhibit its use for military purposes. The IAEA was set up as an autonomous organization on 29 July 1957. Prior to this, in 1953, U.S. President Dwight D. Eisenhower envisioned the creation of this international body to control and develop the use of atomic energy, in his "Atoms for Peace" speech before the UN General Assembly.[14] The organization and its former Director General, Mohamed ElBaradei, were jointly awarded the Nobel Peace Prize announced on 7 October 2005. As of March 2015, the IAEA's membership is 164 countries.[15]

text: Due to historical reasons and the political nature of its work, the IAEA is not a specialized agency. Instead, its relationship to the United Nations is governed by a special agreement as well as by its statute that commits the IAEA to report annually to the General Assembly and, when appropriate, to the Security Council.[16]

text: International Organization for Migration (IOM)[edit]

text: Since September 2016, IOM has been a related organization to the United Nations.IOM Becomes a Related Organization to the UN Headquarters are in Geneva, Switzerland.

text: Organization for the Prohibition of Chemical Weapons[edit]

text: The Organization for the Prohibition of Chemical Weapons (OPCW) is an intergovernmental organization, located in The Hague, Netherlands. The organization promotes and verifies the adherence to the Chemical Weapons Convention which prohibits of the use of chemical weapons and requires their destruction. The verification consists both of evaluation of declarations by members states and on-site inspections.

text: World Trade Organization (WTO)[edit]

text: The WTO was established instead of the failed proposal for a specialized agency dealing with trade issues, the International Trade Organization. WTO headquarters are in Geneva, Switzerland.

text: Summary[edit]

text:
No.
Logo
Official name
Abbreviation
Location (Country)
Location (City)
Established
Precursor established
Members states
Other participants
Map and reference

-

United Nations
UN
 United States
New York City
1945
1920

the UN members

observer states: Holy See, Palestine
observer entities: Order of Malta
observer regional organizations:[17] European Union
other observer entities and organizations[18]

 [1]

Specialized agencies

1

Food and Agriculture Organization
FAO
 Italy
Rome
1945
—

the UN members except Liechtenstein
Cook Islands, Niue

associate members: Faroe Islands, Tokelau
member organization: European Union

 [2]

2

International Civil Aviation Organization
ICAO
 Canada
Montreal
1947
—

the UN members except Dominica, Liechtenstein, Tuvalu
Cook Islands

—
 [3]

3

International Fund for Agricultural Development
IFAD
 Italy
Rome
1977
—

the UN members except Andorra, Australia, Bahrain, Belarus, Brunei, Bulgaria, Czech Republic, Latvia, Liechtenstein, Lithuania, Federated States of Micronesia, Monaco, Montenegro, Palau, Poland, Russia, San Marino, Serbia, Singapore, Slovenia, Slovakia, Turkmenistan, Ukraine
Cook Islands, Niue

observers: Holy See

 [4]

4

International Labour Organization
ILO
  Switzerland
Geneva
1919
—

the UN members except Andorra, Bhutan, Liechtenstein, Micronesia, Monaco, Nauru, North Korea, Tonga

—
 [5]

5

International Maritime Organization
IMO
 United Kingdom
London
1959
—

the UN members except Afghanistan, Andorra, Armenia, Belarus, Bhutan, Botswana, Burkina Faso, Burundi, Central African Republic, Chad, Kyrgyzstan, Laos, Lesotho, Liechtenstein, Mali, Micronesia, Nauru, Niger, Rwanda, South Sudan, Swaziland, Tajikistan, Uzbekistan, Zambia
Cook Islands

associate members: Faroe Islands, Hong Kong, Macao

 [6]

6

International Monetary Fund
IMF
 United States
Washington, D.C.
1945
—

the UN members except Andorra, Cuba, Liechtenstein, Monaco, and North Korea;
Kosovo

—
 [7]

7

International Telecommunication Union
ITU
  Switzerland
Geneva
1865
—

the UN members except Palau
Vatican City

observers: Palestine

 [8]

8

United Nations Educational, Scientific and Cultural Organization
UNESCO
 France
Paris
1946
1922

the UN members except Liechtenstein
Cook Islands, Niue, Palestine

associate members: Aruba, British Virgin Islands, Cayman Islands, Curaçao, Faroe Islands, Macau, Sint Maarten, Tokelau
observers: Holy See
NOC only: Liechtenstein, Hong Kong, Bermuda, Guam, American Samoa, Puerto Rico, US Virgin Islands

 [9]

9

United Nations Industrial Development Organization
UNIDO
 Austria
Vienna
1985
1966

the UN members except Andorra, Antigua and Barbuda, Australia, Brunei, Canada, Estonia, Iceland, Kiribati, Latvia, Liechtenstein, Lithuania, Marshall Islands, Micronesia, Nauru, New Zealand (as of 31 December 2013), Palau, San Marino, Singapore, Solomon Islands, South Sudan, United Kingdom, United States

observers: Holy See, Order of Malta

 [10]

10

Universal Postal Union
UPU
  Switzerland,
Bern
1874
—

the UN members except Andorra, Marshall Islands, the Federated States of Micronesia, Palau
Vatican City

member countries: Aruba, Curaçao and Sint Maarten, British Overseas Territories
observers: Palestine

 [11]

11

World Bank Group
WBG
 United States
Washington, D.C.
1945
—

the UN members except Andorra, Cuba, Liechtenstein, Monaco, North Korea
Kosovo

—
 [12]

12

World Health Organization
WHO
  Switzerland
Geneva
1948
1907

the UN members except Liechtenstein
Cook Islands, Niue

associate members: Puerto Rico, Tokelau
observers: Chinese Taipei, Holy See, Palestine, Order of Malta

 [13]

13

World Intellectual Property Organization
WIPO
  Switzerland
Geneva
1967
—

the UN members except Marshall Islands, Micronesia, Nauru, Palau, Solomon Islands, Timor-Leste, South Sudan
Holy See, Niue

observers: Palestine

 [14]

14

World Meteorological Organization
WMO
  Switzerland
Geneva
1950
1873

the UN members except Andorra, Equatorial Guinea, Grenada, Liechtenstein, Marshall Islands, Nauru, Palau, Saint Kitts and Nevis, Saint Vincent and the Grenadines, and San Marino
Cook Islands, Niue

member territories: British Caribbean Territories, Curacao and Sint Maartin, French Polynesia, Hong Kong, Macau, New Caledonia

 [15]

15

World Tourism Organization
UNWTO
 Spain
Madrid
1974
1925

the UN members except Antigua and Barbuda, Barbados, Belgium, Belize, Canada, Comoros, Denmark, Dominica, Estonia, Finland, Grenada, Guyana, Iceland, Ireland, Kiribati, Liberia, Liechtenstein, Luxembourg, Marshall Islands, Micronesia, Myanmar, Nauru, New Zealand, Palau, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Samoa, Singapore, Solomon Islands, Somalia, Suriname, Sweden, Tonga, Trinidad and Tobago, Tuvalu, United Arab Emirates, United Kingdom, United States

associate members: Aruba, Flemish Community, Hong Kong, Macau, Madeira, Puerto Rico
observers: Holy See, Palestine

 [16]

Related organizations

16

Comprehensive Nuclear-Test-Ban Treaty Organization Preparatory Commission
CTBTO Prep Com
 Austria
Vienna
1996
—

the UN members except Bhutan, Cuba, Dominica, India, Mauritius, North Korea, Pakistan, Saudi Arabia, Somalia, South Sudan, Syria, Tonga, Tuvalu
Cook Islands, Holy See and Niue

—
 [17]

17

International Atomic Energy Agency
IAEA
 Austria
Vienna
1957
—

the UN members except Andorra, Bhutan, Cape Verde, Comoros, Equatorial Guinea, Gambia, Grenada, Guinea, Guinea-Bissau, Kiribati, Maldives, Micronesia, Nauru, North Korea, Saint Kitts and Nevis, Saint Lucia, Samoa, São Tomé and Príncipe, Solomon Islands, Somalia, South Sudan, Suriname, Timor-Leste, Tonga, Tuvalu
Holy See

—
 [18]

18

Organisation for the Prohibition of Chemical Weapons
OPCW
 Netherlands
Hague
1997
—

the UN members except Egypt, Israel, North Korea and South Sudan
Cook Islands, Holy See and Niue

—
 [19]

19

World Trade Organization
WTO
  Switzerland
Geneva
1995
1948

the UN members except Algeria, Andorra, Azerbaijan, Bahamas, Belarus, Bhutan, Bosnia and Herzegovina, Comoros, Equatorial Guinea, Eritrea, Ethiopia, Iran, Iraq, Kiribati, Lebanon, Libya, Marshall Islands, Micronesia, Monaco, Nauru, North Korea, Palau, San Marino, São Tomé and Príncipe, Serbia, Somalia, South Sudan, Sudan, Syria, Timor-Leste, Turkmenistan, Tuvalu, Uzbekistan
customs territory members: European Union, Hong Kong, Macau, Chinese Taipei

observers: Algeria, Andorra, Azerbaijan, Bahamas, Belarus, Bhutan, Bosnia and Herzegovina, Comoros, Equatorial Guinea, Ethiopia, Iran, Iraq, Lebanon, Libya, São Tomé and Príncipe, Serbia, Sudan, Syria, Uzbekistan, Holy See

 [20]