Hand mit Ringen (Hand with Ring): print of Wilhelm Röntgen's first "medical" X-ray, of his wife's hand, taken on 22 December 1895 and presented to Professor Ludwig Zehnder of the Physik Institut, University of Freiburg, on 1 January 1896. Events 1790 - The Turkish fortress of Izmail is stormed and captured by Suvorov and his Russian armies Year 1895 ( MDCCCXCV) was a Common year starting on Tuesday (link will display full calendar of the Gregorian calendar (or a Common year Ludwig Louis Albert Zehnder (b 1854 d 1949 Swiss physicist inventor of an Interferometer (See Mach-Zehnder Interferometer) New Year See also New Year The Ancient Romans began their consular year on January 1st since 153 BC Year 1896 ( MDCCCXCVI) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian Calendar (or a Leap year The dark oval on the third finger is a shadow produced by her ring. ^[1][2]

An X-ray (or Röntgen ray) is a form of electromagnetic radiation with a wavelength in the range of 10 to 0. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. 01 nanometers, corresponding to frequencies in the range 30 PHz to 30 EHz. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a Frequency is a measure of the number of occurrences of a repeating event per unit Time. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. They are longer than Gamma rays but shorter than UV rays. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays X-rays are primarily used for diagnostic radiography and crystallography. For medical radiography see Radiology Radiography is the use of X-rays to view unseen or hard-to-image objects X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters X-rays are a form of ionizing radiation and as such can be dangerous. Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation In many languages it is called Röntgen radiation after one of the first investigators of the X-rays, Wilhelm Conrad Röntgen. Wilhelm Conrad Röntgen (27 March 1845 &ndash 10 February 1923 was a German physicist, who on 8 November 1895 produced and detected Electromagnetic

Unit of measure and exposure

The rem is the traditional unit of dose equivalent. The Röntgen ( roentgen) equivalent in man or rem (symbol rem) This describes the energy delivered by γ or X-radiation (indirectly ionizing radiation) for humans. Gamma (uppercase &Gamma, lowercase γ Γάμμα is the third letter of the Greek alphabet. The SI counterpart is the sievert (Sv). The sievert (symbol Sv is the SI derived unit of dose equivalent. One sievert is equal to 100 rem. Because the rem is a relatively large unit, typical equivalent dose is measured in millirem (mrem) - 1/1000 rem, or in microsievert (μSv) - 1/1000000 Sv -, whereby 1 mrem equals 10 μSv.

The average person living in the United States is exposed to approximately 150 mrem annually from background sources alone. The United States of America —commonly referred to as the Background radiation is the Ionizing radiation emitted from a variety of natural and artificial Radiation sources

Reported dosage due to dental X-rays seems to vary significantly. Depending on the source, a typical dental X-ray of a human results in an exposure of perhaps, 3^[3], 40^[4], 300^[5], or as many as 900^[6] mrems (30 to 9,000 μSv). The sievert (symbol Sv is the SI derived unit of dose equivalent.

Physics

When medical X-rays are being produced, a thin metallic sheet is placed between the emitter and the target, effectively filtering out the lower energy (soft) X-rays. This is often placed close to the window of the X-ray tube. An X-ray tube is a Vacuum tube that produces X-rays They are part of X-ray machines X-rays are part of the Electromagnetic spectrum, an The resultant X-ray is said to be hard. Soft X-rays overlap the range of extreme ultraviolet. Extreme Ultra-Violet radiation (EUV is generally considered to be the part of the Electromagnetic spectrum spanning from 120 nm down to 10 nm The frequency of hard X-rays is higher than that of soft X-rays, and the wavelength is shorter. Hard X-rays overlap the range of "long"-wavelength (lower energy) gamma rays, however the distinction between the two terms depends on the source of the radiation, not its wavelength; X-ray photons are generated by energetic electron processes, gamma rays by transitions within atomic nuclei. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom

The basic production of X-rays is by accelerating electrons in order to collide with a metal target. (In medical applications, this 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 soft X-rays are needed as in mammography. Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 Rhenium (ˈriːniəm is a Chemical element with the symbol Re and Atomic number 75 Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo 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). Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Iron (ˈаɪɚn is a Chemical element with the symbol Fe (ferrum and Atomic number 26 Here the electrons suddenly decelerate upon colliding with the metal target and if enough energy is contained within the electron it is able to knock out an electron from the inner shell of the metal atom and as a result electrons from higher energy levels then fill up the vacancy and X-ray photons are emitted. An electron shell may be crudely thought of as an Orbit followed by Electrons around an Atom nucleus. This process is extremely inefficient (~0. 1%) and thus to produce reasonable flux of X-rays plenty of energy has to be wasted into heat which has to be removed.

The spectral lines generated depends 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. In X-ray spectroscopy, K-alpha emission lines result when an electron transitions to the innermost "K" shell (principal quantum number 1 from a 2p orbital of the There is also a continuum Bremsstrahlung radiation given off by the electrons as they are scattered by the strong electric field near the high-Z (proton number) nuclei. Bremsstrahlung ( pronounced, from German de ''bremsen'' "to brake" and de ''Strahlung'' "radiation" i The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive

Radiographs obtained using x-rays can be used to identify a wide spectra of pathology. Due to their short wavelength, in medical applications X-rays act more like a particle than a wave. This is in contrast to their application in crystallography, where their wave-like nature is most important.

For most modern non-medical applications, X-ray production is achieved by synchrotrons (see synchrotron light). A synchrotron is a particular type of cyclic Particle accelerator in which the magnetic field (to turn the particles so they circulate and the electric field (to accelerate This article is mostly concerned with applications of Synchrotron radiation.

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. Angiography or arteriography is a Medical imaging technique in which an X-ray image is taken to visualize the inside or lumen, of blood vessels A second image is then taken of the same region after iodinated contrast material has been injected into the blood vessels within this area. These two images are then digitally altered, leaving an image of only the iodinated contrast outlining the blood vessels. The doctor (Radiologist) or surgeon then compares the image obtained to normal anatomical images to determine if there is any damage or blockage of the vessel.

To take an X-ray of the bones, short X-ray pulses are shot through a body with radiographic film behind. The bones absorb the most photons by the photoelectric process, because they are more electron dense. Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons The X-rays that do not get absorbed turn the photographic film from white to black, leaving a white shadow of bones on the film.

Detectors

Photographic plate

The detection of X-rays is based on various methods. The most commonly known methods are a photographic plate, X-ray film in a cassette, and rare earth screens. Photographic plates preceded Photographic film as a mean of photography This article is mainly concerned with Still photography film For Motion picture film please see Film stock. Rare earth elements and rare earth metals are according to IUPAC, the collection of seventeen Chemical elements in the Periodic table, namely Regardless of what is "catching" the image, they are all categorized as "Image Receptors(IR)".

Before computers and before digital imaging, a photographic plate was used to produce radiographic images. Photographic plates preceded Photographic film as a mean of photography The images were produced right on the glass plates. However, film replaced these plates and was used in hospitals to produce images. A hospital is an institution for Health care providing treatment by specialised staff and equipment and often but not always providing for However, computed & digital radiography has started to replace film. Although, film technology is still used in industrial radiography processes (to inspect welded seams). Photographic plates are a thing of history, and their replacement (intensifying screens) is now becoming part of that same history. Silver (necessary to the radiographic & photographic industry) is a non-renewable resource, that has now been replaced by digital (DR) and computed (CR) technology. Where film required wet processing facilities on site, these new technologies do not. Archiving of these new technologies is also space saving for facilities.

Regardless of whether the image receptor technology is plate, film or CR/DR Since photographic plates were sensitive to X-rays, they provide a convenient and easy means of recording the image, but they required a lot of exposure (to the patient). This is where intensifying screens came into the picture. The use of such, allowed for a lower dose to the patient – because the screens took the X-ray information and "intensified" it so that it could be recorded on the film lying next to the intensifying screen.

The part of the patient to be X-rayed is placed between the X-ray source and the image receptor to produce what is a shadow of all the internal structure of that particular part of the body being X-rayed. X-rays are somewhat blocked ("attenuated") by dense tissues such as bone, and pass more easily through soft tissues. Those areas where the X-rays strike the image receptor will produce photographic density (ie. it will turn black when developed). So where the X-rays pass through "soft" parts of the body such as organs, muscle, and skin, the plate or film turns black.

Contrast compounds containing barium or iodine, which are radiopaque, can be ingested in the gastrointestinal tract (barium) or injected in the artery or veins to highlight these vessels. Barium (ˈbɛəriəm is a Chemical element. It has the symbol Ba, and Atomic number 56 Iodine (ˈaɪədaɪn ˈaɪədɪn or /ˈaɪədiːn/ from ιώδης iodes "violet" is a Chemical element that has the symbol I and Atomic Radiopacity refers to the relative inability of electromagnetism to pass through a particular material particularly X-rays. The contrast compounds have high atomic numbered elements in them that (like bone) essentially block the X-rays and hence the once hollow organ or vessel can be more readily seen. In the pursuit of a non-toxic contrast material, many types of high atomic number elements were experimented with. For example, the first time the forefathers used contrast it was chalk, and was used on a cadaver's vessels. Unfortunately, some elements chosen proved to be harmful – for example, many years ago thorium was used as a contrast medium (Thorotrast) – which turned out to be toxic in some cases (causing injury and occasionally death from the effects of thorium poisioning). Thorium (ˈθɔːriəm is a Chemical element with the symbol Th and Atomic number 90 Contrast material used today has come a long way, and while there is no way to determine who may have a sensitivity to the contrast – the occasions of having an "allergic-type reaction" are very low. (The risk is compared to that associated with penicillin . . . that is, just as many people are allergic to penicillin as they are to radiographic contrast material. )

Photostimulable phosphors (PSPs)

An increasingly common method of detecting X-rays is the use of Photostimulable Luminescence (PSL), pioneered by Fuji in the 1980s. In modern hospitals a PSP plate is used in place of the photographic plate. After the plate is X-rayed, excited electrons in the phosphor material remain 'trapped' in 'colour centres' in the crystal lattice until stimulated by a laser beam passed over the plate surface. The light given off during laser stimulation is collected by a photomultiplier tube and the resulting signal is converted into a digital image by computer technology, which gives this process its common name, computed radiography (also referred to as digital radiography). Computed Radiography (CR uses very similar equipment to conventional radiography except that in place of a film to create the image an imaging plate is used The PSP plate can be used over and over again, and existing X-ray equipment requires no modification to use them.

Geiger counter

Initially, most common detection methods were based on the ionization of gases, as in the Geiger-Müller counter: a sealed volume, usually a cylinder, with a mica, polymer or thin metal window contains a gas, and a wire, and a high voltage is applied between the cylinder (cathode) and the wire (anode). In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound A Geiger counter, also called a Geiger-Müller counter, is a type of Particle detector that measures Ionizing radiation. A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device An anode is an Electrode through which Electric current flows into a polarized electrical device When an X-ray photon enters the cylinder, it ionizes the gas and forms ions and electrons. Electrons accelerate toward the anode, in the process causing further ionization along their trajectory. This process, known as an avalanche, is detected as a sudden flow of current, called a "count" or "event".

Ultimately, the electrons form a virtual cathode around the anode wire drastically reducing the electric field in the outer portions of the tube. This halts the collisional ionizations and limits further growth of avalanches. As a result, all "counts" on a Geiger counter are the same size and it can give no indication as to the particle energy of the radiation, unlike the proportional counter. A proportional counter is a measurement device to count particles of Ionizing radiation and measure their Energy. The intensity of the radiation is measurable by the Geiger counter as the counting-rate of the system.

In order to gain energy spectrum information a diffracting crystal may be used to first separate the different photons, the method is called wavelength dispersive X-ray spectroscopy (WDX or WDS). Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle The Wavelength dispersive X-ray spectroscopy (WDXRF or WDS is a method used to count the number of X-rays of a specific wavelength diffracted by a crystal The Wavelength dispersive X-ray spectroscopy (WDXRF or WDS is a method used to count the number of X-rays of a specific wavelength diffracted by a crystal Position-sensitive detectors are often used in conjunction with dispersive elements. Other detection equipment may be used which are inherently energy-resolving, such as the aforementioned proportional counters. A proportional counter is a measurement device to count particles of Ionizing radiation and measure their Energy. In either case, use of suitable pulse-processing (MCA) equipment allows digital spectra to be created for later analysis.

For many applications, counters are not sealed but are constantly fed with purified gas (thus reducing problems of contamination or gas aging). These are called "flow counter".

Scintillators

Some materials such as sodium iodide (NaI) can "convert" an X-ray photon to a visible photon; an electronic detector can be built by adding a photomultiplier. Sodium iodide is a white Crystalline Salt with Chemical formula Na[[Iodine I]] used in radiation detection treatment of Iodine deficiency Photomultiplier tubes ( photomultipliers or PMT s for short members of the class of Vacuum tubes and more specifically Phototubes are extremely These detectors are called "scintillators", filmscreens or "scintillation counters". A scintillator is a substance that absorbs high-energy (ie Ionizing) electromagnetic or charged Particle radiation then in response fluoresces A scintillation counter measures Ionizing radiation. The Sensor, called a Scintillator, consists of a transparent Crystal, usually phosphor The main advantage of using these is that an adequate image can be obtained while subjecting the patient to a much lower dose of X-rays.

Image intensification

X-ray during Cholecystectomy

X-rays are also used in "real-time" procedures such as angiography or contrast studies of the hollow organs (e. Cholecystectomy (/ˌkɔləsɪsˈtɛktəmi/ plural cholecystectomies is the surgical removal of the Gallbladder. Angiography or arteriography is a Medical imaging technique in which an X-ray image is taken to visualize the inside or lumen, of blood vessels g. barium enema of the small or large intestine) using fluoroscopy acquired using an X-ray image intensifier. lower gastrointestinal series, also called a barium enema, is a medical procedure used to examine and diagnose problems with the human colon (large intestine Fluoroscopy is an imaging technique commonly used by Physicians to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope An X-ray image intensifier (XRII sometimes referred to as a C-Arm or Fluoroscope in medical settings is a highly complex piece of equipment which uses Angioplasty, medical interventions of the arterial system, rely heavily on X-ray-sensitive contrast to identify potentially treatable lesions. Angioplasty is the technique of mechanically widening a narrowed or totally obstructed Blood vessel; typically as a result of Atherosclerosis.

Direct semiconductor detectors

Since the 1970s, new semiconductor detectors have been developed (silicon or germanium doped with lithium, Si(Li) or Ge(Li)). A semiconductor detector is a device that uses a semiconductor (usually Silicon or Germanium) to detect Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32 Lithium (ˈlɪθiəm is a Chemical element with the symbol Li and Atomic number 3 X-ray photons are converted to electron-hole pairs in the semiconductor and are collected to detect the X-rays. When the temperature is low enough (the detector is cooled by Peltier effect or even cooler liquid nitrogen), it is possible to directly determine the X-ray energy spectrum; this method is called energy dispersive X-ray spectroscopy (EDX or EDS); it is often used in small X-ray fluorescence spectrometers. The thermoelectric effect is the direct conversion of temperature differences to electric Voltage and vice versa Liquid nitrogen (liquid density at the Triple point is 0707 g/mL is the liquid produced industrially in large quantities by Fractional distillation of Energy dispersive X-ray spectroscopy (EDS EDX or EDXRF is an analytical technique used for the elemental analysis or chemical characterization of a sample X-ray fluorescence (XRF is the emission of characteristic "secondary" (or fluorescent X-rays from a material that has been excited by bombarding with high-energy Spectroscopy was originally the study of the interaction between Radiation and Matter as a function of Wavelength (λ These detectors are sometimes called "solid state detectors". Cadmium telluride (CdTe) and its alloy with zinc, cadmium zinc telluride detectors have an increased sensitivity, which allows lower doses of X-rays to be used. Cadmium telluride (CdTe is a Crystalline compound formed from Cadmium and Tellurium with a zinc blende (cubic crystal structure Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 Cadmium zinc telluride, (CdZnTe or CZT, is (as the name indicates a compound of Cadmium, Zinc and Tellurium or more strictly speaking an alloy

Practical application in medical imaging didn't start taking place until the 1990s. Medical imaging refers to the techniques and processes used to create Images of the human body (or parts thereof for clinical purposes ( Medical procedures seeking to Currently amorphous selenium is used in commercial large area flat panel X-ray detectors for mammography and chest radiography. Selenium (səˈliniəm is a Chemical element with the Atomic number 34 represented by the chemical symbol Se, an atomic mass of 78 Mammography is the process of using low-dose X-rays (usually around 0 For medical radiography see Radiology Radiography is the use of X-rays to view unseen or hard-to-image objects Current research and development is focused around pixel detectors, such as CERN's energy resolving Medipix detector. The European Organization for Nuclear Research (Organisation Européenne pour la Recherche Nucléaire known as CERN Medipix is a family of photon counting pixel detector developed by an international collaboration hosted by CERN.

Note: A standard semiconductor diode, such as a 1N4007, will produce a small amount of current when placed in an X-ray beam. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Dioden2jpg|thumb|right|150px|Figure 2 Various semiconductor diodes A test device once used by Medical Imaging Service personnel was a small project box that contained several diodes of this type in series, which could be connected to an oscilloscope as a quick diagnostic. If two or more circuit components are connected end to end like a daisy chain it is said they are connected in series. An oscilloscope (commonly abbreviated to scope or O-scope) is a type of Electronic test equipment that allows signal Voltages to be viewed

Silicon drift detectors (SDDs), produced by conventional semiconductor fabrication, now provide a cost-effective and high resolving power radiation measurement. Semiconductor device fabrication is the process used to create chips the Integrated circuits that are present in everyday Electrical and electronic Unlike conventional X-ray detectors, such as Si(Li)s, they do not need to be cooled with liquid nitrogen.

Scintillator plus semiconductor detectors (indirect detection)

With the advent of large semiconductor array detectors it has become possible to design detector systems using a scintillator screen to convert from X-rays to visible light which is then converted to electrical signals in an array detector. Indirect Flat Panel Detectors (FPDs) are in widespread use today in medical, dental, veterinary and industrial applications. A common form of these detectors is based on amorphous silicon TFT/photodiode arrays. Amorphous silicon (a-Si is the non-crystalline Allotropic form of Silicon. A photodiode is a type of Photodetector capable of converting Light into either current or Voltage, depending upon the mode of operation

The array technology is a variant on the amorphous silicon TFT arrays used in many flat panel displays, like the ones in computer laptops. Flat panel displays encompass a growing number of technologies enabling video displays that are lighter and much thinner than traditional television and video displays that use Cathode The array consists of a sheet of glass covered with a thin layer of silicon that is in an amorphous or disordered state. At a microscopic scale, the silicon has been imprinted with millions of transistors arranged in a highly ordered array, like the grid on a sheet of graph paper. Each of these thin film transistors (TFTs) are attached to a light-absorbing photodiode making up an individual pixel (picture element). In Digital imaging, a pixel ( pict ure el ement is the smallest piece of information in an image Photons striking the photodiode are converted into two carriers of electrical charge, called electron-hole pairs. In Physics, a charge carrier denotes a free (mobile unbound particle carrying an Electric charge. Since the number of charge carriers produced will vary with the intensity of incoming light photons, an electrical pattern is created that can be swiftly converted to a voltage and then a digital signal, which is interpreted by a computer to produce a digital image. Although silicon has outstanding electronic properties, it is not a particularly good absorber of X-ray photons. For this reason, X-rays first impinge upon scintillators made from eg. A scintillator is a substance that absorbs high-energy (ie Ionizing) electromagnetic or charged Particle radiation then in response fluoresces gadolinium oxysulfide or caesium iodide. Gadolinium oxysulfide ( Gd 2 O 2 S) also called gadolinium sulfoxylate or GOS, is an Inorganic compound Caesium iodide (CsI is an Ionic compound often used as the input Phosphor of an X-ray image intensifier tube found in Fluoroscopy equipment The scintillator absorbs the X-rays and converts them into visible light photons that then pass onto the photodiode array.

Visibility to the human eye

While generally considered invisible to the human eye, in special circumstances X-rays can be visible. ^[8] 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. Wilhelm Conrad Röntgen (27 March 1845 &ndash 10 February 1923 was a German physicist, who on 8 November 1895 produced and detected Electromagnetic ^[9] 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. In scientific inquiry an experiment ( Latin: Ex- periri, "to try out" is a method of investigating particular types of research questions or 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. Image talkNew_radiation_symbol_ISO_21482svg for details --> 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. Rhodopsin, also known as visual purple, is a Pigment of the Retina that is responsible for both the formation of the Photoreceptor cells and the Phosphorescence is a specific type of Photoluminescence related to fluorescence.

Medical uses

X-Ray Image of the Paranasal Sinuses, Lateral Projection

Since Röntgen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in medical imaging. Medical imaging refers to the techniques and processes used to create Images of the human body (or parts thereof for clinical purposes ( Medical procedures seeking to Radiology is a specialized field of medicine. Radiology is the medical specialty directing Medical imaging technologies to diagnose and treat diseases Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the Radiographers employ radiography and other techniques for diagnostic imaging. For medical radiography see Radiology Radiography is the use of X-rays to view unseen or hard-to-image objects Medical imaging refers to the techniques and processes used to create Images of the human body (or parts thereof for clinical purposes ( Medical procedures seeking to Indeed, this is probably the most common use of X-ray technology.

X-rays are especially useful in the detection of pathology of the skeletal system, but are also useful for detecting some disease processes in soft tissue. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce In Medicine, the term soft tissue refers to tissues that connect support or surround other structures and organs of the body 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 ileus (blockage of the intestine), free air (from visceral perforations) and free fluid (in ascites). A chest X-ray, commonly abbreviated CXR, is a projection radiograph ( X-ray) taken by a Radiographer, of the Thorax which is used Pneumonia is an inflammatory illness of the Lung. Frequently it is described as lung Parenchyma / alveolar inflammation and abnormal Lung cancer is a Disease of uncontrolled Cell growth in tissues of the Lung. Pulmonary Edema (American English or oedema (British English is swelling and/or fluid accumulation in the Lungs It leads to impaired gas exchange and may cause An abdominal x-ray is an X-ray the Abdomen. It is sometimes abbreviated to AXR or KUB (for Kidneys, Ureters, and Urinary bladder Ileus is a disruption of the normal propulsive gastrointestinal motor activity from non-mechanical mechanisms In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists In Medicine ( Gastroenterology) ascites (also known as peritoneal cavity fluid, peritoneal fluid excess, hydroperitoneum or more In some cases, the use of X-rays is debatable, such as gallstones (which are rarely radiopaque) or kidney stones (which are often visible, but not always). In Medicine, gallstones (choleliths are Crystalline bodies formed within the body by accretion or concretion of normal or abnormal Bile component Radiopacity refers to the relative inability of electromagnetism to pass through a particular material particularly X-rays. Kidney stones, also called renal calculi, are solid concretions (crystal aggregations of dissolved minerals in Urine; calculi typically form Also, traditional plain X-rays pose very little use in the imaging of soft tissues such as the brain or muscle. The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the Imaging alternatives for soft tissues are computed axial tomography (CAT or CT scanning), magnetic resonance imaging (MRI) or ultrasound. Computed tomography (CT is a Medical imaging method employing Tomography. Since 2005, X-rays are listed as a carcinogen by the U. The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation S. government. ^[10]

Radiotherapy, a curative medical intervention, now used almost exclusively for cancer, employs higher energies of radiation. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled

The efficiency of X-ray tubes is less than 2%. Most of the energy is used to heat up the anode.

Other uses

Each dot, called a reflection, in this diffraction pattern forms from the constructive interference of scattered X-rays passing through a crystal. The data can be used to determine the crystalline structure.

Other notable uses of X-rays include

• 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 analyzed to reveal the nature of that lattice. X-ray crystallography is a method of determining the arrangement of Atoms within a Crystal, in which a beam of X-rays strikes a crystal and scatters Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle A related technique, fiber diffraction, was used by Rosalind Franklin to discover the double helical structure of DNA). Fiber diffraction is an important simplification of the general Scattering technique in which molecular structure is determined from scattering data (usually of X-rays electrons Rosalind Elsie Franklin ( 25 July, 1920 Notting Hill, London – 16 April, 1958 Chelsea London) was an In Geometry a double helix (plural helices) typically consists of two congruent helices with the same axis differing by a translation Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known ^[11]
• X-ray astronomy, which is an observational branch of astronomy, which deals with the study of X-ray emission from celestial objects. X-ray astronomy is an observational branch of Astronomy, which deals with the study of X-ray emission from celestial objects Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study
• X-ray microscopic analysis, which uses electromagnetic radiation in the soft X-ray band to produce images of very small objects. An X-ray microscope uses Electromagnetic radiation in the soft X-ray band to produce images of very small objects Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter.
• X-ray fluorescence, a technique in which X-rays are generated within a specimen and detected. X-ray fluorescence (XRF is the emission of characteristic "secondary" (or fluorescent X-rays from a material that has been excited by bombarding with high-energy The outgoing energy of the X-ray can be used to identify the composition of the sample.
• Paintings are often X-rayed to reveal the underdrawing and pentimenti or alterations in the course of painting, or by later restorers. Underdrawing is the Drawing done on a painting ground before paint is applied for example an Imprimatura or an Underpainting. A pentimento (plural pentimenti) is an alteration in a painting evidenced by traces of previous work showing that the artist has changed his mind as to the composition during Many pigments such as lead white show well in X-ray photographs. For the drug referred to as "pigment" see Black tar heroin. Lead paint is Paint containing Lead, a heavy metal, that is used as pigment with Lead(II chromate ( Pb[[Chromium Cr]] O4

History

Among the important early researchers in X-rays were Professor Ivan Pulyui, Sir William Crookes, Johann Wilhelm Hittorf, Eugen Goldstein, Heinrich Hertz, Philipp Lenard, Hermann von Helmholtz, Nikola Tesla, Thomas Edison, Charles Glover Barkla, Max von Laue, and Wilhelm Conrad Röntgen. Ivan Pulyui (Іван Пулюй Johann Puluj (born February 2, 1845 in Hrymayliv village died January 31, 1918 in Prague) Sir William Crookes, OM, FRS (17 June 1832 – 4 April 1919 was an English Chemist and Physicist. Johann Wilhelm Hittorf ( March 27, 1824 &ndash November 28, 1914) was a German Physicist who was born in Bonn, and died Eugen Goldstein ( September 5, 1850 &ndash December 25, 1930) was a German Physicist. Heinrich Rudolf Hertz ( February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory Philipp Eduard Anton von Lénárd ( June 7, 1862 &ndash May 20, 1947) was a German physicist and the winner of the There have already been discussions about Tesla's ethnicity on the talk page Charles Glover Barkla ( June 27, 1877 &ndash October 23, 1944) was an English physicist. Max Theodor Felix von Laue ( October 9, 1879 &ndash April 24, 1960) was a German physicist who won the Nobel Prize in Physics Wilhelm Conrad Röntgen (27 March 1845 &ndash 10 February 1923 was a German physicist, who on 8 November 1895 produced and detected Electromagnetic

Johann Hittorf

Physicist Johann Hittorf (1824 – 1914) observed tubes with energy rays extending from a negative electrode. Johann Wilhelm Hittorf ( March 27, 1824 &ndash November 28, 1914) was a German Physicist who was born in Bonn, and died This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. These rays produced a fluorescence when they hit the glass walls of the tubes. In 1876 the effect was named "cathode rays" by Eugen Goldstein, and today are known to be streams of electrons. Cathode rays (also called an electron beam or e-beam) are streams of Electrons observed in Vacuum tubes i Eugen Goldstein ( September 5, 1850 &ndash December 25, 1930) was a German Physicist. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Later, English physicist William Crookes investigated the effects of electric currents in gases at low pressure, and constructed what is called the Crookes tube. Sir William Crookes, OM, FRS (17 June 1832 – 4 April 1919 was an English Chemist and Physicist. A Crookes tube is an early experimental Discharge tube, invented by British physicist William Crookes and others around 1875 in which Cathode rays It is a glass cylinder mostly (but not completely) evacuated, containing electrodes for discharges of a high voltage electric current. He found, when he placed unexposed photographic plates near the tube, that some of them were flawed by shadows, though he did not investigate this effect. Crookes also noted that his cathode rays caused the glass walls of his tube to glow a dull blue colour. Crookes failed to realise that it wasn't actually the cathode rays that caused the blue glow, but the low-level X-rays produced when the cathode rays struck the glass.

Ivan Pulyui

In 1877 Ukranian-born Pulyui, a lecturer in experimental physics at the University of Vienna, constructed various designs of vacuum discharge tube to investigate their properties. Ukraine (Україна Ukrayina, /ukrɑˈjinɑ/ is a country in Eastern Europe. Ivan Pulyui (Іван Пулюй Johann Puluj (born February 2, 1845 in Hrymayliv village died January 31, 1918 in Prague) The University of Vienna (Universität Wien is a Public university located in Vienna, Austria. The Geissler tube is a glass tube for demonstrating the principles of electrical Glow discharge. ^[12] He continued his investigations when appointed professor at the Prague Polytechnic and in 1886 he found that that sealed photographic plates became dark when exposed to the emanations from the tubes. Czech Technical University in Prague (CTU České vysoké učení technické v Praze &ndash ČVUT in Czech) is one of the largest universities in the 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. Wilhelm Conrad Röntgen (27 March 1845 &ndash 10 February 1923 was a German physicist, who on 8 November 1895 produced and detected Electromagnetic ^[12] 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. The University of Strasbourg in Strasbourg, Alsace, France, founded in 1631 was divided in the 1970s into three separate institutions with a total ^[12]

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. Dartmouth College ( is a private, Coeducational University located in Hanover, New Hampshire, U This was a result of Pulyui's inclusion of an oblique "target" of mica, used for holding samples of fluorescent material, within the tube. The word "mica" is thought to be derived from the Latin word la micare, "glitteren" in reference to the brilliant appearance of this mineral (especially Fluorescence is a Luminescence that is mostly found as an 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 Edwin 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. Events 1112 - Ramon Berenguer III of Barcelona and Douce I of Provence marry uniting the fortunes of those two states Year 1896 ( MDCCCXCVI) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian Calendar (or a Leap year Photographic plates preceded Photographic film as a mean of photography ^[13]

Nikola Tesla

In April 1887, Nikola Tesla began to investigate X-rays using high voltages and tubes of his own design, as well as Crookes tubes. There have already been discussions about Tesla's ethnicity on the talk page A Crookes tube is an early experimental Discharge tube, invented by British physicist William Crookes and others around 1875 in which Cathode rays From his technical publications, it is indicated that he invented and developed a special single-electrode X-ray tube ^{[14] [15]}, which differed from other X-ray tubes in having no target electrode. The principle behind Tesla's device is called the Bremsstrahlung process, in which a high-energy secondary X-ray emission is produced when charged particles (such as electrons) pass through matter. Bremsstrahlung ( pronounced, from German de ''bremsen'' "to brake" and de ''Strahlung'' "radiation" i By 1892, Tesla performed several such experiments, but he did not categorize the emissions as what were later called X-rays. Tesla generalized the phenomenon as radiant energy of "invisible" kinds. Radiant energy is the Energy of Electromagnetic waves The quantity of radiant energy may be calculated by integrating Radiant flux (or power ^{[16] [17]} Tesla stated the facts of his methods concerning various experiments in his 1897 X-ray lecture ^[18] before the New York Academy of Sciences. The New York Academy of Sciences is the third oldest scientific society in the United States Also in this lecture, Tesla stated the method of construction and safe operation of X-ray equipment. His X-ray experimentation by vacuum high field emissions also led him to alert the scientific community to the biological hazards associated with X-ray exposure. ^[19]

Fernando Sanford

X-rays were first generated and detected by Fernando Sanford (1854-1948), the foundation Professor of Physics at Stanford University, in 1891. Leland Stanford Junior University, commonly known as Stanford University or simply Stanford, is a private Research university located in 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. Heinrich Rudolf Hertz ( February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory Philipp Eduard Anton von Lénárd ( June 7, 1862 &ndash May 20, 1947) was a German physicist and the winner of the 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. Events 1066 - Harold Godwinson is crowned King of England. 1205 - Philip of Swabia becomes King Year 1893 ( MDCCCXCIII) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common Physical Review (frequently abbreviated as Phys Rev) is one of the oldest and most-respected Scientific journals publishing research on all aspects of The San Francisco Examiner is a US daily Newspaper. It has been published continuously in San Francisco, California, since ^[20]

Heinrich Hertz

In 1892, Heinrich Hertz began experimenting and demonstrated that cathode rays could penetrate very thin metal foil (such as aluminium). Heinrich Rudolf Hertz ( February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory WikipediaNaming Philipp Lenard, a student of Heinrich Hertz, further researched this effect. Philipp Eduard Anton von Lénárd ( June 7, 1862 &ndash May 20, 1947) was a German physicist and the winner of the He developed a version of the Crookes tube and studied the penetration by X-rays of various materials. A Crookes tube is an early experimental Discharge tube, invented by British physicist William Crookes and others around 1875 in which Cathode rays Philipp Lenard, though, did not realize that he was producing X-rays. 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 (Wiedmann's Annalen, Vol. XLVIII). However, he did not work with actual X-rays.

Wilhelm Röntgen

On November 8, 1895, Wilhelm Conrad Röntgen, a German physics professor, began observing and further documenting X-rays while experimenting with Lenard and Crookes tubes. Events 1519 - Hernán Cortés enters Tenochtitlán and Aztec ruler Moctezuma welcomes him with great a Celebration Year 1895 ( MDCCCXCV) was a Common year starting on Tuesday (link will display full calendar of the Gregorian calendar (or a Common year Wilhelm Conrad Röntgen (27 March 1845 &ndash 10 February 1923 was a German physicist, who on 8 November 1895 produced and detected Electromagnetic Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. Röntgen, on December 28, 1895, wrote a preliminary report "On a new kind of ray: A preliminary communication". Events 1065 - Westminster Abbey is Consecrated. 1308 - The reign of Emperor Hanazono, Emperor of Year 1895 ( MDCCCXCV) was a Common year starting on Tuesday (link will display full calendar of the Gregorian calendar (or a Common year He submitted it to the Würzburg's Physical-Medical Society journal. Würzburg (ˈvʏɐ̯ʦbʊɐ̯k is a city in the region of Franconia which lies in the northern tip of Bavaria, Germany ^[21] This was the first formal and public recognition of the categorization of 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. Röntgen received the first Nobel Prize in Physics for his discovery. The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences.

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. ^[22] Röntgen was investigating cathode rays with a fluorescent screen painted with barium platinocyanide and a Crookes tube which he had wrapped in black cardboard so the visible light from the tube wouldn't interfere. Fluorescence is a Luminescence that is mostly found as an A Crookes tube is an early experimental Discharge tube, invented by British physicist William Crookes and others around 1875 in which Cathode rays He noticed a faint green glow from the screen, about 1 meter away. The invisible rays coming from the tube to make the screen glow were passing through the cardboard. 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 translated "On a New Kind of Radiation" and gave a demonstration in 1896.

Röntgen discovered its medical use when he saw a picture of his wife's hand on a photographic plate formed due to X-rays. His wife's hand's photograph was the first ever photograph of a human body part using X-rays.

Thomas Edison

Diagram of a water cooled X-ray tube. (simplified/outdated)

In 1895, Thomas Edison investigated materials' ability to fluoresce when exposed to X-rays, and found that calcium tungstate was the most effective substance. Scheelite is a Calcium Tungstate Mineral with the Chemical formula Ca[[tungsten W]] O 4 Around March 1896, the fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903 after the death of Clarence Madison Dally, one of his glassblowers. Clarence Madison Dally (1865-1904 was an American Glassblower, noted as an assistant to Thomas Edison in his work on X-rays and as an early victim of 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. Cancer (medical term Malignant Neoplasm) is a class of Diseases in which a group of cells display uncontrolled Amputation is the removal of a body extremity by trauma or Surgery. "At the 1901 Pan-American Exposition in Buffalo, New York, an assassin shot President William McKinley twice at close range with a . William McKinley Jr ( January 29, 1843 September 14, 1901) was the twenty-fifth President of the United States, and the last 32 caliber revolver. " The first bullet was removed but the second remained lodged somewhere in his stomach. McKinley survived for some time and requested that Thomas Edison "rush an X-ray machine to Buffalo to find the stray bullet. It arrived but wasn't used . . . McKinley died of septic shock due to bacterial infection. "^[23]

The 20th century and beyond

Before the 20th century and for a short while after, X-rays were generated in cold cathode tubes. These tubes 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. One of the problems with early X-ray tubes is that the generated X-rays caused the glass to absorb the gas and consequently the efficiency quickly falls off. Larger and more frequently used tubes were provided with a means of restoring the air. This often took the form of small side tube which contained a small piece of mica – a substance that traps comparatively large quantities of air within its structure. A small electrical heater heats the mica and causes it to release a small amount of air restoring the tube's efficiency. However the mica itself has a limited life and the restore process was consequently difficult to control.

In 1904, Sir John Ambrose Fleming invented the thermionic diode valve (tube). Sir John Ambrose Fleming ( November 29, 1849 - April 18, 1945) was an English Electrical engineer and Physicist This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. This used a heated cathode which permitted current to flow in a vacuum. The principle was quickly applied to X-ray tubes, and hard vacuum heated cathode X-ray tubes completely solved the problem of efficiency reduction.

Two years later, physicist Charles Barkla discovered that X-rays could be scattered by gases, and that each element had a characteristic X-ray. Charles Glover Barkla ( June 27, 1877 &ndash October 23, 1944) was an English physicist. He won the 1917 Nobel Prize in Physics for this discovery. The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. Max von Laue, Paul Knipping and Walter Friedrich observed for the first time the diffraction of X-rays by crystals in 1912. Max Theodor Felix von Laue ( October 9, 1879 &ndash April 24, 1960) was a German physicist who won the Nobel Prize in Physics Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle This discovery, along with the early works of Paul Peter Ewald, William Henry Bragg and William Lawrence Bragg gave birth to the field of X-ray crystallography. Paul Peter Ewald ( January 23, 1888 in Berlin, Germany &ndash August 22, 1985 in Ithaca, New York Sir William Henry Bragg OM, KBE (2 July 1862 – 10 March 1942 was a British Physicist and Chemist who uniquely shared the Sir William Lawrence Bragg CH, FRS, ( 31 March 1890 – 1 July 1971) was an Australian Physicist Crystallography is the experimental science of determining the arrangement of Atoms in Solids In older usage it is the scientific study of Crystals The The Coolidge tube was invented the following year by William D. Coolidge which permitted continuous production of X-rays; this type of tube is still in use today. An X-ray tube is a Vacuum tube that produces X-rays They are part of X-ray machines X-rays are part of the Electromagnetic spectrum, an William David Coolidge ( October 23, 1873 &ndash February 3, 1975) was an American physicist, who made major contributions

ROSAT image of X-ray fluorescence of, and occultation of the X-ray background by, the Moon. ROSAT (short for Rö ntgen' sat' ellit was a German X-ray satellite telescope Fluorescence is a Luminescence that is mostly found as an In Shia Islam The Occultation is a term used to designate the hidden state of the Imam of the Time. The observed X-ray background is thought to result from at the "soft" end (below 0

The use of X-rays for medical purposes (to develop into the field of radiation therapy) was pioneered by Major John Hall-Edwards in Birmingham, England. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant Birmingham ( ˈbɜːmɪŋəm Ber -ming-um England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland In 1908, he had to have his left arm amputated owing to the spread of X-ray dermatitis[1].

The X-ray microscope was invented in the 1950s. An X-ray microscope uses Electromagnetic radiation in the soft X-ray band to produce images of very small objects 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. The Chandra X-ray Observatory is a Satellite launched on STS-93 by NASA on July 23, 1999. Events 1632 - Three hundred colonists bound for New France depart from Dieppe France. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Unlike visible light, which is 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 novas, neutron stars that build up layers of plasma that then explode into space. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type

An X-ray laser device was proposed as part of the Reagan administration's Strategic Defense Initiative in the 1980s, but the first and only test of the device (a sort of laser "blaster", or death ray, powered by a thermonuclear explosion) gave inconclusive results. The Strategic Defense Initiative (SDI was a proposal by US President Ronald Reagan on March 23, 1983 to use ground and space-based systems to protect The Strategic Defense Initiative (SDI was a proposal by US President Ronald Reagan on March 23, 1983 to use ground and space-based systems to protect The death ray or death beam was a theoretical Particle beam or Electromagnetic weapon of the 1920s through the 1930s that was claimed to have been invented 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). George Walker Bush ( born July 6 1946 is the forty-third and current President of the United States. National missile defense (NMD as a generic term is a type of Missile defense: a military strategy and associated systems to shield an entire country against incoming

See also

References

• NASA Goddard Space Flight centre introduction to X-rays.

External links

• X-Ray Discussion Group
• An Example of a Radiograph
• A Photograph of an X-ray Machine
• An X-ray tube demonstration (Animation)
• 1896 Article: "On a New Kind of Rays"
• X-ray Tube in Action (Animation)
• Cathode Ray Tube Collection
• X-Ray Art by Nick Veasey