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57-722: X-rays were discovered in 1895 by the German scientist Wilhelm Conrad Röntgen , who named it X-radiation to signify an unknown type of radiation. X-rays can penetrate many solid substances such as construction materials and living tissue, so X-ray radiography is widely used in medical diagnostics (e.g., checking for broken bones ) and material science (e.g., identification of some chemical elements and detecting weak points in construction materials). However X-rays are ionizing radiation and exposure can be hazardous to health, causing DNA damage, cancer and, at higher intensities, burns and radiation sickness . Their generation and use

114-455: A Ruhmkorff coil connected to a cold cathode Crookes X-ray tube . A spark gap was typically connected to the high voltage side in parallel to the tube and used for diagnostic purposes. The spark gap allowed detecting the polarity of the sparks, measuring voltage by the length of the sparks thus determining the "hardness" of the vacuum of the tube, and it provided a load in the event the X-ray tube

171-522: 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. This work was further explored by Humphry Davy and his assistant Michael Faraday . Starting in 1888, Philipp Lenard conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air. He built

228-485: A Crookes tube with a "window" at the end made of thin aluminium, facing the cathode so the cathode rays would strike it (later called a "Lenard tube"). 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. Helmholtz formulated mathematical equations for X-rays. He postulated

285-671: A cancer (then called X-ray dermatitis) sufficiently advanced by 1904 to cause him to write papers and give public addresses on the dangers of X-rays. His left arm had to be amputated at the elbow in 1908, and four fingers on his right arm soon thereafter, leaving only a thumb. He died of cancer in 1926. His left hand is kept at Birmingham University . 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. A typical early 20th-century medical X-ray system consisted of

342-597: A characteristic X-ray spectrum . He won the 1917 Nobel Prize in Physics for this discovery. 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 . In 1913 , Henry Moseley performed crystallography experiments with X-rays emanating from various metals and formulated Moseley's law which relates

399-563: A couple of minutes for a thorax. The plates may have a small addition of fluorescent salt to reduce exposure times. 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

456-487: A dispersion theory before Röntgen made his discovery and announcement. He based it on the electromagnetic theory of light . However, he did not work with actual X-rays. In early 1890, photographer William Jennings and associate professor of the University of Pennsylvania Arthur W. Goodspeed were making photographs of coins with electric sparks. On 22nd February after the end of their experiments two coins were left on

513-411: A flash of light from a fluorescent screen immediately before the covered tube he was switching on punctured. When Stanford University physics professor Fernando Sanford conducted his "electric photography" experiments in 1891-1893 by photographing coins in the light of electric sparks, like Jennings and Goodspeed, he may have unknowingly generated and detected X-rays. His letter of 6 January 1893 to

570-608: A foreword by Boulenger, was published in 1897. The first medical X-ray made in the United States was obtained using a discharge tube of Ivan Puluj '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 Puluj tube produced X-rays. This was a result of Puluj's inclusion of an oblique "target" of mica , used for holding samples of fluorescent material, within

627-444: A futile attempt to save his life; in 1904, he became the first known death attributed to X-ray exposure. During the time the fluoroscope was being developed, Serbian American physicist Mihajlo Pupin , using a calcium tungstate screen developed by Edison, found that using a fluorescent screen decreased the exposure time it took to create an X-ray for medical imaging from an hour to a few minutes. In 1901, U.S. President William McKinley

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684-491: 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. 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

741-647: A hand). Through February, there were 46 experimenters taking up the technique in North America alone. 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. On 14 February 1896, Hall-Edwards was also the first to use X-rays in a surgical operation. In early 1896, several weeks after Röntgen's discovery, Ivan Romanovich Tarkhanov irradiated frogs and insects with X-rays, concluding that

798-503: A new kind of ray: A preliminary communication" and on 28 December 1895, submitted it to Würzburg 's Physical-Medical Society journal. 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. Some early texts refer to them as Chi-rays, having interpreted "X" as the uppercase Greek letter Chi , Χ . There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this

855-493: A period of time and suffered pain, swelling, and blistering. Other effects were sometimes blamed for the damage including ultraviolet rays and (according to Tesla) ozone. Many physicians claimed there were no effects from X-ray exposure at all. On 3 August 1905, in San Francisco, California, Elizabeth Fleischman , an American X-ray pioneer, died from complications as a result of her work with X-rays. Hall-Edwards developed

912-457: A screen coated with barium platinocyanide . On 5 February 1896, live imaging devices were developed by both Italian scientist Enrico Salvioni (his "cryptoscope") and William Francis Magie of Princeton University (his "Skiascope"), both using barium platinocyanide. American inventor Thomas Edison started research soon after Röntgen's discovery and investigated materials' ability to fluoresce when exposed to X-rays, finding that calcium tungstate

969-419: A stack of photographic plates before Goodspeed demonstrated to Jennings the operation of Crookes tubes . While developing the plates, Jennings noticed disks of unknown origin on some of the plates, but nobody could explain them, and they moved on. Only in 1896 they realized that they accidentally made an X-ray photograph (they didn't claim a discovery). Also in 1890, Roentgen's assistant Ludwig Zehnder noticed

1026-464: A variety of techniques that use phase information of an X-ray beam to form the image. Due to its good sensitivity to density differences, it is especially useful for imaging 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 using different principles to convert phase variations in

1083-403: Is a likely reconstruction by his biographers: 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 (3.3 ft) away. Röntgen realized some invisible rays coming from

1140-412: Is generally greatly outweighed by the benefits of the examination. The ionizing capability of X-rays can be used in cancer treatment to kill malignant cells using radiation therapy . It is also used for material characterization using X-ray spectroscopy . Hard X-rays can traverse relatively thick objects without being much absorbed or scattered . For this reason, X-rays are widely used to image

1197-457: Is higher. The high amount of calcium ( Z = 20 {\textstyle Z=20} ) in bones, together with their high density, is what makes them show up so clearly on medical radiographs. 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

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1254-535: Is often referred to as tender X-rays . 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;

1311-492: Is strictly controlled by public health authorities. X-rays were originally noticed in science as a type of unidentified radiation emanating from discharge tubes by experimenters investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. Early researchers noticed effects that were attributable to them in many of the early Crookes tubes (invented around 1875 ). Crookes tubes created free electrons by ionization of

1368-451: 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. The probability of a photoelectric absorption per unit mass is approximately proportional to Z 3 / E 3 {\textstyle Z^{3}/E^{3}} , where Z {\textstyle Z} is the atomic number and E {\textstyle E}

1425-523: Is the energy of the incident photon. 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

1482-910: 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 . In 1894 , Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this invisible, radiant energy . After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design, as well as Crookes tubes. On 8 November 1895 , German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard tubes and Crookes tubes and began studying them. He wrote an initial report "On

1539-550: 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 defunded (though was later revived by the second Bush Administration as National Missile Defense using different technologies). Phase-contrast X-ray imaging refers to

1596-488: The attenuation length of 600 eV (~2 nm) X-rays in water is less than 1 micrometer. 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 . This definition has several problems: other processes can also generate these high-energy photons , or sometimes

1653-444: 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. In about 1906, the physicist Charles Barkla discovered that X-rays could be scattered by gases, and that each element had

1710-808: The X-rays emerging from an object into intensity variations. These include propagation-based phase contrast, Talbot interferometry, refraction-enhanced imaging, and X-ray interferometry. These methods provide higher contrast compared to normal absorption-based X-ray imaging, making it possible to distinguish from each other details that have almost similar density. 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. 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 . The intermediate range with photon energies of several keV

1767-458: The air, known as "softeners". These often took the form of a small side tube that 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. In 1904 , John Ambrose Fleming invented

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1824-474: The application so as to give sufficient transmission through the object and at the same time provide good contrast in the image. 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

1881-428: The early 1920s through to the 1950s, X-ray machines were developed to assist in the fitting of shoes and were sold to commercial shoe stores. Concerns regarding the impact of frequent or poorly controlled use were expressed in the 1950s, leading to the practice's eventual end that decade. The X-ray microscope was developed during the 1950s. The Chandra X-ray Observatory , launched on 23 July 1999 , has been allowing

1938-466: The electromagnetic radiation emitted by X-ray tubes generally has a longer wavelength and lower photon energy than the radiation emitted by radioactive nuclei . 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

1995-422: The exploration of the very violent processes in the universe that 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 . An X-ray laser device was proposed as part of

2052-516: 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. Medical science also used the motion picture to study human physiology. In 1913, a motion picture was made in Detroit showing a hard-boiled egg inside a human stomach. This early X-ray movie

2109-446: The first Nobel Prize in Physics for his discovery. Röntgen immediately noticed X-rays could have medical applications. Along with his 28 December Physical-Medical Society submission, he sent a letter to physicians he knew around Europe (1 January 1896). News (and the creation of "shadowgrams") spread rapidly with Scottish electrical engineer Alan Archibald Campbell-Swinton being the first after Röntgen to create an X-ray photograph (of

2166-538: The frequency of the X-rays to the atomic number of the metal. The Coolidge X-ray tube was invented the same year by William D. Coolidge . It made possible the continuous emissions of X-rays. Modern X-ray tubes are based on this design, often employing the use of rotating targets which allow for significantly higher heat dissipation than static targets, further allowing higher quantity X-ray output for use in high-powered applications such as rotational CT scanners. The use of X-rays for medical purposes (which developed into

2223-427: 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

2280-530: 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 m (0.1  Å ), defined as gamma radiation. 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

2337-424: 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 [1.3 cm] from the hair." Beyond burns, hair loss, and cancer, X-rays can be linked to infertility in males based on the amount of radiation used. In August 1896, H. D. Hawks,

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2394-437: The path of the bullet, and McKinley died of septic shock due to bacterial infection six days later. 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 William Lofland Dudley of Vanderbilt University reported hair loss after Dudley

2451-441: The positions of atoms in crystals . 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

2508-475: The ranges of 6–20  MeV , can in this context also be referred to as X-rays. 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 burns and radiation sickness , while lower doses can give an increased risk of radiation-induced cancer . In medical imaging, this increased cancer risk

2565-582: The rays "not only photograph, but also affect the living function". At around the same time, the zoological illustrator James Green began to use X-rays to examine fragile specimens. George Albert Boulenger first mentioned this work in a paper he delivered before the Zoological Society of London in May 1896. The book Sciagraphs of British Batrachians and Reptiles (sciagraph is an obsolete name for an X-ray photograph), by Green and James H. Gardiner, with

2622-404: 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. The earliest experimenter thought to have (unknowingly) produced X-rays was William Morgan . In 1785 , he presented

2679-405: The tube was suitable for shoulders and knees. An 18-to-23-centimeter (7 to 9 in) spark would indicate a higher vacuum suitable for imaging the abdomen of larger individuals. Since the spark gap was connected in parallel to the tube, the spark gap had to be opened until the sparking ceased to operate the tube for imaging. Exposure time for photographic plates was around half a minute for a hand to

2736-437: 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. 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

2793-699: 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. Many experimenters, including Röntgen himself in his original experiments, came up with methods to view X-ray images "live" using some form of luminescent screen. Röntgen used

2850-429: The vacant electron position and produce either a characteristic X-ray or an Auger electron . These effects can be used for elemental detection through X-ray spectroscopy or Auger electron spectroscopy . 1895 in science The year 1895 in science and technology involved some significant events, listed below. 1893#January–March 1893 ( MDCCCXCIII ) was a common year starting on Sunday of

2907-797: 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. Sensationalist reactions to the new discovery included publications linking the new kind of rays to occult and paranormal theories, such as telepathy. The name X-rays 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 , Ukrainian , Danish , Polish , Czech , Bulgarian , Swedish , Finnish , Portuguese , Estonian , Slovak , Slovenian , Turkish , Russian , Latvian , Lithuanian , Albanian , Japanese , Dutch , Georgian , Hebrew , Icelandic , and Norwegian . Röntgen received

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2964-471: 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" 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 5 centimeters (2 in) in diameter on

3021-419: Was disconnected. To detect the hardness of the tube, the spark gap was initially opened to the widest setting. While the coil was operating, the operator reduced the gap until sparks began to appear. A tube in which the spark gap began to spark at around 6.4 centimeters (2.5 in) was considered soft (low vacuum) and suitable for thin body parts such as hands and arms. A 13-centimeter (5 in) spark indicated

3078-818: Was recorded at a rate of one still image every four seconds. Dr Lewis Gregory Cole of New York was a pioneer of the technique, which he called "serial radiography". In 1918, X-rays were used in association with motion picture cameras to capture the human skeleton in motion. In 1920, it was used to record the movements of tongue and teeth in the study of languages by the Institute of Phonetics in England. 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. From

3135-596: Was shot twice in an assassination attempt while attending the Pan American Exposition in Buffalo, New York . 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 was not used. While the shooting itself had not been lethal, gangrene had developed along

3192-410: Was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death." The discovery of X-rays generated significant interest. Röntgen's biographer Otto Glasser estimated that, in 1896 alone, as many as 49 essays and 1044 articles about the new rays were published. This was probably a conservative estimate, if one considers that nearly every paper around

3249-460: Was the most effective substance. In May 1896, he developed the first mass-produced live imaging device, his "Vitascope", later called the fluoroscope , which became the standard for medical X-ray examinations. Edison dropped X-ray research around 1903, before the death of Clarence Madison Dally , one of his glassblowers. Dally had a habit of testing X-ray tubes on his own hands, developing a cancer in them so tenacious that both arms were amputated in

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