Editing X-ray (section)

===20th century and beyond===
[[File:Historical X-ray nci-vol-1893-300.jpg|thumb|A patient being examined with a thoracic [[fluoroscope]] in [[1940 in science|1940]], which displayed continuous moving images. This image was used to argue that [[ionizing radiation|radiation exposure]] during the X-ray procedure would be negligible.]]

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.<ref>{{Cite web |title=National Museum of Health and Medicine (NMHM): Discovery of the X-ray: A New Kind of Invisible Light: Röntgen and the Discovery |url=https://medicalmuseum.health.mil/index.cfm?p=visit.exhibits.virtual.xraydiscovery.index |access-date=2025-03-06 |website=medicalmuseum.health.mil}}</ref>

A typical early 20th-century medical X-ray system consisted of a [[Induction coil|Ruhmkorff coil]] connected to a [[X-ray tube#Crookes tube (cold cathode tube)|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.<ref name="Scha1905">{{cite book |title=Electro-medical Instruments and their Management | vauthors = Schall K |publisher=Bemrose & Sons Ltd. Printers |date=1905 |pages=[https://archive.org/details/electromedicali00ltdgoog/page/n106 96], 107 |url=https://archive.org/details/electromedicali00ltdgoog}}</ref> 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 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 {{convert|2.5|in|cm|sp=us|order=flip}} was considered soft (low vacuum) and suitable for thin body parts such as hands and arms. A {{convert|5|in|cm|sp=us|adj=on|order=flip}} spark indicated the tube was suitable for shoulders and knees. An {{convert|7|to|9|in|cm|sp=us|adj=on|order=flip}} 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 a couple of minutes for a thorax. The plates may have a small addition of fluorescent salt to reduce exposure times.<ref name="Scha1905" />

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 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.{{cn|date=December 2024}}

In [[1904 in science|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.{{cn|date=December 2024}}

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 in science|1917]] [[Nobel Prize in Physics]] for this discovery.<ref>{{Cite web |title=Nobel Prize in Physics 1917 |url=https://www.nobelprize.org/prizes/physics/1917/barkla/facts/ |access-date=2025-02-02 |website=NobelPrize.org |language=en-US}}</ref>

In [[1912 in science|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]].<ref name="Stoddart">{{cite journal |last1=Stoddart |first1=Charlotte |title=Structural biology: How proteins got their close-up |journal=Knowable Magazine |date=March 2022 |doi=10.1146/knowable-022822-1 |doi-access=free }}</ref>

In [[1913 in science|1913]], [[Henry Moseley]] performed crystallography experiments with X-rays emanating from various metals and formulated [[Moseley's law]] which relates the frequency of the X-rays to the atomic number of the metal.<ref>{{cite journal |last1=Soltis |first1=Tomas |last2=Folan |first2=Lorcan M. |last3=Eltareb |first3=Waleed |title=One hundred years of Moseley's law: An undergraduate experiment with relativistic effects |journal=American Journal of Physics |date=May 2017 |volume=85 |issue=5 |pages=352–358 |doi=10.1119/1.4977793 |bibcode=2017AmJPh..85..352S }}</ref>

The [[X-ray tube#Coolidge tube (hot cathode tube)|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.{{cn|date=December 2024}}

[[File:Abell 2125.jpg|thumb|upright=0.8|left|Chandra's image of the galaxy cluster Abell 2125 reveals a complex of several massive multimillion-degree-Celsius gas clouds in the process of merging.]]

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|Birmingham]], England. Then in 1908, he had to have his left arm amputated because of the spread of [[radiation dermatitis|X-ray dermatitis]] on his arm.<ref>Birmingham City Council: [http://www.birmingham.gov.uk/xray Major John Hall-Edwards] {{webarchive |url=https://web.archive.org/web/20120928204852/http://www.birmingham.gov.uk/xray |date=28 September 2012 }}</ref>

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 was recorded at a rate of one still image every four seconds.<ref>{{Cite news|date=4 April 1913|title=X-ray movies show hard boiled egg fighting digestive organs (1913)|pages=2|work=The News-Palladium|url=https://www.newspapers.com/clip/64031702/x-ray-movies-show-hard-boiled-egg/|access-date=2020-11-26}}</ref> Dr Lewis Gregory Cole of New York was a pioneer of the technique, which he called "serial radiography".<ref>{{Cite news|date=22 June 1913|title=X-ray moving pictures latest (1913)|pages=32|work=Chicago Tribune|url=https://www.newspapers.com/clip/64031812/x-ray-moving-pictures-latest-1913/|access-date=2020-11-26}}</ref><ref>{{Cite news|date=10 May 1915|title=Homeopaths to show movies of body's organs at work (1915)|pages=6|work=The Central New Jersey Home News|url=https://www.newspapers.com/clip/64031868/homeopaths-to-show-movies-of-bodys/|access-date=2020-11-26}}</ref> In 1918, X-rays were used in association with [[Movie camera|motion picture cameras]] to capture the human skeleton in motion.<ref>{{Cite news|date=15 March 1918|title=How X-Ray Movies Are Taken (1918)|pages=2|work=Davis County Clipper|url=https://www.newspapers.com/clip/64031520/how-x-ray-movies-are-taken-1918/|access-date=2020-11-26}}</ref><ref>{{Cite news|date=12 January 1919|title=X-ray movies (1919)|pages=16|work=Tampa Bay Times|url=https://www.newspapers.com/clip/64031338/x-ray-movies-1919/|access-date=2020-11-26}}</ref><ref>{{Cite news|date=7 January 1918|title=X-ray movies perfected. Will show motions of bones and joints of human body. (1918)|pages=7|work=The Sun|url=https://www.newspapers.com/clip/64031941/x-ray-movies-perfected-will-show/|access-date=2020-11-26}}</ref> 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.<ref>{{Cite news|date=2 January 1920|title=Talk is cheap? X-ray used by Institute of Phonetics (1920)|pages=13|work=New Castle Herald|url=https://www.newspapers.com/clip/64031597/talk-is-cheap-x-ray-used-by-institute/|access-date=2020-11-26}}</ref>

In [[1914 in science|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.<ref>{{Cite web|url=http://theconversation.com/marie-curie-and-her-x-ray-vehicles-contribution-to-world-war-i-battlefield-medicine-83941|title=Marie Curie and her X-ray vehicles' contribution to World War I battlefield medicine| vauthors = Jorgensen TJ |date=10 October 2017|website=The Conversation|access-date=23 February 2018}}</ref>

From the early 1920s through to the 1950s, X-ray machines were developed to assist in the fitting of shoes<ref>{{Cite news|date=25 August 1921|title=X-Rays for Fitting Boots.|pages=4|work=Warwick Daily News (Qld.: 1919–1954)|url=http://nla.gov.au/nla.news-article177254793|access-date=2020-11-27}}</ref> and were sold to commercial shoe stores.<ref>{{Cite news|url=http://nla.gov.au/nla.news-article177100333|title=T. C. BEIRNE'S X-RAY SHOE FITTING|date=17 July 1925|work=Telegraph (Brisbane, Qld. : 1872–1947)|access-date=2017-11-05|pages=8}}</ref><ref>{{Cite news|url=http://nla.gov.au/nla.news-article58359293|title=THE PEDOSCOPE|date=15 July 1928|work=Sunday Times (Perth, WA : 1902–1954)|access-date=2017-11-05|pages=5}}</ref><ref>{{Cite news|url=http://nla.gov.au/nla.news-article195854195|title=X-RAY SHOE FITTINGS|date=27 July 1955|work=Biz (Fairfield, NSW : 1928–1972)|access-date=2017-11-05|pages=10}}</ref> Concerns regarding the impact of frequent or poorly controlled use were expressed in the 1950s,<ref>{{Cite news|url=http://nla.gov.au/nla.news-article212595591|title=SHOE X-RAY DANGERS|date=28 February 1951|work=Brisbane Telegraph (Qld. : 1948–1954)|access-date=2017-11-05|pages=7}}</ref><ref>{{Cite news|url=http://nla.gov.au/nla.news-article130371085|title=X-ray shoe sets in S.A. 'controlled'|date=27 April 1951|work=News (Adelaide, SA : 1923–1954)|access-date=2017-11-05|pages=12}}</ref> leading to the practice's eventual end that decade.<ref>{{Cite news|url=http://nla.gov.au/nla.news-article91592036|title=Ban On Shoe X-ray Machines Resented|date=26 June 1957|work=Canberra Times (ACT : 1926–1995)|access-date=2017-11-05|pages=4}}</ref>

The [[X-ray microscope]] was developed during the late 1940s and early 1950s.<ref>{{Cite web |title=X-ray microscope {{!}} High-Resolution, Non-Destructive, Imaging {{!}} Britannica |url=https://www.britannica.com/technology/X-ray-microscope |access-date=2025-02-17 |website=www.britannica.com |language=en}}</ref><ref>{{Cite web |date=2020-10-17 |title=Albert Baez Page of the NSHP |url=http://www.hispanicphysicists.org/recognition/bio(baez).html |access-date=2025-02-17 |archive-url=https://web.archive.org/web/20201017111846/http://www.hispanicphysicists.org/recognition/bio(baez).html |archive-date=17 October 2020 }}</ref><ref>{{Cite web |last=Aksnes |first=Ingrid |date=2020-11-08 |title=History of X-rays - 125 years in the making (pt 1) |url=https://www.excillum.com/history-of-x-rays-early-years/#:~:text=Outside%20of%20medical%20applications,%20another,the%20object%20at%20the%20detector. |access-date=2025-02-17 |website=Excillum |language=en-US}}</ref>

The [[Chandra X-ray Observatory]], launched on [[1999#July|23 July 1999]], has been allowing the exploration of the very violent processes in the [[universe]] that produce X-rays. Unlike [[Light|visible light]], which gives a relatively stable view of the universe, the X-ray universe is unstable. It features [[star]]s being torn apart by [[black hole]]s, [[Interacting galaxy|galactic collisions]], and [[nova]]e, and [[neutron star]]s that build up layers of [[Plasma (physics)|plasma]] that then [[Explosion|explode]] into [[Outer space|space]].{{cn|date=December 2024}}

[[File:Phase-contrast x-ray image of spider.jpg|thumb|upright=0.8|Phase-contrast X-ray image of a spider]]
An [[X-ray laser]] device was proposed as part of the [[presidency of Ronald Reagan|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 [[presidency of George W. Bush|Bush Administration]] as [[National Missile Defense]] using different technologies).{{cn|date=December 2024}}

[[Phase-contrast X-ray imaging]] refers to 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 the X-rays emerging from an object into intensity variations.<ref>{{Cite journal | vauthors = Fitzgerald R |title= Phase-sensitive x-ray imaging |date= 2000 |journal= Physics Today |volume= 53 |issue= 7 |pages= 23–26 |doi= 10.1063/1.1292471 |bibcode= 2000PhT....53g..23F |doi-access= free }}</ref><ref name=David>{{Cite journal |vauthors = David C, Nöhammer B, Solak H, Ziegler |title= Differential x-ray phase contrast imaging using a shearing interferometer |journal= Applied Physics Letters |date= 2002 |volume= 81 |issue= 17 |pages= 3287–3289 |doi= 10.1063/1.1516611 |bibcode= 2002ApPhL..81.3287D|doi-access= free }}</ref> These include propagation-based phase contrast,<ref>{{Cite journal | vauthors =Wilkins SW, Gureyev TE, Gao D, Pogany A, Stevenson AW |date= 1996 |title= Phase-contrast imaging using polychromatic hard X-rays |journal= Nature |volume= 384 |pages= 335–338 |doi= 10.1038/384335a0 |bibcode= 1996Natur.384..335W |issue= 6607 }}</ref> [[Talbot effect|Talbot]] interferometry,<ref name=David/> refraction-enhanced imaging,<ref>{{Cite journal | vauthors = Davis TJ, Gao D, Gureyev TE, Stevenson AW, Wilkins SW |date= 1995 |title= Phase-contrast imaging of weakly absorbing materials using hard X-rays |journal= Nature |volume= 373 |pages= 595–598 |doi= 10.1038/373595a0 |bibcode= 1995Natur.373..595D |issue= 6515 }}</ref> and X-ray interferometry.<ref>{{cite journal | vauthors = Momose A, Takeda T, Itai Y, Hirano K | title = Phase-contrast X-ray computed tomography for observing biological soft tissues | journal = Nature Medicine | volume = 2 | issue = 4 | pages = 473–475 | date = April 1996 | pmid = 8597962 | doi = 10.1038/nm0496-473 }}</ref> 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 [[X-ray tube#Microfocus X-ray tube|microfocus]] X-ray sources, [[X-ray optics]], and high resolution X-ray detectors.{{cn|date=December 2024}}