Editing X-ray (section)

==History==

=== Pre-Röntgen observations and research ===
[[File:Crookes' type discharge tubes Wellcome M0015832EA.jpg|thumb|upright|Example of a [[Crookes tube]], a type of [[discharge tube]] that emitted X-rays]]

X-rays were originally noticed in science as a type of unidentified [[radiation]] emanating from [[discharge tube]]s by experimenters investigating [[cathode ray]]s 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 tube]]s (invented around [[1875 in science|1875]]). Crookes tubes created free electrons by [[ionization]] of the residual air in the tube by a high [[Direct current|DC]] [[voltage]] of anywhere between a few [[kilovolt]]s and 100&nbsp;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.<ref>{{cite journal |doi=10.1038/npre.2009.3267.4|title=The History, Development and Impact of Computed Imaging in Neurological Diagnosis and Neurosurgery: CT, MRI, and DTI|journal=Nature Precedings|date=2009| vauthors = Filler A |doi-access=free}}</ref>

The earliest experimenter thought to have (unknowingly) produced X-rays was [[William Morgan (actuary)|William Morgan]]. In 1785, he presented a paper to the [[Royal Society of London]] describing the effects of passing [[Electric current|electrical currents]] through a partially evacuated glass tube, producing a glow created by X-rays.<ref name="Morg1785">{{cite journal |title=Electrical Experiments Made in Order to Ascertain the Non-Conducting Power of a Perfect Vacuum, &c. | vauthors = Morgan W |journal=Philosophical Transactions of the Royal Society |volume=75 |pages=272–278 |publisher=Royal Society of London  |date=24 February 1785 |url=https://archive.org/details/philtrans00580668 |doi=10.1098/rstl.1785.0014|doi-access=free }}</ref><ref>{{cite journal | vauthors = Anderson JG |title=William Morgan and X-rays |journal=Transactions of the Faculty of Actuaries |volume=17 |pages=219–221 |date =January 1945 |url = https://www.actuaries.org.uk/documents/william-morgan-and-x-rays |doi=10.1017/s0071368600003001}}</ref> This work was further explored by [[Humphry Davy]] and his assistant [[Michael Faraday]].{{cn|date=December 2024}}

Starting in 1888, Philipp Lenard conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air. He built 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.<ref name="Thomson182-186">{{cite book |last1=Thomson |first1=Joseph John |chapter=Leonard's Experiments |pages=182–186 |hdl=2027/uiug.30112112077497?urlappend=%3Bseq=196%3Bownerid=13510798903097783-200 |hdl-access=free |title=The Discharge of Electricity Through Gases |date=1900 |publisher=C. Scribner's Sons }}</ref>

Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his discovery and announcement. He based it on the [[electromagnetic theory of light]].<ref>''Wiedmann's Annalen'', Vol. XLVIII.</ref>{{Full citation needed|date=October 2021}} However, he did not work with actual X-rays.

In early 1890, photographer [[William Nicholson Jennings|William Jennings]] and associate professor of the [[University of Pennsylvania]] Arthur W. Goodspeed were making photographs of coins with electric sparks. On 22 February after the end of their experiments two coins were left on a stack of photographic plates before Goodspeed demonstrated to Jennings the operation of [[Crookes tube]]s. 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).<ref>{{cite journal |last1=Walden |first1=T L |title=The first radiation accident in America: a centennial account of the x-ray photograph made in 1890. |journal=Radiology |date=December 1991 |volume=181 |issue=3 |pages=635–639 |doi=10.1148/radiology.181.3.1947073 |pmid=1947073 }}</ref>

Also in 1890, Roentgen's assistant [[Ludwig Zehnder]] noticed a flash of light from a fluorescent screen immediately before the covered tube he was switching on punctured.<ref>{{cite journal |last1=Peh |first1=W. C. |title=Part II - Controversies Surrounding and Following Rontgen's Discovery |journal=Singapore Medical Journal |date=October 1995 |volume=36 |issue=5 |pages=554–558 |pmid=8882548 |url=http://www.smj.org.sg/sites/default/files/3605/3605hdxray1.pdf }}</ref>

When [[Stanford University]] physics professor [[Fernando Sanford]] conducted his "electric photography" experiments in 1891–1893 by photographing coins in the light of electric sparks,<ref name=":2">{{Cite book |url=https://books.google.com/books?id=pjwiKBTJsQkC&pg=PA63 |title=Illustrated Electrical Review: A Journal of Scientific and Electrical Progress |date=1894 |publisher=Electrical Review Publishing Company |language=en}}</ref> like Jennings and Goodspeed, he may have unknowingly generated and detected X-rays. His letter of [[1893#January–March|6 January 1893]] to the ''[[Physical Review]]'' was duly published<ref name=":2" /> and an article entitled ''Without Lens or Light, Photographs Taken With Plate and Object in Darkness'' appeared in the ''[[San Francisco Examiner]]''.<ref>{{Cite journal |vauthors=Wyman T |date=Spring 2005 |title=Fernando Sanford and the Discovery of X-rays |journal="Imprint", from the Associates of the Stanford University Libraries |pages=5–15}}</ref>

In [[1894 in science|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]].<ref name="Scenes from the past: Nikola Tesla">{{cite journal | vauthors = Hrabak M, Padovan RS, Kralik M, Ozretic D, Potocki K | title = Scenes from the past: Nikola Tesla and the discovery of X-rays | journal = Radiographics | volume = 28 | issue = 4 | pages = 1189–1192 | date = July 2008 | pmid = 18635636 | doi = 10.1148/rg.284075206 | doi-access = free }}</ref><ref>{{Cite book | vauthors = Chadda PK | title = Hydroenergy and Its Energy Potential | date = 2009 | publisher = Pinnacle Technology | isbn = 978-1-61820-149-2 | page = 88 }}</ref> After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design,<ref>Tesla's technical publications indicate that he invented and developed a single-electrode X-ray tube. Morton, William James and Hammer, Edwin W. (1896) ''American Technical Book Co.'', p. 68. {{US patent|514170}}, "Incandescent Electric Light". {{US patent|454622}} "System of Electric Lighting". These differed from other X-ray tubes in having no target electrode and worked with the output of a [[Tesla coil]].</ref> as well as Crookes tubes.

===Discovery by Röntgen===
[[File:WilhelmRöntgen.JPG|thumb|upright|[[Wilhelm Röntgen]]]]

On [[1895#October–December|8 November 1895]], German physics professor [[Wilhelm Röntgen]] stumbled on X-rays while experimenting with Lenard tubes and [[Crookes tube]]s and began studying them. He wrote an initial report "On a new kind of ray: A preliminary communication" and on 28 December 1895, submitted it to [[Würzburg]]'s Physical-Medical Society journal.<ref>{{Cite journal | vauthors = Stanton A |title= Wilhelm Conrad Röntgen On a New Kind of Rays: translation of a paper read before the Würzburg Physical and Medical Society, 1895 |journal= [[Nature (journal)|Nature]] |volume= 53 |issue= 1369 |pages= 274–6 |date= 23 January 1896 |doi= 10.1038/053274b0 |bibcode= 1896Natur..53R.274.|doi-access= free }} see also pp. 268 and 276 of the same issue.</ref> 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 [[Chi (letter)|Greek letter Chi]], ''Χ''.<ref>{{Cite journal |last1=Garcia |first1=J. |last2=Buchwald |first2=N. A. |last3=Feder |first3=B. H. |last4=Koelling |first4=R. A. |last5=Tedrow |first5=L. |date=1964 |title=Sensitivity of the head to X-ray |journal=Science |volume=144 |issue=3625 |pages=1470–1472 |doi=10.1126/science.144.3625.1470 |issn=0036-8075 |pmid=14171545 |bibcode=1964Sci...144.1470G |quote=Rats have been trained to respond to signals consisting of very low doses of chi-ray directed to the head.}}</ref><ref>{{Cite journal |last1=Baganha |first1=M. F. |last2=Marques |first2=M. A. |last3=Botelho |first3=M. F. |last4=Teixeira |first4=M. L. |last5=Carvalheira |first5=V. |last6=Calisto |first6=J. |last7=Silva |first7=A. |last8=Fernandes |first8=A. |last9=Torres |first9=M. |last10=Brito |first10=J. |date=1993 |title=Tomodensitometry and radioisotopic methods in the study of unilateral lung hyperlucencies of vascular origin |journal=Acta Médica Portuguesa |volume=6 |issue=1 |pages=19–24 |pmid=8475784 }}</ref><ref>{{Cite journal |last1=Takahashi |first1=K. |last2=Case |first2=B. W. |last3=Dufresne |first3=A. |last4=Fraser |first4=R. |last5=Higashi |first5=T. |last6=Siemiatycki |first6=J. |date=1994 |title=Relation between lung asbestos fibre burden and exposure indices based on job history |journal=Occupational and Environmental Medicine |volume=51 |issue=7 |pages=461–469 |doi=10.1136/oem.51.7.461 |pmc=1128015 |pmid=8044245 }}</ref>

There are conflicting accounts of his discovery because Röntgen had his [[Nachlass|lab notes]] burned after his death, but this is a likely reconstruction by his biographers:<ref>{{Cite web | vauthors = Peters P |date=1995 |title=W. C. Roentgen and the discovery of x-rays |website=Textbook of Radiology |publisher=Medcyclopedia.com, GE Healthcare |url=http://www.medcyclopaedia.com/library/radiology/chapter01.aspx |archive-url=https://archive.today/20080511205052/http://www.medcyclopaedia.com/library/radiology/chapter01.aspx |archive-date=11 May 2008 |access-date=5 May 2008 }}</ref><ref name="Glasser">{{Cite book | vauthors = Glasser O |title= Wilhelm Conrad Röntgen and the early history of the roentgen rays |publisher= Norman Publishing |date= 1993 |pages= 10–15 |url= https://books.google.com/books?id=5GJs4tyb7wEC&pg=PA10 |isbn= 978-0930405229}}</ref> 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 {{convert|1|m|ft|sp=us}} away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow. He found they could also pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper.<ref>{{cite news | vauthors = Arthur C |title=Google doodle celebrates 115 years of X-rays |url=https://www.theguardian.com/technology/blog/2010/nov/08/google-doodle-x-ray-115-year-anniversary |newspaper=The Guardian |publisher=Guardian US |access-date=5 February 2019|date=8 November 2010 }}</ref>

[[File:First medical X-ray by Wilhelm Röntgen of his wife Anna Bertha Ludwig's hand - 18951222.jpg|thumb|upright=0.9|left|''Hand mit Ringen'' (Hand with Rings): print of Wilhelm Röntgen's first "medical" X-ray, of his wife's hand, taken on 22 December 1895 and presented to [[Ludwig Zehnder]] of the Physik Institut, [[University of Freiburg]], on 1 January 1896<ref>{{Cite book | vauthors = Kevles BH |title= Naked to the Bone Medical Imaging in the Twentieth Century |publisher= [[Rutgers University Press]] |date= 1996 |location= Camden, New Jersey |pages= [https://archive.org/details/isbn_9780813523583/page/19 19–22] |isbn= 978-0-8135-2358-3 |url= https://archive.org/details/isbn_9780813523583/page/19 }}</ref><ref>{{Cite web | vauthors = Sample S |title= X-Rays |website= The Electromagnetic Spectrum |publisher= [[NASA]] |date= 27 March 2007 |url= http://science.hq.nasa.gov/kids/imagers/ems/xrays.html |access-date= 3 December 2007}}</ref>]]

Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays. The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death."<ref name="pbs">{{Cite web|url=https://www.pbs.org/newshour/health/i-have-seen-my-death-how-the-world-discovered-the-x-ray|title='I Have Seen My Death': How the World Discovered the X-Ray| vauthors = Markel H |date=20 December 2012|website=PBS NewsHour|publisher=PBS|access-date=23 March 2019}}</ref>

The discovery of X-rays generated significant interest. Röntgen's biographer [[Otto Glasser]] estimated that, in [[1896 in science|1896]] alone, as many as 49 essays and 1044 articles about the new rays were published.<ref>{{cite book |last1=Glasser |first1=Otto |title=Dr. W.C. Röntgen |date=1958 |publisher=Thomas |oclc=598678738 }}{{pn|date=April 2025}}</ref> This was probably a conservative estimate, if one considers that nearly every paper around the world extensively reported about the new discovery, with a magazine such as ''[[Science (journal)|Science]]'' dedicating as many as 23 articles to it in that year alone.<ref>{{cite journal |last1=Natale |first1=Simone |title=THE INVISIBLE MADE VISIBLE: X-rays as attraction and visual medium at the end of the nineteenth century |journal=Media History |date=November 2011 |volume=17 |issue=4 |pages=345–358 |doi=10.1080/13688804.2011.602856 |hdl=2134/19408 |hdl-access=free }}</ref> Sensationalist reactions to the new discovery included publications linking the new kind of rays to occult and paranormal theories, such as telepathy.<ref>{{Cite journal |vauthors=Natale S |date=4 August 2011 |title=A Cosmology of Invisible Fluids: Wireless, X-Rays, and Psychical Research Around 1900 |journal=Canadian Journal of Communication |volume=36 |issue=2 |pages=263–276 |doi=10.22230/cjc.2011v36n2a2368 |doi-access=free |hdl=2318/1770480 |hdl-access=free }}</ref><ref>{{cite journal | vauthors = Grove AW | title = Röntgen's ghosts: photography, X-rays, and the Victorian imagination | journal = Literature and Medicine | volume = 16 | issue = 2 | pages = 141–173 | date = 1997 | pmid = 9368224 | doi = 10.1353/lm.1997.0016 }}</ref>

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 language|German]], [[Hungarian language|Hungarian]], [[Ukrainian language|Ukrainian]], [[Danish language|Danish]], [[Polish language|Polish]], [[Czech language|Czech]], [[Bulgarian language|Bulgarian]], [[Swedish language|Swedish]], [[Finnish language|Finnish]], [[Portuguese Language|Portuguese]], [[Estonian language|Estonian]], [[Slovak language|Slovak]], [[Slovenian language|Slovenian]], [[Turkish language|Turkish]],  [[Russian language|Russian]], [[Latvian language|Latvian]], [[Lithuanian language|Lithuanian]], [[Albanian language|Albanian]], [[Japanese language|Japanese]], [[Dutch language|Dutch]], [[Georgian language|Georgian]], [[Hebrew language|Hebrew]], [[Icelandic language|Icelandic]], and [[Norwegian language|Norwegian]].{{original research inline|date=October 2024}}

Röntgen received the first [[Nobel Prize in Physics]] for his discovery.<ref>{{Cite web |url=https://www.nobelprize.org/nobel_prizes/physics/articles/karlsson/ |title=The Nobel Prizes in Physics 1901–2000 | vauthors = Karlsson EB |date=9 February 2000 |publisher=The Nobel Foundation |access-date=24 November 2011 |location=Stockholm }}</ref>

===Advances in radiology===
[[File:Crookes tube xray experiment.jpg|thumb|Taking an X-ray image with early [[Crookes tube]] apparatus, late 1800s. The Crookes tube is visible in center. The standing man is viewing his hand with a [[fluoroscope]] screen. The seated man is taking a [[radiograph]] of his hand by placing it on a [[photographic plate]]. No precautions against radiation exposure are taken; its hazards were not known at the time.]]
[[File:Professor-Karl-Gustav-Lennander-in-1897-removing-a-pistol-bullet-from-the-occipital-lobe-of-the-brain-in-a-young-man-aft.jpg|thumb|upright|Surgical removal of a bullet whose location was diagnosed with X-rays (see inset) in 1897]]

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).<ref name=Feldman1989>{{cite journal | vauthors = Feldman A | title = A sketch of the technical history of radiology from 1896 to 1920 | journal = Radiographics | volume = 9 | issue = 6 | pages = 1113–1128 | date = November 1989 | pmid = 2685937 | doi = 10.1148/radiographics.9.6.2685937 }}</ref> 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 a hand). Through February, there were 46 experimenters taking up the technique in North America alone.<ref name=Feldman1989/>

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.<ref>{{Cite web|url=http://www.birmingham.gov.uk/xray |title=Major John Hall-Edwards |access-date=2012-05-17 |publisher=Birmingham City Council |archive-url=https://web.archive.org/web/20120928204852/http://www.birmingham.gov.uk/xray |archive-date=28 September 2012 }}</ref>

[[File:James Green & James H. Gardiner - Sciagraphs of British Batrachians and Reptiles - 1897 - Ycba f6c56349-13da-4efc-a671-e40af53b0823.jpg|thumb|Images by James Green, from "Sciagraphs of British Batrachians and Reptiles" (1897), featuring (from left) ''Rana esculenta'' (now ''[[Pelophylax lessonae]]''), ''Lacerta vivipara'' (now ''[[Zootoca vivipara]]''), and ''[[Lacerta agilis]]'']]

In early 1896, several weeks after Röntgen's discovery, [[Ivan Romanovich Tarkhanov]] irradiated frogs and insects with X-rays, concluding that the rays "not only photograph, but also affect the living function".<ref>{{cite book |last1=Kudryashov |first1=Yurii Borisovich |title=Radiation Biophysics (ionizing Radiations) |date=2008 |publisher=Nova Publishers |isbn=978-1-60021-280-2 |page=xxi }}</ref> 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 a foreword by Boulenger, was published in 1897.<ref Name="YCBA">{{Cite web |title=Green, James (Zoological Artist), Sciagraphs of British batrachians and reptiles, 1897 |url=https://collections.britishart.yale.edu/catalog/orbis:12428971 |publisher=Yale Centre for British Art |access-date=24 November 2021}}</ref><ref>{{cite journal |title=Sciagraphs of British Batrachians and Reptiles1 |journal=Nature |date=1 April 1897 |volume=55 |issue=1432 |pages=539–540 |doi=10.1038/055539a0 |bibcode=1897Natur..55..539. |doi-access=free }}</ref>

The first medical X-ray made in the United States was obtained using a discharge tube of [[Ivan Puluj]]'s design.<ref>{{cite journal |last1=Mayba |first1=Ihor I. |last2=Gaiua |first2=Roman |last3=Kyle |first3=Robert A. |last4=Shampo |first4=Marc A. |title=Ukrainian Physicist Contributes to the Discovery of X-Rays |journal=Mayo Clinic Proceedings |date=July 1997 |volume=72 |issue=7 |pages=658 |doi=10.1016/S0025-6196(11)63573-8 |pmid=9212769 }}</ref> 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 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 [[photographic plate|gelatin photographic plates]] obtained from Howard Langill, a local photographer also interested in Röntgen's work.<ref name= PKS>{{cite journal | vauthors = Spiegel PK | title = The first clinical X-ray made in America—100 years | journal = AJR. American Journal of Roentgenology | volume = 164 | issue = 1 | pages = 241–243 | date = January 1995 | pmid = 7998549 | doi = 10.2214/ajr.164.1.7998549 | doi-access = free }}</ref>

[[File:X-ray 1896 nouvelle iconographie de salpetriere.jpg|thumb|left|1896 plaque published in ''"Nouvelle Iconographie de la Salpetrière"'', a medical journal. In the left a hand deformity, in the right same hand seen using [[radiography]]. The authors named the technique ''Röntgen photography''.]]

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.<ref name=Feldman1989/> Röntgen used 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]] was the most effective substance. In May 1896, he developed the first mass-produced live imaging device, his "Vitascope", later called the [[fluoroscopy|fluoroscope]], which became the standard for medical X-ray examinations.<ref name=Feldman1989/> 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 [[amputation|amputated]] in a futile attempt to save his life; in 1904, he became the first known death attributed to X-ray exposure.<ref name=Feldman1989/> 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.<ref>Nicolaas A. Rupke, ''Eminent Lives in Twentieth-Century Science and Religion'', page 300, Peter Lang, 2009 {{ISBN|3631581203}}</ref><ref name=Feldman1989/>

In 1901, [[assassination of William McKinley|U.S. President William McKinley was shot twice]] in an assassination attempt while attending the [[Pan-American Exposition|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 generator|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 the path of the bullet, and McKinley died of [[septic shock]] due to bacterial infection six days later.<ref>{{Cite web|title=Visible Proofs: Forensic Views of the Body: Galleries: Cases: Could X-rays Have Saved President William McKinley?|url=https://www.nlm.nih.gov/exhibition/visibleproofs/galleries/cases/mckinley.html|access-date=2022-01-24|website=NLM.NIH.gov}}</ref>

===Hazards discovered===
With the widespread experimentation with X‑rays after their discovery in [[1895 in science|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 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"<ref>{{cite journal | vauthors = Daniel J | title = THE X-RAYS | journal = Science | volume = 3 | issue = 67 | pages = 562–563 | date = April 1896 | pmid = 17779817 | doi = 10.1126/science.3.67.562 | bibcode = 1896Sci.....3..562D | url = https://zenodo.org/record/1448086 }}</ref><ref>{{Cite book |title=The South in the Building of the Nation: Biography A-J | vauthors = Fleming WL |page=300 |publisher=Pelican Publishing |isbn=978-1589809468|date=1909 }}</ref><ref>{{Cite book |url=https://books.google.com/books?id=IioKBAAAQBAJ&pg=PA174 |title=Understanding Ionizing Radiation and Protection |date=Mar 2014 |page=174|author1=Ce4Rt }}</ref> volunteered. Daniel reported that 21 days after taking a picture of Dudley's [[human skull|skull]] (with an exposure time of one hour), he noticed a bald spot {{convert|2|in|cm|sp=us|order=flip|0}} in diameter on the part of his head nearest the X-ray tube: "A plate holder with the plates towards the side of the skull was fastened and a [[coin]] placed between the skull and the head. The tube was fastened at the other side at a distance of one-half-inch [{{convert|.5|in|cm|disp=out}}] from the hair."<ref>{{Cite book |url=https://books.google.com/books?id=5GJs4tyb7wEC&pg=PA294|title=Wilhelm Conrad Röntgen and the Early History of the Roentgen Rays | vauthors = Glasser O |page=294 |date=1934 |publisher=Norman Publishing |isbn=978-0930405229}}</ref> Beyond burns, hair loss, and cancer, X-rays can be linked to infertility in males based on the amount of radiation used.{{cn|date=December 2024}}

In August 1896, H. D. Hawks, a graduate of Columbia College, suffered severe hand and chest burns from an X-ray demonstration. It was reported in ''Electrical Review'' and led to many other reports of problems associated with X-rays being sent in to the publication.<ref>{{cite journal | vauthors = Sansare K, Khanna V, Karjodkar F | title = Early victims of X-rays: a tribute and current perception | journal = Dento Maxillo Facial Radiology | volume = 40 | issue = 2 | pages = 123–125 | date = February 2011 | pmid = 21239576 | pmc = 3520298 | doi = 10.1259/dmfr/73488299 }}</ref> Many experimenters including [[Elihu Thomson]] at Edison's lab, [[William J. Morton]], and [[Nikola Tesla]] also reported burns. Elihu Thomson deliberately exposed a finger to an X-ray tube over a period of time and suffered pain, swelling, and blistering.<ref name="physics.isu.edu">{{Cite web|title=ISU Health Physics Radinf – First 50 Years|url=https://sites.google.com/isu.edu/health-physics-radinf/history-of-radiation-and-radiation-protection/first-50-years|access-date=2022-01-24|website=Sites.Google.com }}</ref> Other effects were sometimes blamed for the damage including ultraviolet rays and (according to Tesla) ozone.<ref name="Scenes from the past: Nikola Tesla" /> Many physicians claimed there were no effects from X-ray exposure at all.<ref name="physics.isu.edu" /> 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.<ref>California, San Francisco Area Funeral Home Records, 1835–1979. Database with images. FamilySearch. Jacob Fleischman in the entry for Elizabeth Aschheim. 3 August 1905. Citing funeral home J.S. Godeau, San Francisco, San Francisco, California. Record book Vol. 06, p. 1–400, 1904–1906. San Francisco Public Library. San Francisco History and Archive Center.</ref><ref>Editor. (5 August 1905). Aschheim. Obituaries. ''San Francisco Examiner''. San Francisco, California.</ref><ref>Editor. (5 August 1905). Obituary Notice. Elizabeth Fleischmann. ''San Francisco Chronicle''. Page 10.</ref>

Hall-Edwards developed 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,<ref name="BirminghamCouncil">{{cite web |title=Major John Hall-Edwards |url=http://www.birmingham.gov.uk/xray |publisher=Birmingham City Council |access-date=23 April 2010 |archive-url=https://web.archive.org/web/20120928204852/http://www.birmingham.gov.uk/xray |archive-date=28 September 2012}}</ref><ref>{{Cite web |date=15 June 2018 |title=JOHN HALL-EDWARDS |url=https://engole.info/john-hall-edwards/ |access-date=2023-10-27 |website=Engole the Elven for Knowledge}}</ref> 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]].{{cn|date=December 2024}}

===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}}