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1895: X-strale ontdek


Op 8 November 1895 het William Röntgen 'n ontdekking gemaak wat 'n rewolusie in fisika en medisyne sou veroorsaak.

Destyds werk Röntgen aan die Universiteit van Würzburg. Sy eksperimente het gefokus op die lig wat uit 'Crookes -buise' gestuur word, glasbuise met die lug wat daaruit gedryf word en met elektrodes. As 'n hoë elektriese spanning deur die buis gestuur word, is die resultaat 'n groen fluoresserende lig. Röntgen besef dat toe hy 'n stuk dik swart kaart om die buis draai, 'n groen gloed op 'n oppervlak 'n paar meter verder verskyn. Hy het tot die gevolgtrekking gekom dat die gloed veroorsaak word deur onsigbare strale wat die kaart kan binnedring.

Dan besoek die Bodleian -biblioteek in Oxford, met een en 'n kwart miljoen historiese kaarte. Onder die hulp van professor Jerry Brotton bespreek hulle saam die belangrikheid van antieke kartografie en kyk hulle na sommige van die juwele van die versameling.

Kyk nou

In die komende weke het Röntgen voortgegaan om met sy nuwe strale te eksperimenteer. Hy het besef dat hulle deur ander stowwe as papier kon gaan. Trouens, hulle kon deur die sagte weefsels van die liggaam gaan en beelde van die bene en metaal skep. Tydens sy eksperimente het hy 'n beeld gemaak van sy vrou se hand wat haar trouring gedra het.

kommer oor X-straalbrille het gelei tot die vervaardiging van loodonderklere

Die nuus oor die ontdekking van Röntgen het wêreldwyd versprei en die mediese gemeenskap het vinnig besef dat dit 'n groot deurbraak was. Binne 'n jaar is die nuwe X-straal gebruik vir die diagnose en behandeling. Dit sou egter baie langer neem voordat die wetenskaplike gemeenskap die skade wat bestraling aangerig het, begryp.

Die röntgenfoto het ook die publiek se verbeelding aangegryp. Mense het in die tou gestaan ​​om 'beenportrette' te laat neem en kommer oor X-straalbrille het gelei tot die vervaardiging van loodonderklere om beskeidenheid te beskerm.

Die kurator van die Britse museum, St John Simpson, praat oor die Sasaniese ryk, die Silk Road en nuwe argeologiese bewyse vir handel en beweging oor die grense van die laat oudheid.

Kyk nou

In 1901 ontvang Röntgen die eerste romanprys in fisika. Hy het die geld van die Nobelprys aan die Universiteit van Würzburg geskenk en nooit patente op sy werk aangeneem om dit wêreldwyd te gebruik nie.


Wilhelm Conrad Röntgen

Ons redakteurs gaan na wat u ingedien het, en bepaal of hulle die artikel moet hersien.

Wilhelm Conrad Röntgen, Röntgen ook gespel Roentgen, (gebore 27 Maart 1845, Lennep, Pruise [nou Remscheid, Duitsland] - oorlede op 10 Februarie 1923, München, Duitsland), fisikus wat in 1901 die eerste Nobelprys vir Fisika ontvang het vir sy ontdekking van X -strale, wat die tydperk van die moderne fisika bekend gemaak het en 'n omwenteling in diagnostiese medisyne gemaak het.

Röntgen studeer aan die Polytechnic in Zürich en was daarna professor in fisika aan die universiteite van Straatsburg (1876–79), Giessen (1879–88), Würzburg (1888–1900) en München (1900–20). Sy navorsing bevat ook werk oor elastisiteit, kapillêre werking van vloeistowwe, spesifieke verhitting van gasse, geleiding van hitte in kristalle, opname van hitte deur gasse en piëzo -elektrisiteit.

In 1895, terwyl hy met elektriese stroomvloei in 'n gedeeltelik ontruimde glasbuis (katodestraalbuis) eksperimenteer, het Röntgen opgemerk dat 'n nabygeleë stuk barium platinosianied lig afgee wanneer die buis in werking was. Hy het aangevoer dat toe die katodestrale (elektrone) die glaswand van die buis tref, onbekende straling gevorm word wat deur die kamer beweeg, die chemikalie tref en die fluoressensie veroorsaak. Verdere ondersoek het aan die lig gebring dat papier, hout en aluminium onder andere deursigtig is vir hierdie nuwe vorm van bestraling. Hy het gevind dat dit fotografiese plate beïnvloed, en omdat dit geen merkbare eienskappe van lig, soos weerkaatsing of breking, vertoon het nie, het hy verkeerdelik gedink dat die strale nie met lig verband hou nie. Vanweë die onsekerheid daarvan noem hy die verskynsel X-straling, hoewel dit ook bekend staan ​​as Röntgen-bestraling. Hy het die eerste röntgenfoto's geneem, van die binnekant van metaalvoorwerpe en van die bene in die hand van sy vrou.

Hierdie artikel is die laaste hersien en bygewerk deur Amy Tikkanen, bestuurder van korreksies.


X-strale: die grondslag van moderne radiologie, 1896-1930

Die skrywers beskryf die aanvanklike impak en verreikende gevolge van die ontdekking van x-strale in 1895. Roentgen besef vinnig die belangrikheid van hierdie geheimsinnige nuwe soort straal wat hy ontdek het. Reeds in 1896 word x-strale reeds in chirurgie en medisyne gebruik, wat Bell se telefoniese naaldsonde vervang het, wat slegs metaalvoorwerpe met klank kon opspoor en dus beperk was tot die ligging van voorwerpe soos koeëls om te verwyder. Namate die röntgendiagnose meer akkuraat geword het, is radiologiese tegnieke oor die jare geleidelik verbeter en gevorder vanaf die ondersoek van die skelet tot die beelding van komplekse interne organe. Die x-straal het noodsaaklik geword in die opsporing van tuberkulose, waarvoor dit vandag nog gebruik word. Deur die gebruik van ondeursigtige stowwe, soos bariumsulfaat, is dit moontlik om die spysverteringskanaal te visualiseer, en later het fotografiese tegnieke die brein en byna alle dele van die liggaam sigbaar gemaak. Intussen is die gevare van bestraling erken en na 1930 is veiligheidsmaatreëls ingestel om radioloë en pasiënte teen oormatige blootstelling te beskerm. In die honderd jaar sedert sy ontdekking, het die steeds groter wordende omvang van radiologie dit 'n fundamentele bron gemaak in mediese diagnose en behandeling.


Geskiedenis van medisyne: Dr. Roentgen se toevallige x-strale

In die huidige wêreld bestel dokters X-strale om allerhande probleme te diagnoseer: 'n gebreekte been, longontsteking, hartversaking en nog baie meer. Mammografie, die standaard siftingsmetode vir borskanker, gebruik X-strale. Ons dink skaars daaroor, dit is so oral. Maar nie so lank gelede kon 'n gebreekte been, 'n gewas of 'n ingeslukte voorwerp nie gevind word sonder om 'n persoon oop te sny nie.

Wilhelm Roentgen, professor in fisika in Wurzburg, Beiere, het in 1895-per ongeluk-X-strale ontdek terwyl hy getoets het of katodestrale deur glas kan gaan. Sy katodebuis was bedek met swaar swart papier, so hy was verbaas toe 'n gloeiende groen lig tog ontsnap en op 'n nabygeleë fluorescerende skerm uitsteek. Deur eksperimentering het hy gevind dat die geheimsinnige lig deur die meeste stowwe sou gaan, maar dat daar skaduwees van vaste voorwerpe sou bly. Omdat hy nie geweet het wat die strale is nie, noem hy dit 'X', wat 'onbekende' strale beteken.

Roentgen het vinnig gevind dat X-strale ook deur menslike weefsel sou gaan, wat die bene en weefsel daaronder sigbaar maak. Die nuus van sy ontdekking het wêreldwyd versprei, en binne 'n jaar het dokters in Europa en die Verenigde State X-strale gebruik om skote, beenbreuke, nierstene en ingeslukte voorwerpe op te spoor. Eerbewyse vir sy werk het ingestroom-insluitend die eerste Nobelprys vir fisika in 1901.

Die kliniese gebruik van die X-straal het floreer, met min agting vir moontlike newe-effekte van blootstelling aan bestraling. Daar was 'n paar vroeë vermoedens van wetenskaplikes, waaronder Thomas Edison, Nikola Tesla en William J. Morton, wat elkeen beserings aangemeld het wat hulle vermoed het as gevolg van eksperimente met X-strale. Maar oor die algemeen was vroeë gebruik van X-strale wydverspreid en onbeperk, selfs in die mate dat skoenwinkels gedurende die 1930's en 1940's gratis X-strale aangebied het sodat kliënte die bene in hul voete kon sien.

Ons het nou 'n baie beter begrip van die risiko's verbonde aan röntgenstraling en het protokolle ontwikkel om onnodige blootstelling aansienlik te verminder. En hoewel X -strale 'n hoeksteen van die moderne medisyne bly, het hul ontdekking die weg gebaan vir die ontwikkeling van die huidige wye spektrum van beeldtegnieke, insluitend magnetiese resonansie beelding (MRI), rekenaartomografie (CT), ultraklank, eggokardiografie en vele ander - - sommige vermy die gebruik van bestraling heeltemal. Nie 'n slegte erfenis vir 'n toevallige ontdekking nie.


'N Wekroep …

Interessant genoeg was dit nie die x-straal wat die feit bekend gemaak het dat ioniserende bestraling nie iets was om mee te speel nie. Dit was eerder die ongelukke van die soortgelyke nuutheid van die tyd, Radium, wat die meeste nonsens beëindig het.

Radium is 'n element wat groot hoeveelhede alfa-deeltjies en gammastrale afgee wat, soos x-strale, die vermoë het om enige kwaal te genees. As sodanig is dit bygevoeg tot alles van polsbandjies tot drinkwater en is dit deur die publiek gekoop in hul massas.

Omstreeks 1917 werk duisende vroue in winkels om die horlosies van horlosies te verf met 'n radiumbevattende, ligte verf. Ideaal gesproke sou dit niks besonders gewees het nie, maar ongelukkig verloor kwaste hul vorm na 'n paar houe. Om hulle skerp te hou, sou vroue hul mond gebruik om hul vorm aan te pas.

Baie vroue sterf uiteindelik aan radiumkaak, 'n been siekte wat dikwels daartoe lei dat die kakebeen letterlik afval. Dit, tesame met die dood van die sosiale persoon Eben Byers, het uiteindelik die publiek laat weet, groot hoeveelhede bestraling is gevaarlik.


Wilhelm Conrad Röntgen neem die eerste röntgenfoto

Op 8 November 1895 het Wilhelm Conrad Röntgen (per ongeluk) 'n beeld ontdek wat uit sy katodestraalgenerator gegiet is, wat ver buite die moontlike omvang van die katodestrale (nou bekend as 'n elektronstraal) geprojekteer is. Verdere ondersoek het getoon dat die strale gegenereer is by die kontakpunt van die katodestraalbalk aan die binnekant van die vakuumbuis, dat dit nie deur magnetiese velde afgebuig is nie en dat dit baie soorte materie binnegedring het.

'N Week na sy ontdekking het Rontgen 'n x-straalfoto van sy vrou se hand geneem wat haar trouring en haar bene duidelik onthul het. Die foto het die algemene publiek geëlektrifiseer en groot wetenskaplike belangstelling vir die nuwe vorm van bestraling gewek. Röntgen noem die nuwe vorm van bestraling x-straling (X staan ​​vir "Onbekend"). Vandaar die term x-strale (ook bekend as Röntgen strale, hoewel hierdie term buiten Duitsland buitengewoon is).


Inhoud

Waarnemings en navorsing voor Röntgen Bewerk

Voordat hulle in 1895 ontdek is, was X-strale slegs 'n soort ongeïdentifiseerde straling wat afkomstig is van eksperimentele afvoerbuise. Dit is opgemerk deur wetenskaplikes wat katodestrale ondersoek wat deur sulke buise vervaardig word, wat energieke elektronstrale is wat die eerste keer in 1869 waargeneem is. aan hulle, soos hieronder uiteengesit. Crookes -buise het gratis elektrone geskep deur die oorblywende lug in die buis te ioniseer deur 'n hoë DC spanning tussen 'n paar kilovolt en 100 kV. Hierdie spanning het die elektrone wat van die katode af kom, versnel tot 'n hoë snelheid wat hulle X-strale gemaak het toe hulle die anode of die glaswand van die buis getref het. [4]

Die eerste eksperimenteerder wat vermoedelik (onwetend) X-strale gemaak het, was die aktuaris William Morgan. In 1785 het hy 'n referaat aan die Royal Society of London voorgelê waarin die gevolge beskryf word van die deurlaat van elektriese strome deur 'n gedeeltelik ontruimde glasbuis, wat 'n gloed veroorsaak deur röntgenstrale. [5] [6] Hierdie werk is verder ondersoek deur Humphry Davy en sy assistent Michael Faraday.

Toe Fernando Sanford, professor in fisika by die Stanford-universiteit, sy "elektriese fotografie" skep, het hy ook onbewustelik X-strale gemaak en opgespoor. Van 1886 tot 1888 het hy in die Hermann Helmholtz -laboratorium in Berlyn gestudeer, waar hy kennis gemaak het met die katodestrale wat in vakuumbuise gegenereer is toe 'n spanning oor afsonderlike elektrodes aangewend is, soos voorheen bestudeer deur Heinrich Hertz en Philipp Lenard. Sy brief van 6 Januarie 1893 (beskryf sy ontdekking as 'elektriese fotografie') aan The Physical Review is behoorlik gepubliseer en 'n artikel getiteld Sonder lens of lig, foto's geneem met plaat en voorwerp in duisternis verskyn in die San Francisco Examiner. [7]

Vanaf 1888 het Philipp Lenard eksperimente uitgevoer om te sien of katodestrale uit die Crookes -buis in die lug kan beweeg. Hy bou 'n Crookes -buis met 'n "venster" aan die einde van dun aluminium, wat na die katode kyk, sodat die katodestrale dit sou tref (later 'Lenard -buis' genoem). Hy het agtergekom dat iets deurgekom het, wat fotografiese plate blootstel en fluoressensie veroorsaak. Hy het die indringende krag van hierdie strale deur verskillende materiale gemeet. Daar word voorgestel dat ten minste sommige van hierdie "Lenard-strale" eintlik X-strale was. [8]

In 1889, gebore in Oekraïne, Ivan Puluj, 'n dosent in eksperimentele fisika aan die Polytechnic in Praag, wat sedert 1877 verskillende ontwerpe van gasgevulde buise gebou het om hul eienskappe te ondersoek, 'n referaat gepubliseer oor hoe verseëlde fotografiese plate donker geword het toe dit blootgestel was aan die emanasies uit die buise. [9]

Hermann von Helmholtz het wiskundige vergelykings vir X-strale geformuleer. Hy het 'n verspreidingsteorie gepostuleer voordat Röntgen sy ontdekking en aankondiging gemaak het. Dit is gevorm op grond van die elektromagnetiese ligteorie. [10] Hy het egter nie met werklike X-strale gewerk nie.

In 1894 het Nikola Tesla beskadigde film in sy laboratorium opgemerk wat blykbaar verband hou met Crookes -buiseksperimente en het dit begin ondersoek stralingsenergie van "onsigbare" soorte. [11] [12] Nadat Röntgen die X-straal geïdentifiseer het, het Tesla sy eie X-straalbeelde begin maak met behulp van hoogspannings en buise van sy eie ontwerp, [13] sowel as Crookes-buise.

Ontdekking deur Röntgen Edit

Op 8 November 1895 het die Duitse fisika-professor Wilhelm Röntgen op X-strale gestruikel terwyl hy met Lenard-buise en Crookes-buise geëksperimenteer het. Hy skryf 'n aanvanklike verslag "Op 'n nuwe soort straal: 'n voorlopige mededeling" en stuur dit op 28 Desember 1895 in Würzburg se tydskrif Physical-Medical Society. [14] Dit was die eerste vraestel wat op X-strale geskryf is. Röntgen verwys na die bestraling as "X", om aan te dui dat dit 'n onbekende tipe straling is. Die naam het vasgehou, hoewel (oor Röntgen se groot besware) baie van sy kollegas voorgestel het om hulle te bel Röntgen strale. Daar word nog steeds in sulke tale na hulle verwys, insluitend Duits, Hongaars, Oekraïens, Deens, Pools, Bulgaars, Sweeds, Fins, Ests, Turks, Russies, Lets, Litaus, Japannees, Nederlands, Georgies, Hebreeus en Noors. Röntgen ontvang die eerste Nobelprys vir Fisika vir sy ontdekking. [15]

Daar is teenstrydige weergawes van sy ontdekking omdat Röntgen sy laboratoriumnotas na sy dood laat verbrand het, maar dit is 'n waarskynlike rekonstruksie deur sy biograwe: [16] [17] Röntgen ondersoek katodestrale uit 'n Crookes -buis wat hy in swart karton toegedraai het sodat die sigbare lig uit die buis nie inmeng nie, met behulp van 'n fluoresserende skerm wat met barium platinosianied geverf is. Hy het 'n dowwe groen gloed van die skerm, ongeveer 1 meter verder, opgemerk. Röntgen besef dat onsigbare strale wat uit die buis kom, deur die karton gaan om die skerm te laat gloei. Hy het gevind dat hulle ook deur boeke en papiere op sy lessenaar kan gaan. Röntgen het hom daarop toegelê om hierdie onbekende strale stelselmatig te ondersoek. Twee maande na sy eerste ontdekking het hy sy koerant gepubliseer. [18]

Röntgen het hul mediese gebruik ontdek toe hy 'n foto van sy vrou se hand gemaak het op 'n fotografiese bord wat gevorm is as gevolg van X-strale. Die foto van sy vrou se hand was die eerste foto van 'n menslike liggaamsdeel met behulp van X-strale. Toe sy die prentjie sien, het sy gesê: "Ek het my dood gesien." [21]

Die ontdekking van X-strale het 'n ware sensasie geprikkel. Die biograaf van Röntgen, Otto Glasser, het geraam dat slegs 189 essays en 1044 artikels oor die nuwe strale in 1896 gepubliseer is. [22] Dit was waarskynlik 'n konserwatiewe skatting, as 'n mens in ag neem dat byna elke koerant oor die hele wêreld omvattend oor die nuwe ontdekking berig het, met 'n tydskrif soos Wetenskap in die jaar alleen 23 artikels daaraan gewy. [23] Sensasionistiese reaksies op die nuwe ontdekking sluit in publikasies wat die nuwe soort strale verbind met okkultiese en paranormale teorieë, soos telepatie. [24] [25]

Vooruitgang in radiologie Wysig

Röntgen het dadelik agtergekom X-strale kan mediese toepassings hê. Saam met sy voorlegging van 28 Desember het hy 'n brief gestuur aan dokters wat hy in Europa geken het (1 Januarie 1896). [26] Nuus (en die skepping van "shadowgrams") het vinnig versprei met die Skotse elektriese ingenieur Alan Archibald Campbell-Swinton wat die eerste na Röntgen was om 'n X-straal (van 'n hand) te maak. Gedurende Februarie was daar 46 proefpersone wat die tegniek alleen in Noord -Amerika gebruik het. [26]

Die eerste gebruik van X-strale onder kliniese toestande was op 11 Januarie 1896 deur John Hall-Edwards in Birmingham, Engeland, toe hy 'n naald wat in die hand van 'n medewerker vasgesteek is, met 'n radiografie neem. Op 14 Februarie 1896 was Hall-Edwards ook die eerste om X-strale te gebruik tydens 'n chirurgiese operasie. [27] Vroeg 1896, 'n paar weke na Röntgen se ontdekking, bestraal Ivan Romanovich Tarkhanov paddas en insekte met X-strale, tot die gevolgtrekking dat die strale "nie net fotografeer nie, maar ook die lewende funksie beïnvloed". [28]

Die eerste mediese röntgenfoto wat in die Verenigde State gemaak is, is verkry met behulp van 'n ontladingsbuis van Pului se ontwerp. In Januarie 1896, by die lees van Röntgen se ontdekking, het Frank Austin van Dartmouth College al die afvoerbuise in die fisika-laboratorium getoets en bevind dat slegs die Pului-buis röntgenstrale lewer. Dit was die gevolg van Pului se insluiting van 'n skuins "teiken" van mika, wat gebruik word om monsters van fluoresserende materiaal in die buis te hou. Op 3 Februarie 1896 het Gilman Frost, professor in medisyne aan die kollege, en sy broer Edwin Frost, professor in fisika, die pols van Eddie McCarthy, wat Gilman 'n paar weke vroeër vir 'n breuk behandel het, aan die X-strale blootgestel en die gevolglike beeld van die gebreekte been op gelatienfotografiese borde verkry van Howard Langill, 'n plaaslike fotograaf wat ook belangstel in Röntgen se werk. [29]

Baie eksperimenteerders, insluitend Röntgen self in sy oorspronklike eksperimente, het metodes bedink om X-straalbeelde "lewendig" te sien met behulp van 'n vorm van ligskerm. [26] Röntgen gebruik 'n skerm bedek met barium platinosianied. Op 5 Februarie 1896 is lewendige beeldapparate ontwikkel deur beide die Italiaanse wetenskaplike Enrico Salvioni (sy "kriptoskoop") en professor McGie van die Princeton -universiteit (sy "Skiascope"), wat beide barium platinocyanide gebruik het. Die Amerikaanse uitvinder Thomas Edison het met navorsing begin kort na Röntgen se ontdekking en het ondersoek ingestel na die vermoë van materiaal om te fluorseer wanneer dit aan röntgenstrale blootgestel word, en bevind dat kalsium-wolfram die doeltreffendste stof is. In Mei 1896 ontwikkel hy die eerste massa-vervaardigde lewende beeldapparaat, sy "Vitascope", later die fluoroskoop genoem, wat die standaard geword het vir mediese X-straalondersoeke. [26] Edison het omstreeks 1903 X-straal-navorsing laat vaar, voor die dood van Clarence Madison Dally, een van sy glasblasers. Dally het die gewoonte gehad om X-straalbuise met sy eie hande te toets en 'n kanker te ontwikkel wat so hardnekkig was dat albei arms in 1904 geamputeer is in 'n vergeefse poging om sy lewe te red. . [26] Gedurende die tyd dat die fluoroskoop ontwikkel is, het die Serwies-Amerikaanse fisikus Mihajlo Pupin, met behulp van 'n kalsiumstatskerm wat deur Edison ontwikkel is, bevind dat die gebruik van 'n fluorescerende skerm die blootstellingstyd verminder om 'n röntgenstraal te maak vir mediese beelding van 'n uur tot 'n paar minute. [30] [26]

In 1901 is die Amerikaanse president, William McKinley, twee keer in 'n sluipmoordaanval doodgeskiet. Terwyl een koeël net sy borsbeen bewei het, het 'n ander êrens diep in sy buik gebly en kon nie gevind word nie. 'N Bekommerde assistent van McKinley het 'n boodskap aan die uitvinder Thomas Edison gestuur om 'n röntgenmasjien na Buffalo te jaag om die verdwaalde koeël te vind. Dit het gekom, maar is nie gebruik nie. Terwyl die skietery self nie dodelik was nie, het gangreen langs die koeël se pad ontwikkel, en McKinley is ses dae later aan 'n septiese skok dood weens bakteriese infeksie. [31]

Gevare ontdek Edit

Met die wydverspreide eksperimentering met x -strale na hul ontdekking in 1895 deur wetenskaplikes, dokters en uitvinders, kom baie verhale oor brandwonde, haarverlies en nog erger in tegniese tydskrifte van destyds. In Februarie 1896 het professor John Daniel en dr.William Lofland Dudley van die Vanderbilt-universiteit haarverlies gerapporteer nadat dr. Dudley 'n röntgenfoto gemaak het. 'N Kind wat in die kop geskiet is, is in 1896 na die Vanderbilt -laboratorium gebring. Voordat hy probeer om die koeël te vind, is 'n eksperiment probeer, waarvoor Dudley "met sy kenmerkende toewyding aan die wetenskap" [32] [33] [34] vrywillig was . Daniel het berig dat hy 21 dae nadat hy 'n foto van Dudley se skedel geneem het (met 'n blootstellingstyd van een uur), 'n kaal kol van 5,1 cm in deursnee op die deel van sy kop wat die naaste aan die X-straalbuis was, opgemerk het: "A plaathouer met die plate aan die kant van die skedel vasgemaak en 'n muntstuk tussen die skedel en die kop geplaas. Die buis is aan die ander kant op 'n afstand van 'n half duim van die hare vasgemaak. " [35]

In Augustus 1896 het dr. HD. Hawks, 'n gegradueerde van die Columbia College, het ernstige brandwonde aan die hand en bors opgedoen as gevolg van 'n x-straal demonstrasie. Dit is aangemeld in Elektriese hersiening en het daartoe gelei dat baie ander verslae van probleme wat verband hou met x-strale na die publikasie gestuur is. [36] Baie eksperimente, waaronder Elihu Thomson in die laboratorium van Edison, William J. Morton, en Nikola Tesla het ook brandwonde aangemeld. Elihu Thomson het oor 'n tydperk doelbewus 'n vinger aan 'n x-straalbuis blootgestel en pyn, swelling en blase opgedoen. [37] Ander gevolge is soms die skuld vir die skade, insluitend ultravioletstrale en (volgens Tesla) osoon. [38] Baie dokters beweer dat daar geen gevolge was van blootstelling aan röntgenstrale nie. [37] Op 3 Augustus 1905, in San Francisco, Kalifornië, sterf Elizabeth Fleischman, 'n Amerikaanse X-straalpionier, aan komplikasies as gevolg van haar werk met röntgenstrale. [39] [40] [41]

20ste eeu en verder Edit

Die vele toepassings van X-strale het onmiddellik enorme belangstelling gewek. Werkswinkels het gespesialiseerde weergawes begin maak van Crookes-buise vir die opwekking van X-strale, en hierdie eerste generasie koue katode of Crookes X-straalbuise is tot ongeveer 1920 gebruik.

'N Tipiese mediese x-straalstelsel uit die vroeë 20ste eeu bestaan ​​uit 'n Ruhmkorff-spoel wat aan 'n koue katode Crookes X-straalbuis gekoppel is. 'N Vonkgaping is tipies parallel met die buis aan die hoogspanningkant gekoppel en vir diagnostiese doeleindes gebruik. [42] Die vonkgaping kon die polariteit van die vonke opspoor, spanning aan die lengte van die vonke meet en sodoende die "hardheid" van die vakuum van die buis bepaal, en dit het 'n las gegee as die röntgenbuis ontkoppel word . Om die hardheid van die buis op te spoor, is die vonkgaping aanvanklik in die grootste omvang oopgemaak. Terwyl die spoel werk, verminder die operateur die gaping totdat vonke begin verskyn. 'N Buis waarin die vonkgaping ongeveer 2 1/2 duim begin vonkel, is as sag (lae vakuum) beskou en geskik vir dun liggaamsdele soos hande en arms. 'N Vonk van 5 duim dui aan dat die buis geskik is vir skouers en knieë. 'N Vonk van 7 tot 9 duim dui op 'n hoër vakuum wat geskik is vir die beelding van die buik van groter individue. Aangesien die vonkgaping parallel met die buis verbind is, moes die vonkgaping oopgemaak word totdat die vonk opgehou het om die buis vir beelding te laat werk. Blootstellingstyd vir fotografiese plate was ongeveer 'n halfminuut vir 'n hand tot 'n paar minute vir 'n toraks. Die plate kan 'n klein toevoeging van fluoresserende sout bevat om blootstellingstye te verminder. [42]

Crookes -buise was onbetroubaar. Hulle moes 'n klein hoeveelheid gas (altyd lug) bevat, aangesien 'n stroom nie in so 'n buis sal vloei as dit volledig ontruim is nie. Met verloop van tyd het die X-strale egter veroorsaak dat die glas die gas absorbeer, wat veroorsaak dat die buis 'harder' X-strale genereer totdat dit gou ophou werk. Groter en meer gereeld gebruikte buise is voorsien van toestelle om die lug te herstel, bekend as "versagters". Dit het dikwels die vorm aanneem van 'n klein sybuis wat 'n klein stukkie mica bevat, 'n mineraal wat relatief groot hoeveelhede lug in sy struktuur vasvang. 'N Klein elektriese verwarmer het die glimmer verhit, wat veroorsaak dat dit 'n klein hoeveelheid lug vrylaat en sodoende die buis se doeltreffendheid herstel. Die glimmer het egter 'n beperkte lewensduur, en die herstelproses was moeilik om te beheer.

In 1904 het John Ambrose Fleming die termioniese diode uitgevind, die eerste soort vakuumbuis. Dit het 'n warm katode gebruik wat veroorsaak het dat 'n elektriese stroom in 'n vakuum vloei. Hierdie idee is vinnig op X-straalbuise toegepas, en gevolglik het verhitte katode-röntgenbuise, genaamd "Coolidge-buise", die lastige koue katodebuise teen ongeveer 1920 heeltemal vervang.

In ongeveer 1906 het die fisikus Charles Barkla ontdek dat X-strale deur gasse verstrooi kan word, en dat elke element 'n kenmerkende X-straal spektrum het. Hy het die Nobelprys vir Natuurkunde in 1917 vir hierdie ontdekking gewen.

In 1912 het Max von Laue, Paul Knipping en Walter Friedrich die eerste keer die diffraksie van X-strale deur kristalle waargeneem. Hierdie ontdekking, tesame met die vroeë werk van Paul Peter Ewald, William Henry Bragg en William Lawrence Bragg, het geboorte gegee aan die gebied van X-straalkristallografie.

In 1913 het Henry Moseley kristallografie-eksperimente uitgevoer met X-strale afkomstig van verskillende metale en die wet van Moseley geformuleer wat die frekwensie van die X-strale verband hou met die atoomgetal van die metaal.

Die Coolidge X-straalbuis is dieselfde jaar uitgevind deur William D. Coolidge. Dit het die deurlopende vrystelling van X-strale moontlik gemaak. Moderne X-straalbuise is gebaseer op hierdie ontwerp, wat dikwels gebruik maak van roterende teikens wat aansienlik hoër hitte-afvoer moontlik maak as statiese teikens, wat verder 'n groter hoeveelheid X-straaluitset moontlik maak vir gebruik in kragtige toepassings, soos roterende CT-skandeerders.

Die gebruik van röntgenstrale vir mediese doeleindes (wat ontwikkel het tot die gebied van bestralingsterapie) was 'n baanbreker by majoor John Hall-Edwards in Birmingham, Engeland. Toe, in 1908, moes hy sy linkerarm laat amputeer weens die verspreiding van X-straal dermatitis op sy arm. [43]

Mediese wetenskap het ook die rolprent gebruik om menslike fisiologie te bestudeer. In 1913 is 'n rolprent in Detroit gemaak waarin 'n hardgekookte eier in 'n menslike maag verskyn. Hierdie vroeë x-straalfilm is elke vier sekondes opgeneem teen 'n snelheid van een stilbeeld. [44] Dr Lewis Gregory Cole van New York was 'n pionier in die tegniek, wat hy 'seriële radiografie' genoem het. [45] [46] In 1918 is x-strale saam met rolprentkameras gebruik om die menslike skelet in beweging op te neem. [47] [48] [49] In 1920 is dit gebruik om die bewegings van tong en tande in die studie van tale deur die Institute of Phonetics in Engeland op te teken. [50]

In 1914 het Marie Curie radiologiese motors ontwikkel om soldate wat in die Eerste Wêreldoorlog beseer is, te ondersteun. Die motors sou vinnige röntgenfoto's van gewonde soldate moontlik maak sodat die slagveldchirurge vinnig en akkurater kon werk. [51]

Vanaf die vroeë 1920's tot die 1950's is röntgenmasjiene ontwikkel om skoene by te pas [52] en is dit aan kommersiële skoenwinkels verkoop. [53] [54] [55] Kommer oor die uitwerking van gereelde of swak beheerde gebruik is in die vyftigerjare uitgespreek, [56] [57] het daartoe gelei dat die praktyk uiteindelik die einde van die dekade tot 'n einde gekom het. [58]

Die X-straalmikroskoop is gedurende die 1950's ontwikkel.

Die Chandra X-straal-sterrewag, wat op 23 Julie 1999 gelanseer is, het die verkenning van die baie gewelddadige prosesse in die heelal wat X-strale produseer, moontlik gemaak. Anders as sigbare lig, wat 'n relatief stabiele beeld van die heelal gee, is die X-straal heelal onstabiel. Dit bevat sterre wat verskeur word deur swart gate, galaktiese botsings en novae, en neutronsterre wat lae plasma opbou wat dan in die ruimte ontplof.

'N Röntgenlasertoestel is voorgestel as deel van die Reagan Administration se Strategic Defense Initiative in die 1980's, maar die enigste toets van die toestel ('n soort laser "blaster" of doodstraal, aangedryf deur 'n termonukleêre ontploffing) het onoortuigende resultate gelewer. Om tegniese en politieke redes is die algehele projek (insluitend die röntgenlaser) gefinansier (hoewel dit later deur die tweede Bush-administrasie herleef is as National Missile Defense met behulp van verskillende tegnologieë).

Fase-kontras X-straalbeeld verwys na 'n verskeidenheid tegnieke wat fase-inligting van 'n samehangende X-straalbundel gebruik om sagte weefsels te beeld. Dit het 'n belangrike metode geword vir die visualisering van sellulêre en histologiese strukture in 'n wye reeks biologiese en mediese studies. Daar is verskeie tegnologieë wat gebruik word vir X-straal fase-kontrasbeeldvorming, wat almal verskillende beginsels gebruik om fasevariasies in die X-strale wat uit 'n voorwerp verskyn, om te skakel in intensiteitsvariasies. [59] [60] Dit sluit in voortplantingsgebaseerde fasekontras, [61] Talbot-interferometrie, [60] brekingversterkte beeldvorming, [62] en X-straalinterferometrie. [63] Hierdie metodes bied groter kontras in vergelyking met normale opname-kontras-röntgenbeeld, wat dit moontlik maak om kleiner besonderhede te sien. 'N Nadeel is dat hierdie metodes meer gesofistikeerde toerusting benodig, soos sinchrotron- of mikrofokus-röntgenbronne, röntgenoptika en hoëresolusie-röntgenopnemers.

Sagte en harde X-strale Redigeer

X-strale met hoë foton energieë bo 5-10 kV (golflengte onder 0,2-0,1 nm) word genoem harde X-strale, terwyl diegene met laer energie (en langer golflengte) genoem word sagte X-strale. [64] Daar word dikwels na die tussenreeks met foton energieë van verskeie keV verwys sagte X-strale. Vanweë hul indringende vermoë word harde X-strale wyd gebruik om die binnekant van voorwerpe voor te stel, byvoorbeeld in mediese radiografie en lughawensekuriteit. Die term X-straal word metoniem gebruik om te verwys na 'n radiografiese beeld wat met hierdie metode gemaak is, benewens die metode self. Aangesien die golflengtes van harde X-strale soortgelyk is aan die grootte van atome, is dit ook nuttig vir die bepaling van kristalstrukture deur röntgenkristallografie. Daarteenoor word sagte röntgenstrale maklik geabsorbeer in die lug, die dempingslengte van 600 eV (

2 nm) X-strale in water is minder as 1 mikrometer. [65]

Gammastrale Redigeer

Daar is geen konsensus vir 'n definisie wat onderskei tussen X-strale en gammastrale nie. Een algemene praktyk is om te onderskei tussen die twee tipes straling op grond van hul bron: X-strale word deur elektrone uitgestraal, terwyl gammastrale deur die atoomkern uitgestraal word. [66] [67] [68] [69] Hierdie definisie het verskeie probleme: ander prosesse kan ook hierdie hoë-energie fotone genereer, of soms is die metode van opwekking nie bekend nie. Een algemene alternatief is om X- en gammastraling te onderskei op grond van golflengte (of, gelykwaardig, frekwensie of foton energie), met straling korter as 'n willekeurige golflengte, soos 10 −11 m (0.1 Å), gedefinieer as gammastraling . [70] Hierdie kriterium ken 'n foton toe aan 'n ondubbelsinnige kategorie, maar is slegs moontlik as golflengte bekend is. (Sommige metingstegnieke onderskei nie tussen gedetecteerde golflengtes nie.) Hierdie twee definisies val egter dikwels saam omdat die elektromagnetiese straling wat deur X-straalbuise uitgestraal word, oor die algemeen 'n langer golflengte en 'n laer fotonenergie het as die straling wat deur radioaktiewe kerne uitgestraal word. [66] Occasionally, one term or the other is used in specific contexts due to historical precedent, based on measurement (detection) technique, or based on their intended use rather than their wavelength or source. Thus, gamma-rays generated for medical and industrial uses, for example radiotherapy, in the ranges of 6–20 MeV, can in this context also be referred to as X-rays. [71]

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

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

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

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

Photoelectric absorption Edit

The probability of a photoelectric absorption per unit mass is approximately proportional to Z 3 /E 3 , where Z is the atomic number and E is the energy of the incident photon. [72] This rule is not valid close to inner shell electron binding energies where there are abrupt changes in interaction probability, so called absorption edges. However, the general trend of high absorption coefficients and thus short penetration depths for low photon energies and high atomic numbers is very strong. For soft tissue, photoabsorption dominates up to about 26 keV photon energy where Compton scattering takes over. For higher atomic number substances this limit is higher. The high amount of calcium (Z = 20) in bones, together with their high density, is what makes them show up so clearly on medical radiographs.

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

Compton scattering Edit

Compton scattering is the predominant interaction between X-rays and soft tissue in medical imaging. [73] Compton scattering is an inelastic scattering of the X-ray photon by an outer shell electron. Part of the energy of the photon is transferred to the scattering electron, thereby ionizing the atom and increasing the wavelength of the X-ray. The scattered photon can go in any direction, but a direction similar to the original direction is more likely, especially for high-energy X-rays. The probability for different scattering angles is described by the Klein–Nishina formula. The transferred energy can be directly obtained from the scattering angle from the conservation of energy and momentum.

Rayleigh scattering Edit

Rayleigh scattering is the dominant elastic scattering mechanism in the X-ray regime. [74] Inelastic forward scattering gives rise to the refractive index, which for X-rays is only slightly below 1. [75]

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

Production by electrons Edit

Characteristic X-ray emission lines for some common anode materials. [76] [77]
Anode
materiaal
Atomic
nommer
Photon energy [keV] Wavelength [nm]
Kα1 Kβ1 Kα1 Kβ1
W 74 59.3 67.2 0.0209 0.0184
Mo 42 17.5 19.6 0.0709 0.0632
Cu 29 8.05 8.91 0.154 0.139
Ag 47 22.2 24.9 0.0559 0.0497
Ga 31 9.25 10.26 0.134 0.121
In 49 24.2 27.3 0.0512 0.455

X-rays can be generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate the electrons released by a hot cathode to a high velocity. The high velocity electrons collide with a metal target, the anode, creating the X-rays. [78] In medical X-ray tubes the target is usually tungsten or a more crack-resistant alloy of rhenium (5%) and tungsten (95%), but sometimes molybdenum for more specialized applications, such as when softer X-rays are needed as in mammography. In crystallography, a copper target is most common, with cobalt often being used when fluorescence from iron content in the sample might otherwise present a problem.

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

  1. Characteristic X-ray emission (X-ray electroluminescence): If the electron has enough energy, it can knock an orbital electron out of the inner electron shell of the target atom. After that, electrons from higher energy levels fill the vacancies, and X-ray photons are emitted. This process produces an emission spectrum of X-rays at a few discrete frequencies, sometimes referred to as spectral lines. Usually, these are transitions from the upper shells to the K shell (called K lines), to the L shell (called L lines) and so on. If the transition is from 2p to 1s, it is called Kα, while if it is from 3p to 1s it is Kβ. The frequencies of these lines depend on the material of the target and are therefore called characteristic lines. The Kα line usually has greater intensity than the Kβ one and is more desirable in diffraction experiments. Thus the Kβ line is filtered out by a filter. The filter is usually made of a metal having one proton less than the anode material (e.g., Ni filter for Cu anode or Nb filter for Mo anode).
  2. Bremsstrahlung: This is radiation given off by the electrons as they are scattered by the strong electric field near the high-Z (proton number) nuclei. These X-rays have a continuous spectrum. The frequency of bremsstrahlung is limited by the energy of incident electrons.

So, the resulting output of a tube consists of a continuous bremsstrahlung spectrum falling off to zero at the tube voltage, plus several spikes at the characteristic lines. The voltages used in diagnostic X-ray tubes range from roughly 20 kV to 150 kV and thus the highest energies of the X-ray photons range from roughly 20 keV to 150 keV. [79]

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

A specialized source of X-rays which is becoming widely used in research is synchrotron radiation, which is generated by particle accelerators. Its unique features are X-ray outputs many orders of magnitude greater than those of X-ray tubes, wide X-ray spectra, excellent collimation, and linear polarization. [80]

Short nanosecond bursts of X-rays peaking at 15-keV in energy may be reliably produced by peeling pressure-sensitive adhesive tape from its backing in a moderate vacuum. This is likely to be the result of recombination of electrical charges produced by triboelectric charging. The intensity of X-ray triboluminescence is sufficient for it to be used as a source for X-ray imaging. [81]

Production by fast positive ions Edit

X-rays can also be produced by fast protons or other positive ions. The proton-induced X-ray emission or particle-induced X-ray emission is widely used as an analytical procedure. For high energies, the production cross section is proportional to Z1 2 Z2 −4 , waar Z1 refers to the atomic number of the ion, Z2 refers to that of the target atom. [82] An overview of these cross sections is given in the same reference.

Production in lightning and laboratory discharges Edit

X-rays are also produced in lightning accompanying terrestrial gamma-ray flashes. The underlying mechanism is the acceleration of electrons in lightning related electric fields and the subsequent production of photons through Bremsstrahlung. [83] This produces photons with energies of some few keV and several tens of MeV. [84] In laboratory discharges with a gap size of approximately 1 meter length and a peak voltage of 1 MV, X-rays with a characteristic energy of 160 keV are observed. [85] A possible explanation is the encounter of two streamers and the production of high-energy run-away electrons [86] however, microscopic simulations have shown that the duration of electric field enhancement between two streamers is too short to produce a significant number of run-away electrons. [87] Recently, it has been proposed that air perturbations in the vicinity of streamers can facilitate the production of run-away electrons and hence of X-rays from discharges. [88] [89]

X-ray detectors vary in shape and function depending on their purpose. Imaging detectors such as those used for radiography were originally based on photographic plates and later photographic film, but are now mostly replaced by various digital detector types such as image plates and flat panel detectors. For radiation protection direct exposure hazard is often evaluated using ionization chambers, while dosimeters are used to measure the radiation dose a person has been exposed to. X-ray spectra can be measured either by energy dispersive or wavelength dispersive spectrometers. For x-ray diffraction applications, such as x-ray crystallography, hybrid photon counting detectors are widely used. [90]

Since Röntgen's discovery that X-rays can identify bone structures, X-rays have been used for medical imaging. [91] The first medical use was less than a month after his paper on the subject. [29] Up to 2010, five billion medical imaging examinations had been conducted worldwide. [92] Radiation exposure from medical imaging in 2006 made up about 50% of total ionizing radiation exposure in the United States. [93]

Projectional radiographs Edit

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

Projectional radiographs are useful in the detection of pathology of the skeletal system as well as for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer, or pulmonary edema, and the abdominal x-ray, which can detect bowel (or intestinal) obstruction, free air (from visceral perforations) and free fluid (in ascites). X-rays may also be used to detect pathology such as gallstones (which are rarely radiopaque) or kidney stones which are often (but not always) visible. Traditional plain X-rays are less useful in the imaging of soft tissues such as the brain or muscle. One area where projectional radiographs are used extensively is in evaluating how an orthopedic implant, such as a knee, hip or shoulder replacement, is situated in the body with respect to the surrounding bone. This can be assessed in two dimensions from plain radiographs, or it can be assessed in three dimensions if a technique called '2D to 3D registration' is used. This technique purportedly negates projection errors associated with evaluating implant position from plain radiographs. [94] [95]

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

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

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

Computed tomography Edit

Computed tomography (CT scanning) is a medical imaging modality where tomographic images or slices of specific areas of the body are obtained from a large series of two-dimensional X-ray images taken in different directions. [96] These cross-sectional images can be combined into a three-dimensional image of the inside of the body and used for diagnostic and therapeutic purposes in various medical disciplines.

Fluoroscopy Edit

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

Radiotherapy Edit

The use of X-rays as a treatment is known as radiation therapy and is largely used for the management (including palliation) of cancer it requires higher radiation doses than those received for imaging alone. X-rays beams are used for treating skin cancers using lower energy x-ray beams while higher energy beams are used for treating cancers within the body such as brain, lung, prostate, and breast. [97] [98]

Diagnostic X-rays (primarily from CT scans due to the large dose used) increase the risk of developmental problems and cancer in those exposed. [99] [100] [101] X-rays are classified as a carcinogen by both the World Health Organization's International Agency for Research on Cancer and the U.S. government. [92] [102] It is estimated that 0.4% of current cancers in the United States are due to computed tomography (CT scans) performed in the past and that this may increase to as high as 1.5–2% with 2007 rates of CT usage. [103]

Experimental and epidemiological data currently do not support the proposition that there is a threshold dose of radiation below which there is no increased risk of cancer. [104] However, this is under increasing doubt. [105] It is estimated that the additional radiation from diagnostic X-rays will increase the average person's cumulative risk of getting cancer by age 75 by 0.6–3.0%. [106] The amount of absorbed radiation depends upon the type of X-ray test and the body part involved. [107] CT and fluoroscopy entail higher doses of radiation than do plain X-rays.

To place the increased risk in perspective, a plain chest X-ray will expose a person to the same amount from background radiation that people are exposed to (depending upon location) every day over 10 days, while exposure from a dental X-ray is approximately equivalent to 1 day of environmental background radiation. [108] Each such X-ray would add less than 1 per 1,000,000 to the lifetime cancer risk. An abdominal or chest CT would be the equivalent to 2–3 years of background radiation to the whole body, or 4–5 years to the abdomen or chest, increasing the lifetime cancer risk between 1 per 1,000 to 1 per 10,000. [108] This is compared to the roughly 40% chance of a US citizen developing cancer during their lifetime. [109] For instance, the effective dose to the torso from a CT scan of the chest is about 5 mSv, and the absorbed dose is about 14 mGy. [110] A head CT scan (1.5mSv, 64mGy) [111] that is performed once with and once without contrast agent, would be equivalent to 40 years of background radiation to the head. Accurate estimation of effective doses due to CT is difficult with the estimation uncertainty range of about ±19% to ±32% for adult head scans depending upon the method used. [112]

The risk of radiation is greater to a fetus, so in pregnant patients, the benefits of the investigation (X-ray) should be balanced with the potential hazards to the fetus. [113] [114] In the US, there are an estimated 62 million CT scans performed annually, including more than 4 million on children. [107] Avoiding unnecessary X-rays (especially CT scans) reduces radiation dose and any associated cancer risk. [115]

Medical X-rays are a significant source of human-made radiation exposure. In 1987, they accounted for 58% of exposure from human-made sources in the United States. Since human-made sources accounted for only 18% of the total radiation exposure, most of which came from natural sources (82%), medical X-rays only accounted for 10% of totaal American radiation exposure medical procedures as a whole (including nuclear medicine) accounted for 14% of total radiation exposure. By 2006, however, medical procedures in the United States were contributing much more ionizing radiation than was the case in the early 1980s. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources. The increase is traceable to the growth in the use of medical imaging procedures, in particular computed tomography (CT), and to the growth in the use of nuclear medicine. [93] [116]

Dosage due to dental X-rays varies significantly depending on the procedure and the technology (film or digital). Depending on the procedure and the technology, a single dental X-ray of a human results in an exposure of 0.5 to 4 mrem. A full mouth series of X-rays may result in an exposure of up to 6 (digital) to 18 (film) mrem, for a yearly average of up to 40 mrem. [117] [118] [119] [120] [121] [122] [123]

Financial incentives have been shown to have a significant impact on X-ray use with doctors who are paid a separate fee for each X-ray providing more X-rays. [124]

Early photon tomography or EPT [125] (as of 2015) along with other techniques [126] are being researched as potential alternatives to X-rays for imaging applications.

Other notable uses of X-rays include:

    in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analysed to reveal the nature of that lattice. A related technique, fiber diffraction, was used by Rosalind Franklin to discover the double helical structure of DNA. [127] , which is an observational branch of astronomy, which deals with the study of X-ray emission from celestial objects. analysis, which uses electromagnetic radiation in the soft X-ray band to produce images of very small objects. , a technique in which X-rays are generated within a specimen and detected. The outgoing energy of the X-ray can be used to identify the composition of the sample. uses X-rays for inspection of industrial parts, particularly welds. , most often x-rays of paintings to reveal underdrawing, pentimenti alterations in the course of painting or by later restorers, and sometimes previous paintings on the support. Many pigments such as lead white show well in radiographs.
  • X-ray spectromicroscopy has been used to analyse the reactions of pigments in paintings. For example, in analysing colour degradation in the paintings of van Gogh. [128]
  • Authentication and quality control of packaged items. (computed tomography), a process that uses X-ray equipment to produce three-dimensional representations of components both externally and internally. This is accomplished through computer processing of projection images of the scanned object in many directions. luggage scanners use X-rays for inspecting the interior of luggage for security threats before loading on aircraft. truck scanners and domestic police departments use X-rays for inspecting the interior of trucks.
  • X-ray art and fine art photography, artistic use of X-rays, for example the works by Stane Jagodič
  • X-ray hair removal, a method popular in the 1920s but now banned by the FDA. [130] were popularized in the 1920s, banned in the US in the 1960s, in the UK in the 1970s, and later in continental Europe. is used to track movement of bones based on the implantation of markers is a chemical analysis technique relying on the photoelectric effect, usually employed in surface science. is the use of high energy X-rays generated from a fission explosion (an A-bomb) to compress nuclear fuel to the point of fusion ignition (an H-bomb).

While generally considered invisible to the human eye, in special circumstances X-rays can be visible. Brandes, in an experiment a short time after Röntgen's landmark 1895 paper, reported after dark adaptation and placing his eye close to an X-ray tube, seeing a faint "blue-gray" glow which seemed to originate within the eye itself. [131] Upon hearing this, Röntgen reviewed his record books and found he too had seen the effect. When placing an X-ray tube on the opposite side of a wooden door Röntgen had noted the same blue glow, seeming to emanate from the eye itself, but thought his observations to be spurious because he only saw the effect when he used one type of tube. Later he realized that the tube which had created the effect was the only one powerful enough to make the glow plainly visible and the experiment was thereafter readily repeatable. The knowledge that X-rays are actually faintly visible to the dark-adapted naked eye has largely been forgotten today this is probably due to the desire not to repeat what would now be seen as a recklessly dangerous and potentially harmful experiment with ionizing radiation. It is not known what exact mechanism in the eye produces the visibility: it could be due to conventional detection (excitation of rhodopsin molecules in the retina), direct excitation of retinal nerve cells, or secondary detection via, for instance, X-ray induction of phosphorescence in the eyeball with conventional retinal detection of the secondarily produced visible light.

Though X-rays are otherwise invisible, it is possible to see the ionization of the air molecules if the intensity of the X-ray beam is high enough. The beamline from the wiggler at the ID11 at the European Synchrotron Radiation Facility is one example of such high intensity. [132]

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

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

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

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

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


Inleiding

In the early days, while American workers were busily exploring and reporting the beneficial use of X-rays, less welcome news was beginning to trickle in from many parts of the USA. The rays, it was discovered, produced undesirable changes in exposed tissues. In the 116th anniversary year of the discovery of X-rays, when Roentgen and others were glorified for their discovery and use of X-rays, this article throws light on some of the early victims and martyrs. Given the ambiguity of universal guidelines in obtaining a cone beam CT (CBCT) scan and the undue use of panoramic and full-mouth periapicals at tertiary care centres, oral radiologists may end up making unnecessary examinations, which can result in undue radiation exposure. This highlights the need to look back through history.

Historical perspective

It was barely 14 days after the announcement of the discovery of Roentgen rays that Friedrich Otto Walkhoff took the first dental radiograph. He took an ordinary photographic glass plate, wrapped it in a rubber dam, held it in his mouth between his teeth and tongue and then lay on the floor for a 25 min exposure. Walkhoff said that those 25 min of exposure were a torture to him. 1 However, the exact nature of this torture has not been described. Later, in 1896, Walkhoff succeeded in making extra-oral pictures with an exposure time of 30 min. He noticed a loss of hair on the side of the head of some of the patients he irradiated, 2 but as there was no mention of blisters on the skin it is assumed that the absorbed dose was less than 300 rads.

In 1896, Otto Walkhoff and Fritz Giesel established the first dental roentgenological laboratory in the world. For many years the laboratory provided practitioners with images of the jaw and head. Fritz Giesel later died in 1927 of metastatic carcinoma caused by heavy radiation exposure to his hands. 3

In February 1896 a child who had been accidentally shot in the head was brought to the laboratory at Vanderbilt University (Tennessee, USA). Before attempting to locate the bullet in the child, Professor Daniel and Dr Dudley decided to undertake an experiment. Dr Dudley, with his characteristic devotion to science, lent himself to this experiment. A plate holder containing the sensitive plate was tied to one side of Dudley's head and the tube attached to the opposite side of the head. The tube was placed 0.5 inches away from Dudley's hair and activated for 1 h. After 21 days all the hair fell out from the space under discharge, which was approximately 2 inches in diameter. 4

On 12 August 1896, Electrical Review reported that Dr HD Hawks, a graduate of the 1896 class of Columbia College, gave a demonstration with a powerful X-ray unit in the vicinity of New York. 5 After 4 days, he was compelled to stop work. He noticed a drying of the skin, which he ignored. The hand began to swell and gave the appearance of a deep skin burn. After 2 weeks the skin came off the hand, the knuckles become very sore, fingernail growth stopped and the hair on the skin exposed to X-rays fell out. His eyes were bloodshot and his vision became considerably impaired. His chest was also burnt. Mr Hawks' physician treated this as a case of dermatitis. Hawks tried protecting his hands with petroleum jelly, then gloves and finally by covering it with tin foil. Within 6 weeks Hawks was partially recovered and was making light of his injuries. Electrical Review concluded by asking to hear from any of its readers who had had similar experiences.

GA Frei of Frei and Co., a Boston manufacturer of X-ray tubes, replied the next day: Mr K, an employee of the company, complained of peculiar itching and burning in his left hand and thought it was due to poisoning with chemicals. Mr K used to regularly attend to testing of tubes during and after the exhausting process at the rooms. The same phenomenon also appeared on Frei's hand. The letter concluded by stating that further developments would be carefully monitored. 5

A distressing case was reported in September 1896. William Levy had been shot in the head by an escaping bank robber 10 years previously. The bullet entered his skull just above the left ear and presumably proceeded towards the back of the head. Having heard about X-rays, he decided he wanted the bullet localized and extracted. Levy approached Professor Jones of the Physical Laboratory, University of Minnesota. Professor Jones, who was familiar with Daniel and Dudley's experiments, warned Levy against the exposure, but Levy was undeterred and an exposure was made on 8 July 1896. Exposures were made with the tube over his forehead, in front of his open mouth and behind his right ear. Levy sat through the exposures from 8 o'clock in the morning until 10 o'clock at night. Within 24 h his entire head was blistered, within a few days his head was an angry sore and his lips were badly swollen, cracked and bleeding. His right ear had doubled in size and the hair on his right side had entirely fallen out. Professor Jones concluded that the one feature that was satisfactory to the patient was that a good picture of the bullet was obtained, showing it to be about an inch beneath the skull under the occipital protuberance. 6

Dr Stickney reported a case in December 1896 of a woman who complained of abdominal pain. A radiograph of the patient, Mrs Q, was taken in the abdominal region. The focus of X-rays was over the liver. 3 exposures were made of 20 min, 30 min and 35 min. Two days later she developed burns over the region. The condition worsened until the surface sloughed. 7

The above cases of Hawks, Dudley and Stickney all reported skin blisters and it could therefore be assumed that the absorbed dose of the victims was at least 1500 rads. Serious damage from the rays was also reported from the Edison Laboratory. Elihu Thomson of General Electric cited two Edison cases in a letter dated 1 December 1896 to Dr EA Codman of Boston. Thomson referred to these cases as serious because they took place over the hands and arms of the victims and they had to stop working with X-rays altogether. The story goes that one of them was told by his physician that if he continued to work with X-rays it would be necessary to amputate his hands. The worker threatened with amputation was probably Clarence Dally, Thomson Edison's glassblower.

Clarence Dally was likely to have had an absorbed dose of approximately 3000 rads to necessitate amputation. It needs to be noted that not everyone had the same experience. Dr Williams reported in 1897 that in approximately 250 patients, who he examined with X-rays, he had not seen any harmful effects. 8

Professor Stine of Armour Institute of Technology reported that a patient who was exposed for 2 h for 2 successive days with the plate a few inches from the skin developed itching and irritation. A few days later the skin swelled and became inflamed, and the area immediately surrounding the exposure was tanned and dry. In time the skin peeled off and resembled bad sunburn. Professor Stine, however, concluded that the effect was due to ultraviolet rays and not X-rays. 9

Dr EA Codman, in 1902, conscientiously reviewed all papers on X-ray injuries. Of the 88 X-ray injuries published, 55 had occurred in 1896, 12 in 1897, 6 in 1898, 9 in 1899, 3 in 1900 and 1 in 1901. The decline could be due to the fact that X-ray injuries were no longer in the news and therefore went unreported unless they exhibited unusual features. 10

Clarence Dally (1865�) is thought to be the first to die as result of X-ray exposure. He died of metastatic carcinoma at only 39 years old.

The next death to be reported was that of Elizabeth F Ascheim (1859�) of San Francisco. Deaths reported thereafter included those of Wolfram C Fuchs (1865�), who opened the X-ray laboratory in Chicago in 1896 and made the first X-ray film of a brain tumour in 1899, and Dr William Carl Egelhoff (1872�). Among the victims who suffered the most was Dr Walter James Dodd (1869�). He was operated on 32 times and died of metastatic carcinoma of the lung on 18 December 1916. 11

The deaths of tube manufacturers have included Rome Vernon Wagner (1869�), his brother Thurman Lester Wagner (1876�), Burton Eugene Baker (1871�), Henry Green (1860�), John Bawer (unknown year of birth�) and Robert H Machlett (1872�). 12

The case of C. Edmund Kells is well known. Kells developed a radiogenic neoplasm in 1922 and endured increasing discomfort and excruciating pain. Kells did not listen to the warning given by William Rollins regarding radiation hazards. He had undergone 42 operations and several amputations (some have reported 100). On 7 May 1928 Kells triggered a 0.32 calibre bullet into his brain. 3

Dr Perry Brown, an eminent Boston radiologist, published his collection of biological essays 𠇊merican martyrs to science through Roentgen rays” in 1936. He reported the deaths of Mihran Kasabian of Philadelphia (1870�), Eugene Caldwell of New York (1870�), Herbert Robert of St Louis (1852�), Fredrick H Baetjer of Baltimore (1874�) and a number of others whose lives deserve to be remembered. However, his own story was missing Dr Brown died of X-ray induced cancer in 1950. 11

Dr Cannon began using X-rays in 1896 when he was a medical student. In 1931 he developed itching of skin and fresh red papular lesions on his back, chest, thighs, knees and elbows. Dr Cannon suggested that repeated biopsies be made so that it would provide more information on this poorly understood condition. He developed several lesions all over the body, many of which continuously recurred.

In April 1944, a recurrent basal cell carcinoma of the nostril was excised. In 1945 he passed the 14 th anniversary of the onset of mycosis fungoidosis — an amazingly long survival. On 1 October 1945 he died of recurrent pulmonary infection. 6

It would be generous to accept Dr Grubbe's account precisely as he wrote it, for he truly was an X-ray martyr. Dr Grubbe suffered at least 83 surgical operations to relieve his discomfort and to stop the progress of gangrene from his left hand to his arm, elbow and finally shoulder. Grubbe's face was grossly disfigured with cancer. He became sterile. His marriage was left childless, a misfortune he attributed to the X-rays. He lived in agony for many years, yet he continued to work with the rays.

In his autobiography he maintained “my courage is my work. I treat patients who suffer more or are encumbered more than me, and so I go on. By helping others I help myself”. He went on to predict “I will die from the effects of early uncontrolled exposures to X-rays. And like many of the early pioneers, I too, will die a victim of natural science, a martyr to the X-rays.”

Dr Grubbe, in the chapter “The effect of the X-rays on author’s body”, concluded on a noble note: “I have lived large enough to see the child that I fathered develop into a sturdy, mature and worthwhile product and I hope as I approach the evening of my day, to see even more uses of X-ray energy in the alleviation of the ills of mankind.” Dr. Grubbe died of metastatic cancer on 26 March 1960. 13 It could be hypothesized that Kells and Grubbe had a consistent absorbed dose of 3000 rads.


November 28, 1895: Granddaddy of All American Auto Races

A Brief History On November 28, 1895, the first American auto race took place, the Chicago Times-Herald Race, a 54 mile event with a grand prize of $5000. (If that prize sounds lame, remember that this is worth over $140,000 in today’s money.) Digging Deeper As the automobile was a new-fangled invention at the time, a proper name for the motorized conveyance had not yet been agreed upon and the Times-Herald called their event a “Moto-cycle Race.” Originally meant to be a race from Chicago to Milwaukee, the roads of the day were not smooth enough for those primitive cars&hellip


120 YEARS SINCE THE DISCOVERY OF X-RAYS

This paper is intended to celebrate the 120th anniversary of the discovery of X-rays. X-rays (Roentgen-rays) were discovered on the 8th ofNovember, 1895 by the German physicist Wilhelm Conrad Roentgen. Fifty days after the discovery of X-ray, on December 28, 1895. Wilhelm Conrad Roentgen published a paper about the discovery of X-rays - "On a new kind of rays" (Wilhelm Conrad Roentgen: Ober eine neue Art von Strahlen. In: Sitzungsberichte der Wurzburger Physik.-Medic.- Gesellschaft. 1895.). Therefore, the date of 28th ofDecember, 1895 was taken as the date of X-rays discovery. This paper describes the work of Wilhelm Conrad Roentgen, Nikola Tesla, Mihajlo Pupin and Maria Sklodowska-Curie about the nature of X-rays . The fantastic four - Wilhelm Conrad Roentgen, NikolaTesla, Mihajlo ldvorski Pupin and Maria Sklodowska-Curie set the foundation of radiology with their discovery and study of X-rays. Five years after the discovery of X-rays, in 1900, Dr Avram Vinaver had the first X-ray machine installed in abac, in Serbia at the time when many developed countries did not have an X-ray machine and thus set the foundation of radiology in Serbia.


1895: Wilhelm Röntgen Discovers X-rays

On this day, in the late afternoon hours, German physicist Wilhelm Roentgen experimented with a variety of electronic devices, including some of Tesla’s, by putting them under electrical discharge and observing the rays they produce. In one of the experiments in a darkened room, he noticed a glimmer of barium platinocyanide. He concluded that this shimmering was caused by some as yet unknown rays.

He called them X-rays, where X was a designation for something unknown. When he placed various items in the range of these rays, he saw a picture of his skeleton on a barium platinocyanide screen. After that, he continued his research in secret because he was afraid that he might be ridiculed if his observations do not prove to be true. After two weeks, he made a picture of his wife’s hand, on which bones and rings can be seen. The rays were named Röntgen rays after him, although he always preferred the term X-rays.


Kyk die video: Differential Phase Contrast X ray Imaging Basics by Maha Yusuf. (Januarie 2022).