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'''Fluoroscopy''' ({{IPAc-en|f|l|ʊəˈr|ɒ|s|k|ə|p|i}}){{refn|{{cite Merriam-Webster|fluoroscopy}}}}, informally referred to as "'''fluoro'''", is an imaging technique that uses [[X-ray]]s to obtain real-time moving images of the interior of an object. In its primary application of [[medical imaging]], a '''fluoroscope''' ({{IPAc-en|ˈ|f|l|ʊər|ə|ˌ|s|k|oʊ|p}}){{refn|{{cite Merriam-Webster|fluoroscope}}}}{{refn|{{cite Lexico|fluoroscope}} {{Webarchive |url=https://web.archive.org/web/20200322182706/https://www.lexico.com/definition/fluoroscope |url-status=dead |date=2020-03-22}}.}} allows a [[surgeon]] to see the internal [[anatomy|structure]] and [[physiology|function]] of a patient, so that the pumping action of the [[heart]] or the motion of [[swallowing]], for example, can be watched. This is useful for both [[medical diagnosis|diagnosis]] and [[therapy]] and occurs in general [[radiology]], [[interventional radiology]], and image-guided [[surgery]].
In its simplest form, a fluoroscope consists of an [[X-ray generator|X-ray source]] and a [[fluorescence|fluorescent]] screen, between which a patient is placed. However, since the 1950s most fluoroscopes have included [[X-ray image intensifier]]s and [[camera]]s as well, to improve the image's visibility and make it available on a remote display screen. For many decades, fluoroscopy tended to produce live pictures that were not recorded, but since the 1960s, as technology improved, recording and playback became the norm.
Fluoroscopy is similar to [[radiography]] and [[X-ray computed tomography]] (X-ray CT) in that it generates images using X-rays. The original difference was that radiography fixed still images on [[photographic film|film]], whereas fluoroscopy provided live moving pictures that were not stored. However,
==Mechanism of action==
Although visible light can be '''seen''' by the naked eye (and thus forms images that people can look at), it does not penetrate most objects (only [[transparency and translucency|translucent or transparent]] ones). In contrast, X-rays can penetrate a wider variety of objects (such as the human body), but they are invisible to the naked eye. To take advantage of the penetration for image-forming purposes, one must somehow convert the X-rays' [[intensity (physics)|intensity]] variations (which correspond to material contrast and thus image contrast) into a form that is visible. Classic film-based radiography achieves this by the variable chemical changes that the X-rays induce in the [[photographic film|film]], and classic fluoroscopy achieves it by [[fluorescence]], in which certain materials convert X-ray energy (or other parts of the [[electromagnetic spectrum|spectrum]]) into visible light. This use of fluorescent materials to make a [[wikt:-scope#Suffix|viewing scope]] is how fluoroscopy got its name.
As the X-rays pass through the patient, they are [[attenuation|attenuated]] by varying amounts as they [[refraction|pass through]] or [[reflection (physics)|reflect off]] the different [[tissue (biology)|tissues]] of the body, casting an X-ray [[shadow]] of the [[radiodensity|radiopaque]] tissues (such as [[bone tissue]]) on the fluorescent screen. Images on the screen are produced as the unattenuated or mildly attenuated X-rays from [[radiodensity|radiolucent]] tissues interact with atoms in the screen through the [[photoelectric effect]], giving their energy to the [[electron]]s. While much of the energy given to the electrons is dissipated as [[heat]], a fraction of it is given off as visible light.
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===Gastrointestinal fluoroscopy===
[[Image:Normal barium swallow animation.gif|thumb|right|A [[barium swallow]] exam taken via fluoroscopy.]]
Fluoroscopy can be used to examine the digestive system using a substance that is opaque to X-rays (usually [[barium sulfate]] or [[Diatrizoic acid|gastrografin]]), which is introduced into the digestive system either by swallowing or as an [[enema]]. This is normally as part of a double-contrast technique, using positive and negative contrast. Barium sulfate coats the walls of the digestive tract (positive contrast), which allows the shape of the digestive tract to be outlined as white or clear on an X-ray. Air may then be introduced (negative contrast), which looks black on the film. The barium meal is an example of a [[contrast agent]] swallowed to examine the upper digestive tract. While soluble barium compounds are very toxic, the insoluble barium sulfate is nontoxic because its low solubility prevents the body from absorbing it. Investigations of the [[Human gastrointestinal tract|gastrointestinal tract]] include [[barium enema]]s, [[defecating proctogram]]s, [[barium meal]]s and [[barium swallow|swallows]], and [[enteroclysis]].<ref>{{Cite book |last1=Levine |first1=Marc S. |url=https://books.google.com/books?id=ffIb3KF-mUAC&q=Gastrointestinal+fluoroscopy |title=Practical Fluoroscopy of the GI and GU Tracts |last2=Ramchandani |first2=Parvati |last3=Rubesin |first3=Stephen E. |date=2012-01-26 |publisher=Cambridge University Press |isbn=978-1-107-00180-0 |language=en}}</ref>
===Other medical uses===
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===Digital electronic era===
[[Digital electronics]] were applied to fluoroscopy beginning in the early 1960s, when [[Frederick G. Weighart]]<ref name="US_Patent_3277302">{{US Patent|3277302}}, titled "X-Ray Apparatus Having Means for Supplying An Alternating Square Wave Voltage to the X-Ray Tube", granted to Weighart on October 4, 1964, showing its patent application date as May 10, 1963 and at lines 1-6 of its column 4, also, noting James F. McNulty's earlier filed co-pending application for an essential component of invention</ref><ref name="US_Patent_3482093">{{US Patent|3482093}}, see also this patent, titled "Fluoroscopy", referencing US Patent 3277302 to Weighart and detailing the fluoroscopy procedure for nondestructing testing.</ref> and James F. McNulty<ref>U.S. Patent 3,289,000, titled "Means for Separately Controlling the Filament Current and Voltage on a X-Ray Tube", granted to McNulty on November 29, 1966 and showing its patent application date as March 5, 1963</ref> (
From the late 1980s onward, [[digital imaging]] technology was reintroduced to fluoroscopy after development of improved detector systems. Modern improvements in screen [[phosphors]], [[digital image processing]], [[image analysis]], and [[flat panel detectors]] have allowed for increased image quality while minimizing the [[radiation dose]] to the patient. Modern fluoroscopes use [[caesium iodide]] (CsI) screens and produce noise-limited images, ensuring that the minimal radiation dose results while still obtaining images of acceptable quality.
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[[File:Fluoroscopy burn.jpg|thumb|Fluoroscopy burn from long exposure]]
Because fluoroscopy involves the use of X-rays, a form of [[ionizing radiation]], fluoroscopic procedures pose a potential for increasing the patient's risk of [[radiation-induced cancer]]
A study of radiation-induced skin injuries was performed in 1994 by the U.S. [[Food and Drug Administration]] (FDA)<ref>{{ cite web | url = https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm116682.htm | title = Radiation-induced Skin Injuries from Fluoroscopy | publisher = FDA }}</ref><ref>{{Cite journal | last1 = Shope | first1 = T. B. | title = Radiation-induced skin injuries from fluoroscopy | journal = Radiographics | volume = 16 | issue = 5 | pages = 1195–1199 | year = 1996 | pmid = 8888398| url = http://radiographics.rsna.org/content/16/5/1195.full.pdf | doi=10.1148/radiographics.16.5.8888398}}</ref> followed by an advisory to minimize further fluoroscopy-induced injuries.<ref>{{ cite web | url = https://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/PublicHealthNotifications/UCM063084 | title = Public Health Advisory on Avoidance of Serious X-Ray-Induced skin Injuries to Patients During Fluoroscopically-Guided Procedures | publisher = FDA | date = September 30, 1994 }}</ref> The problem of radiation injuries due to fluoroscopy has been further addressed in review articles in 2000<ref>{{Cite journal | last1 = Valentin | first1 = J. | title = Avoidance of radiation injuries from medical interventional procedures | journal = Annals of the ICRP | volume = 30 | issue = 2 | pages = 7–67 | year = 2000 | pmid = 11459599| doi = 10.1016/S0146-6453(01)00004-5| s2cid = 70923586 | doi-access = free }}</ref> and 2010.<ref>{{Cite journal | last1 = Balter | first1 = S. | last2 = Hopewell | first2 = J. W. | last3 = Miller | first3 = D. L. | last4 = Wagner | first4 = L. K. | last5 = Zelefsky | first5 = M. J. | title = Fluoroscopically Guided Interventional Procedures: A Review of Radiation Effects on Patients' Skin and Hair | doi = 10.1148/radiol.2542082312 | journal = Radiology | volume = 254 | issue = 2 | pages = 326–341 | year = 2010 | pmid = 20093507 | url = http://radiology.rsna.org/content/254/2/326.full.pdf| doi-access = free }}</ref>
While deterministic radiation effects are a possibility, [[radiation burns]] are not typical
[[X-ray image intensifier]]s generally have radiation-reducing systems such as pulsed rather than constant radiation, along with "last image hold", which "freezes" the screen and makes it available for examination without exposing the patient to unnecessary radiation.<ref>{{ cite web | url = http://www.walterrobinson.com/images/Walt_PPT/ppt_pres/sld044.htm | publisher = Walter L. Robinson & Associates | title = Last Image Hold Feature | work = Fluoroscopic Radiation Management | access-date = April 3, 2010 }}</ref>
Image intensifiers have been introduced that increase the brightness of the screen, so that the patient can be exposed to a lower dose of X-rays.<ref>{{Cite journal|last1=Wang|first1=J.|last2=Blackburn|first2=T. J.|date=September 2000|title=The AAPM/RSNA physics tutorial for residents: X-ray image intensifiers for fluoroscopy|journal=Radiographics|volume=20|issue=5|pages=1471–1477|doi=10.1148/radiographics.20.5.g00se181471|issn=0271-5333|pmid=10992034|doi-access=
==Equipment==
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* [https://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115354.htm Fluoroscopy] FDA Radiological Health Program
* "[
* [https://www.youtube.com/watch?v=2CL2EznIUC4 Fluoroscopy video in the medical field]
* [https://www.youtube.com/watch?v=_EQsPmT9F-8 Fluoroscopy video in the Nondestructive Testing field]
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