Fluoroscopy
Fluoroscopy | |
---|---|
Other names | fluorography, cinefluorography, photofluorography. |
ICD-10-PCS | B?1 |
MeSH | D005471 |
Fluoroscopy (/flʊəˈrɒskəpi/)[1], informally referred to as "fluoro", is an imaging technique that uses X-rays to obtain real-time moving images of the interior of an object. In its primary application of medical imaging, a fluoroscope (/ˈflʊərəˌskoʊp/)[2][3] allows a surgeon to see the internal structure and 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 diagnosis and therapy and occurs in general radiology, interventional radiology, and image-guided surgery.
In its simplest form, a fluoroscope consists of an
Fluoroscopy is similar to
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 translucent or tansparent 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 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 film, and classic fluoroscopy achieves it by fluorescence, in which certain materials convert X-ray energy (or other parts of the spectrum) into visible light. This use of fluorescent materials to make a viewing scope is how fluoroscopy got its name.
As the X-rays pass through the patient, they are
Early radiologists would adapt their eyes to view the dim fluoroscopic images by sitting in darkened rooms, or by wearing
Nowadays, in all forms of digital X-ray imaging (radiography, fluoroscopy, and CT) the conversion of X-ray energy into visible light can be achieved by the same types of electronic sensors, such as
Medical use
Fluoroscopy has become an important tool in medical imaging to render moving pictures during a surgery or any other procedure.
Surgical fluoroscopy
Fluoroscopy is used in various types of surgical procedure, such as orthopaedic surgery and podiatric surgery. In both of those, it is used to guide fracture reduction and in use in certain procedures that have extensive hardware.[clarification needed][5]
Urology
In urology, fluoroscopy is used in retrograde pyelography and micturating cystourethrography to detect various abnormalities related to the urinary system.[6]
Cardiology
In cardiology, fluoroscopy is used for diagnostic angiography,
Gastrointestinal fluoroscopy
Fluoroscopy can be used to examine the digestive system using a substance that is opaque to X-rays (usually
Other medical uses
- Liver biopsy is performed under fluoroscopic guidance at many centers.
- Angiography of the leg, heart, and cerebral vessels.[9]
- Placement of a peripherally inserted central catheter
- Placement of a weighted feeding tube (e.g. Dobhoff) into the duodenum after previous attempts without fluoroscopy have failed
- Discography, an invasive diagnostic procedure for evaluation for intervertebral disc pathology.[10][11]
- In lumbar puncture, fluoroscopy helps to guide where the needles of the spinal tap can go, and may reduce the number of attempts required for a successful lumbar puncture.
Other uses
Fluoroscopy is also used in
History
Early era
Fluoroscopy's origins and
In the late 1890s,
During this infant commercial development, many incorrectly predicted that the moving images of fluoroscopy would completely replace roentgenographs (radiographic still image films), but the then superior diagnostic quality of the roentgenograph and their already alluded-to safety enhancement of lower
X-ray shoe fitting
More trivial uses of the technology emerged in the early 1920s, including a shoe-fitting fluoroscope that was used at shoe stores and department stores.[14][15][16][17][18][19][20][21][22][23][24][25][26][27] Concerns regarding the impact of frequent or poorly controlled use were expressed in the late 1940s and 1950s. Issues raised by doctors and health professionals included the potential for burns to the skin, damage to bone, and abnormal development of the feet.[28][29][30][31][32] These concerns lead to the development of new guidelines,[33][34][35] regulations[36][37][38] and ultimately the practice's end by the early 1960s.[39][40][41][42][43][44][45] Shoe salesmen and industry representatives sometimes defended their use, claiming that there was no evidence of harm, and that their use prevented harm to the feet caused by poorly-fitted shoes.[46]
Fluoroscopy was discontinued in shoe-fitting because the radiation exposure risk outweighed the trivial benefit. Only important applications such as health care, bodily safety, food safety, nondestructive testing, and scientific research meet the risk-benefit threshold for use.
Analog electronic era
Digital electronic era
Digital electronics were applied to fluoroscopy beginning in the early 1960s, when Frederick G. Weighart[48][49] and James F. McNulty[50] (1929-2014) at Automation Industries, Inc., then, in El Segundo, California produced on a fluoroscope the world's first image to be digitally generated in real-time, while developing a later commercialized portable apparatus for the onboard nondestructive testing of naval aircraft. Square wave signals were detected on a fluorescent screen to create the image.
From the late 1980s onward,
Etymology
Many names exist in the medical literature for moving pictures taken with X-rays. They include fluoroscopy, fluorography, cinefluorography, photofluorography, fluororadiography, kymography (electrokymography, roentgenkymography), cineradiography (cine), videofluorography, and videofluoroscopy. Today, the word "fluoroscopy" is widely understood to be a
As soon as X-rays (and their application of seeing inside the body) were discovered in the 1890s, both looking and recording were pursued. Both live moving images and recorded still images were available from the beginning with simple equipment; thus, both "looking with a fluorescent screen" (fluoro- + -scopy) and "recording/engraving with radiation" (radio- + -graphy) were immediately named with Neo-Latin words—both words are attested since 1896.[52]
The quest for recorded moving images, though, was a more complex challenge. In the 1890s, moving pictures of any kind (whether taken with visible light or with invisible radiation) were emerging technologies. Because the word "photography" (literally "recording/engraving with light") was long since established as connoting a still-image medium, the word "cinematography" (literally "recording/engraving movement") was coined for the new medium of visible-light moving pictures. Soon, several new words were coined for achieving moving radiographic pictures. This was often done either by filming a simple fluoroscopic screen with a movie camera (variously called fluorography, cinefluorography, photofluorography, or fluororadiography) or by taking serial radiographs rapidly to serve as the frames in a movie (cineradiography). Either way, the resulting film reel could be displayed by a movie projector. Another group of techniques included various kinds of kymography, whose common theme was capturing recordings in a series of moments, with a concept similar to movie film, although not necessarily with movie-type playback; rather, the sequential images would be compared frame by frame (a distinction comparable to tile mode versus cine mode in today's CT terminology). Thus, electrokymography and roentgenkymography were among the early ways to record images from a simple fluoroscopic screen.
Television also was under early development during these decades (1890s–1920s), but even after commercial TV began widespread adoption after World War II, it remained a live-only medium for a time. In the mid-1950s, a commercialized ability to capture the moving pictures of television onto magnetic tape (with a video tape recorder) was developed. This soon led to the addition of the "video-" prefix to the words fluorography and fluoroscopy, with the words videofluorography and videofluoroscopy attested since 1960.[53] In the 1970s, videotape moved from TV studios and medical imaging into the consumer market with home video via VHS and Betamax, and those formats were also incorporated into medical video equipment.
Thus, over time the cameras and
Whereas the word "cine" (/ˈsɪni/) in general usage refers to cinema (that is, a movie)[52][54] or to certain film formats (cine film) for recording such a movie, in medical usage it refers to cineradiography or, in recent decades, to any digital imaging mode that produces cine-like moving images (for example, newer CT and MRI systems can put out to either cine mode or tile mode). Cineradiography records 30-frame/second fluoroscopic images of internal organs such as the heart taken during injection of contrast dye to better visualize regions of stenosis, or to record motility in the body's gastrointestinal tract. The predigital technology is being replaced with digital imaging systems. Some of these decrease the frame rate, but also decrease the absorbed dose of radiation to the patient. As they improve, frame rates will likely increase.
Today, owing to technological convergence, the word "fluoroscopy" is widely understood to be a hypernym of all the earlier names for moving pictures taken with X-rays, both live and recorded. Also owing to technological convergence, radiography, CT, and fluoroscopy are now all digital imaging modes using X-rays with image-analysis software and easy data storage and retrieval. Just as movies, TV, and web videos are to a substantive extent no longer separate technologies, but only variations on common underlying digital themes, so, too, are the X-ray imaging modes, and indeed, the term "X-ray imaging" is the ultimate hypernym that unites all of them, even subsuming both fluoroscopy and four-dimensional CT (4DCT), which is the newest form of moving pictures taken with X-rays.[55] Many decades may pass before the earlier hyponyms fall into disuse, not the least because the day when 4D CT displaces all earlier forms of moving X-ray imaging may yet be distant.
Adverse effects
The use of X-rays, a form of
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. In addition to the cancer risk and other stochastic radiation effects, deterministic radiation effects have also been observed ranging from mild erythema, equivalent of a sunburn, to more serious burns.[56] Radiation doses to the patient depend greatly both on the size of the patient and length of the procedure, with typical skin dose rates quoted as 20–50 mGy/min.[57] Exposure times vary depending on the procedure being performed, ranging from minutes to hours.[57]
A study of radiation-induced skin injuries was performed in 1994 by the U.S. Food and Drug Administration (FDA)[58][59] followed by an advisory to minimize further fluoroscopy-induced injuries.[60] The problem of radiation injuries due to fluoroscopy has been further addressed in review articles in 2000[61] and 2010.[62]
While deterministic radiation effects are a possibility,
X-ray image intensifiers 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.[63]
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.[64] Whilst this reduces the risk of ionisation occurring, it does not remove it entirely.
Equipment
X-ray image intensifiers
The invention of
Modern image intensifiers no longer use a separate fluorescent screen. Instead, a caesium iodide phosphor is deposited directly on the photocathode of the intensifier tube. On a typical general-purpose system, the output image is approximately 105 times brighter than the input image. This brightness gain comprises a flux gain (amplification of photon number) and minification gain (concentration of photons from a large input screen onto a small output screen) each of about 100. This level of gain is sufficient that quantum noise, due to the limited number of X-ray photons, is a significant factor limiting image quality.
Within the XRII, five mini components make up this intensifier, which are:
- The glass envelope helps maintain the tube vacuum to allow control of the electron flow, but it has no actual functional part in the image formation.
- Input phosphor, when the X-rays interact with this piece, its energy is converted into a burst of visible light photons as they occur like this on the intensifying screen/monitor.
- The photocathode is a thin metal layer, that is usually composed of caesium and antimony compounds that respond to stimulation by the light with the emission of the electron.
- The electrostatic focusing lenses are located along the length of the tube and are responsible for the focusing of the electrons across the tube from the input to the output phosphor.
- The output phosphor is usually made up of cadmium sulfide crystals and is what records the arrival of the photoelectrons and normally results in 50–70 times gain.[clarification needed] [66][67]
Image intensifiers are available with input diameters up to 45 cm, and a resolution of around two to three line pairs/mm.
Flat-panel detectors
The introduction of flat-panel detectors allows for the replacement of the image intensifier in fluoroscope design. Flat-panel detectors offer increased sensitivity to X-rays, so have the potential to reduce patient radiation dose. Temporal resolution is also improved over image intensifiers, reducing motion blurring. Contrast ratio is also improved over image intensifiers; flat-panel detectors are linear over a very wide latitude, whereas image intensifiers have a maximum contrast ratio of about 35:1. Spatial resolution is roughly equal, although an image intensifier operating in magnification mode may be slightly better than a flat panel.
Flat-panel detectors are considerably more expensive to purchase and repair than image intensifiers, so their use adoption is primarily in specialties that require high-speed imaging, e.g., vascular imaging and cardiac catheterization.
Contrast agents
A number of substances have been used as radiocontrast agents, including silver, bismuth, caesium, thorium, tin, zirconium, tantalum, tungsten, and lanthanide compounds. The use of thoria (thorium dioxide) as an agent was rapidly stopped, as thorium causes liver cancer.[68]
Most modern injected radiographic positive contrast media are iodine-based. Iodinated contrast comes in two forms - ionic and nonionic compounds. Nonionic contrast is significantly more expensive than ionic (about three to five times the cost), but nonionic contrast tends to be safer for the patient, causing fewer allergic reactions and uncomfortable side effects such as hot sensations or flushing. Most imaging centers now use nonionic contrast exclusively, finding that the benefits to patients outweigh the expense.
Negative radiographic contrast agents are
Imaging concerns
In addition to spatial blurring factors that plague all X-ray imaging devices, caused by such things as Lubberts effect, K-fluorescence reabsorption, and electron range, fluoroscopic systems also experience temporal blurring due to system latency. This temporal blurring has the effect of averaging frames together. While this helps reduce noise in images with stationary objects, it creates motion blurring for moving objects. Temporal blurring also complicates measurements of system performance for fluoroscopic systems.
References
- ^ "fluoroscopy". Merriam-Webster.com Dictionary.
- ^ "fluoroscope". Merriam-Webster.com Dictionary.
- ^ "fluoroscope". Lexico UK English Dictionary. Oxford University Press. n.d. Archived 2020-03-22 at the Wayback Machine.
- ^ "Red Goggles (ca. 1940s)". Museum of Radiation and Radioactivity. Retrieved 2022-03-23.
- ISBN 978-0-8493-1506-0.
- ISBN 978-3-030-73565-4.
- ISBN 978-1-4612-3534-7.
- ISBN 978-1-107-00180-0.
- ISBN 978-1-59259-331-6.
- PMID 34283485, retrieved 2022-03-21
- ISBN 978-3-540-49929-9.
- ISBN 978-0-674-00740-6.
- ^ New York World "Edison Fears Hidden Perils of the X Rays" Monday, August 3, 1903, page 1
- ^ "X-Rays for Fitting Boots". Warwick Daily News (Qld. : 1919 -1954). 1921-08-25. p. 4. Retrieved 2020-11-27.
- ^ "X-ray shoe fitting, London (1921)". Democrat and Chronicle. 1921-07-03. p. 2. Retrieved 2017-11-05.
- ^ "X-ray shoe fitting with foot-o-scope (1922)". The Scranton Republican. 1922-09-27. p. 9. Retrieved 2017-11-05.
- ^ "X-ray shoe fitting machine (1923)". El Paso Herald. 1923-04-04. p. 3. Retrieved 2017-11-05.
- ORAU.
- ^ "T. C. BEIRNE'S X-RAY SHOE FITTING". Telegraph (Brisbane, Qld. : 1872 - 1947). 1925-07-17. p. 8. Retrieved 2017-11-05.
- ^ "THE PEDOSCOPE". Sunday Times (Perth, WA : 1902 - 1954). 1928-07-15. p. 5. Retrieved 2017-11-05.
- ^ "X-ray shoe fitting advertisement (1931)". The Fresno Morning Republican. 1931-09-01. p. 22. Retrieved 2020-11-26.
- ^ "Arrow shoe store gets new x-ray machine (1937)". Lancaster New Era. 1937-06-11. p. 4. Retrieved 2020-11-26.
- ^ "X-RAY SHOE FITTINGS". Biz (Fairfield, NSW : 1928 - 1972). 1955-07-27. p. 10. Retrieved 2017-11-05.
- ^ "The most expensive shoe in the world is the shoe that doesn't fit - x-ray shoe fitting (1934)". Nashville Banner. 1934-09-20. p. 3. Retrieved 2020-11-26.
- ^ ""Yes, X-ray is the modern way to fit shoes!" advertisement (1938)". The Central New Jersey Home News. 1938-03-17. p. 3. Retrieved 2020-11-26.
- ^ "Your children need x-ray shoe fitting - advertisement (1941)". The Wellsboro Gazette. 1941-07-09. p. 4. Retrieved 2017-11-05.
- ^ "New X-Ray Shoe Machine Provides Better Fitting (1935)". The Eugene Guard. 1935-05-30. p. 8. Retrieved 2017-11-05.
- ^ "X-Ray machines for shoe fitting kept in repair (1951)". Panama City News-Herald. 1951-10-08. p. 12. Retrieved 2017-11-05.
- ^ "SHOE X-RAY DANGERS". Brisbane Telegraph (Qld. : 1948 - 1954). 1951-02-28. p. 7. Retrieved 2017-11-05.
- ^ "X-ray shoe sets in S.A. 'controlled'". News (Adelaide, SA : 1923 - 1954). 1951-04-27. p. 12. Retrieved 2017-11-05.
- ^ "Warning to parents about x-ray shoe fittings (1957)". Rocky Mount Telegram. 1957. p. 10. Retrieved 2017-11-05.
- ^ "The Doctor Says: repeated x-ray shoe fittings may be injurious to feet (1952)". Mt. Vernon Register-News. 1952-04-17. p. 4. Retrieved 2017-11-05.
- ^ "Dangers of X-ray machines for shoe fitting - The Physicians Forum (1949)". The Gazette and Daily. 1949-10-27. p. 23. Retrieved 2020-11-26.
- ^ "Danger from x-ray machines (1950)". The Mason City Globe-Gazette. 1950-12-14. p. 28. Retrieved 2017-11-05.
- ^ "Frequently dangerous - X-ray shoe fitting care urged (1951)". The Orlando Sentinel. 1951-09-27. p. 9. Retrieved 2020-11-26.
- ^ "Shoe shop x-rays to be supervised, Australia (1951)". The Age. 1951-02-28. p. 5. Retrieved 2017-11-05.
- ^ "X-ray fitting time limited (1951)". Marysville Journal-Tribune. 1951. p. 3. Retrieved 2017-11-05.
- ^ "X-ray shoe fitting stores required to register by July 1 (1953)". The Brooklyn Daily Eagle. 1953-05-25. p. 3. Retrieved 2017-11-05.
- ^ "State to Enforce Ban on X-Ray Shoe Fitting Machines (1958)". The Daily Advertiser. 1958-11-18. p. 14. Retrieved 2020-11-26.
- ^ "Bill to ban x-ray machines in shoe stores hits snag, Ohio (1957)". The Sandusky Register. 1957-04-16. p. 1. Retrieved 2017-11-05.
- ^ "Pennsylvania halts x-ray shoe fitting (1957)". The Eugene Guard. 1957. p. 10. Retrieved 2017-11-05.
- ^ "Ban On Shoe X-ray Machines Resented". Canberra Times (ACT : 1926 - 1995). 1957-06-26. p. 4. Retrieved 2017-11-05.
- ^ "Stricter X-Ray Control Drafted (1962)". The Daily Times. 1962-12-22. p. 12. Retrieved 2017-11-05.
- ^ "X-rays cause more radiation than H-bomb (1956)". Marysville Journal-Tribune. 1956-10-24. p. 1. Retrieved 2017-11-05.
- ^ "Waukegan bars shoe store x-rays, Illinois (1958)". Mt. Vernon Register-News. 1958-08-28. p. 19. Retrieved 2017-11-05.
- ^ "The Journal Letter Box - X-ray shoe fitting (1950)". Edmonton Journal. 1950-01-31. p. 4. Retrieved 2020-11-26.
- ^ "Electrons Now Brighten X Ray." Popular Science, August 1948, pp. 132-133.
- ^ U.S. patent 3,277,302, 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
- ^ U.S. patent 3,482,093, see also this patent, titled "Fluoroscopy", referencing US Patent 3277302 to Weighart and detailing the fluoroscopy procedure for nondestructing testing.
- ^ 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
- ^ Google Ngram of the entire fluoroscopy word list.
- ^ a b Merriam-Webster, Merriam-Webster's Collegiate Dictionary, Merriam-Webster, archived from the original on 2020-10-10, retrieved 2015-02-14.
- ^ Google Ngram of videofluorography and videofluoroscopy.
- Oxford Dictionaries, Oxford Dictionaries Online, Oxford University Press, archived from the originalon May 16, 2001.
- UPMC Cancer Center, What is a 4D CT Scan?, retrieved 2015-02-14.
- PMID 22307864.
- ^ PMID 11452079.
- ^ "Radiation-induced Skin Injuries from Fluoroscopy". FDA.
- PMID 8888398.
- ^ "Public Health Advisory on Avoidance of Serious X-Ray-Induced skin Injuries to Patients During Fluoroscopically-Guided Procedures". FDA. September 30, 1994.
- S2CID 70923586.
- PMID 20093507.
- ^ "Last Image Hold Feature". Fluoroscopic Radiation Management. Walter L. Robinson & Associates. Retrieved April 3, 2010.
- PMID 10992034.
- PMID 10992034.
- ^ Murphy, Andrew. "Image Intensifier: Radiology Reference Article." Radiopaedia Blog RSS, 2020, https://radiopaedia.org/articles/image-intensifier?lang=us
- ^ Huzaifa Oxford Biomedical Engineer Follow. "Fluoroscopy Presentation." SlideShare, 1 September 2014, https://www.slideshare.net/HuzaifaOxford/fluoroscopy-presentation
- ISBN 978-1-56670-223-2.
External links
- Fluoroscopy FDA Radiological Health Program
- "Were those old shoe store fluoroscopes a health hazard?" at The Straight Dope, 27 November 1987
- Fluoroscopy video in the medical field
- Fluoroscopy video in the Nondestructive Testing field