Fluoroscopy
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Fluoroscopy () is an imaging technique that uses
X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10  nanometers, corresponding to frequencies in the range 30&nb ...
s to obtain real-time moving images of the interior of an object. In its primary application of medical imaging, a fluoroscope () allows a
physician A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through th ...
to see the internal structure and
function Function or functionality may refer to: Computing * Function key, a type of key on computer keyboards * Function model, a structured representation of processes in a system * Function object or functor or functionoid, a concept of object-oriente ...
of a patient, so that the pumping action of the
heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
or the motion of swallowing, for example, can be watched. This is useful for both
diagnosis Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engin ...
and
therapy A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a medical diagnosis. As a rule, each therapy has indications and contraindications. There are many different ...
and occurs in general
radiology Radiology ( ) is the medical discipline that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiat ...
, interventional radiology, and image-guided surgery. In its simplest form, a fluoroscope consists of an X-ray source and a
fluorescent Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...
screen, between which a patient is placed. However, since the 1950s most fluoroscopes have included
X-ray image intensifier An X-ray image intensifier (XRII) is an image intensifier that converts X-rays into visible light at higher intensity than the more traditional fluorescent screens can. Such intensifiers are used in X-ray imaging systems (such as fluoroscopes) ...
s and
camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...
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 Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeu ...
and
X-ray computed tomography An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30  ...
(X-ray CT) in that it generates images using X-rays. The original difference was that radiography fixed still images on film whereas fluoroscopy provided live moving pictures that were not stored. However, today radiography, CT, and fluoroscopy are all
digital imaging Digital imaging or digital image acquisition is the creation of a digital representation of the visual characteristics of an object, such as a physical scene or the interior structure of an object. The term is often assumed to imply or include t ...
modes with image analysis software and data storage and retrieval.


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 In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions ...
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 Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...
, in which certain materials convert X-ray energy (or other parts of the
spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...
) 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 attenuated by varying amounts as they pass through or reflect off the different tissues of the body, casting an X-ray
shadow A shadow is a dark area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, ...
of the
radiopaque Radiodensity (or radiopacity) is opacity to the radio wave and X-ray portion of the electromagnetic spectrum: that is, the relative inability of those kinds of electromagnetic radiation to pass through a particular material. Radiolucency or hypod ...
tissues (such as
bone tissue A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, a ...
) on the fluorescent screen. Images on the screen are produced as the unattenuated or mildly attenuated X-rays from
radiolucent Radiodensity (or radiopacity) is opacity to the radio wave and X-ray portion of the electromagnetic spectrum: that is, the relative inability of those kinds of electromagnetic radiation to pass through a particular material. Radiolucency or hypod ...
tissues interact with atoms in the screen through the
photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...
, giving their energy to the
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...
s. While much of the energy given to the electrons is dissipated as
heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...
, a fraction of it is given off as visible light. Early radiologists would adapt their eyes to view the dim fluoroscopic images by sitting in darkened rooms, or by wearing red adaptation goggles. After the development of
X-ray image intensifier An X-ray image intensifier (XRII) is an image intensifier that converts X-rays into visible light at higher intensity than the more traditional fluorescent screens can. Such intensifiers are used in X-ray imaging systems (such as fluoroscopes) ...
s, the images were
bright Bright may refer to: Common meanings *Bright, an adjective meaning giving off or reflecting illumination; see Brightness *Bright, an adjective meaning someone with intelligence People * Bright (surname) * Bright (given name) *Bright, the stage na ...
enough to see without goggles under normal ambient light. 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
flat panel detector Flat-panel detectors are a class of solid-state x-ray digital radiography devices similar in principle to the image sensors used in digital photography and video. They are used in both projectional radiography and as an alternative to x-ray ima ...
s, which convert the X-ray energy into electrical
signals In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
: small bursts of electric current that convey information that a computer can analyze, store, and output as images. As fluorescence is a special case of
luminescence Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light". It is thus a form of cold-body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions or stress on a crys ...
, digital X-ray imaging is conceptually similar to digital
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
imaging (
scintigraphy Scintigraphy (from Latin ''scintilla'', "spark"), also known as a gamma scan, is a diagnostic test in nuclear medicine, where radioisotopes attached to drugs that travel to a specific organ or tissue (radiopharmaceuticals) are taken internally and ...
,
SPECT Single-photon emission computed tomography (SPECT, or less commonly, SPET) is a nuclear medicine tomographic imaging technique using gamma rays. It is very similar to conventional nuclear medicine planar imaging using a gamma camera (that is, ...
, and
PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence ...
) in that in both of these imaging mode families, the information conveyed by the variable attenuation of invisible electromagnetic radiation as it passes through tissues with various radiodensities is converted by an electronic sensor into an electric signal that is processed by a computer and output as a visible-light image.


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 Podiatry () or podiatric medicine () is a branch of medicine devoted to the study, diagnosis, medical and surgical treatment of disorders of the foot, ankle, and leg. A Doctor of Podiatric Medicine (DPM), or a podiatrist, is a healthcare p ...
. In both of those, it is used to guide fracture reduction and in use in certain procedures that have extensive hardware.


Urology

In urology, fluoroscopy is used in retrograde pyelography and micturating cystourethrography to detect various abnormalities related to the urinary system.


Cardiology

In cardiology, fluoroscopy is used for diagnostic angiography, percutaneous coronary interventions, (
pacemakers An artificial cardiac pacemaker (or artificial pacemaker, so as not to be confused with the natural cardiac pacemaker) or pacemaker is a medical device that generates electrical impulses delivered by electrodes to the chambers of the heart eit ...
,
implantable cardioverter defibrillator An implantable cardioverter-defibrillator (ICD) or automated implantable cardioverter defibrillator (AICD) is a device implantable inside the body, able to perform defibrillation, and depending on the type, cardioversion and pacing of the h ...
s, and cardiac resynchronization devices).


Gastrointestinal fluoroscopy

Fluoroscopy can be used to examine the digestive system using a substance that is opaque to X-rays (usually barium sulfate or
gastrografin Diatrizoate, also known as amidotrizoate, is a contrast agent used during X-ray imaging. This includes visualizing veins, the urinary system, spleen, and joints, as well as computer tomography (CT scan). It is given by mouth, injection into a vei ...
), which is introduced into the digestive system either by swallowing or as an
enema An enema, also known as a clyster, is an injection of fluid into the lower bowel by way of the rectum.Cullingworth, ''A Manual of Nursing, Medical and Surgical'':155 The word enema can also refer to the liquid injected, as well as to a device ...
. 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 gastrointestinal tract include
barium enema A lower gastrointestinal series is a medical procedure used to examine and diagnose problems with the human colon of the large intestine. Radiographs (X-ray pictures) are taken while barium sulfate, a radiocontrast agent, fills the colon via an ...
s,
defecating proctogram Defecography (also known as proctography, defecating/defecation proctography, evacuating/evacuation proctography or dynamic rectal examination) is a type of medical radiological imaging in which the mechanics of a patient's defecation are visual ...
s,
barium meal An upper gastrointestinal series, also called a barium swallow, barium study, or barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as ba ...
s and swallows, and
enteroclysis An upper gastrointestinal series, also called a barium swallow, barium study, or barium meal, is a series of radiographs used to examine the gastrointestinal tract for abnormalities. A contrast medium, usually a radiocontrast agent such as barium ...
.


Other medical uses

*
Liver biopsy Liver biopsy is the biopsy (removal of a small sample of tissue) from the liver. It is a medical test that is done to aid diagnosis of liver disease, to assess the severity of known liver disease, and to monitor the progress of treatment. Medica ...
is performed under fluoroscopic guidance at many centers. *
Angiography Angiography or arteriography is a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers. Modern angiography is perfor ...
of the leg, heart, and cerebral vessels. * Placement of a
peripherally inserted central catheter A peripherally inserted central catheter (PICC or PIC line), less commonly called a percutaneous indwelling central catheter, is a form of intravenous access that can be used for a prolonged period of time (e.g., for long chemotherapy regimens ...
* Placement of a weighted feeding tube (e.g. Dobhoff) into the duodenum after previous attempts without fluoroscopy have failed *
Discography Discography is the study and cataloging of published sound recordings, often by specified artists or within identified music genres. The exact information included varies depending on the type and scope of the discography, but a discography entry ...
, an invasive diagnostic procedure for evaluation for intervertebral disc pathology. * 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 airport security scanners to check for hidden weapons or bombs. These machines use lower doses of radiation than medical fluoroscopy. The reason for higher doses in medical applications is that they are more demanding about tissue contrast, and for the same reason they sometimes require
contrast media A contrast agent (or contrast medium) is a substance used to increase the contrast of structures or fluids within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasound, which is different from radiop ...
.


History


Early era

Fluoroscopy's origins and radiography's origins can both be traced back to 8 November 1895, when
Wilhelm Röntgen Wilhelm Conrad Röntgen (; ; 27 March 184510 February 1923) was a German mechanical engineer and physicist, who, on 8 November 1895, produced and detected electromagnetic radiation in a wavelength range known as X-rays or Röntgen rays, an achie ...
, or in English script Roentgen, noticed a barium
platinocyanide Platinocyanide, also known as tetracyanoplatinate (IUPAC), cyanoplatinate, or platinocyanate, is a polyatomic ion with the molecular formula t(CN)4sup>2−. The name also applies to compounds containing this ion, which are salts of the hypothetical ...
screen fluorescing as a result of being exposed to what he would later call X-rays (algebraic x variable signifying "unknown"). Within months of this discovery, the first crude fluoroscopes were created. These experimental fluoroscopes were simply thin cardboard screens that had been coated on the inside with a layer of fluorescent metal salt, attached to a funnel-shaped cardboard eyeshade which excluded room light with a viewing eyepiece which the user held up to his eye. The fluoroscopic image obtained in this way was quite faint. Even when finally improved and commercially introduced for
diagnostic imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues ( physiology). Medical imaging seeks to r ...
, the limited light produced from the fluorescent screens of the earliest commercial scopes necessitated that a
radiologist Radiology ( ) is the medical discipline that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiat ...
sit for a period in the darkened room where the imaging procedure was to be performed, to first accustom his eyes to increase their sensitivity to perceive the faint image. The placement of the radiologist behind the screen also resulted in significant dosing of the radiologist. In the late 1890s,
Thomas Edison Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventi ...
began investigating materials for ability to fluoresce when X-rayed, and by the turn of the century he had invented a fluoroscope with sufficient image intensity to be commercialized. Edison had quickly discovered that
calcium tungstate Scheelite is a calcium tungstate mineral with the chemical formula Ca W O4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist K. Scheele (1742-1786). Well-formed crystals are sought by collectors ...
screens produced brighter images. Edison, however, abandoned his researches in 1903 because of the health hazards that accompanied use of these early devices. Clarence Dally, a glass blower of lab equipment and tubes at Edison's laboratory was repeatedly exposed, developing radiation poisoning, later dying from an aggressive cancer. Edison himself damaged an eye in testing these early fluoroscopes. 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
radiation dose Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...
via shorter exposure prevented this from occurring. Another factor was that plain films inherently offered recording of the image in a simple and inexpensive way, whereas recording and playback of fluoroscopy remained a more complex and expensive proposition for decades to come ( discussed in detail below). Red adaptation goggles were developed by
Wilhelm Trendelenburg Ernst Wilhelm Theodor Trendelenburg (16 July 1877 – 16 March 1946) was a German physiologist known for his work in physiological optics. He studied physiology at the University of Freiburg, receiving his doctorate from the University of Leipzig ...
in 1916 to address the problem of
dark adaptation Darkness, the direct opposite of lightness, is defined as a lack of illumination, an absence of visible light, or a surface that absorbs light, such as black or brown. Human vision is unable to distinguish colors in conditions of very low l ...
of the eyes, previously studied by
Antoine Beclere Antoine is a French given name (from the Latin ''Antonius'' meaning 'highly praise-worthy') that is a variant of Danton, Titouan, D'Anton and Antonin. The name is used in France, Switzerland, Belgium, Canada, West Greenland, Haiti, French Guiana ...
. The resulting red light from the goggles' filtration correctly sensitized the physician's eyes prior to the procedure, while still allowing him to receive enough light to function normally.


X-ray shoe fitting

More trivial uses of the technology emerged in the early 1920s, including a
shoe-fitting fluoroscope Shoe-fitting fluoroscopes, also sold under the names X-ray Shoe Fitter, Pedoscope and Foot-o-scope, were X-ray fluoroscope machines installed in shoe stores from the 1920s until about the 1970s in the United States, Canada, United Kingdom, Austral ...
that was used at shoe stores and department stores. 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. These concerns lead to the development of new guidelines, regulations and ultimately the practice's end by the early 1960s. 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. 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 Research is " creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness ...
meet the risk-benefit threshold for use.


Analog electronic era

Analog electronics Analogue electronics ( en-US, analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional relat ...
revolutionized fluoroscopy. The development of the
X-ray image intensifier An X-ray image intensifier (XRII) is an image intensifier that converts X-rays into visible light at higher intensity than the more traditional fluorescent screens can. Such intensifiers are used in X-ray imaging systems (such as fluoroscopes) ...
by Westinghouse in the late 1940s in combination with closed circuit TV cameras of the 1950s allowed for brighter pictures and better
radiation protection Radiation protection, also known as radiological protection, is defined by the International Atomic Energy Agency (IAEA) as "The protection of people from harmful effects of exposure to ionizing radiation, and the means for achieving this". Expos ...
. The red adaptation goggles became obsolete as image intensifiers allowed the light produced by the fluorescent screen to be amplified and made visible in a lighted room. The addition of the
camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...
enabled viewing of the image on a monitor, allowing a radiologist to view the images in a separate room away from the risk of radiation exposure. The commercialization of
video tape recorder A video tape recorder (VTR) is a tape recorder designed to record and playback video and audio material from magnetic tape. The early VTRs were open-reel devices that record on individual reels of 2-inch-wide (5.08 cm) tape. They were u ...
s beginning in 1956 allowed the TV images to be recorded and played back at will.


Digital electronic era

Digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usual ...
were applied to fluoroscopy beginning in the early 1960s, when Frederick G. Weighart, 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, see also this patent, titled "Fluoroscopy", referencing US Patent 3277302 to Weighart and detailing the fluoroscopy procedure for nondestructing testing. and James F. McNulty (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 Naval aviation is the application of military air power by navies, whether from warships that embark aircraft, or land bases. Naval aviation is typically projected to a position nearer the target by way of an aircraft carrier. Carrier-base ...
. Square wave signals were detected on a fluorescent screen to create the image. From the late 1980s onward,
digital imaging Digital imaging or digital image acquisition is the creation of a digital representation of the visual characteristics of an object, such as a physical scene or the interior structure of an object. The term is often assumed to imply or include t ...
technology was reintroduced to fluoroscopy after development of improved detector systems. Modern improvements in screen
phosphors A phosphor is a substance that exhibits the phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescent or phosphorescent substances which glow on exposure to ultraviolet or v ...
,
digital image processing Digital image processing is the use of a digital computer to process digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allo ...
, image analysis, and
flat panel detectors Flat-panel detectors are a class of solid-state x-ray digital radiography devices similar in principle to the image sensors used in digital photography and video. They are used in both projectional radiography and as an alternative to x-ray imag ...
have allowed for increased image quality while minimizing the
radiation dose Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...
to the patient. Modern fluoroscopes use
caesium iodide Caesium iodide or cesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly ...
(CsI) screens and produce noise-limited images, ensuring that the minimal radiation dose results while still obtaining images of acceptable quality.


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
hypernym In linguistics, semantics, general semantics, and ontologies, hyponymy () is a semantic relation between a hyponym denoting a subtype and a hypernym or hyperonym (sometimes called umbrella term or blanket term) denoting a supertype. In other ...
of all the aforementioned terms, which explains why it is the most commonly used and why the others are declining in usage. The profusion of names is an
idiomatic Idiom, also called idiomaticness or idiomaticity, is the syntactical, grammatical, or structural form peculiar to a language. Idiom is the realized structure of a language, as opposed to possible but unrealized structures that could have develop ...
artifact of
technological change Technological change (TC) or technological development is the overall process of invention, innovation and diffusion of technology or processes.From ''The New Palgrave Dictionary otechnical change by S. Metcalfe.  •biased and biased techno ...
, as follows: 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 The English suffix -graphy means a "field of study" or related to "writing" a book, and is an anglicization of the French ''-graphie'' inherited from the Latin ''-graphia'', which is a transliterated direct borrowing from Greek. Arts * Cartogr ...
) were immediately named with
New Latin New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...
words—both words are attested since 1896. 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 Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employe ...
" (literally "recording/engraving with light") was long since established as connoting a still-image medium, the word "
cinematography Cinematography (from ancient Greek κίνημα, ''kìnema'' "movement" and γράφειν, ''gràphein'' "to write") is the art of motion picture (and more recently, electronic video camera) photography. Cinematographers use a lens to foc ...
" (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 A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either on an image sensor or onto film stock, in order to produce a moving image to project onto a movie sc ...
(variously called fluorography, cinefluorography,
photofluorography Photofluorography (sometimes called just fluorography) is photography of X-ray images from a fluorescent screen. It is commonly used in some countries for chest X-ray screening, e.g. to diagnose tuberculosis (see Abreugraphy for more information o ...
, 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 A movie projector is an opto-mechanical device for displaying motion picture film by projecting it onto a screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras. Mod ...
. 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 Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
also was under early development during these decades (1890s–1920s), but even after commercial TV began widespread adoption after
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
, 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 A video tape recorder (VTR) is a tape recorder designed to record and playback video and audio material from magnetic tape. The early VTRs were open-reel devices that record on individual reels of 2-inch-wide (5.08 cm) tape. They were u ...
) 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. In the 1970s, video tape moved from TV studios and medical imaging into the consumer market with
home video Home video is prerecorded media sold or rented for home viewing. The term originates from the VHS and Betamax era, when the predominant medium was videotapes, but has carried over to optical disc formats such as DVD, Blu-ray and streaming me ...
via VHS and Betamax, and those formats were also incorporated into medical video equipment. Thus, over time the cameras and
recording media Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are consi ...
for fluoroscopic imaging have progressed: The original kind of fluoroscopy, and the common kind for its first half century of existence, simply used none, because for most diagnosis and treatment, they were not essential. For those investigations that needed to be transmitted or recorded (such as for training or research),
movie camera A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either on an image sensor or onto film stock, in order to produce a moving image to project onto a movie sc ...
s using film (such as 16 mm film) were the medium. In the 1950s, analog electronic
video camera A video camera is an optical instrument that captures videos (as opposed to a movie camera, which records images on film). Video cameras were initially developed for the television industry but have since become widely used for a variety of oth ...
s (at first only producing live output, but later using video tape recorders) appeared. Since the 1990s, digital video cameras,
flat panel detector Flat-panel detectors are a class of solid-state x-ray digital radiography devices similar in principle to the image sensors used in digital photography and video. They are used in both projectional radiography and as an alternative to x-ray ima ...
s, and storage of data to local servers or (more recently) secure
cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...
servers have been used. Late-model fluoroscopes all use
digital image processing Digital image processing is the use of a digital computer to process digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allo ...
and image analysis software, which not only helps to produce optimal image clarity and contrast, but also allows that result with a minimal radiation dose (because
signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
can take tiny inputs from low radiation doses and amplify them while to some extent also differentiating signal from noise). Whereas the word "cine" () in general usage refers to cinema (that is, a movie) or to certain film formats (
cine film Ciné film or cine film is the term commonly used in the UK and historically in the US to refer to the 8 mm, Super 8, 9.5 mm, and 16 mm motion picture film formats used for home movies. It is not normally used to refer to ...
) 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 Digital imaging or digital image acquisition is the creation of a digital representation of the visual characteristics of an object, such as a physical scene or the interior structure of an object. The term is often assumed to imply or include t ...
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 Technological convergence is the tendency for technologies that were originally unrelated to become more closely integrated and even unified as they develop and advance. For example, watches, telephones, television, computers, and social media ...
, 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. 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 ionizing radiation, requires the potential risks from a procedure to be carefully balanced with the benefits of the procedure to the patient. Because the patient must be exposed to a continuous source of X-rays instead of a momentary pulse, a fluoroscopy procedure generally subjects a patient to a higher absorbed dose of radiation than an ordinary (still)
radiograph Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
. Only important applications such as health care, bodily safety, food safety, nondestructive testing, and scientific
research Research is " creative and systematic work undertaken to increase the stock of knowledge". It involves the collection, organization and analysis of evidence to increase understanding of a topic, characterized by a particular attentiveness ...
meet the risk-benefit threshold for use. In the first half of the 20th century,
shoe-fitting fluoroscope Shoe-fitting fluoroscopes, also sold under the names X-ray Shoe Fitter, Pedoscope and Foot-o-scope, were X-ray fluoroscope machines installed in shoe stores from the 1920s until about the 1970s in the United States, Canada, United Kingdom, Austral ...
s were used in shoe stores, but their use was discontinued because it is no longer considered acceptable to use radiation exposure, however small the dose, for nonessential purposes. Much research has been directed toward reducing radiation exposure, and recent advances in fluoroscopy technology such as
digital image processing Digital image processing is the use of a digital computer to process digital images through an algorithm. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing. It allo ...
and flat panel detectors, have resulted in much lower radiation doses than former procedures. 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 Exposure to ionizing radiation is known to increase the future incidence of cancer, particularly leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most wi ...
,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 sun burn, to more serious burns. 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. Exposure times vary depending on the procedure being performed, ranging from minutes to hours. A study of radiation-induced skin injuries was performed in 1994 by the U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA) followed by an advisory to minimize further fluoroscopy-induced injuries. The problem of radiation injuries due to fluoroscopy has been further addressed in review articles in 2000 and 2010. While deterministic radiation effects are a possibility,
radiation burns A radiation burn is a damage to the skin or other biological tissue and organs as an effect of radiation. The radiation types of greatest concern are thermal radiation, radio frequency energy, ultraviolet light and ionizing radiation. The most ...
are not typical of standard fluoroscopic procedures. Most procedures sufficiently long in duration to produce radiation burns are part of necessary life-saving operations.
X-ray image intensifier An X-ray image intensifier (XRII) is an image intensifier that converts X-rays into visible light at higher intensity than the more traditional fluorescent screens can. Such intensifiers are used in X-ray imaging systems (such as fluoroscopes) ...
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. 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. Whilst this reduces the risk of ionisation occurring, it does not remove it entirely.


Equipment


X-ray image intensifiers

The invention of
X-ray image intensifier An X-ray image intensifier (XRII) is an image intensifier that converts X-rays into visible light at higher intensity than the more traditional fluorescent screens can. Such intensifiers are used in X-ray imaging systems (such as fluoroscopes) ...
s in the 1950s allowed the image on the screen to be visible under normal lighting conditions, and provided the option of recording the images with a conventional camera. Subsequent improvements included the coupling of, at first, video cameras, and later,
digital camera A digital camera is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film. Digital cameras are now widely incorporated into mobile devices ...
s using
image sensor An image sensor or imager is a sensor that detects and conveys information used to make an image. It does so by converting the variable attenuation of light waves (as they pass through or reflect off objects) into signals, small bursts of c ...
s such as
charge-coupled device A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
s or active pixel sensors to permit recording of moving images and electronic storage of still images. Modern image intensifiers no longer use a separate fluorescent screen. Instead, a
caesium iodide Caesium iodide or cesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly ...
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 Quantum noise is noise arising from the indeterminate state of matter in accordance with fundamental principles of quantum mechanics, specifically the uncertainty principle and via zero-point energy fluctuations. Quantum noise is due to the appa ...
, 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. Image intensifiers are available with input diameters up to 45 cm, and a resolution 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 agent Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography ( contrast CT), projectional radiography, and fluoroscopy. Radiocontrast agents are typically i ...
s, including
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
,
bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...
, caesium,
thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...
,
tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
,
zirconium Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'' ...
,
tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that ...
,
tungsten Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isol ...
, and lanthanide compounds. The use of thoria (thorium dioxide) as an agent was rapidly stopped, as thorium causes
liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
. 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
air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...
and
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
(CO2). The latter is easily absorbed by the body and causes less spasm. It can also be injected into the blood, where air absolutely cannot due to the risk of an air embolism.


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 The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...
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 blur Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or lo ...
ring for moving objects. Temporal blurring also complicates measurements of system performance for fluoroscopic systems.


References


External links


Fluoroscopy
FDA Radiological Health Program *

at
Straight Dope "The Straight Dope" was a question-and-answer newspaper column written under the pseudonym Cecil Adams. Contributions were made by multiple authors, and it was illustrated (also pseudonymously) by Slug Signorino. It was first published in 1973 i ...
, 27 November 1987
Fluoroscopy video in the medical field

Fluoroscopy video in the Nondestructive Testing field
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