Skip to main content
Select Source:

Radiology

Radiology

Radiology is a branch of medical science in which various forms of radiant energy are used to diagnose and treat disorders and diseases. For nearly 80 years, radiology was based primarily on the use of X rays. Since the 1970s, however, several new imaging techniques have been developed. Some, like computed tomography, makes use of X rays along with other technology, such as computer technology. Others, like ultrasound and magnetic resonance imaging, use forms of radiant energy other than X rays.

Radiant energy

The term radiant energy refers to any form of electromagnetic energy, such as cosmic rays, gamma rays, X rays, infrared radiation, visible light, ultraviolet radiation, radar, radio waves, and microwaves. These forms of energy are classified together because they all travel by means of waves. They differ from each other only in their frequencies (the number of times per second that waves vibrate) and wavelengths (the distance between two peaks in any wave).

Words to Know

Angiography: Imaging of a blood vessel by injecting a radiopaque substance in the bloodstream and exposing the body to X rays.

Computerized axial tomography (CAT): A body imaging technique in which X-ray photographs taken from a number of angles are combined by means of a computer program.

Diagnosis: Identification of a disease or disorder.

Electromagnetic radiation: Radiation that transmits energy through the interaction of electricity and magnetism.

Imaging: The process by which a "picture" is taken of the interior of a body.

Myelography: Imaging of the spinal code by radiologic techniques.

Positron emission tomography (PET): A radiologic imaging technique that makes use of photographs produced by radiation given off by radioactive materials injected into a person's body.

Radiant energy: Any form of electromagnetic energy.

Radiation therapy: The use of X rays or other radioactive substances to treat disease.

Radiopaque: Any substance through which X rays cannot pass.

Ultrasound: A form of energy that consists of waves traveling with frequencies higher than can be heard by humans; also, a technique for imaging the human body and other objects using ultrasound energy.

X rays: Electromagnetic radiation of a wavelength just shorter than ultraviolet radiation but longer than gamma rays that can penetrate solids.

Various forms of radiant energy interact with matter in different ways. For example, visible light does not pass through most forms of matter. If you hold a sheet of paper between yourself and a friend, you will not be able to see your friend. Light waves from the friend are not able to pass through the paper.

Forms of radiant energy with higher frequencies than visible light are able to penetrate matter better than does visible light. For example, if you were to place a sheet of paper between yourself and an X-ray machine, X rays would be able to pass through the paper and to strike your body.

X rays for diagnosis

The ability of X rays to pass through matter makes them useful as a diagnostic tool to identify a disease or disorder. As an example, suppose that a doctor believes that a child has broken a bone in her arm. In order to confirm this diagnosis, the doctor may take an X ray of the child's arm. In this process, the child's arm is placed beneath a machine that emits X rays. Those X rays pass through flesh in the arm without being stopped. But the X rays are not able to pass through bone as easily. A photographic plate placed beneath the child's arm "takes a picture" of X rays that have passed through the arm. Fleshy parts of the arm show up as exposed areas, while bone shows up as unexposed areas. A doctor can look at the photograph produced and determine whether the bone is solid or has been broken. Making pictures of the interior of a person's body by a process such as this is known as imaging.

Over the years, radiologists have developed more sophisticated ways of using X rays for diagnosis. For example, regions of the body in which tissue is more dense than in other regions can be detected by X-ray imaging. The presence of such dense spots may indicate the presence of a tumor or some other abnormal structure.

Radiologists also make use of substances through which X rays cannot pass, substances that are called radiopaque. Suppose that a radiopaque substance is injected into a person's bloodstream and an X ray made of the person's arm. This process is known as angiography. The radiopaque substance in the bloodstream will show up on the X-ray photograph and allow a doctor to determine the presence of abnormalities in veins, arteries, or other parts of the circulatory system.

Another form of angiography is called myelography. In this process, a radiopaque substance is injected in the membrane covering the spine, and an X-ray photograph is taken. The resulting image can be used to diagnose problems with the spine.

Computers and radiology

In recent decades, radiologists have developed a variety of techniques in which the powers of X rays and computers have been brought together. The earliest of these techniques was computerized axial tomography (CAT). In computerized axial tomography, an X-ray machine is rotated around a person's body. Pictures are taken of some specific part of the body from many different angles. Those pictures are then put together by a computer to provide a three-dimensional image of the body part being studied.

A variation of the CAT technique is known as positron emission tomography (PET). In this technique, a radioactive material is injected into a person's body. That radioactive material emits positrons (positive electrons) and gamma rays. A scanner "reads" the gamma rays in much the same ways that X rays are scanned in a CAT machine. However, the specific radioactive material used in the process can be chosen to produce much finer images than are available with a CAT scan. Another variation of the PET process is called single photon emission computerized tomography (SPECT).

One of the first techniques used in radiology not based on X rays was ultrasound. Ultrasound is a form of energy that consists of waves traveling with frequencies higher than can be heard by humans. Ultrasound has some of the same abilities to pass through human tissue as do X rays. One of the first uses of ultrasound was to detect defects in metallic structures. Later, it became a common and powerful tool for imaging a fetus while it is still in the uterus (womb). In this procedure, a sound transmitter is used to send waves into the pregnant woman's body from various angles. As these waves bounce back off the uterus and the fetus, they are recorded both on a television screen and in a photograph. With this technology, a physician can recognize problems that may exist within the fetus or the pregnant woman's uterus.

Therapeutic applications

Radiological techniques can also be used for therapeutic purposes, methods used to treat diseases and disorders. The use of radiology for therapy depends on the fact that X rays kill living cells. Under normal circumstances, this fact provides a good reason for people to avoid coming into contact with X rays. The destruction of healthy cells by X rays is, in fact, one of the ways in which cancers may develop.

This same fact, however, provides the basis for treating cancer. Cancer is a disease characterized by the rapid, out-of-control growth of cells. Suppose that a person has been diagnosed with cancer of the spleen, for example. That diagnosis means that cells in the spleen have begun to grow much more rapidly than normal. It follows that one way to treat this condition is to bombard the spleen with X rays. Since the cancer cells are the cells growing most rapidly, they are most likely to be the cells killed by the X rays. The fact that healthy cells are also killed in this process is shown by the side-effects of radiation therapy: loss of hair, nausea, loss of weight, among others. In fact, the success of radiation therapy depends to some extent on the physician's ability to focus the cell-killing X rays on cancer cells and to protect healthy cells from those same X rays.

[See also X rays ]

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Radiology." UXL Encyclopedia of Science. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"Radiology." UXL Encyclopedia of Science. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/radiology

"Radiology." UXL Encyclopedia of Science. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

radiology, branch of medicine specializing in the use of X rays, gamma rays, radioactive isotopes, and other forms of radiation in the diagnosis and treatment of disease. X ray machines and fluoroscopes are essential in diagnosing bone fractures, tumors, and other abnormalities of the internal organs. The computerized axial tomography (CAT) scan uses computer technology to focus X rays on precise sections of the body. Magnetic resonance imaging (MRI) utilizes supercooled magnets to concentrate and focus radiation in very small areas of the body, rendering sharp detail. Radioactive isotopes are also employed in diagnosis, e.g. iodine–131 is used to confirm cases of suspected thyroid disorder. In radiotherapy, X rays, gamma rays, and other radiation sources are used in the treatment of cancer and related diseases.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/radiology

"radiology." The Columbia Encyclopedia, 6th ed.. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

ra·di·ol·o·gy / ˌrādēˈäləjē/ • n. the science dealing with X-rays and other high-energy radiation, esp. the use of such radiation for the diagnosis and treatment of disease. DERIVATIVES: ra·di·o·log·ic / ˌrādēəˈläjik/ adj. ra·di·o·log·i·cal / ˌrādēəˈläjikəl/ adj. ra·di·o·log·i·cal·ly / ˌrādēəˈläjik(ə)lē/ adv. ra·di·ol·o·gist / -jist/ n.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/radiology-0

"radiology." The Oxford Pocket Dictionary of Current English. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/radiology-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

radiology (ray-di-ol-ŏji) n. the branch of medicine involving the study of radiographs or other imaging technologies (such as ultrasound and magnetic resonance imaging) to diagnose or treat disease. diagnostic r. see radiography. interventional r. the performance of therapeutic or diagnostic procedures under the control of an appropriate imaging technique, such as X-ray fluoroscopy, ultrasound, computerized tomography, or magnetic resonance imaging. therapeutic r. see radiotherapy.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." A Dictionary of Nursing. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." A Dictionary of Nursing. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/radiology

"radiology." A Dictionary of Nursing. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/caregiving/dictionaries-thesauruses-pictures-and-press-releases/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

radiology The study and use of X-rays, radioactive materials, and other ionizing radiations for medical purposes, especially for diagnosis (diagnostic radiology) and the treatment of cancer and allied diseases (therapeutic radiology or radiotherapy).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." A Dictionary of Biology. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." A Dictionary of Biology. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiology

"radiology." A Dictionary of Biology. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

radiology Medical speciality concerned with the use of radiation and radioactive materials in the diagnosis and treatment of disease. See also radiography; radiotherapy

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." World Encyclopedia. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." World Encyclopedia. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/radiology

"radiology." World Encyclopedia. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

radiology •haji • algae • Angie •argy-bargy, Panaji •edgy, sedgy, solfeggi, veggie, wedgie •cagey, stagy •mangy, rangy •Fiji, gee-gee, squeegee •Murrumbidgee, ridgy, squidgy •dingy, fringy, mingy, stingy, whingy •cabbagy • prodigy • effigy • villagey •porridgy • strategy • cottagey •dodgy, podgy, splodgy, stodgy •pedagogy •Georgie, orgy •ogee • Fuji •bhaji, budgie, pudgy, sludgy, smudgy •bulgy •bungee, grungy, gungy, scungy, spongy •allergy, analogy, genealogy, hypallage, metallurgy, mineralogy, tetralogy •elegy •antilogy, trilogy •aetiology (US etiology), amphibology, anthology, anthropology, apology, archaeology (US archeology), astrology, biology, campanology, cardiology, chronology, climatology, cosmology, craniology, criminology, dermatology, ecology, embryology, entomology, epidemiology, etymology, geology, gynaecology (US gynecology), haematology (US hematology), hagiology, horology, hydrology, iconology, ideology, immunology, iridology, kidology, meteorology, methodology, musicology, mythology, necrology, neurology, numerology, oncology, ontology, ophthalmology, ornithology, parasitology, pathology, pharmacology, phraseology, phrenology, physiology, psychology, radiology, reflexology, scatology, Scientology, seismology, semiology, sociology, symbology, tautology, technology, terminology, theology, topology, toxicology, urology, zoology • eulogy • energy • synergy • apogee • liturgy • lethargy •burgee, clergy •zymurgy • dramaturgy

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." Oxford Dictionary of Rhymes. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." Oxford Dictionary of Rhymes. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/radiology

"radiology." Oxford Dictionary of Rhymes. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/humanities/dictionaries-thesauruses-pictures-and-press-releases/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

radiology

radiology This medical specialty originally involved the use of X-rays in the diagnosis and treatment of disease. Improved technology over the years with computer analysis of images has led to many sophisticated developments. Computed tomography (CT scans), developed by Sir Godfrey Hounsfield in 1972, was probably the most spectacular advance in radiology, using X-rays to provide three-dimensional information. Along with a progressive increase in the use of X-rays in diagnosis, other methods such as those utilizing gamma rays from radioactive isotopes (isotope scans), and positron emission tomography (PET scans), became incorporated into the modern practice of radiology. More recently radiologists have become involved also in ultrasound and magnetic resonance imaging (MRI) which do not involve ionizing radiation. Further sophistication has led to Doppler ultrasound, duplex scanning, and MRI angiography. These diagnostic methods are all known as organ imaging or imaging techniques and are described more fully elsewhere. They display in superb detail various organs or blood vessels and are very much a part of a modern radiologist's activities.

When one reflects that X-rays were only discovered in 1895, the developments have been quite staggering and expensive. Who could have foreseen, a hundred years ago, that putting patients inside magnets (MRI) could produce images? We are in the Golden Age of radiology with not enough gold to do all that is possible. Present day radiologists must be aware of the potential of these imaging methods, ensuring that optimal diagnostic pathways are followed. Radiologists now tend to subspecialize: neuroradiologists work solely within the nervous system, while others develop expertise in chest, bone, or gastrointestinal investigations.

Interventional radiology — dealing not with diagnosis but with treatment — is now a special field where various procedures are carried out using radiology for a visual display. Thus, under X-ray control, a catheter or needle may be positioned for various purposes; narrowed blood vessels in the leg or heart can be dilated (angioplasty); stents can be placed to widen arteries, bronchial airways, or ducts in the urinary or biliary tracts; tumours can be embolized (injected with material to block their blood vessels) to reduce their size; and abscesses can be drained.

J. K. Davidson


See also imaging techniques; magnetic resonance imaging; radioactivity; radiotherapy; X-rays.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"radiology." The Oxford Companion to the Body. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"radiology." The Oxford Companion to the Body. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/radiology

"radiology." The Oxford Companion to the Body. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/radiology

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Radiology

Radiology

The x ray: fundamental building block of radiology

How the x ray works

Ultrasound

Computers and the new era of radiology

Computed tomography

Magnetic resonance imaging

Positron emission tomography

Interventional radiology

Resources

Radiology is a branch of medical science that uses x rays and other forms of technology to image internal structures in the body. For nearly 80 years radiology was based primarily on the x ray, but since the 1970s several new imaging techniques have been developed. Some, like computed tomography, integrates x-ray and computer technology. Others, like ultrasound and magnetic resonance imaging are nonradiologic techniques, meaning they do not use x rays or other forms of radiant energy to probe the human body. Although radiotherapy based on the x ray has been used to treat cancer since the beginning of the twentieth century, most radiologists are primarily concerned with imaging the body to diagnose disease. However,

interventional radiology is a rapidly expanding discipline in which radiologists work either alone or hand-in-hand with surgeons to treat vascular and other diseases.

The x ray: fundamental building block of radiology

The science of radiology was born in 1895 when Wilhelm Roentgen (18451923) discovered the x ray. The German scientist was studying high voltage discharges in vacuum tubes when he noticed that the Crookes tube he was focusing on caused a piece of screen coated with the chemical barium platinocyanide to fluoresce or glow. Roentgen quickly realized that he had produced a previously unknown type of invisible radiation. In addition, this radiant energy could pass through solids like paper and wood. He also discovered that when he placed a hand between the beams source and the chemically coated screen, he could see the bones inside the fingers depicted on the screen. Roentgen quickly found that he could record the image with photographic paper.

Roentgens discovery changed the course of medicine. With the ability to look inside the body without surgery, physicians had a new diagnostic tool that could actually locate tumors or foreign objects, like bullets, thus greatly enhancing a surgeons ability to operate successfully. Roentgen called the new radiant energy x rays and, six years after his discovery, was awarded the Nobel Prize in physics.

How the x ray works

X rays are a type of radiant energy that occurs when a tungsten (a hard metallic element) target is bombarded with an electron beam. X rays are similar to visible light in that they radiate in all directions from their source. They differ, however, in that x rays are of shorter wavelength than ultraviolet light. This difference is the basis of radiology since the shorter wavelength allows x rays to penetrate many substances that are opaque to light.

An x ray of bones, organs, tumors, and other areas of the body is obtained through a cassette that holds a fluorescent screen. When activated by x rays, this screen emits light rays which produce a photochemical effect of the x rays on film. When light or x rays hit photographic film, a photochemical process takes place that results in the negative film turning black while the places not exposed to light remain clear. Images are obtained when the paper print of a negative reverses the image values. In the normal photographic process, an entire hand would be imaged because normal light cannot pass through the hand, thus creating the image on film. The desired x-ray image is obtained because x rays pass through outer tissue and are absorbed by bones and other structures, allowing them to be captured on film.

Over the years, radiology has fine tuned this approach to develop different x-ray devices for imaging specific areas of the body. For example, mammography is the radiological imaging of a womans breast to determine the presence of diseases like breast cancer. Another major advance in x-ray technology was the development of radiopaque substances. When injected into the body, these substances, which do not allow x rays to pass through them, provide images of structures that would otherwise not appear on the x ray. For example, angiography is the imaging of blood vessels after injecting them with a radiopaque material. Myelography is the imaging of the spinal cord with x rays after injecting a radiopaque substance into a membrane covering the spine.

Ultrasound

Ultrasound was the first nonradiologic technique used to image the body. Ultrasound in radiology stems from the development of pulse-echo radar during World War II (19391945). First used to detect defects in metal structures, ultrasound, or sonography, became a useful diagnostic tool in the late 1950s and early 1970s. As its name suggests, ultrasound uses sound waves rather than electromagnetic radiation to image structures.

A common use of ultrasound is to provide images of a fetus. A sound transmitter is used to send waves into the body from various angles. As these waves bounce back off the uterus and the fetus, they are recorded both on a television screen and in a photograph. With the more advanced Doppler ultrasound, this technology can be used for everything from imaging atherosclerotic disease (the thickening of arteries) to evaluating the prostate and rectum.

Computers and the new era of radiology

Except for ultrasound, from the day Roentgen discovered the x ray until the early 1970s, radiology relied solely on the application of x rays through refined radiographic techniques. These applications were limited by the x rays ability to discern only four different kinds of matter in the body: air, fat, water (which helps make up tissue), and minerals (like bone). In addition, while the x ray images bone well, it cannot image what lies behind the bone unless angiography is used. For example, a standard x ray could reveal damage to the skull but would not reveal tumors or bleeding vessels in the brain unless they calcified or caused changes to the skull. Although the development of angiography allowed scientists to view the arteries in the brain, angiography is somewhat painful for the patient and does not reveal smaller but still serious tumors and lesions.

The high-tech era of radiology coincided with rapid advances in computer technology. By using computers to analyze and interpret vast quantities of data, scientists began to develop new and better ways to image the body. Imaging processes like computed tomography, positron emission tomography, magnetic resonance imaging, and single photo emission computed tomography all rely on the computer. With these techniques, radiologists are able to diagnose a wider range of diseases and abnormalities within the body.

Computed tomography

In 1972, radiology took a giant step forward with the development of computed tomography (CT). Although still relying on the x ray, this radiographic technique uses a computer to process the vast amount of data obtained from an electronically detected signal. Since different tissues will absorb different amounts of x rays, CT passes x-ray beams through the body at different angles on one specific plane, providing detailed cross sections of a specific area. This information is scanned into a digital code which the computer can transform into a video picture. These images are much superior to conventional x-ray film and can also be made into three-dimensional images, allowing the radiologist to view a structure from different angles.

As a result of this technology, physicians could view precise and small tissues in areas like the brain without causing discomfort to the patient. CT also led scientists and engineers to conduct new research into how the computer could be used to make better images of body structures.

Magnetic resonance imaging

Although magnetic resonance imaging (MRI) dates back to 1946, it was used primarily to study atoms and molecules and to identify their properties. In 1978, the first commercial MRI scanner was available, but it was not until the 1980s that MRI became a useful tool for looking into the human body. MRI works by using a huge magnet to create a magnetic field around the patient. This field causes protons in the patients body to line up in a uniform formation. A radio pulse is then sent through the patient, which results in the protons being knocked out of alignment. When the radio pulse is turned off, the protons create a faint but recordable pulse as they spin or spiral back into position. A computer is used to turn these signals into images.

This nonradiological technique has many benefits. It does not use ionizing radiation, which can be harmful to humans. In addition, it has superb low-contrast resolution, allowing radiologists to view and diagnose a wider range of diseases and injuries within the patient, including brain tumors and carotid artery obstructions. More recent advances in MRI technology are allowing scientists to look into how the brain actually functions.

Positron emission tomography

Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are two more technologies that rely on computers. PET has been used primarily to study the dynamics of the human body. In other words, not just to see images, but to understand the processes that go on in certain areas of the body. For example, radioisotopes (naturally occurring or artificially developed radioactive substances) injected into a patient can be imaged through PET computerized technology, allowing scientists to watch how metabolism works in the brain and other parts of the body. With this technology, scientists can watch glucose metabolism, oxygen consumption, blood flow, and drug interactions.

SPECT uses radionuclides (radioactive atoms) to produce images similar to CT scans, but in much more precise three-dimensional images. The use of dual cameras, one above and one below the patient, enables radiologists to obtain simultaneous images that are then processed by computers to provide improved resolution of a structure in less time. In addition, small organs, like thyroid glands, can be better imaged for both diagnosis and research.

Interventional radiology

Interventional radiology is one of the more recent developments in radiology. As a subspecialty, it has evolved from a purely diagnostic application to a therapeutic specialty involving such procedures as balloon dilation of arteries, drainage of abscesses, removal of gallstones, and treatment of benign and malignant structures.

KEY TERMS

Radiant Anything that produces rays, such as light or heat.

Radioisotopes An unstable isotope that emits radiation when it decays or returns to a stable state.

Radionuclide Radioactive or unstable nuclide.

Radiopaque Anything that is opaque or impenetrable to x rays.

Radiotherapy The use of x rays or other radioactive substances to treat disease.

Interventional radiologists, who often work closely with surgeons, use a number of imaging tools to perform procedures like image-guided needle biopsy (removal of tissue or fluids) and percutaneous (through the skin) needle biopsy of thoracic lesions. These procedures rely heavily on the development of imaging technologies like CT and various instruments such as catheters and guide wires. Advantages of interventional radiology over surgery include reduced need for anesthesia, shorter time to perform procedures, and improved therapeutic results.

Resources

BOOKS

Erkonen, William E., and Wilbur L. Smith. Radiology 101: The Basics and Fundamentals of Imaging. 2nd ed. Philadelphia: Lippincott Williams Wilkins, 2004.

Novelline, Robert. Squires Fundamentals of Radiology. 6th ed. Cambridge, MA: Harvard University Press, 2004.

Selman, Joseph. The Fundamentals of X ray and Radium Physics. Springfield: Charles C. Thomas, 1994.

David Petechuk

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Radiology." The Gale Encyclopedia of Science. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"Radiology." The Gale Encyclopedia of Science. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/radiology-1

"Radiology." The Gale Encyclopedia of Science. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/radiology-1

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

Radiology

Radiology

Radiology is a branch of medical science that uses x rays and other forms of technology to image internal structures in the body. For nearly 80 years radiology was based primarily on the x ray, but since the 1970s several new imaging techniques have been developed. Some, like computed tomography, integrates x-ray and computer technology. Others, like ultrasound and magnetic resonance imaging are nonradiologic techniques, meaning they do not use x rays or other forms of radiant energy to probe the human body. Although radiotherapy based on the x ray has been used to treat cancer since the beginning of the 20th century, most radiologists are primarily concerned with imaging the body to diagnose disease . However, interventional radiology is a rapidly expanding discipline in which radiologists work either alone or hand-in-hand with surgeons to treat vascular and other diseases.


The X ray: fundamental building block of radiology

The science of radiology was born in 1895 when Wilhelm Roentgen discovered the x ray. The German scientist was studying high voltage discharges in vacuum tubes when he noticed that the Crookes tube he was focusing on caused a piece of screen coated with the chemical barium platinocyanide to fluoresce or glow. Roentgen quickly realized that he had produced a previously unknown type of invisible radiation . In addition, this radiant energy could pass through solids like paper and wood . He also discovered that when he placed a hand between the beam's source and the chemically coated screen, he could see the bones inside the fingers depicted on the screen. Roentgen quickly found that he could record the image with photographic paper.

Roentgen's discovery changed the course of medicine. With the ability to look inside the body without surgery , physicians had a new diagnostic tool that could actually locate tumors or foreign objects, like bullets, thus greatly enhancing a surgeon's ability to operate successfully. Roentgen called the new radiant energy x rays and, six years after his discovery, was awarded the Nobel Prize in physics .


How the x ray works

X rays are a type of radiant energy that occurs when a tungsten (a hard metallic element) target is bombarded with an electron beam. X rays are similar to visible light in that they radiate in all directions from their source. They differ, however, in that x rays are of shorter wavelength than ultraviolet light. This difference is the basis of radiology since the shorter wavelength allows x rays to penetrate many substances that are opaque to light.

An x ray of bones, organs, tumors, and other areas of the body is obtained through a cassette that holds a fluorescent screen. When activated by x rays, this screen emits light rays which produce a photochemical effect of the x rays on film. When light or x rays hit photographic film, a photochemical process takes place that results in the negative film turning black while the places not exposed to light remain clear. Images are obtained when the paper print of a negative reverses the image values. In the normal photographic process, an entire hand would be imaged because normal light cannot pass through the hand, thus creating the image on film. The desired x-ray image is obtained because x rays pass through outer tissue and are absorbed by bones and other structures, allowing them to be captured on film.

Over the years, radiology has fine tuned this approach to develop different x-ray devices for imaging specific areas of the body. For example, mammography is the radiological imaging of a woman's breast to determine the presence of diseases like breast cancer. Another major advance in x-ray technology was the development of radiopaque substances. When injected into the body, these substances, which do not allow x rays to pass through them, provide images of structures that would otherwise not appear on the x ray. For example, angiography is the imaging of blood vessels after injecting them with a radiopaque material. Myelography is the imaging of the spinal cord with x rays after injecting a radiopaque substance into a membrane covering the spine.

Ultrasound

Ultrasound was the first nonradiologic technique used to image the body. Ultrasound in radiology stems from the development of pulse-echo radar during World War II. First used to detect defects in metal structures, ultrasound, or sonography, became a useful diagnostic tool in the late 1950s and early 1970s. As its name suggests, ultrasound uses sound waves rather than electro-magnetic radiation to image structures.

A common use of ultrasound is to provide images of a fetus. A sound transmitter is used to send waves into the body from various angles. As these waves bounce back off the uterus and the fetus, they are recorded both on a television screen and in a photograph. With the more advanced Doppler ultrasound, this technology can be used for everything from imaging atherosclerotic disease (the thickening of arteries ) to evaluating the prostate and rectum.


Computers and the new era of radiology

Except for ultrasound, from the day Roentgen discovered the x ray until the early 1970s, radiology relied solely on the application of x rays through refined radiographic techniques. These applications were limited by the x ray's ability to discern only four different kinds of matter in the body: air, fat , water (which helps make up tissue), and minerals (like bone). In addition, while the x ray images bone well, it cannot image what lies behind the bone unless angiography is used. For example, a standard x ray could reveal damage to the skull but would not reveal tumors or bleeding vessels in the brain unless they calcified or caused changes to the skull. Although the development of angiography allowed scientists to view the arteries in the brain, angiography is somewhat painful for the patient and does not reveal smaller but still serious tumors and lesions.

The high-tech era of radiology coincided with rapid advances in computer technology. By using computers to analyze and interpret vast quantities of data, scientists began to develop new and better ways to image the body. Imaging processes like computed tomography, positron emission tomography, magnetic resonance imaging, and single photo emission computed tomography all rely on the computer. With these techniques, radiologists are able to diagnose a wider range of diseases and abnormalities within the body.


Computed tomography

In 1972, radiology took a giant step forward with the development of computed tomography (CT). Although still relying on the x ray, this radiographic technique uses a computer to process the vast amount of data obtained from an electronically detected signal. Since different tissues will absorb different amounts of x rays, CT passes x-ray beams through the body at different angles on one specific plane , providing detailed cross sections of a specific area. This information is scanned into a digital code which the computer can transform into a video picture. These images are much superior to conventional x-ray film and can also be made into three-dimensional images, allowing the radiologist to view a structure from different angles.

As a result of this technology, physicians could view precise and small tissues in areas like the brain without causing discomfort to the patient. CT also led scientists and engineers to conduct new research into how the computer could be used to make better images of body structures.


Magnetic resonance imaging

Although magnetic resonance imaging (MRI) dates back to 1946, it was used primarily to study atoms and molecules and to identify their properties. In 1978, the first commercial MRI scanner was available, but it was not until the 1980s that MRI became a useful tool for looking into the human body. MRI works by using a huge magnet to create a magnetic field around the patient. This field causes protons in the patient's body to "line up" in a uniform formation. A radio pulse is then sent through the patient, which results in the protons being knocked out of alignment. When the radio pulse is turned off, the protons create a faint but recordable pulse as they spin or spiral back into position. A computer is used to turn these signals into images.

This nonradiological technique has many benefits. It does not use ionizing radiation , which can be harmful to humans. In addition, it has superb low-contrast resolution, allowing radiologists to view and diagnose a wider range of diseases and injuries within the patient, including brain tumors and carotid artery obstructions. More recent advances in MRI technology are allowing scientists to look into how the brain actually functions.


Positron emission tomography

Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are two more technologies that rely on computers. PET has been used primarily to study the dynamics of the human body. In other words, not just to see images, but to understand the processes that go on in certain areas of the body. For example, radioisotopes (naturally occurring or artificially developed radioactive substances) injected into a patient can be imaged through PET computerized technology, allowing scientists to watch how metabolism works in the brain and other parts of the body. With this technology, scientists can watch glucose metabolism, oxygen consumption, blood flow, and drug interactions.

SPECT uses radionuclides (radioactive atoms) to produce images similar to CT scans, but in much more precise three-dimensional images. The use of dual cameras, one above and one below the patient, enables radiologists to obtain simultaneous images that are then processed by computers to provide improved resolution of a structure in less time. In addition, small organs, like thyroid glands , can be better imaged for both diagnosis and research.


Interventional radiology

Interventional radiology is one of the more recent developments in radiology. As a subspecialty, it has evolved from a purely diagnostic application to a therapeutic specialty involving such procedures as balloon dilation of arteries, drainage of abscesses, removal of gallstones, and treatment of benign and malignant structures.

Interventional radiologists, who often work closely with surgeons, use a number of imaging tools to perform procedures like image-guided needle biopsy (removal of tissue or fluids) and percutaneous (through the skin) needle biopsy of thoracic lesions. These procedures rely heavily on the development of imaging technologies like CT and various instruments such as catheters and guide wires. Advantages of interventional radiology over surgery include reduced need for anesthesia , shorter time to perform procedures, and improved therapeutic results.


Resources

books

Selman, Joseph. The Fundamentals of X ray and RadiumPhysics. Springfield: Charles C. Thomas, 1994.

periodicals

Evans, Ronald G. "Radiology." Journal of the American Medical Association (June 1, 1994): 1714-1715.

Hiatt, Mark. "Computers and the Revolution in Radiology." Journal of the American Medical Association (April 5, 1995): 1062.

Raichle, Marcus E. "Visualizing the Mind." Scientific American (April 1994): 58-62.


David Petechuk

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radiant

—Anything that produces rays, such as light or heat.

Radioisotopes

—An unstable isotope that emits radiation when it decays or returns to a stable state.

Radionuclide

—Radioactive or unstable nuclide.

Radiopaque

—Anything that is opaque or impenetrable to x rays.

Radiotherapy

—The use of x rays or other radioactive substances to treat disease.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Radiology." The Gale Encyclopedia of Science. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"Radiology." The Gale Encyclopedia of Science. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/radiology-0

"Radiology." The Gale Encyclopedia of Science. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/radiology-0

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.