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Dictionary:
x-ray X-ray (ĕks'rā') |
[From the fact that it was a previously unknown form of radiation when first discovered.]
| 5min Related Video: X-rays |
| Oncology Encyclopedia: X Rays |
Key Terms: Angiography, Computed tomography, Contrast dye, Fluoroscopy, Gene therapy, Interventional radiography, Pleural effusion.
Definition
X rays are a type of radiation used in imaging and therapy that uses short wavelength energy beams capable of penetrating most substances except heavy metals.
Purpose
Diagnostic x rays are some of the most powerful medical imaging tools available. Other imaging techniques that do not use x rays include magnetic resonance imaging (MRI), ultrasonography, and radionucleotide imaging. Based on the symptoms presented by the patient, the physician can request specific x rays (such as chest x rays) that help diagnose many types of cancers, including sarcomas, lymphomas, and lung cancers. X rays allow the physician to visualize certain internal body conditions with little or no invasive procedures. Conditions may be visualized on photographic film, or for more complex and detailed information, computed tomography (CT scan), fluroscopy, or angiography might be used.
Precautions
Before consenting to any x-ray procedure, the patient should consider the impact of existing medical conditions or medications. Sensitivities to contrast dyes may produce allergic reactions. Pregnant women or those who suspect they might be pregnant should consult a physician prior to x-ray treatments to avoid injury to the fetus. Nursing mothers may be required to store enough milk to last for 48 hours following certain procedures. Patient age should always be taken into consideration when choosing the type and intensity of x ray. Patients should be aware that some prescribed cancer medications act as radiosensitizers and amplify the effect of x rays. Any patient with a suppressed immune system or diabetes may require special x-ray procedures.
Description
X-ray procedures are administered in a hospital or clinical setting. Most procedures may be conducted on an outpatient basis. The time required for the procedure may vary from a few minutes to more than an hour. There is little or no discomfort associated with diagnostic x rays. The general procedure for diagnostic x rays include:
Preparation
Diagnostic x rays require little preparation. The patient may be required to abstain from food and liquids for a certain period prior to the x ray. For some x rays, enemas may be necessary or a contrast agent may be administered immediately prior to or during the procedure.
Aftercare
For non-invasive diagnostic x-ray procedures, the patient is dismissed immediately after the films have been reviewed, and little or no aftercare is necessary.
Risks
A general rule for x rays suggests that the beneficial effects of x rays far exceed the risks involved. As a result of certified training and strict guideline compliance, risks from technical application are essentially nonexistent. However, for any x-ray procedure, radiation exposure is always a concern, and although uncommon, the risk of infection during invasive techniques can not be discounted.
Normal Results
Diagnostic x rays provide detailed information that the physician can use to determine the best approach to correct or control a medical problem. Normal results would indicate no existing abnormalities.
Abnormal Results
Abnormal results would indicate irregularities such as a tumor, an enlarged lymph node, or pleural effusion. Although highly unlikely, diagnostic x-ray films can be misread and the wrong diagnosis made.
Resources
Books
Brant, William E., and Clyde A. Helms, editors. Fundamentals of Diagnostic Radiology. 2nd ed. Baltimore: Williams & Wilkins, 1999.
Periodicals
Henchke, Claudia, et al. "Early Lung Cancer Action Project: Overall Design and Findings from Baseline Screening." Lancet 354 (July 1999): 99–105.
Other
"CT Screening Detects Majority of Lung Cancer Cases Missed by X ray." RSNA Meeting. Dec., 1998. [cited March 29, 2001 and June 28, 2001].
Harrison, Pam. Lung Cancer Detected Earlier with CT Scan than with X ray. 2000 Reuters Ltd. 29 March 2001. [cited June 28, 2001].
Marchant, Joan. "Pixels Join Cancer Fight." The Guardian. Dec. 1999. [cited April 21, 2001 and June 28, 2001].
Questions to Ask the Doctor
| Sci-Tech Encyclopedia: X-rays |
X-rays, or roentgen rays, are electromagnetic waves in which periodically variable electric and magnetic fields are perpendicular to each other and to the direction of propagation. Thus they are identical in nature with visible light and all the other types of radiation that constitute the electromagnetic spectrum. In general, x-rays are generated as the result of energy transitions of atomic electrons caused by the bombardment of a material of high atomic weight by high-energy electrons. See also Electromagnetic radiation.
Following W. R. Röntgen's discovery of “a new kind of ray” in 1895, other scientists found the essential experimental conditions to prove that x-rays can be polarized, diffracted by crystals, refracted in prisms and in crystals, reflected by mirrors, and diffracted by ruled gratings. See also X-ray optics.
The range of x-rays in the electromagnetic spectrum, as excited in x-ray tubes by the bombardment of anode targets by cathode electrons under a high accelerating potential, overlaps the ultraviolet range on the order of 100 nanometers on the long-wavelength side, and the shortest-wavelength limit moves downward as voltages increase. An accelerating potential of 109 volts, now readily generated, produces a wavelength of 10−15 m (10−6 nm). An average wavelength used in research is 0.1 nm, or about 1/6000 the wavelength of yellow light. See also X-ray tube.
In diffraction, refraction, polarization, and interference phenomena, x-rays, together with all other related radiations, appear to act as waves. In other phenomena—such as the appearance of sharp spectral lines, a definite short-wavelength limit of the continuous “white” spectrum, the shift in wavelength of x-rays scattered by electrons in atoms (Compton effect), and the photoelectric effect—the energy seems to be propagated and transferred in quanta, called photons. See also Compton effect; Electron diffraction; Neutron diffraction; Photoemission;
Important uses have been found for x-rays in many fields of scientific endeavor, for example, roentgen spectrometry and roentgen diffractometry. Extensive tables of the wavelengths of x-ray emission lines in series (K, L, M, and so on) and so-called absorption edges, characteristic of the chemical elements, afford the necessary information for chemical analyses, exactly as in the case of optical emission spectra and for derivation of theories of atomic structure to account for the origin of spectra. See also Historadiography; Microradiography; Radiation biology; Radiography; Radiology; X-ray crystallography; X-ray diffraction; X-ray fluorescence analysis; X-ray microscope; X-ray powder methods.
| World of the Body: X-rays |
Wilhelm Conrad Röntgen, Professor of Physics in Wurzburg, Bavaria, accidentally discovered X-rays in November 1895 while studying cathode rays in a low pressure gas discharge tube. Alone in his laboratory on a Friday evening, he placed his hand in the path of the invisible rays which he was investigating, and saw an image of the bones on the screen beyond. Later, using a photographic plate instead of a screen, he made the first X-ray photograph — of his wife's hand, her wedding ring clearly visible. This was a highly significant breakthrough in the history of medicine because it made so many other things possible. It opened a window to what goes on in our bodies and in our heads. While news flashed round the world and most read of the discovery in the newspapers, Röntgen sent copies of his scientific paper to only two people in Britain: Lord Kelvin in Glasgow, for whom he had the highest esteem, and Professor Shuster in Manchester. Kelvin passed his copy to Dr John Macintyre, ‘Medical Electrician’ at the Glasgow Royal Infirmary. Like many others — physicists, electrical engineers, and doctors — in those early hectic days, and perhaps the most energetic of all the medical pioneers, Macintyre quickly grasped the significance of this ‘new light’ as it was then known. His X-ray department was up and running by March 1896 — one of the first radiological departments in the world. He subsequently had many other ‘firsts’: an X-ray of a kidney stone, a halfpenny in the gullet of a child, and, most spectacular, a ‘cineradiogram’ showing movements of a frog's legs. He probably did not produce the first medical radiograph in Britain: this is attributed to another Scot, Campbell Swinton, electrician and photographer in London, who also gave the first public demonstration of X-rays to the Royal Photographic Society in February 1896 — just one day before an open-air demonstration by a Birmingham GP, Hall-Edwards; he was also one of the first to apply X-rays to diagnosis: in that same month he took a photograph which located a needle in a woman's hand. There followed a distinct move to treat these new rays as public entertainment, but while some treated Röntgen's discovery with a certain hilarity and scepticism, like a freak show, the medical profession quickly recognized its potential. In the months following the news, scientists and doctors on both sides of the Atlantic were among the earliest pioneers working feverishly to reproduce X-rays and radiographs (medical X-ray photographs). Among the first medical radiologists, along with John Macintyre, were Sidney Rowland, who demonstrated X-rays to the Medical Society of London, and greatly advanced the cause whilst an undergraduate scholar in 1896 at St Bartholomew's Hospital; and Francis H. Williams in Boston, MA, who published a book in 1902 on the diagnostic and therapeutic use of X-rays, and in the 1920s wrote of his reminiscences as a pioneer.
— J. K. Davidson
Bibliography
See also imaging techniques; radiation, ionizing; radiology.
| Food and Fitness: X-ray |
Radiation that can penetrate body structures to varying degrees. X-rays are used in radiography to produce photographic images of internal structures. They are used in the diagnosis of sports injuries where there is a suspected fracture.
| Dental Dictionary: x-ray |
A type of electromagnetic radiation characterized by wavelengths between approximately 103 Å and 10-4 Å, corresponding to photon energies of about 20 eV to 125 MeV. X-rays are invisible; penetrative, especially at higher photon energies; and travel with the same speed as visible light. Typical production involves bombarding a target of high atomic number with fast electrons in a high vacuum; they are also emitted as a product of some radioactive disintegrations (specifically originating from the extranuclear part of the atom). X-rays were first discovered by Wilhelm C. Roentgen in 1895; hence the term roentgen rays, often applied to mechanically generated x-rays. Roentgen called them x-rays after the mathematic symbol x for an unknown.
| Medical Test: X-rays |
| Where It's Done | Who Does It | How Long It Takes | Discomfort/Pain |
| Doctor's office, radiology unit, outpatient clinic, or diagnostic clinic. | Technician, radiologist, or other doctor. | 5-10 minutes. | None, but some people find it uncomfortable to remain still during the procedure. |
| Results Ready When | Special Equipment | Risks/Complications | Average Cost |
| Often in a few minutes; may take longer in some cases. | X-ray unit, which varies for special studies such as mammography. | Small risk from radiation exposure; use of contrast agent can cause allergic reaction. | Depends on the study and the number of X-rays taken. |
Radiography.
PurposeThere are many different types of X-rays; the following are among the most common:
A radiologist or other medical specialist will interpret the films.
Advantages| Children's Health Encyclopedia: X Rays |
Definition
X rays are electromagnetic radiation that differentially penetrates structures within the body and creates images of these structures on photographic film or a fluorescent screen. These images are called diagnostic x rays.
Purpose
Diagnostic x rays are useful in detecting abnormalities within the body. They are a painless, non-invasive way to help diagnose problems such as broken bones, tumors, dental decay, and the presence of foreign bodies.
Description
X rays are a form of radiation similar to light rays, except that they are more energetic than light rays and are invisible to the human eye. They are created when an electric current is passed through a vacuum tube. X rays were accidentally discovered in 1895 by German physicist Wilhem Roentgen (1845-1923), who was later awarded the first Nobel Prize in physics for his discovery. Roentgen was also a photographer and almost immediately realized that the shadows created when x rays passed through the body could be permanently recorded on photographic plates. His first x-ray picture was of his wife's hand. Within a few years, x rays became a valued diagnostic tool of physicians world-wide.
How X Rays Work
X rays pass easily through air and soft tissue of the body. When they encounter more dense material, such as a tumor, bone, or a metal fragment, they are stopped. Diagnostic x rays are performed by positioning the part of the body to be examined between a focused beam of x rays and a plate containing film. This process is painless. The greater the density of the material that the x rays pass through, the more rays are absorbed. Thus bone absorbs more x rays than muscle or fat, and tumors may absorb more x rays than surrounding tissue. The x rays that pass through the body strike the photographic plate and interact with silver molecules on the surface of the film.
Once the film plates have been processed, dense material such as bone shows up as white, while softer tissue shows up as shades of gray, and airspaces look black. A radiologist, who is a physician trained to interpret diagnostic x rays, examines the pictures and reports to the doctor who ordered the tests. Plain film x rays normally take only a few minutes to perform and can be done in a hospital, radiological center, clinic, doctor's or dentist's office, or at bedside with a portable x-ray machine.
Special Types of X-Ray Procedures
Mammograms are fixed plate x rays that are designed to locate tumors within the breasts. Dental x rays are designed to locate decay within the tooth. Sometimes a liquid called contrast material (for example, barium) is used to help outline internal organs such as the intestines. The contrast material absorbs x rays, helping to make soft tissue more easily visible on the x-ray films. Contrast material is commonly used in making x rays of the digestive system. The contrast liquid can be swallowed or injected, depending on the part of the body being x rayed. This may cause some minor discomfort.
Fluoroscopy is a special x-ray technique that produces real-time images on a television monitor. With fluoroscopy, contrast material is injected into a blood vessel. The physician can then watch the real-time movement of the contrast material to determine if there are blockages in circulation. Fluoroscopy is also used to help guide catheters into place in the heart during cardiac catheterization or to guide an endoscope during endoscopic surgery.
Computed tomography or CT scan works on the same principles as fixed plate x rays, only with a CT scan, an x ray tube rotates around the individual, taking hundreds of images that are then compiled by a computer to produce a two-dimensional cross section of the body. Although many images are taken to produce a CT scan, the total dose of radiation the individual is exposed to is low. Other common imaging techniques such as magnetic resonance imaging (MRI) and ultrasound do not use x rays.
How X Rays Are Performed
Fixed plate x rays are extremely common diagnostic tests. A trained x-ray technologist takes the x ray. The individual is first asked to remove clothing and jewelry and to wear a hospital gown. The x ray technologist positions the patient appropriately, so that the part of the body to be x rayed will be between the x-ray beam and the film plate. Usually the individual either lies on an adjustable table or stands. Parts of the body that are especially sensitive to damage by x rays (for example, the reproductive organs, the thyroid) are shielded with a lead apron. Lead is very dense and effectively protects the body by stopping all x rays.
It is essential to remain motionless during the x ray, since movement causes the resulting picture to be blurry. Sometimes patients are asked to hold their breath briefly during the procedure. Children who are not old enough follow directions or who cannot stay still may need to be restrained or given medication to sedate them in order to keep them still enough to obtain useful results. Sometimes parents can stay with children during an x ray, unless the mother is pregnant, in which case she must protect the fetus from x-ray exposure.
If a contrast material is to be used, the individual will be given special instructions to prepare for the procedure and may be asked to remain afterwards until recovery is complete. (See Preparation and Aftercare below.)
Precautions
Although unnecessary exposure to radiation should be avoided, the low levels of radiation one is exposed to during an x ray does not cause harm with a few exceptions. Pregnant women should not have x rays unless in emergencies the benefits highly outweigh the risks. Exposure of the fetus to x rays, especially during early pregnancy can increase the risk of the child later developing leukemia. Body parts not being x rayed should be shielded with a lead apron, especially the testes, ovaries, and thyroid.
Preparation
No special preparation is needed for fixed plate x rays unless contrast material is used. When x rays are scheduled that involve the use of contrast material, the physician will give specific instructions for preparation. For example, in a lower GI series, the individual may have to fast and use special laxatives to cleanse the bowel before swallowing the contrast material. Parents can prepare children for x rays be explaining what will happen and that these tests are short and painless.
Aftercare
Little aftercare is needed following an x ray. In complicated x rays where contrast material is injected into a blood vessel, the individual may need to remain under medical care for a short while to assure that there is no allergic reaction to the contrast material and recovery is complete.
Risks
Low dose exposure to x rays creates minimal cell damage and minimal risk when x rays are performed in an accredited facility. There is an increased risk that a developing fetus will develop leukemia during childhood if exposed to x-ray radiation; pregnant or potentially pregnant women should avoid x rays. There is also a slight risk of an allergic reaction to the contrast material or dye used in certain x rays.
Parental Concerns
Some parents are concerned about health consequences of their child's exposure to x-ray radiation. However, doses of radiation received in most x rays are quite similar to the environmental (background) radiation one is exposed to simply by living on Earth. Although unnecessary x rays should be avoided, in most cases, the benefits greatly outweigh the potentially small increased risk of exposure.
See also Computed tomography.
Resources
Books
Faculty Members at the Yale University School of Medicine and G.S. Sharpe Communications, Inc. "Chapter 3 Diagnostic Imaging." The Patient's Guide to Medical Tests, 2nd ed. New York: Houghton Mifflin, 2002.
Periodicals
Cooper, Phyllis G. "X-Rays During Pregnancy." Clinical Reference Systems Annual, 2002 p3574.
Organizations
American College of radiology 1891 Preston White Drive, Reston, Virginia 20191-4397. Telephone (800) 227-5463. www/acr.org/flash.html
Radiological Society of North America. 820 Jorie Boulevard, Oak Brook, Illinois 60523-2251. Telephone: (800) 381-6660. www.rsna.org
Web Sites
Cameron, John R. "Understanding X-rays." eMedicine.com Consumer Health 2003 [cited 22 September 2004]. www.emedicinehealth.com/fulltext/12071.htm
Children's Virtual Hospital. "X-Rays." Children's Hospital of Iowa/University of Iowa. 2004 [cited 18 September 2004]. www.vh.org/pediatric/patient/pediatrics/cqqa/xrays.html
Harvard Medical Schools Consumer Health Education. "X-Rays." InteliHealth Procedures and Treatments 3 June 2003 (cited 22 September 2004) www.intelihealth.com
[Article by: Tish Davidson, A.M.]
| Britannica Concise Encyclopedia: X-ray |
For more information on X-ray, visit Britannica.com.
| Sports Science and Medicine: X-rays |
Electromagnetic radiation of very short wavelength, which can penetrate body structures to varying degrees. X-rays are used in radiography to produce photographic images of the body structures, and they are used in some forms of radiotherapy.
| Columbia Encyclopedia: X ray |
Production of X Rays
An important source of X rays is synchrotron radiation. X rays are also produced in a highly evacuated glass bulb, called an X-ray tube, that contains essentially two electrodes-an anode made of platinum, tungsten, or another heavy metal of high melting point, and a cathode. When a high voltage is applied between the electrodes, streams of electrons (cathode rays) are accelerated from the cathode to the anode and produce X rays as they strike the anode.
Two different processes give rise to radiation of X-ray frequency. In one process radiation is emitted by the high-speed electrons themselves as they are slowed or even stopped in passing near the positively charged nuclei of the anode material. This radiation is often called brehmsstrahlung [Ger.,=braking radiation]. In a second process radiation is emitted by the electrons of the anode atoms when incoming electrons from the cathode knock electrons near the nuclei out of orbit and they are replaced by other electrons from outer orbits. The spectrum of frequencies given off with any particular anode material thus consists of a continuous range of frequencies emitted in the first process, and superimposed on it a number of sharp peaks of intensity corresponding to discrete frequencies at which X rays are emitted in the second process. The sharp peaks constitute the X-ray line spectrum for the anode material and will differ for different materials.
Applications of X Rays
Most applications of X rays are based on their ability to pass through matter. This ability varies with different substances; e.g., wood and flesh are easily penetrated, but denser substances such as lead and bone are more opaque. The penetrating power of X rays also depends on their energy. The more penetrating X rays, known as hard X rays, are of higher frequency and are thus more energetic, while the less penetrating X rays, called soft X rays, have lower energies. X rays that have passed through a body provide a visual image of its interior structure when they strike a photographic plate or a fluorescent screen; the darkness of the shadows produced on the plate or screen depends on the relative opacity of different parts of the body.
Photographs made with X rays are known as radiographs or skiagraphs. Radiography has applications in both medicine and industry, where it is valuable for diagnosis and nondestructive testing of products for defects. Fluoroscopy is based on the same techniques, with the photographic plate replaced by a fluorescent screen (see fluorescence; fluoroscope); its advantages over radiography in time and cost are balanced by some loss in sharpness of the image. X rays are also used with computers in CAT (computerized axial tomography) scans to produce cross-sectional images of the inside of the body.
Another use of radiography is in the examination and analysis of paintings, where studies can reveal such details as the age of a painting and underlying brushstroke techniques that help to identify or verify the artist. X rays are used in several techniques that can provide enlarged images of the structure of opaque objects. These techniques, collectively referred to as X-ray microscopy or microradiography, can also be used in the quantitative analysis of many materials. One of the dangers in the use of X rays is that they can destroy living tissue and can cause severe skin burns on human flesh exposed for too long a time. This destructive power is used in X-ray therapy to destroy diseased cells.
Discovery and Early Scientific Use
X rays were discovered in 1895 by W. C. Roentgen, who called them X rays because their nature was at first unknown; they are sometimes also called Roentgen, or Röntgen, rays. X-ray line spectra were used by H. G. J. Moseley in his important work on atomic numbers (1913) and also provided further confirmation of the quantum theory of atomic structure. Also important historically is the discovery of X-ray diffraction by Max von Laue (1912) and its subsequent application by W. H. and W. L. Bragg to the study of crystal structure.
Bibliography
See D. Graham and T. Eddie, X-ray Techniques in Art Galleries and Museums (1985); B. H. Kevles, Naked to the Bone: Medical Imaging in the Twentieth Century (1997).
| Biology Q&A: What are X-rays? |
X-rays are electromagnetic radiation with
short wavelengths (10-3 nanometers) and a great amount of energy.
They were discovered in 1898 by William Conrad Roentgen (1845-1923).
X-rays are frequently used in medicine because they are able to pass through
opaque, dense structures such as bone and form an image on a photographic
plate.
Previous question:
What is the electromagnetic spectrum?
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What is X-ray crystallography?
| Science Dictionary: x-ray |
A form of electromagnetic radiation with very high frequency and energy. X-rays lie between ultraviolet radiation and gamma radiation on the electromagnetic spectrum.
| Health Dictionary: x-ray |
| Veterinary Dictionary: x-ray |
Electromagnetic radiation of wavelengths ranging between 5.0 × 10−6 and 5.0 × 10−4 μm (including grenz rays).
X-rays are produced by the collision of a beam of electrons with a metal target in an x-ray tube. Called also roentgen rays. The penetrability and hardness of the x-rays increases with the voltage applied to the x-ray tube, which controls the speed with which the electrons strike the target. For diagnostic radiography, tube voltages in the range 50 to 120 kilovolts peak (kVp) are normally used. For radiation therapy, voltages in the 1 to 2 megavolt range are used for most treatment. Accelerating electrons to speeds high enough to produce megavoltage x-rays requires a linear accelerator (lineac).
The x-ray exposure is proportional to the tube current (milliamperage) and also to the exposure time. In diagnostic radiography, the tube voltage and current and exposure time are selected to produce a high-quality radiograph with the correct contrast and film density. In radiation therapy, these exposure factors are selected to deliver a precisely calculated radiation dose to the tumor. The total dose is usually fractionated so that tumor cells can be oxygenated as surrounding cells die; this increases the sensitivity of the cells to radiation.
Body tissues and other substances are classified according to the degree to which they allow the passage of x-rays (radiolucency) or absorb x-rays (radiopacity). Gases are very radiolucent; fatty tissue is moderately radiolucent. Compounds containing high-atomic-weight elements, such as barium and iodine, are very radiopaque; bone and deposits of calcium salts are moderately radiopaque. Water; muscle, skin, blood and cartilage and other connective tissue; and cholesterol and uric acid stones have intermediate density. See also radiation and radiation therapy.
A double contrast study uses both a radiopaque and a radiolucent contrast medium; for example, the walls of the stomach or intestine are coated with barium and the lumen is filled with air. The resulting radiographs clearly show the pattern of mucosal ridges.
| Dream Symbol: X-ray |
Being X-rayed in a dream may signal wanting to see through a situation or the intentions of someone who is emotionally significant in one's life.
| Wikipedia: X-ray |
X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3 × 1016 Hz to 3 × 1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays. In many languages, X-radiation is called Röntgen radiation after Wilhelm Conrad Röntgen, who is generally credited as their discoverer, and who had called them X-rays to signify an unknown type of radiation.[3]:1-2
X-rays can penetrate solid objects, and their largest use is to take images of the inside of objects in diagnostic radiography and crystallography. As a result, the term X-ray is metonymically used to refer to a radiographic image produced using this method, in addition to the method itself. X-rays are a form of ionizing radiation, and exposure to them can be a health hazard.
X-rays from about 0.12 to 12 keV (10 to 0.10 nm wavelength), are classified as soft X-rays, and from about 12 to 120 keV (0.10 to 0.010 nm wavelength) as hard X-rays, due to their penetrating abilities.
The distinction between X-rays and gamma rays has changed in recent decades. Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays).[4] So older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10−11 m, defined as gamma rays.[5] However, as shorter wavelength continuous spectrum "X-ray" sources such as linear accelerators and longer wavelength "gamma ray" emitters were discovered, the wavelength bands largely overlapped. The two types of radiation are now usually distinguished by their origin: X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus.[4][6][7][8]
Contents |
The measure of X-rays ionizing ability is called the exposure:
However, the effect of ionizing radiation on matter (especially living tissue) is more closely related to the amount of energy deposited rather than the charge. This is called the absorbed dose:
The equivalent dose is the measure of the biological effect of radiation on human tissue. For X-rays it is equal to the absorbed dose.
Medical X-rays are a major source of manmade radiation exposure, accounting for 58% in the USA in 1987, but since most radiation exposure is natural (82%) it only accounts for 10% of total USA radiation exposure.[9]
Reported dosage due to dental X-rays seems to vary significantly. Depending on the source, a typical dental X-ray of a human results in an exposure of perhaps, 3,[10] 40,[11] 300,[12] or as many as 900[13] mrems (30 to 9,000 μSv).
| Target | Kβ₁ | Kβ₂ | Kα₁ | Kα₂ |
|---|---|---|---|---|
| Fe | 0.17566 | 0.17442 | 0.193604 | 0.193998 |
| Co | 0.162079 | 0.160891 | 0.178897 | 0.179285 |
| Ni | 0.15001 | 0.14886 | 0.165791 | 0.166175 |
| Cu | 0.139222 | 0.138109 | 0.154056 | 0.154439 |
| Zr | 0.070173 | 0.068993 | 0.078593 | 0.079015 |
| Mo | 0.063229 | 0.062099 | 0.070930 | 0.071359 |
X-rays are generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate electrons released by a hot cathode to a high velocity. The high velocity electrons collide with a metal target, the anode, creating the X-rays.[15] In medical X-ray tubes the target is usually tungsten or a more crack-resistant alloy of rhenium (5%) and tungsten (95%), but sometimes molybdenum for more specialized applications, such as when soft X-rays are needed as in mammography. In crystallography, a copper target is most common, with cobalt often being used when fluorescence from iron content in the sample might otherwise present a problem.
The maximum energy of the produced X-ray photon is limited by the energy of the incident electron, which is equal to the voltage on the tube, so an 80 kV tube cannot create X-rays with an energy greater than 80 keV. When the electrons hit the target, X-rays are created by two different atomic processes:
So the resulting output of a tube consists of a continuous bremsstrahlung spectrum falling off to zero at the tube voltage, plus several spikes at the characteristic lines. The voltages used in diagnostic X-ray tubes, and thus the highest energies of the X-rays, range from roughly 20 to 150 kV.[16]
In medical diagnostic applications, the low energy (soft) X-rays are unwanted, since they are totally absorbed by the body, increasing the dose. So a thin metal (often aluminum, but can be one of many X-ray filters) sheet is placed over the window of the X-ray tube, filtering out the low energy end of the spectrum. This is called hardening the beam.
Both X-ray production processes are extremely inefficient (~1%) and thus to produce a usable flux of X-rays plenty of energy has to be wasted into heat, which has to be removed from the X-ray tube.
Radiographs obtained using X-rays can be used to identify a wide spectrum of pathologies. Due to their short wavelength, in medical applications, X-rays act more like a particle than a wave. This is in contrast to their application in crystallography, where their wave-like nature is most important.
To take an X-ray of the bones, short X-ray pulses are shot through a body with radiographic film behind. The bones absorb the most photons by the photoelectric process, because they are more electron-dense. The X-rays leave a latent image in the photographic film; when it is subsequently developed, the parts of the image corresponding to higher X-ray exposure are dark, leaving a white shadow of bones on the film.
To generate an image of the cardiovascular system, including the arteries and veins (angiography) an initial image is taken of the anatomical region of interest. A second image is then taken of the same region after iodinated contrast material has been injected into the blood vessels within this area. These two images are then digitally subtracted, leaving an image of only the iodinated contrast outlining the blood vessels. The radiologist or surgeon then compares the image obtained to normal anatomical images to determine if there is any damage or blockage of the vessel.
A specialized source of X-rays which is becoming widely used in research is synchrotron radiation, which is generated by particle accelerators. Its unique features are brightness many orders of magnitude greater than X-ray tubes, wide spectrum, high collimation, and linear polarization.[17]
The detection of X-rays is based on various methods. The most commonly known methods are a photographic plate, X-ray film in a cassette, and rare earth screens. Regardless of what is "catching" the image, they are all categorized as "Image Receptors" (IR).
Before computers and before digital imaging, a photographic plate was used to produce radiographic images. The images were produced right on the glass plates. Film replaced these plates and was used in hospitals to produce images. Now computed & digital radiography has started to replace film in medicine, though film technology remains in use in industrial radiography processes (e.g. to inspect welded seams). Photographic plates are a thing of history, and their replacement (intensifying screens) is now becoming part of that same history. Silver (necessary to the radiographic & photographic industry) is a non-renewable resource, that has now been replaced by digital (DR) and computed (CR) technology. Where film required wet processing facilities, these new technologies do not. Archiving of these new technologies also saves space.
Since photographic plates are sensitive to X-rays, they provide a means of recording the image, but require a lot of exposure (to the patient), so intensifying screens were devised. They allow a lower dose to the patient, because the screens take the X-ray information and intensify it so that it can be recorded on film positioned next to the intensifying screen.
The part of the patient to be X-rayed is placed between the X-ray source and the image receptor to produce a shadow of the internal structure of that particular part of the body. X-rays are partially blocked ("attenuated") by dense tissues such as bone, and pass more easily through soft tissues. Areas where the X-rays strike darken when developed, causing bones to appear lighter than the surrounding soft tissue.
Contrast compounds containing barium or iodine, which are radiopaque, can be ingested in the gastrointestinal tract (barium) or injected in the artery or veins to highlight these vessels. The contrast compounds have high atomic numbered elements in them that (like bone) essentially block the X-rays and hence the once hollow organ or vessel can be more readily seen. In the pursuit of a non-toxic contrast material, many types of high atomic number elements were evaluated. For example, the first time the forefathers used contrast it was chalk, and was used on a cadaver's vessels. Unfortunately, some elements chosen proved to be harmful – for example, thorium was once used as a contrast medium (Thorotrast) – which turned out to be toxic in some cases (causing injury and occasionally death from the effects of thorium poisoning). Modern contrast material has improved, and while there is no way to determine who may have a sensitivity to the contrast, the incidence of "allergic-type reactions" are low. (The risk is comparable to that associated with penicillin.[citation needed])
An increasingly common method is the use of photostimulated luminescence (PSL), pioneered by Fuji in the 1980s. In modern hospitals a photostimulable phosphor plate (PSP plate) is used in place of the photographic plate. After the plate is X-rayed, excited electrons in the phosphor material remain "trapped" in "colour centres" in the crystal lattice until stimulated by a laser beam passed over the plate surface. The light given off during laser stimulation is collected by a photomultiplier tube and the resulting signal is converted into a digital image by computer technology, which gives this process its common name, computed radiography (also referred to as digital radiography). The PSP plate can be reused, and existing X-ray equipment requires no modification to use them.
Initially, most common detection methods were based on the ionization of gases, as in the Geiger-Müller counter: a sealed volume, usually a cylinder, with a mica, polymer or thin metal window contains a gas, a cylindrical cathode and a wire anode; a high voltage is applied between the cathode and the anode. When an X-ray photon enters the cylinder, it ionizes the gas and forms ions and electrons. Electrons accelerate toward the anode, in the process causing further ionization along their trajectory. This process, known as a Townsend avalanche, is detected as a sudden current, called a "count" or "event".
In order to gain energy spectrum information, a diffracting crystal may be used to first separate the different photons. The method is called wavelength dispersive X-ray spectroscopy (WDX or WDS). Position-sensitive detectors are often used in conjunction with dispersive elements. Other detection equipment that is inherently energy-resolving may be used, such as the aforementioned proportional counters. In either case, use of suitable pulse-processing (MCA) equipment allows digital spectra to be created for later analysis.
For many applications, counters are not sealed but are constantly fed with purified gas, thus reducing problems of contamination or gas aging. These are called "flow counters".
Some materials such as sodium iodide (NaI) can "convert" an X-ray photon to a visible photon; an electronic detector can be built by adding a photomultiplier. These detectors are called "scintillators", filmscreens or "scintillation counters". The main advantage of using these is that an adequate image can be obtained while subjecting the patient to a much lower dose of X-rays.
X-rays are also used in "real-time" procedures such as angiography or contrast studies of the hollow organs (e.g. barium enema of the small or large intestine) using fluoroscopy acquired using an X-ray image intensifier. Angioplasty, medical interventions of the arterial system, rely heavily on X-ray-sensitive contrast to identify potentially treatable lesions.
Since the 1970s, new semiconductor detectors have been developed (silicon or germanium doped with lithium, Si(Li) or Ge(Li)). X-ray photons are converted to electron-hole pairs in the semiconductor and are collected to detect the X-rays. When the temperature is low enough (the detector is cooled by Peltier effect or even cooler liquid nitrogen), it is possible to directly determine the X-ray energy spectrum; this method is called energy dispersive X-ray spectroscopy (EDX or EDS); it is often used in small X-ray fluorescence spectrometers. These detectors are sometimes called "solid state detectors". Detectors based on cadmium telluride (CdTe) and its alloy with zinc, cadmium zinc telluride, have an increased sensitivity, which allows lower doses of X-rays to be used.
Practical application in medical imaging started in the 1990s. Currently amorphous selenium is used in commercial large area flat panel X-ray detectors for mammography and chest radiography. Current research and development is focused around pixel detectors, such as CERN's energy resolving Medipix detector.
Note: A standard semiconductor diode, such as a 1N4007, will produce a small amount of current when placed in an X-ray beam. A test device once used by Medical Imaging Service personnel was a small project box that contained several diodes of this type in series, which could be connected to an oscilloscope as a quick diagnostic.
Silicon drift detectors (SDDs), produced by conventional semiconductor fabrication, now provide a cost-effective and high resolving power radiation measurement. Unlike conventional X-ray detectors, such as Si(Li)s, they do not need to be cooled with liquid nitrogen.
With the advent of large semiconductor array detectors it has become possible to design detector systems using a scintillator screen to convert from X-rays to visible light which is then converted to electrical signals in an array detector. Indirect Flat Panel Detectors (FPDs) are in widespread use today in medical, dental, veterinary and industrial applications.
The array technology is a variant on the amorphous silicon TFT arrays used in many flat panel displays, like the ones in computer laptops. The array consists of a sheet of glass covered with a thin layer of silicon that is in an amorphous or disordered state. At a microscopic scale, the silicon has been imprinted with millions of transistors arranged in a highly ordered array, like the grid on a sheet of graph paper. Each of these thin film transistors (TFTs) is attached to a light-absorbing photodiode making up an individual pixel (picture element). Photons striking the photodiode are converted into two carriers of electrical charge, called electron-hole pairs. Since the number of charge carriers produced will vary with the intensity of incoming light photons, an electrical pattern is created that can be swiftly converted to a voltage and then a digital signal, which is interpreted by a computer to produce a digital image. Although silicon has outstanding electronic properties, it is not a particularly good absorber of X-ray photons. For this reason, X-rays first impinge upon scintillators made from e.g. gadolinium oxysulfide or caesium iodide. The scintillator absorbs the X-rays and converts them into visible light photons that then pass onto the photodiode array.
While generally considered invisible to the human eye, in special circumstances X-rays can be visible.[18] Brandes, in an experiment a short time after Röntgen's landmark 1895 paper, reported after dark adaptation and placing his eye close to an X-ray tube, seeing a faint "blue-gray" glow which seemed to originate within the eye itself.[19] Upon hearing this, Röntgen reviewed his record books and found he too had seen the effect. When placing an X-ray tube on the opposite side of a wooden door Röntgen had noted the same blue glow, seeming to emanate from the eye itself, but thought his observations to be spurious because he only saw the effect when he used one type of tube. Later he realized that the tube which had created the effect was the only one powerful enough to make the glow plainly visible and the experiment was thereafter readily repeatable. The knowledge that X-rays are actually faintly visible to the dark-adapted naked eye has largely been forgotten today; this is probably due to the desire not to repeat what would now be seen as a recklessly dangerous and potentially harmful experiment with ionizing radiation. It is not known what exact mechanism in the eye produces the visibility: it could be due to conventional detection (excitation of rhodopsin molecules in the retina), direct excitation of retinal nerve cells, or secondary detection via, for instance, X-ray induction of phosphorescence in the eyeball with conventional retinal detection of the secondarily produced visible light.
Though X-rays are otherwise invisible it is possible to see the ionization of the air molecules if the intensity of the X-ray beam is high enough. The beamline from the wiggler at the ID11 at ESRF is one example of such high intensity.[20]
Since Röntgen's discovery that X-rays can identify bony structures, X-rays have been developed for their use in medical imaging. Radiology is a specialized field of medicine. Radiologists employ radiography and other techniques for diagnostic imaging. This is probably the most common use of X-ray technology.
X-rays are especially useful in the detection of pathology of the skeletal system, but are also useful for detecting some disease processes in soft tissue. Some notable examples are the very common chest X-ray, which can be used to identify lung diseases such as pneumonia, lung cancer or pulmonary edema, and the abdominal X-ray, which can detect intestinal obstruction, free air (from visceral perforations) and free fluid (in ascites). X-rays may also be used to detect pathology such as gallstones (which are rarely radiopaque) or kidney stones (which are often visible, but not always). Traditional plain X-rays are less useful in the imaging of soft tissues such as the brain or muscle. Imaging alternatives for soft tissues are computed axial tomography (CAT or CT scanning), magnetic resonance imaging (MRI) or ultrasound. Since 2005, X-rays are listed as a carcinogen by the U.S. government.[21]. The use of X-rays as a treatment is known as radiotherapy and is largely used for the management (including palliation) of cancer; it requires higher radiation energies than for imaging alone.
X-rays are a relatively safe method of investigation and the radiation exposure is low. But in pregnant patients, the benefits of the investigation (X-ray) should be balanced with the potential hazards to the unborn fetus.[22][23]
Lead is the most common shield against X-rays because of its high density (11340 kg/m3), ease of installation and low cost. The maximum range of a high-energy photon such as an X-ray in matter is infinite; at every point in the matter traversed by the photon, there is a probability of interaction. Thus there is a very small probability of no interaction over very large distances. The shielding of photons is therefore exponential; doubling the thickness of shielding will square the shielding effect.
The following table shows the recommended thickness of lead shielding in function of X-ray energy, from the Recommendations by the Second International Congress of Radiology.[24]
| X-Rays generated by peak voltages not exceeding |
Minimum thickness of Lead |
|---|---|
| 75 kV | 1.0 mm |
| 100 kV | 1.5 mm |
| 125 kV | 2.0 mm |
| 150 kV | 2.5 mm |
| 175 kV | 3.0 mm |
| 200 kV | 4.0 mm |
| 225 kV | 5.0 mm |
| 300 kV | 9.0 mm |
| 400 kV | 15.0 mm |
| 500 kV | 22.0 mm |
| 600 kV | 34.0 mm |
| 900 kV | 51.0 mm |
Other notable uses of X-rays include
Wilhelm Conrad Röntgen is usually credited as the discoverer of X-rays because he was the first to systematically study them, though he is not the first to have observed their effects. He is also the one who gave them the name "X-rays", though many referred to these as "Röntgen rays" for several decades after their discovery.
X-rays were found emanating from Crookes tubes, experimental discharge tubes invented around 1875, by scientists investigating the cathode rays, that is energetic electron beams, that were first created in the tubes. Crookes tubes created electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube. Many of the early Crookes tubes undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below. Wilhelm Röntgen was the first to systematically study them, in 1895.[26]
Among the important early researchers in X-rays were Ivan Pulyui, William Crookes, Johann Wilhelm Hittorf, Eugen Goldstein, Heinrich Hertz, Philipp Lenard, Hermann von Helmholtz, Nikola Tesla, Thomas Edison, Charles Glover Barkla, Max von Laue, and Wilhelm Conrad Röntgen.
German physicist Johann Hittorf (1824–1914), a coinventor and early researcher of the Crookes tube, found when he placed unexposed photographic plates near the tube, that some of them were flawed by shadows, though he did not investigate this effect.
In 1877 Ukranian-born Pulyui, a lecturer in experimental physics at the University of Vienna, constructed various designs of vacuum discharge tube to investigate their properties.[27] He continued his investigations when appointed professor at the Prague Polytechnic and in 1886 he found that that sealed photographic plates became dark when exposed to the emanations from the tubes. Early in 1896, just a few weeks after Röntgen published his first X-ray photograph, Pulyui published high-quality X-ray images in journals in Paris and London.[27] Although Pulyui had studied with Röntgen at the University of Strasbourg in the years 1873–75, his biographer Gaida (1997) asserts that his subsequent research was conducted independently.[27]
In April 1887, Nikola Tesla began to investigate X-rays using high voltages and tubes of his own design, as well as Crookes tubes. From his technical publications, it is indicated that he invented and developed a special single-electrode X-ray tube,[28][29] which differed from other X-ray tubes in having no target electrode. The principle behind Tesla's device is called the Bremsstrahlung process, in which a high-energy secondary X-ray emission is produced when charged particles (such as electrons) pass through matter. By 1892, Tesla performed several such experiments, but he did not categorize the emissions as what were later called X-rays. Tesla generalized the phenomenon as radiant energy of "invisible" kinds.[30][31] Tesla stated the facts of his methods concerning various experiments in his 1897 X-ray lecture before the New York Academy of Sciences.[32] Also in this lecture, Tesla stated the method of construction and safe operation of X-ray equipment. His X-ray experimentation by vacuum high field emissions also led him to alert the scientific community to the biological hazards associated with X-ray exposure.[33]
X-rays were generated and detected by Fernando Sanford (1854–1948), the foundation Professor of Physics at Stanford University, in 1891. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as previously studied by Heinrich Hertz and Philipp Lenard. His letter of January 6, 1893 (describing his discovery as "electric photography") to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner.[34]
Philipp Lenard, a student of Heinrich Hertz, wanted to see whether cathode rays could pass out of the Crookes tube into the air. He built a Crookes tube (later called a "Lenard tube") with a "window" in the end made of thin aluminum, facing the cathode so the cathode rays would strike it.[35] He found that something came through, that would expose photographic plates and cause fluorescence. He measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were actually X-rays.[36] Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his discovery and announcement. It was formed on the basis of the electromagnetic theory of light.[37] However, he did not work with actual X-rays.
On November 8, 1895, German physics professor Wilhelm Conrad Röntgen stumbled on X-rays while experimenting with Lenard and Crookes tubes and began studying them. He wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to the Würzburg's Physical-Medical Society journal.[38] This was the first paper written on X-rays. Röntgen referred to the radiation as "X", to indicate that it was an unknown type of radiation. The name stuck, although (over Röntgen's great objections) many of his colleagues suggested calling them Röntgen rays. They are still referred to as such in many languages, including German. Röntgen received the first Nobel Prize in Physics for his discovery.
There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a likely reconstruction by his biographers:[39] Röntgen was investigating cathode rays with a fluorescent screen painted with barium platinocyanide and a Crookes tube which he had wrapped in black cardboard so the visible light from the tube wouldn't interfere. He noticed a faint green glow from the screen, about 1 meter away. He realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow. He found they could also pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper.
Röntgen discovered its medical use when he saw a picture of his wife's hand on a photographic plate formed due to X-rays. His wife's hand's photograph was the first ever photograph of a human body part using X-rays.
In 1895, Thomas Edison investigated materials' ability to fluoresce when exposed to X-rays, and found that calcium tungstate was the most effective substance. Around March 1896, the fluoroscope he developed became the standard for medical X-ray examinations. Nevertheless, Edison dropped X-ray research around 1903 after the death of Clarence Madison Dally, one of his glassblowers. Dally had a habit of testing X-ray tubes on his hands, and acquired a cancer in them so tenacious that both arms were amputated in a futile attempt to save his life. At the 1901 Pan-American Exposition in Buffalo, New York, an assassin shot President William McKinley twice at close range with a .32 caliber revolver. The first bullet was removed but the second remained lodged somewhere in his stomach. McKinley survived for some time and requested that Thomas Edison "rush an X-ray machine to Buffalo to find the stray bullet. It arrived but wasn't used . . . McKinley died of septic shock due to bacterial infection."[40]
The first medical X-ray made in the United States was obtained using a discharge tube of Pulyui's design. In January 1896, on reading of Röntgen's discovery, Frank Austin of Dartmouth College tested all of the discharge tubes in the physics laboratory and found that only the Pulyui tube produced X-rays. This was a result of Pulyui's inclusion of an oblique "target" of mica, used for holding samples of fluorescent material, within the tube. On 3 February 1896 Gilman Frost, professor of medicine at the college, and his brother Edwin Frost, professor of physics, exposed the wrist of Eddie McCarthy, whom Edwin had treated some weeks earlier for a fracture, to the X-rays and collected the resulting image of the broken bone on gelatin photographic plates obtained from Howard Langill, a local photographer also interested in Röntgen's work.[41]
The many applications of X-rays immediately generated enormous interest. Workshops began making specialized versions of Crookes tubes for generating X-rays, and these first generation cold cathode or Crookes X-ray tubes were used until about 1920.
Crookes tubes were unreliable. They had to contain a small quantity of gas (invariably air) as a current will not flow in such a tube if they are fully evacuated. However as time passed the X-rays caused the glass to absorb the gas, causing the tube to generate "harder" X-rays until it soon stopped operating. Larger and more frequently used tubes were provided with devices for restoring the air, known as "softeners". These often took the form of a small side tube which contained a small piece of mica: a substance that traps comparatively large quantities of air within its structure. A small electrical heater heated the mica and caused it to release a small amount of air, thus restoring the tube's efficiency. However the mica had a limited life and the restore process was consequently difficult to control.
In 1904, John Ambrose Fleming invented the thermionic diode valve (vacuum tube). This used a hot cathode which permitted current to flow in a vacuum. This idea was quickly applied to X-ray tubes, and heated cathode X-ray tubes, called Coolidge tubes, replaced the troublesome cold cathode tubes by about 1920.
Two years later, physicist Charles Barkla discovered that X-rays could be scattered by gases, and that each element had a characteristic X-ray. He won the 1917 Nobel Prize in Physics for this discovery. Max von Laue, Paul Knipping and Walter Friedrich observed for the first time the diffraction of X-rays by crystals in 1912. This discovery, along with the early works of Paul Peter Ewald, William Henry Bragg and William Lawrence Bragg gave birth to the field of X-ray crystallography. The Coolidge tube was invented the following year by William D. Coolidge which permitted continuous production of X-rays; this type of tube is still in use today.
The use of X-rays for medical purposes (to develop into the field of radiation therapy) was pioneered by Major John Hall-Edwards in Birmingham, England. In 1908, he had to have his left arm amputated owing to the spread of X-ray dermatitis. [42] The X-ray microscope was invented in the 1950s.
The Chandra X-ray Observatory, launched on July 23, 1999, has been allowing the exploration of the very violent processes in the universe which produce X-rays. Unlike visible light, which is a relatively stable view of the universe, the X-ray universe is unstable, it features stars being torn apart by black holes, galactic collisions, and novas, neutron stars that build up layers of plasma that then explode into space.
An X-ray laser device was proposed as part of the Reagan Administration's Strategic Defense Initiative in the 1980s, but the first and only test of the device (a sort of laser "blaster", or death ray, powered by a thermonuclear explosion) gave inconclusive results. For technical and political reasons, the overall project (including the X-ray laser) was de-funded (though was later revived by the second Bush Administration as National Missile Defense using different technologies).
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| Translations: X-ray |
Dansk (Danish)
n. - røntgenstråle, røntgenfotografere
v. tr. - røntgenbestråle, røntgenfotografere, røntgenbehandle
idioms:
Français (French)
n. - rayons X, radiographie, radio, radioscopie
v. tr. - radiographier
idioms:
Deutsch (German)
n. - Röntgenstrahl, Röntgenaufnahme, Durchleuchten, Bestrahlen
v. - durchleuchten, röntgen, bestrahlen
idioms:
Ελληνική (Greek)
n. - ακτίνα Χ, ακτινογραφία, ακτινοσκόπηση
v. - ακτινοσκοπώ
idioms:
Italiano (Italian)
radiografare, radiografia, radioscopia, raggi X
idioms:
Português (Portuguese)
n. - raio X (m)
v. - tirar raio X
idioms:
Русский (Russian)
рентгеновские лучи, рентгенограмма, просвечивать рентгеновскими лучами, тщательно проверять, рентгеновский
idioms:
Español (Spanish)
n. - radiografía, rayos X, palabra clave en radiocomunicaciones
v. tr. - tratar o examinar con rayos X, radiografiar
idioms:
Svenska (Swedish)
n. - röntgenstråle, röntgenundersökning, röntgenbild, röntgenapparat
v. - röntga, röntgenbehandla
中文（简体）(Chinese (Simplified))
X光, 照X光
idioms:
中文（繁體）(Chinese (Traditional))
n. - X光
v. tr. - 照X光
idioms:
한국어 (Korean)
n. - X선, 뢴트겐선, X선 사진
v. tr. - X 선 사진을 찍다, X선으로 검사하다
日本語 (Japanese)
n. - X線, エックス線
v. - X線で検査する, レントゲンを撮る
idioms:
עברית (Hebrew)
n. - קרני רנטגן, צילום (או שיקוף) רנטגן
v. tr. - צילם צילום רנטגן, בדק בצילום רנטגן
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| Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more |
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| Medical Test. The Patient's Guide to Medical Tests by Faculty Members at The Yale University of Medicine and G.S. Sharpe Communications, Inc. Copyright © 1997 by Yale University of Medicine and G.S. Sharpe Communications, Inc. Published by Houghton Mifflin Company. All rights reserved. Read more |
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