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A radiograph of a right elbow-joint
A radiograph of a right elbow-joint

For medical radiography see: Radiology

Radiography is the use of X-rays to view unseen or hard-to-image objects. Radiology is the medical specialty directing Medical imaging technologies to diagnose and treat diseases X-radiation (composed of X-rays) is a form of Electromagnetic radiation. The use of non-ionizing radiations (visible light and ultraviolet light) to view objects should be considered as a normal “optical” method (e. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays g. , light microscopy). A microscope ( Greek: ( micron) = small + ( skopein) = to look or see is an instrument for viewing objects that are The modification of an object through the use of ionizing radiation is not radiography. Depending on the nature of the object and the intended outcome it can be radiotherapy, food irradiation, or radiation processing. Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant Food irradiation is the process of exposing food to Ionizing radiation in order to destroy Microorganisms Bacteria, Viruses or Insects [1]

Contents

Medical and industrial radiography

Further information: Projectional radiography

Radiography is used for both medical and industrial applications (see medical radiography and industrial radiography). Projectional radiography or plain film radiography is the practise of producing 2D X-ray images Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the For other uses of this term see Industry (disambiguation An industry (from Latin industrius, "diligent industrious" Radiography is the use of ionising Electromagnetic radiation to view objects Industrial Radiography is the use of ionising Electromagnetic radiation to view objects in a way that can't be seen otherwise If the object being examined is living, whether human or animal, it is regarded as medical; all other radiography is regarded as being industrial radiographic work. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus

History of radiography

Taking an X-ray image with early Crookes tube apparatus, late 1800s.
Taking an X-ray image with early Crookes tube apparatus, late 1800s.

Radiography started in 1895 with the discovery of X-rays, also referred to as Röentgen rays after the man who first described their properties in rigorous detail. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. These previously unknown rays (hence the X) were found to be a type of electromagnetic radiation. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. It wasn't long before X-rays were used in various applications, from helping to fit shoes, to the medical uses that have persisted. X-rays were put to diagnostic use very early, before the dangers of ionizing radiation were discovered. Initially, many kinds of staff conducted radiography in hospitals, including physicists, photographers, doctors, nurses, and engineers. The medical specialty of radiology grew up over many years around the new technology. When new diagnostic tests involving X-rays were developed, it was natural for the radiographers to be trained in and to adopt this new technology. A radiologic technologist, or radiographer, is a healthcare professional who creates medical images of the body to help health care providers diagnose and treat illness and injury This happened first with fluoroscopy, computed tomography (1970s), mammography, ultrasound (1970s), and magnetic resonance imaging (1980s). Fluoroscopy is an imaging technique commonly used by Physicians to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope Computed tomography (CT is a Medical imaging method employing Tomography. Mammography is the process of using low-dose X-rays (usually around 0 Not to be confused with Supersonic. Ultrasound is cyclic Sound pressure with a Frequency greater than the upper Although a nonspecialist dictionary might define radiography quite narrowly as "taking X-ray images", this has long been only part of the work of "X-ray departments", radiographers, and radiologists.

Equipment

For more details on this topic, see radiographic equipment. This is a page devoted to the basic equipment used for radiographic work, both medical and industrial

Sources

A number of sources of X-ray photons have been used; these include sealed X-ray tubes, betatrons, and linear accelerators (linacs). X-radiation (composed of X-rays) is a form of Electromagnetic radiation. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena An X-ray tube is a Vacuum tube that produces X-rays They are part of X-ray machines X-rays are part of the Electromagnetic spectrum, an A betatron is a Cyclotron developed by Donald Kerst at the University of Illinois in 1940 to accelerate electrons For gamma rays, radioactive sources such as 192Ir have been used. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation.

Detectors

A range of detectors including photographic film, scintillator and semiconductor diode arrays have been used to collect images. This article is mainly concerned with Still photography film For Motion picture film please see Film stock. A scintillator is a substance that absorbs high-energy (ie Ionizing) electromagnetic or charged Particle radiation then in response fluoresces A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Dioden2jpg|thumb|right|150px|Figure 2 Various semiconductor diodes

Theory of X-ray attenuation

X-ray photons used for medical purposes are more likely to be formed by an event involving an electron, while gamma ray photons are more likely to be formed from the nucleus of an atom. [1]. In general, medical radiography is done using X-rays formed in an X-ray tube. An X-ray tube is a Vacuum tube that produces X-rays They are part of X-ray machines X-rays are part of the Electromagnetic spectrum, an Nuclear medicine typically involves gamma rays.

The types of electromagnetic radiation of most interest to radiography are X-ray and gamma radiation. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions This radiation is much more energetic than the more familiar types such as radio waves and visible light. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum. It is this relatively high energy which makes gamma rays useful in radiography but potentially hazardous to living organisms.

The radiation is produced by X-ray tubes, high energy X-ray equipment or natural radioactive elements, such as radium and radon, and artificially produced radioactive isotopes of elements, such as cobalt-60 and iridium-192. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Cobalt (ˈkoʊbɒlt is a hard lustrous silver-grey Metal, a Chemical element with symbol Co. Iridium (ɪˈrɪdiəm is a Chemical element that has the symbol Ir and Atomic number 77 Electromagnetic radiation consists of oscillating electric and magnetic fields, but is generally depicted as a single sinusoidal wave. Oscillation is the repetitive variation typically in Time, of some measure about a central value (often a point of Equilibrium) or between two or more different states In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges While in the past radium and radon have both been used for radiography, they have fallen out of use as they are radiotoxic alpha radiation emitters which are expensive; iridium-192 and cobalt-60 are far better photon sources. Radium (ˈreɪdiəm is a radioactive Chemical element which has the symbol Ra and Atomic number 88 Radon (ˈreɪdɒn is the Chemical element that has the symbol Rn and Atomic number 86 Alpha decay is a type of radioactive decay in which an Atomic nucleus emits an Alpha particle (two protons and two neutrons bound together into a particle For further details see commonly used gamma emitting isotopes. Fission products Caesium-137 is a radioactive Isotope which is formed mainly by Nuclear fission.

Such a wave is characterised by its wavelength (the distance from a point on one cycle to the corresponding point on the next cycle) or its frequency (the number of oscillations per second). In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Frequency is a measure of the number of occurrences of a repeating event per unit Time. In a vacuum, all electromagnetic waves travel at the same speed, the speed of light (c). The wavelength (λ, lambda) and the frequency (f) are all related by the equation:

f = \frac{c}{\lambda} \

This is true for all electromagnetic radiation. An equation is a mathematical statement, in symbols, that two things are exactly the same (or equivalent

Electromagnetic radiation is known by various names, depending on its energy. The energy of these waves is related to the frequency and the wavelength by the relationship:

E = hf = h (\frac{c}{\lambda}) \

where h is a constant known as the Planck constant. The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta.

Gamma rays are indirectly ionizing radiation. Image talkNew_radiation_symbol_ISO_21482svg for details --> Ionizing radiation A gamma ray passes through matter until it undergoes an interaction with an atomic particle, usually an electron. Matter is commonly defined as being anything that has mass and that takes up space. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J During this interaction, energy is transferred from the gamma ray to the electron, which is a directly ionizing particle. As a result of this energy transfer, the electron is liberated from the atom and proceeds to ionize matter by colliding with other electrons along its path. Other times, the passing gamma ray interferes with the orbit of the electron, and slows it, releasing energy but not becoming dislodged. The atom is not ionised, and the gamma ray continues on, although at a lower energy. This energy released is usually heat or another, weaker photon, and causes biological harm as a radiation burn. The chain reaction caused by the initial dose of radiation can continue after exposure, much like a sunburn continues to damage skin even after one is out of direct sunlight. A sunburn is a burn to living tissue such as Skin produced by overexposure to Ultraviolet (UV radiation commonly from the Sun 's rays

For the range of energies commonly used in radiography, the interaction between gamma rays and electrons occurs in two ways. One effect takes place where all the gamma ray's energy is transmitted to an entire atom. The gamma ray no longer exists and an electron emerges from the atom with kinetic (motion in relation to force) energy almost equal to the gamma energy. The kinetic energy of an object is the extra Energy which it possesses due to its motion This effect is predominant at low gamma energies and is known as the photoelectric effect. Introduction When a Metallic surface is exposed to Electromagnetic radiation above a certain threshold Frequency, the light is absorbed and Electrons The other major effect occurs when a gamma ray interacts with an atomic electron, freeing it from the atom and imparting to it only a fraction of the gamma ray's kinetic energy. A secondary gamma ray with less energy (hence lower frequency) also emerges from the interaction. This effect predominates at higher gamma energies and is known as the Compton effect. The Compton shift formula Klein-Nishina formulaCompton used a combination of three fundamental formulas representing the various aspects of classical and modern physics combining

In both of these effects the emergent electrons lose their kinetic energy by ionizing surrounding atoms. The density of ions so generated is a measure of the energy delivered to the material by the gamma rays. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge

The most common means of measuring the variations in a beam of radiation is by observing its effect on a photographic film. This effect is the same as that of light, and the more intense the radiation is, the more it darkens, or exposes, the film. In Photography, exposure is the total amount of Light allowed to fall on the photographic medium ( Photographic film or Image sensor) during the Other methods are in use, such as the ionizing effect measured electronically, its ability to discharge an electrostatically charged plate or to cause certain chemicals to fluoresce as in fluoroscopy. Fluorescence is a Luminescence that is mostly found as an Fluoroscopy is an imaging technique commonly used by Physicians to obtain real-time moving images of the internal structures of a patient through the use of a fluoroscope

Obsolete terminology

The term skiagrapher was used until about 1918 to mean radiographer. It was derived from Ancient Greek words for 'shadow' and 'writer'. The Ancient Greek language is the historical stage in the development of the Hellenic language family spanning the Archaic (c

See also

References

  1. ^ Radiation Detection and Measurement 3rd Edition, Glenn F. Knoll : Chapter 1, Page 1: John Wiley & Sons; 3rd Edition edition (26 Jan 2000): ISBN-10: 0471073385

External links

Dictionary

radiography

-noun

  1. the process of making radiographs, and the science of analyzing them
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