Glossary of Terms Pertaining to Dental Radiography

103 terms by RDASophia

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Absorbed Dose

Dose equivalent delivered per unit of time.

Absorption

The transfer of energy from an x-ray beam to the atoms or molecules of the matter through which it passes. The process whereby radiation is stopped and reduced in intensity as |t passes through matter. Lead, which is denser than most materials, is one of the best absorber of x-rays.
(differential, rare earth screen, specific rate of, visible light)

Added Filter

Sheets of metal (usually aluminum or its equivalent) which are placed in the direct path of the x-ray beam.

Aiming Cylinder

A round/circular metal tube/shield attached to the X-ray tube housing or placed in front of the x-ray tube to limit the size of the x-ray beam to a predetermined size and shape.

ALARA

An acronym for As Low As Reasonably Achievable, economic and social factors being taken into consideration. Relates to radiation dose to the patients, the public, and occupationally exposed individuals.

Aluminum Equivalent

The thickness of aluminum affording the same attenuation, under specified conditions. Relates to radiation dose to the patients, the public, and occupationally exposed individuals.

Anode

A positive electrode, also referred to as a target, toward which electrons are accelerated from the cathode. The target is usually composed on tungsten.

Artifact

Any density or mark on a radiograph that is caused by something not belonging to the part of being x-rayed.

Attenuation

The process by which an x-ray beam of radiation is reduced in intensity by absorption or scattering when passing through material.

Protective Barrier

Barrier of attenuating materials used to reduce radiation exposure.

Primary Barrier

Barrier sufficient to attenuate the useful beam to the required degree.

Secondary Barrier

Barrier sufficient to attenuate stray radiation to the required degree.

Beam

A unidirectional flow of electromagnetic radiation.

Primary Radiation or X-ray Beam

That part of the radiation which passes through the window, aperture, cone, or other collimating device of the tube housing. Also called "useful beam."

Cathode

A negative electrode; electrode in the x-ray tube from which electrons are emitted. It consists of one or two filaments and focusing cup.

Centigray

0.01 Gray (Gy). 1 of this is equal to 1 rad.

Central Ray (Central Beam)

Refers to the x-rays in the center of the useful or primary beam.

Characteristic Curve

A type of input-output "curve" used to express the change in density with the change in radiation dose exposure of the photographic or x-ray film. The slope of the straight line port/on in this curve is called "gamma."

Chronic Exposure

Irradiation which is spread out over a period of years. Those who are occupationally exposed to radiation can suffer from chronic exposure.

Collimator

A device for restricting/confining/limiting a beam of radiation within an assigned solid angle.

Compton Scatter Radiation

The incident radiation has sufficient energy to dislodge a bound electron, but attacks a loosely bound electron, dislodges the electron and the remaining radiation energy proceeds in a different direction as scatter radiation. This kind of radiation is the main process responsible for the dose of radiation the patient receives during a radiographic procedure.

Cone

A round/circular metal tube/shield attached to the x-ray tube housing or placed in front of the x-ray tube to limit the size of the x-ray beam to a predetermined size and shape.

Contrast

In radiology, _______ is defined as the difference in density between light and dark areas on the processed film.

Densitometer

An instrument used to measure film density which is degree of blackening of film by measuring the ratio of the light intensity incident on the film to the light intensity transmitted by the film.

Densitometer

A device designed to measure the optical density of an exposed and processed film. It can measure the density of the individual steps on films exposed in this device, and is commonly used for daily processor quality control.

Density

Film blackening (the amount of light transmitted through the film.)

Detail (definition)

Refers to the sharpness of structure lines or contour lines on the processed film.

Developer

The chemical solution (alkaline) use in film processing that makes the latent image visible.

Developer Replenishment

Used to maintained the proper alkalinity, chemical activity, and level of solution in the developer tank.

Diagnostic Type Tube Housing

Means any x-ray tube housing so constructed that the leakage radiation at a distance of one meter rom the target cannot exceed 100 millirads in one hour when the tube is operated at any of its specified ratings.

Diaphragm

A plate, usually lead, with a central aperture so placed as to restrict the useful x-ray beam.

Distortion

Unequal magnification of different portions of body area being x-rayed.

Distortion

A general term denoting the quantity/amount of radiation or energy absorbed per unit mass. For special purposes it must be appropriately qualified.

Dose Equivalent

Means the product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest. The unit of dose equivalent are the rem and the Sievert (Sv). 1 rem= 0.01 Sv.

Dose Rate

Absorbed dose (or dose equivalent) delivered per unit of time.

Dosimeter

An instrument to detect and measure accumulated radiation dose (exposure).

Personal Dosimeters

Devices designed to be worn or carried by an individual for the purpose of determining the dose equivalent received for example:
film badge, pocket chamber, pocket dosimeter, ring badges, thermoluminescent (TLD) badges, etc.

Emulsion

The sensitive layer of photographic or x-ray film containing a silver compound in a layer of gelatin.

Emulsion

The sensitive layer of photographic or x-ray film containing a silver compound in a layer of gelatin.

Exposure or Irradiation Time

The time interval in a radiological examination within which x-rays are incident upon the body part under examination.

Film Badge

A personnel monitoring device which measures radiation exposure and is used for personnel monitoring.

Film Speed

A relative exposure number needed to produce a density of 1/0 above gross fog-used for screen type, dental and medical x-ray films.

Filter/Filtration

Means material placed in the primary or useful x-ray beam to absorb preferentially the less penetrating radiations. The use of appropriate filtration prevents the patient from receiving unnecessary radiation dose.

Inherent filter

Filter in the x-ray tube and its housing such as the glass envelope (window) through which the X-ray beam passes.

Total Filtration

The sum of the inherent and added filters.

Fixer

A chemical solution (acidic) which removes the unexposed and underdeveloped silver halide crystals from the film so it will not discolor or darken with age or exposure to light. Also hardens the gelatin containing the black metallic silver so film may be dried and resist damage from abrasions.

Fixer Retention

The inadequate removal of fixer from the film by the water in the wash tank of the processor; causes eventual brown discoloration of the radiograph.

Focal Spot

A small area on the target of the anode toward which the electrons from the focusing cup of the cathode are directed. X-radiation originates here.

Effective Focal Spot

The apparent size of the radiation source when viewed from the central axis of the useful beam.

Fog or Fogging

A cloudy appearance of the finished radiograph caused by several factors such as old or contaminated processing solutions, exposure to chemical fumes, faulty darkroom safelight, or scatter radiation.

Geometric Unsharpness

Unsharpness of the recording image due to the combined optical effect of finite size of the radiation source and geometric separation of the anatomic area of interest from the image receptor and the collimator.

Gonard Shielding

Devices used during radiographic procedures to protect the reproductive organs from exposure to the useful x-ray beams.

Gray (Gy)

The SI unit of absorbed dose equal to an energy deposition of 1 joule/kg = 10,000 ergs/gm (1__-100rads).

Health Physics

The science of protecting human beings from injury by radiation, and promoting better health through beneficial applications or radiation. (Also called Radiological Health).

Individual

Any human being.

installation

The location where one or more reportable sources of radiation are processed (located).

Intensifying Screens

Devices which increase the brightness of the image produced by the action of x-rays upon a phosphor.

Ion

An atom or molecule which has one or more of its surrounding electrons separated from it and therefore carries a positive electric charge, or a free electron carrying a negative electrical charge.

lon/lonization Chamber

An x-ray measuring device in which gas is ionized in proportion to the quality of x-ray energy passing through the chamber.

ionization

The process whereby one or more electrons is removed from a neutral atom by the action of radiation (the conversion of atoms to ions).

Kilovolt

A unit of electrical potential difference equals to 1,000 volts.

Kilovolt Peak (kVp)

A unit of maximum or crest value of electrical potential difference between the anode and cathode of an x-ray tube; determines the penetrating ability of x-rays and revers to the "quality" of x-rays.

Leakage Radiation

Means all radiation coming from within the x-ray tube housing except the useful beam.

Leukemia

A blood disease which is characterized by overproduction of white blood cells. It may result from overexposure of the bone marrow to radiation.

Magnification

The ratio of image size to object size. The image may be larger than, smaller than, or equal to the object; so magnification can be greater than, equal to, or less than 1.

Milliampere (mA)

The electron current towing across the x-ray tube from the cathode to the anode.

milliampere-seconds (mAs)

Milliampere (mA) multiplied by the time during which the beam strikes an object (measured in seconds) is _________ and is a measure of the "quality" of x-rays.

Mutation

A transformation of the gene which may be induced by radiation and may alter characteristics of the offspring.

Occupational Dose

Means the dose received by any individual in the course of employment. Exception: Radiation dose received for the operator's own personal medical and dental diagnosis or therapy.

Operator's station

The area where the control panel for the operation of an X-ray machine is located. It should be behind a protective barrier either in a separate room, in a protective booth, or behind a shield which will intercept the useful beam and any radiation which has been scattered only once.

Photon

A quality of energy emitter in the form of electromagnetic radiation. X-ray is an example.

Pointer Cone

A means used to indicate the direction of the useful beam and to establish the minimum source-surface distance. It may be a cylinder or a cone and must be open ended.

Quality

A term used to describe the penetrating power of x-rays and is related to the energies of the photons in the useful or primary x-ray beam.

Quality Assurance (QA)

A management tool that includes policies and procedures designed to optimize the performance of facility personnel and equipment.

1. Quality control (QC)
2. Administration
3. Education of personnel
4. Preventive maintenance methods

QA includes all of the following:

Quantity

A term used to describe the number of photons in an x-ray beam.

Rad

The unit of absorbed dose.

One rad

The dose corresponding to the absorption of 100 ergs per gram.

0.01

One rad is ____ Joules per kilogram of any material.

Gray (Gy)

The S1 unit of absorbed dose.

Radiography

utilizing ionizing radiation, this technique involves making shadow images on photographic emulsions. The image is the result of differences in attenuation of the radiation as it passes through the object in its path.

Rem

The special unit of ? of the qualities expressed as dose equivalent. *

rads

The dose equivalent in rems is equal to the absorbed dose in ____ multiplied by the quality factor (1 rem - 0.01 Sievert).

Repeats/Retakes

Additional radiographs taken because of technical or mechanical error. These lead to increased radiation exposure for the patient and the radiation worker and should be avoided.

Resolution

The process or capability of distinguishing closely adjacent optical images.

Scattered Radiation

Means radiation that during passage through matter, has been deviated in direction. It usually has also been modified by a decrease in energy.

Secondary or Stray Radiation

Mean radiation not serving any useful purpose. It includes leakage and scattered radiation.

Shield/Shielding

Material which is interposed between a radiation source and an irradiated site for the purpose of minimizing the radiation hazard (used to prevent or reduce the passage of radiation).

Shield/Shielding

Usually made of lead which is dense and absorbs radiation easily. Used to protect the reproductive organs, testes or ovaries, from the x-ray beam during an examination.

Sievert (Sv)

The SI unit of dose equivalent equal to the produce of a dose of one Gray, the quality factor, and any other applicable modifying factors. ( 1 ___ = 100 rem).

Somatic

Retaining to the body tissue other than reproductive cells.

Source-to-Image Distance (SID)

The distance measured along the central ray from the center of the front surface of the source (x-ray focal spot to the surface of the irradiated object or patient.

Speed Factor

With intensifying screens, the __________ is defined as the ratio of the radiation dose (exposure) without screens to the radiation dose (exposure) required with screens to get the same degree of blackening of x-ray films.

supervision

Responsibility for and control of quality, radiation safety, and technical aspects of all x-ray examinations and procedures.

Survey

Means an evaluation of the radiation hazards incident to the production, use, release, disposal, or presence of sources of radiation.

Target

Material at which electrons from the cathode in an x-ray tube are aimed in order to produce x-rays.

Target-Film Distance

The distance from the x-ray tube target (anode) to the film measured in inches or centimeters.

Target-Skin Distance

The distance from the x-ray target (anode) to the skin of the patient where x-ray beam enters the body.

Useful Beam

Means that part of the radiation which passes through the window, aperture, cone, or other collimating device of the tube housing.

X-Ray

Penetrating electromagnetic radiation whose wavelengths are shorter than those of visible light.

x-rays

For radiographic purposes, ______ are usually produced by bombarding a metallic target with fast electrons in a vacuum.

X-ray Generator

A device which supplies electrical power to the x-ray tube. It does not, as the name implies, actually generate x-rays.

X-ray Personnel

Individual legally allowed to use diagnostic x-rays on human beings. For example, licensed dentist, dental hygienists and dental assistants who have successfully completed a radiation safety course approved by the Board of Dental Examiners.

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