Martin S. Spiller, DMD, Family Dentistry in Townsend, MA

Martin S. Spiller, DMD, Family Dentistry in Townsend, MA







Dentists and allied dental professionals often seek CE courses from ADA CERP recognized providers to fulfill their CE requirements for re-licensure.   Most state and provincial licensing boards will accept CE credits issued by ADA CERP recognized providers. In the spring of 2003, the FDI World Dental Federation became the first internationally based CE provider to be granted ADA CERP recognition.

Please contact your state board directly for their specific rules and regulations. Most states approve supervised self-study courses that are ADA CERP accredited.

Those dentists, hygienists, dental assistants and radiographers interested in receiving 3 continuing education credits for this course may take a 10 question test at a cost of $35 and receive their certificate immediately by clicking here.

Those dentists, hygienists, dental assistants and radiographers interested in receiving 8 continuing education credits for this course may take a 25 question test at a cost of $66 and receive their certificate immediately by clicking here.

Note: There are no questions on tables or Glossary.

Adapted from Miles, Van Dis, Jensen, and Ferretti: Radiographic Imaging for Dental Auxiliaries, Second Edition, 1993


Absorb: To take into the skin or body tissue.

Absorption: A process whereby the intensity of a beam of radiation is reduced because some (or all) of the particles (or photons) of the incident beam are eliminated or reduced in energy by interactions with matter.

Actual Focal spot: The area of the target (tungsten) that is always larger than the effective focal size. It is the area of the anode upon which the electrons strike.

Aluminum Filter: Any of various thicknesses of aluminum used as filtration in an x-ray beam to absorb the longer-wavelength, less-penetrating radiation.

Ampere: The unit of intensity of an electric current produced by 1 volt acting through a resistance of 1 ohm.

Anatomic Landmark: An anatomic structure whose image may serve as an aid in the localization and identification of the regions to be radiographed or the regions in a radiograph.

Angulation: The direction of the primary beam of radiation in relation to object and film.

Anion: An ion carrying a negative charge.

Anode: The positive terminal of an x-ray tube; a tungsten block embedded in a copper stem and set at an angle to the cathode (q.v.) The anode emits x rays from the point of impact of the electron stream from the cathode. An anode that rotates constantly during x-ray production to present a changing focal spot to the electron stream and to permit use of smaller focal spots or higher tube voltages or currents without overheating is called a Rotating Anode.

Anteroposterior Position: An examination in which the film is placed at the posterior (for example the back of the head), with the x rays passing from the anterior to the posterior direction. Abbreviated: A-P.

Area Monitoring: Routine monitoring of the level of radiation in any particular area, building, room, or equipment.

Atom: The smallest part of an element that is capable of entering into a chemical reaction. It consists of a positively charged nucleus and an extranuclear portion composed of electrons equal in number to the nuclear protons.


Atomic Number: The number of electrons outside the nucleus of a neutral atom. It is also the number of protons in the nucleus.

Background Radiation: Background implies radioactivity arising from nature. This includes cosmic rays (q.v.) and radioactive elements in the earth and air.

Backscatter: Radiation deflected by scattering processes at angles greater than 90 degrees to the original direction of the beam of radiation.

Barrier, Protective: A barrier of radiation-absorbing material, such as lead, concrete, or plaster, used to reduce radiation hazards.
Primary Protective Barrier: A barrier sufficient to reduce the useful beam to the permissible dose rate.
Secondary Protective Barrier: A barrier sufficient to reduce the secondary or scatter radiation to the permissible dose rate.

Base: A solution containing fewer hydrogen ions than water. Its pH is greater than 7. Bases can react with acids to form salts.

Beam: An emission of electromagnetic radiation or particles. Central Beam: The center of the beam of x rays emitted from an x-ray tube. Usually called the central ray. Useful Beam: In radiology, that part of the primary radiation that is permitted to emerge from the tubehead assembly of an x-ray machine, as limited by the tubehead port and accessory collimating devices.

Beam Guiding Instrument: Instrument used during radiography to facilitate correct alignment of the central ray.

Binding Energy: The energy needed to eject an electron from the atom.

Bisecting Angle Technique: A technique for the radiographic exposure of intraoral films whereby the central axis or central ray of the x-ray beam is directed at right angles to a plane determined by bisecting the angle formed by (1) the long axis of the tooth or teeth being radiographed and (2) the plane in which the film is positioned behind the teeth.

Bitewing Radiograph: The x-ray shadow images of the crowns, necks, and coronal thirds of the roots of both upper and lower teeth, so called because the patient bites on a cardboard tab or "Wing" placed in the center of the film packet



Bremsstrahlung Radiation: A spectral distribution of x rays ranging from very low energy photons to those produced by the peak kilovoltage applied across an x-ray tube. Bremsstrahlung means "braking radiation", referring to the sudden deceleration of electrons as they interact with highly positively charged nuclei.

Carcinogen: A substance having the ability to produce cancer.

Cassette: A light-tight container in which x-ray films are placed for exposure to x radiation; usually backed with lead to reduce the effect of backscattered radiation (q.v.) Screen Type Cassette: A film holder, usually made of metal with the exposure side made of a low atomic number material such as Bakelite, aluminum, or magnesium; the cassette contains intensifying screens between which a "screen type" film is placed for exposure.

Cathode: A negative electrode from which electrons are emitted. In x-ray tubes, the cathode usually consists of a helical tungsten filament behind which a molybdenum reflector cup is located to focus the electron emission toward the target of the anode.

Cathode Ray: A stream of electrons passing from the hot filament of the cathode to the target or anode in an x-ray tube.

Cathode Ray Tube: A tube cathode containing a spirally wound filament that becomes incandescent, producing electrons when a low-voltage electric current is passed through it.

Central Ray: The theoretical center of the x-ray beam. The term is employed to designate the direction of the x rays in a given projection; the central ray may be considered to extend from the focal spot of the x-ray tube to the x-ray film.

Characteristic (Discrete) Radiation: Electromagnetic radiation produced by electron transitions from higher energy orbitals to replace ejected electrons of inner electron orbitals. The energy of the electromagnetic radiation emitted is unique or characteristic of the emitting atom (element).

Clearing Agent: see Fixer.

Collimation: Any device used for the elimination of the peripheral divergent portion of the useful x-ray beam, such as metal tubes, "cones," or diaphragms interposed in the path of the beam.

Collimator: A lead disc with an aperture of various size and shape. The diaphragm limits the size of the primary beam to the area of interest, thereby minimizing patient exposure to the primary beam.


Compton Scatter Radiation: Commonly called scatter radiation. The incident radiation has sufficient energy to dislodge a bound electron, but it attacks a loosely bound electron and dislodges it; the remaining radiation attacks a loosely bound electron and dislodges it; the remaining radiation energy proceeds in a different direction as scatter radiation.

Cone: A device on a dental x-ray machine that is designed to indicate the direction of the central ray and to serve as a guide in establishing a desired source-to-film distance (SFD)

        Short Cone: A conical or cylindrical cone having as one of its functions the establishment of an anode-to-skin distance of up to approximately 18 cm.

        Long Cone: A cylindrical or rectangular cone designed to establish and extended anode-to-skin skin distance, usually within the range of 27 cm to 36 cm.

Cone Cutting: Failure to cover or expose the entire area of a radiograph with the useful beam, thereby only partially exposing the film.

Cone Distance: The distance between the focal spot and the end of the cone, usually expressed in inches or centimeters.

Constant Potential Kilovoltage; see Kilovoltage

Continuous Spectrum: For electromagnetic radiation, a spectrum that exhibits a gradual variation of wavelength. Examples include the spectrum of light from an incandescent solid and an x-ray spectrum.

Contrast: The difference in image density appearing on a radiograph, representing various degrees of beam attenuation.

        Film Contrast: A characteristic inherent in the type of film used.

        Long-Scale Contrast: An increased range of grays between the blacks and whites on a radiograph. Higher kilovoltages increase this range.

        Short-Scale Contrast: A reduced range of grays between the blacks and whites on a radiograph. Lower kilovoltages decrease this range.

        Subject Contrast: The relative differences in density and thickness of the components of the radiographed subject, as evidenced by the varied radiographic densities caused by the differences in absorbing power of the different kinds of material traversed by an x-ray beam.

Cosmic Rays: Radiation of extremely short wavelengths that originates outside the earth's atmosphere.



Critical Tissues (Organs): Those tissues that either react unfavorably to radiation or, by their nature, attract and absorb specific radiochemicals.

Crookes' Tube: see X-ray Tube

Darkroom: A room that can be completely darkened so that photographic or x-ray film may be processed.

Daylight System: A method of loading, unloading, and feeding films into the processor in normal room light. This system entails the use of special equipment, with no need for a darkroom.

Definition (Image): The property of images pertaining to their sharpness, distinctness, or clarity.

Density (Photographic or Film): The degree of darkening of exposed and processed photographic or x-ray film.

        Background Density: The density of a processed film owing to factors other than the radiation exposure received through the recorded objects or structures.

        Inherent (Film) Density: The density of a processed film owing to such intrinsic factors in the film as the density of the film base and the emulsion gelatin.

        Object (Tissue) Density: The resistance of an object to the passage of x rays.

Developer: A chemical (potassium bromide) used in a developer to check the development of the unexposed silver bromide and to control the working speed of the developer with respect to the exposed silver bromide.

Directly Ionizing Particles: Charged particles having sufficient kinetic energy to produce ionization by collision.

Distal: Remote; farther from any point of reference; e.g., midline.

Distortion: An inaccuracy in the size or shape of an object as it is displayed in the radiograph.

        Magnification Distortion: Proportional enlargement of a radiographic image. It is always present to some degree in oral radiography but is minimized with increased source-to-film distance or decreased object-to-film distance.

        Vertical Distortion: Disproportional change in size, either elongation or foreshortening owing to incorrect vertical angulation or improper film placement.

Dose Equivalent: The product of absorbed dose and modifying factors (i.e., the quality factor, distribution factor, and any other necessary factors). The traditional unit of dose equivalence is the rem (rad X qualifying factors).


Double Exposure: Two superimposed exposures on the same radiographic or photographic film.

Effective Focal Spot: That apparent size and shape of the focal spot when viewed from a position in the useful beam; with the use of a suitable inclined anode face, it is smaller than the actual focal spot size. (See also Line Focus.)

Ektaspeed Film: Direct exposure film with a speed (q.v.) category of approximately 25 R -1

Electrode: Either of the two terminals of an electric source, an anode or a cathode (q.q.v.).

Electromagnetic Radiation: The forms of energy propagated by wave motion as photons or discrete quanta. The radiations have no matter associated with them. They differ widely in wavelength, frequency, and photon energy and have strikingly different properties. Covering an enormous range of wavelengths (from 10 17 to 10 - 6 angstroms), they include radio waves, infrared waves, visible light, ultraviolet radiation, x rays, gamma rays, and cosmic radiation.

Electromagnetic Wave: A wave produced by mutual induction of electric and magnetic fields.

Electron: A negatively charged elementary particle.

Electron Stream: Electrons moving from the cathode to the anode across a potential difference in a low-pressure gas tube or a vacuum tube.

Electron Volt: The kinetic energy gained by an electron falling through a potential difference of 1 volt.

Element: A pure substance consisting of atoms of the same atomic number, which cannot be decomposed by ordinary chemical means.

Elongation: A form of radiographic distortion in which the image is longer than the object radiographed.

Equivalent: The thickness of pure aluminum, concrete, or lead, which would afford the same radiation attenuation, under specified conditions, as any given material being considered.

Exposure: A measure of the ionization produced in air by x radiation or gamma radiation. It is the sum of the electrical charges on all of the ions of one sign produced in air when all of the electrons liberated by the photons in a volume element of air are completely stopped in air,



divided by the mass of the air in the volume element.

Exposure Factors: Radiographic kilovoltage, exposure time, milliamperage, and source-to-film distance: The primary radiographic factors considered when making an exposure.

External Oblique Ridge: A ridge originating from the anterior border of the ramus of the mandible extending to the lateral body of the mandible in the molar region.

Extraoral Radiograph: An examination of the teeth and bones made by placing the film or cassette against the side of the head or face and projecting the x rays from the opposite side.

Filament: A coiled tungsten wire, which emits electrons when heated to incandescence.

Film: A thin, transparent sheet of cellulose acetate or similar material coated on one or both sides with an emulsion sensitive to radiation and light.

        Direct-Exposure Film: Film that is highly sensitive to the direct action of x rays but that has low sensitivity to screen fluorescence (e.g., intraoral dental film).

        Screen Film: A film that is sensitive to the fluorescent light of intensifying screens but not as sensitive to the direct action of x rays (e.g., panoramic film).

        X-ray Film: 1) A film manufactured for use in radiography. or 2) A radiograph.

Film Badge: A metal container of radiographic film used for the detection and measurement of radiation exposure of personnel.

Film Base: The thin, transparent sheet of cellulose acetate or similar material that carries the radiation- and light sensitive emulsion of x-ray films.

Film Packet: A light-proof, moisture-resistant, sealed paper or plastic envelope containing x-ray film, used in making radiographs.

Film Processing: The process of converting a latent image to a visible image by immersion in developer and fixer, followed by rinsing in water and drying.

Film Speed: The amount of exposure to light or x rays (the latter in roentgens) required to produce a given image density. Film speed is expressed as the reciprocal of the exposure in roentgens necessary to produce a density of 1.0 above base and fog; films are classified in six speed groups, from A through F. (See Speed.)

Filter: The material (usually aluminum) placed in the useful primary beam of x radiation.

Fixer (Film or Hypo-): The solution in which the manifest image is fixed and hardened


removing the silver halide crystals from the exposed film that has been unexposed to or unaffected by the action of the x radiation.

Focal Spot: That part of the target on the anode of an x-ray tube that is bombarded by the focused electron stream when the tube is energized.

Focusing Cup: Along with the filament, the focusing cup determines the size and shape of the target (focal) spot. The cup is constructed of molybdenum.

Gamma Radiation: Short wavelength electromagnetic radiation of nuclear origin, within a range of wavelengths from about 10-8 cm to 10-11 cm.

Gelatin: A protein obtained from animal skin and hooves by boiling; used in x-ray film manufacture as a means of suspending the silver halide crystals in the film emulsion.

Gene: The fundamental unit of inheritance that determines and controls transmissible characteristics.

Genetic Effects (Radiation): Changes produced in the genes and chromosomes of all nucleated body cells. In customary usage, the term relates to the effect produced in the reproductive cells.

Geometric Unsharpness: Impairment of image definition owing tot he penumbra (shadow).

Gonad: An ovary or a testis, site of origin of oocytes or spermatozoa.

Gray: A unit of radiation measurement established in 1974 by the International commission on Radiation Units and Measurements. One gray (Gy) = 1 joule/Kg= 100 rad. The gray is a unit of absorbed dose and replaces the rad.

Grid: A device used to prevent as much scattered radiation as possible from reaching an x-ray film during the exposure of a radiograph.

H and D Curve: A characteristic curve of a photographic emulsion obtained by plotting film density against the logarithm of the exposure. Also called the Hurter and Driffield curve (named after the British scientists and founders).

Halides: Compounds of metals with halogen elements; bromide, chlorine, and iodine.

"Hard" Radiation: A slang term for x rays of short wavelengths and high penetrating power. In usage, the shorter the wavelength, the "harder" the radiation.

Impulse: The burst of radiation generated during a half cycle of alternating current.

Indirectly Ionizing Particles: Uncharged particles, which can liberate directly ionizing particles or can initiate a nuclear transformation.



Interpretation (X-ray Film): The study of a radiograph, the interpretation of that which is seen, and the integration of the findings with the case history, laboratory, and clinical examinations, to arrive at a diagnosis. The dentist does not "diagnose" the radiograph; rather, he or she studies and interprets its image.

Interproximal Radiograph (Bitewing Radiograph): A special type of intraoral radiograph for depicting interproximal features of the teeth and interdental bone crests, made on a film positioned by special (bitewing) tabs on which the patient's teeth are closed.

Intraoral Radiograph: Radiograph produced on a film placed intraorally to the teeth.

Ion: An atomic particle, atom, or chemical radical bearing an electrical charge, either negative or positive.

Ionization: The process or the result of a process by which a neutral atom or molecule acquires either a positive or a negative charge.

Ionizing Radiation : Electromagnetic radiation (e.g., x rays or gamma rays) or particulate radiation (e.g., electrons, neutrons, and protons) capable of ionizing air directly or indirectly.

K Electron: an electron having an orbit in the K shell, which is the first shell of electrons surrounding the atom's nucleus.

keV: The symbol for 1000 electron volts.

Kilo (k): a prefix representing 1000.

Kilovoltage (in x=ray machines): The potential difference between the anode and the cathode of an x-ray tube.

        Constant Potential Kilovoltage: The potential formed by a constant voltage generator expressed as constant potential kilovolts (kVcp).

Kilovoltage Peak (kVp): The crest value (in kilovolts) of the potential difference of a pulsating-potential generator. When only half of the wave is used, the value refers to the useful half of the cycle.

Lamina Dura: The thin plate of dense or compact bone that lines the tooth sockets; it appears on a radiograph as a fine radiopaque line passing around the tooth.

Latent Period: The period between the time of exposure of tissue to an injurious agent (e.g., radiation) and the clinical manifestation of a particular response.

Leaded Apron: A lead-impregnated rubber apron that provides protection for patients and personnel from radiation.

Dosimeter (Radiation Meter): An instrument used to detect and measure an accumulated dosage of radiation.

Leukemia: A disease in which there is great overproduction of white blood cells, or a relative overproduction of immature white cells, and great enlargement of the spleen. It can result from exposure to ionizing radiation.

Line Focus: A principle employed in the design of x-ray tubes, by which the effective focal spot (q.v.) is sharply reduced relative to the actual focal spot.

Localization: The making of a radiograph for the purpose of identifying a site in relation to surrounding tissues.

Magnification, Radiographic: The enlargement or distortion of a radiographic image recorded on film emulsion, minimized by reducing the object-to-film distance, and increasing the focus-film distance.

Maximum Permissible Dose (MPD): For radiation workers, 50 mSv per year is permissible. The MPD is the maximum dose of radiation that, in view of present knowledge, would not be expected to produce significant radiation effects.

Mesial: Toward the center of the dental arch.

Milliampere (mA): Electrically, the milliampere is 1/1000 of an ampere (q.v.). In radiography, milliamperage refers to the current flow from the cathode to the anode, which, in turn, regulates the intensity of radiation emitted by the x-ray tube and, hence, directly influences the radiographic density.

Milliampere-Seconds (mAs): The product of the x-ray tube operating amperage and exposure time, in seconds.

Millirad (mrad): One-thousandth of a rad.

Millirem (mrem): One-thousandth of a rem.

Milliroetgen (mR): One-thousandth of a roentgen.

Neutron: An elementary particle having no electrical charge. The neutron is a constituent of the nucleus of all atoms except hydrogen.

Nucleus, Atomic: The small central part of an atom containing the protons and neutrons; most of the atomic mass is concentrated here.

Object-to-Film Distance (OFD): Distance between the object or skin and the cassette or film.

Oblique: An angular view of a surface or object.

Occlusal Plane: The plane of the masticating surfaces of the molar and bicuspid teeth when the maxilla and mandible are closed.

Occlusal Radiograph: a radiograph made with a film designed for placement between the occlusal surfaces of the teeth, with the x-ray beam directed caudad or cephalad.

Osteoradionecrosis: Damage and death of normal bone, which may result from a curative dose of radiation used in the treatment of malignant or nonmalignant disease.



Overdevelopment: Permitting the film to remain in the developer beyond the normal or preset time. This decreases radiographic contrast and increases radiographic density.

Oxidation: A chemical reaction in which an electron is removed from an atom.

Paralleling (Right-Angle) Technique: The production of a radiographic exposure of intraoral film whereby the plane of the film packet is made parallel to the long axis of the tooth being radiographed. The central beam axis or "central ray" of the x ray is directed at right angles to both.

Penetrability: The ability of a beam of x radiation to pass through matter; kilovoltage and filtration determine the degree of penetrability.

Penumbra: The secondary shadow that surrounds the periphery of the primary shadow; the term pertains to the shadow proper. a penumbra is the ill-defined margin or shadow produced by light. In radiography, it is the blurred margin of an image detail, also called geometric unsharpness.

Periapical Radiograph: A radiograph made by intraoral placement of film for recording shadow images of the outline, position, and mesiodistal extent of the teeth and surrounding tissue.

Photoelectric Effect: The ejection of bound electrons by an incident photon such that the whole energy of the photon is absorbed and transitional or characteristic x-ray emissions are produced.

Photoelectron: An electron emitted from a substance under a stimulus or other radiation of appropriate wavelength.

Photon: A quantum of electromagnetic radiation.

Position Indicating Device (PID): A device usually composed of a plastic ring through which a metal rod can be placed to assist in properly aligning the cone and film.

Projection: A term for the position of a part of the patient with relation to the x-ray film and the x-ray beam.

Proton: An elementary nuclear particle with a positive electric charge.

Proximal: Nearest; closest to a point of reference.

Quality Assurance: Maintaining optimal function and, therefore, results of an operation. In radiology this refers to mechanisms to assure continuously optimal functioning of both technical and operational aspects of radiologic procedures- to produce maximal diagnostic information while minimizing patient exposure to radiation.


Quality Factor (QF): The linear-energy-transfer-dependent factor by which absorbed doses are multiplied to obtain (for radiation protection purposes) a quantity that expresses the effect of the absorbed dose on a common scale for all ionizing radiations.

Rad (Radiation Absorbed Dose; Roentgen Absorbed Dose): A unit of measurement for the absorbed dose of any type of ionizing radiation in any medium. One rad is the energy absorption of 100 ergs (Cf. Gray).

Radiation: The emission and propagation of energy, in the form of waves or particles, through space or a material medium.

Radiation Burn: A burn caused by overexposure to radiation energy.

Radiation Dermatitis: Inflammation of the skin resulting from a high dose of radiation. The reaction varies with the quality and quantity of radiation used and is usually transitory.

Radiation Sickness: A syndrome associated with exposure to ionizing radiation that may result in nausea, vomiting, and diarrhea; later symptoms include malaise, depression, epilation. purpura, hemorrhage, fever,and emaciation.

Radiobiology: That branch of biology dealing with radiation effects on biologic systems.

Radiograph: A visible image on a radiation-sensitive film emulsion to ionizing radiation that has passed through an area, region, or substance of interest.

Radiographic Survey: A series of radiographic projections constituting a study.

Radiography: The technical process of positioning, exposing, and processing radiographs.

Radiologic Health: The art and science of protecting humans from injury by radiation, as well as of promoting better health through beneficial applications of radiation.

Radiolucency: The appearance of dark images on film owing to the greater amount of radiation that penetrates the structures and reaches the film.

Radiolucent: Permitting the passage of x rays with relatively little attenuation by absorption.

Radiopacity: The appearance of light images on film owing to the lesser amount of radiation that penetrates the structures and reaches the film.

Radiopaque: A structure that strongly inhibits the passage of x rays.



Radiosensitivity: Relative susceptibility of cells, tissues, organs, organisms, or any substances to the injurious action of radiation.

RBE (Relative Biological Effectiveness): A factor used to compare the biologic effects of absorbed dosages of differing types of ionizing radiation in a particular organism or tissue. The standard of comparison is medium voltage x rays delivered at about 10 rad/min. The unit of RBE is the rem (q.v.).

Relative Risk: The ratio of the risk of biologic harm; in those exposed, to the risk, in those not exposed, to radiation.

REM (Roentgen-Equivalent-Man): A unit of dose of any radiation to body tissue, expressed in terms of its estimated biologic effects relative to an exposure of 1 roentgen of gamma or x radiation.

Resolution (Image): The discernible separation of closely adjacent image details. In optics, to separate and make visible the parts of an image.

Reticulation: A network of corrugations in the emulsion of a radiograph as a result of too great a difference in temperature between any two of the three darkroom solutions.

Roentgen(R): An international unit of exposure based on the ability of radiation to ionize air,ions carrying 1 electrostatic unit of quantity of either positive or negative electricity. (2.083 billion ion pairs).

Roentgen, Wilhelm C.,: The discoverer of x rays on November 8, 1895; he observed that a Crookes' vacuum tube operating at high voltage caused a piece of barium platinocyanide lying a few feet away from the tube to glow in the dark. Dr. Roentgen, a physicist, is known as the "Father of X rays."

Safelight: Special lighting used in the darkroom that permits film to be transferred from cassette to processor without fogging.

Scattered Radiation: Radiation that, during passage through a substance, has been deviated in direction. It may also have been modified by an increase in wavelengths. It is one form of secondary radiation (q.v.).

Secondary Ionization: Particles, usually electrons, ejected by recoil when a primary ionizing particle passes through matter.

Secondary Radiation: Particles or photons produced by the interaction of primary radiation with matter.

Sharpness (Image): The ability of an image to demonstrate an interface line as one-dimensional.


"Soft" Radiation: X rays of relatively long wavelength with relatively little penetrating ability.

Source: The point of emanation of gamma or x rays when used as an origin of radiation.

Spatial Resolution: The smallest distance between two points in an object that can be distinguished as separate detail in the image; generally indicated as a number of black and white line-pairs per millimeter.

Speed, Film: Speed in radiography refers to the relative amount of darkening produced on a film (with reference to film or screen characteristics) from a given amount of radiation. Speed and sensitivity may be used interchangeable. Officially, the speed of a film system is defined as the reciprocal of the exposure in roentgens required to produce a density of 1.0 above base plus fog density. The measurement unit of film speed is R -1.


Speed =    1   



Speed of Light: Light travels 186,000 miles/sec. All electromagnetic radiation travels at the speed of light.

Speed of X rays: X rays travel at the speed of light, 186,000 miles/sec, or at 3 X 108 meters per second in a vacuum.

Static Marks: marks on a radiograph resembling small streaks of lightening; they result from static electricity that occurs when the film is removed from the wrapper paper or when films are separated after being piled on top of one another.

Stop Bath: a solution of water and acetic acid used between the developer and the fixer that stops the development of the film.

Tank, Processing: Metal tanks used to hold processing solutions. Constructed of stainless steel to resist corrosion an permit rapid equalization of temperature control. The outside walls of the tanks are insulated to prevent condensation of moisture and maintain temperature control.

Target: The area on the anode subject to electron bombardment, usually consisting of a tungsten insert on the end face of a solid copper anode.

Target-Film Distance (TFD): This is the same as focal-film distance (FFD), in that it is the distance from the focal spot of the x-ray tube to the x-ray film.

Thermionic Emission: The release of electrons from the cathode filament by heating.



Tissue: An aggregation of similarly specialized cells united in the performance of a particular function.

Ultraspeed Film: Direct exposure film with a speed category of approximately 15 R -1.

Umbra: A complete shadow produced by light, with sharply demarcated margins. In radiography, a sharply delineated image detail.

Underexposed: A condition of a radiograph in which the image displays insufficient silver deposits.

Volt: The unit of electrical pressure or electromotive force necessary to produce a current of 1 ohm.

        Electron Volt: The kinetic energy gained by an electron in falling through a potential difference of 1 volt; 1.6 X 10-12 ergs.

Wave, Electromagnetic: Energy manifested by movements in an advancing series of alternating elevations and depressions.



Wavelength: The distance between the peaks of waves in any waveform, such as light, x rays and other electromotive forms; also the distance from any point on a wave to the identical point on an adjacent wave. In electromagnetic radiation, the wavelength is equal to the velocity of light divided by the frequency of the wave.

Wetting Agent: A solution used in film processing, it follows the washing process to accelerate the flow of water from both film surfaces and to hasten the drying of radiographs.

Whole-Body Radiation: Exposure of the entire body to radiation.

X ray: A type of electromagnetic radiation characterized by wavelengths of 100 angstroms or less.

X-ray Beam: The radiation emerging from an x-ray generator or source.

X-ray Spectrum: A portion of the electromagnetic spectrum with photon energies greater than 100 eV.


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