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44 Cards in this Set
- Front
- Back
What are the two types of images created when performing an xray
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Aerial - invisible pattern in air that represents various x-ray photons as they exit the object
Latent - invisible image on film that is produced in film emulsion after exposure to x-rays |
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What are the 4 types of receptors used in dental x-ray taking
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Conventional -
intra and extraoral Digital - CCD(charged couple devices) and PSP(storage phosphor systems) |
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What is an image receptor
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recording medium that displays information about an object that has been exposed to xrays
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Describe some similar and differing qualities of the 2 types of conventional films
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Intraoral- is a DIRECT exposure film and can give higher resolution, Used for bitewings and PA's
Extraoral - is an INDIRECT or screen film in other words it uses an intensifying screen that emits light. Extraoral used for pans and cephs Both are harmed by exposure to ambient light |
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What is the functions of the lead foil layer in the film package
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protects from backscatter, adds rigidity to package.
MAKE SURE YOU PUT SIDE WITH FOIL AWAY FROM SUBJECT IS SIDE OPPOSITE THE DOT |
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What does the raised dot tell us
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its on the film side and goes towards the xray tube--- used for film orientation
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What is the function of the paper or plastic covering on the film package
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Moisture resistant and protection from visible light
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Should double film packages be processed at one time.
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No they should be processed individually
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What are the four parts of film composition
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Base, adhesive, emulsion and protective coating
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What are the base's functions in a film
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its a thin clear plastice that is flexible and gives blue tint for easy viewing and reduced eye strain, supports emulsion,
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describe the emulsion on a film
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Its radiosensitive and records the image by interaction of xray photons or light
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Why is emulsion coating on both sides of the film
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To increase film speed, reduce exposure time and radiation dose
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What is the main active ingredient of the emulsion
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Silver Halide granules -
AgBr in F speed AgI in ultraspeed(D speed) |
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Describe the vehicle matrix of the emulsion
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gelatinous and non-gelatinous materials that keep Ag halides dispersed and absorbs processing chemicals
Its transparent(transmission of xrays and light) and very porous(chemical penetration) |
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What is the definition of film speed
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also called Film Sensitivity - the amount of radiation required to produce an image of standard density or the efficiency with which a film responds to xray exposure
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T or F Faster films need more radiation and longer exposure times
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False, faster films need less exposure time and less radiation
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What determines film speed
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Size of silver halide granules - Larger the granule size faster the film speed
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What are some of the benefits of faster films
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decreased patient dose, short exposure time and less chance of motion
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What are some of the characteristics of D speed films
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round grain technology that gives high contrast, fine detail but requires higher dose than F speed. Uses AgI instead of AgBr like F speed
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Describe F speed characteristics
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Its a flat or tubular T-grain technology that gives 50% or more reduction in exposure compared to D. it has larger crystals and greater amount of AgBr in emulsion. Gives comparable contrast and resolution to D speed
F speed also accomodates a wider range of processing conditions and is exceptionally tolerant of processing variations |
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T or F film speed can be increased by processing at a slightly higher temp
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T
however its not recommended as it can create fog and graininess |
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What can lower film speed
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processing in diluted processing solution
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Film fog is described as
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unwanted blackness by exposure to radiation other than primary beam
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What is film latitude
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Measure of range of exposures that can be recorded as distinguishable densities on a film
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Films with wide lattitude have what characteristics with respect to contrast
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Lower contrast
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What are the optimal storage conditions for xray film
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50-70 deg F or 10-21 deg C
30-50 % humidity |
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What can storing film in dry conditions lead to
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artifacts or static electricity marks on the processed film
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When storing extraoral film boxes what should you take precaution in doing
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store it on side of box to prevent warping
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Open boxes should be stored in the xray room
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false, store outside the xray room
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What can storage of film in a refrigerator cause
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condensation on film and black marks
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What are some things that can cause film damage
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Heat, light, bending and pressure
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What are the four layers of the intensifying screen used for extra oral films
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Base, reflector, Phosphor layer and overcoat
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What is a synonym for extraoral film
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screen film
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What is the process that happens in an extraoral film which produces the image
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Energy of xray beam converts to light by the phosphors in the intensifying screen being exposed to radiation. this light exposes the film to form the image
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What are the properties of an intensifying screen
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sturdy, moisture resistant, chemically inert, flexible and contains no impurities
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What are the intensifying screen materials
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Calcium tungstate(blue)
Rare earth phosphors used as intens screens 1 Gadolinium oxysulfide(green) 2 lanthanum oxybromide(blue) 3 yttrium tantalate (blue) |
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Why do manufactures recommend matching emission and absorption characteristics of intensifying screens and films
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Different intens screens have different emissions and different films have different absorption characteristics
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What are some of the effective doses of the different types of intensifying screens
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Calcium Tungstate - single panoramic 14 microsieverts
Rare earth Intensifying single panoramic - 7 microsieverts NOTE Poster - Anterior View 7-17 microsieverts but not sure if this is shows difference between 2 types or is an estimater for rare earth's |
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Which type of intens screens require less radiation dose
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Rare Earth
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What are some advantages and disadvantages of extraoral film
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Advanatges
Reduced patient dosage diagnostically acceptable image Disadvantages lack of fine anatomical detail |
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What are some of the uses of extraoral films in dentistry
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Panoramic, Post-Ant or Lateral Cephalometric
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What are the most common causes of poor screen-film contact
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Worn contact area
loose or bent hinges warped screens caused by moisture warped cassette front cracked cassette frame foreign matter under the screen |
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what are some function of grids
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used to reduce scatter radiation
placed betweem subject and film only used when increased contrast is needed |
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What is a disadvantage of grids
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Higher exposure is needed(approx double)
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