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124 Cards in this Set
- Front
- Back
What is xray film coated with?
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emulsion on both sides
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what does film emulsion consist of?
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photosensitive and radiosensitive silver halide grains (mainly silver bromide and small amount of silver iodide)
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what does silver halide crystal contains?
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silver, bromide, and iodide ions
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are free silver ions present in the spaces between the crystalline lattice atoms?
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yes
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what are large iodide ions added to crystal lattice?
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to create physical distortion in regular array of silver and bromide ions to increase emulsion sensitivity
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why do you want an irregular crystal lattice?
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to increase speed of xray and decrease dose
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What film speed uses silver iodide?
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D speed
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sensitivity sites
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latent image sites
where silver halide crystals are chemically sensitized by addition of sulfur compounds at these sites the sulfur cmpds create the sensitivity sites that contribute the latent image formation |
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where does image formation start in crystal lattice?
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at the latent image site
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What happens at the latent image site?
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xray causes release of e- by interaction with bromide ions
Bromide ions are converted to bromine atoms by releasing e- free e- strike a latent image site and impart neg charge to it free silver inons are attracted to the latent image site bc of the neg charge(opp attract) |
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what begins latent image formation?
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sensitivity sites
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How many sensitivity sites does each silver halide crystal have?
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MANY
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During processing, what initiates the conversion of silver ions in the crystal into grains of metallic silver?
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the developer
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Describe processing
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critical stage
good technique is required processing has many steps done in darkroom |
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2 types of processing
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manual and automatic
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4 steps of automatic processing
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1. developin
2. fixation 3. washing 4. drying |
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6 steps of manual processing
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1. wetting
2. developing 3. rinsing 4. fixation 5. washing 6. drying |
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Processing solutions
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developer and fixer
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primary function of developer
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conversion of exposed silver halide into metallic silver atoms
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reducing agen in developer
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Phenidone
it is an electron donor it converts Ag ions into black metallic silver atoms at the latent image site this brings out image fast. Phenidone is oxidized after releasing electron |
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What reduces phenidone back after it has been oxidized?
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hydroquine
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functions of hydroquione
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builds up gray, white and black tones or produces an image w/ contrast
reduces the oxidized phenidone to the original active state so it can continue to reduce silver halide grains to metalic silver by donating e- |
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alkali compounds or activator of developer
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sodium or potassium hydrozide
it provides alkaline medium as developer is only active at pH 10 it softens gelatin for diffustion of developing agent into emulsion |
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What maintains alkaline pH of developer?
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buffers like sodium carbonate
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preservative or antioxidant in developer
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sodium sulfite
it prevents rapid oxidation of developing agent in o2 atmosphere it extends useful life |
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restrainer of developer
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potassium or sodium bromide
restrains development of unexposed silver halide crystals it prevents chemical fog |
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primary function of fixer
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removal of unexposed or undeveloped silver halide crystals and to harden and shrink the film emulsion
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fixing agent or clearing agent of fixer
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ammonium thiosulfate
removes unexposed silver halide grains from the film emulstion |
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what is acidifier of fixer?
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acetic acid buffer system
promotes diffusion of ammonium thiosulfate into emulsion removes silver thiosulfate complex of emulsion blocks development of unexposed crystals |
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Perservative in fixer
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sodium or ammonium sulfite
keeps chem balance prevents oxidation of thiosulfate clearing agent binds with colored oxidized developer carried into fixer and removes it. prevents oxidized developer from staining the film |
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hardener of fixer
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aluminium salts
hardens emulsion during fixing reduces swelling of emulstion during final wash limits water absorption and limits drying time prevents damage to gelatin during handling |
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composition of fixer
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ammonium thiosulfate
acetic acid sodium or ammonium sulfate aluminum salts |
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result of prolonged development
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darder radiographs w/ higher density
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what does excessive fixation result in?
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gradual loss of film density
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when does washing efficiency decline?
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efficiency declines when the wter temp falls below 60 F
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Function of washing
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aids in removal of all residual processing chemicals (thiosulfate ions and silver thiosulfate complexes) that may obscure the diagnostic info in final image
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rxn of discoloration due to improper washing
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thiosulfate + Ag = silver
sulfide silver sulfide is brown |
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function of drying
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removes moisture from film and prepares it for viewing
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what does uneven drying result in?
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distortion of gelatin and thus variation in density may be seen
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steps of manual processing prior to processing
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adequate safelight in darkrom
chck son levels stir sln chck sln temp unwrap exposed film pkt load film on hangers set interval timer start processing |
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manual processing steps
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wetting (30 s)
development (5 min @ 68 F) water rinsing (30 s) fixation (10 min) washing (10-15 min) drying (30 min) |
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recommended temp for manual processing? why?
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temp of 70 degrees is recomendded
fog is minimized contrast and density increase optical quality processing time is practical temp is easily controlled |
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advantages of automatic processing
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shortens time to 1.5-6 min
rollers transport films constant end results less floor space daylight loading possible less equiptment eliminate wet reading of film |
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function of roller in automatic processing
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transport films
massage action, uniform distribution of chemicals uniform processing prevent carry over of slns processing slns and water roller motions stirs sln |
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how does developer smell?
how does fixer smell? |
developer is alkaline and soapy
fixer is acidic and has sharp smell |
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what is different about chemical is automatic x ray developing?
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work at higher conc and temp
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in automatic processing what is added to the developer?
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gluteraldehyde (hardener)
sulfate (minimize swelling) |
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why should processing slns be replenished?
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dev. becomes inactive w/use and by exposure to O2
fixer goes inactive too |
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how to replenish processing slns
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every day even if not been used bc oxidation causes the chemicals to breakdown
replenish 8 oz of sln/30 PA or 5 pano or add 1 oz. per 4 films over 30 |
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why to change processing solutions?
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1. slns deteriorate w/ exposure to air
2. use of exhausted developer results in slower processing and reduced density and contrast 3. exhausted fixer use causes slower removal of unexposed crystals and silver thiosulfate complexes 4. this results in incomplete clearing and films turns brown w/ age |
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what is used to evaluate image quality?
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step wedge
to check image quality expose a film w/ step wedge when slns are changed |
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what does loss of step wedge indicate?
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poor image quality
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when can rapid processing chemicals be used?
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in emergencies and endo
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what is rapid processing?
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more concentrated (15 s development and 15 s. fixation at room temp)
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problem w/ rapid processing?
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discolor over time
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extraoral radiography
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images made of oral and maxiofacial regions with film and xray source placed extraorally
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uses of extraoral radiology
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evaluation of areas not fully covered by intraoral films
visualizations of skull and facial structures |
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film and intensifying screens used with extraoral radiography
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medium or hi speed rare earth screen film
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describe medium speed film with extra oral radiography
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relatively higer resolution and higher radiation dose
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what do lead markers allow?
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for left/ right orientation
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size of skull film
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8 x 10 inch
use posterior anterior view or lateral skull view |
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size of panoramic film
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15 x 30 cm
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size of lateral oblique views of mandible
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5x7 inch
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what uses intesifying screens?
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rare earth elements
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light emited by rare earth screens
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60% of green portion of light wave spectrum
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green sensitve film
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T Mat film by Kodak
this is 2x as fast compared to Calcium Tungstate screen-film combination |
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Kodak's name, phosphor, and emission
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name: lanex
Phosphor: Gadolinium Emission: Green |
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Imation name, phosphor, and emission
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name: Trimax
Phosphor: Gadolinium Emission: Green |
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Sterling name, phosphor, and emission
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name: Quanta
Phosphor: Yttrium Emission: Blue and UV |
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How can screen films be combined to provide good soft tissue visulization?
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Kodak T-Mat L film combined with Kodak Lanex
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T or F: extraoral film is indirect exposure film
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TRUE
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how do extraoral film create image
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phosphors in intensifying screens emit light when exposed to readiation
light exposes film to form an image |
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Types of intensifying screens
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calcium tungstate intesifying screen
rare earth intensifying screen PA |
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Describe calcium tungstate intensfying screen
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effective dose single panoramic film: 14 microSv
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Describe rare earth intensfying screen
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less radiation dose
effective dose single pano film: 7 microSv |
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types of extraoral radiography
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posterior-anterior (PA)
Lateral skull ceph Waters projection caldwell projection Reverse Towne's Projection Submentovertex (Axial) Lateral oblique mandible projection Pano |
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2 ways extraoral radiography can be made
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conventional dental xray unit
advanced types of xray machine designed specifically for extraoral imaging |
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requirement for extraoral radiography
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means of fixing tube head in standardized position
device for reproducible head positioning (cephlostat) |
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Frankfort plane
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superior border of external auditory meatus to infraorbital rim
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Canthomeatal line or Tragocanthal Line
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center point of external auditory meatus to outer canthus of eye
(forms an angle of 10 degrees w/ Frankfort plane) Tilt head down about 10 degrees |
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Cephalometrics
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technique employing oriented radiographs for purpose of making head measurements
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what are cephlometrics used for?
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study craniofacial growth
diagnosis ortho treatment evaluation of treated cases |
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Uses of posteroanterior cephalometric projection
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evaluate skull
pathology trauma developmental abnormalities asymmetrical growth ethmoid sinuses nasal fossa orbits |
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in what direction can you view changes by reading a posterior anterior ceph?
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progressive changes in mediolateral dimension
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film placement with posteroanterior ceph
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cassette positioned vertically in a holding device
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head position when taking a posteroanterior ceph
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centered in center of cassette, midsagittal plane is perpendicular to floor. franfort plane is perpendicular to film
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central ray with posteroanteriior ceph
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central ray directed perpendicular to film
source should be conincident with midsagittal plane of head at level of bridge of nose |
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source distance from midcoronal plane of pt with posteroanterior ceph
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152 cm or 60 in
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where is petrous ridge visualized in posteroranterior ceph?
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superior border of petrous ridge seen in lower third of orbit
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posterior anterior projection exposure parameters vary with what?
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type of machine
source object distance screen film combination |
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what is lateral ceph skull projection used for?
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trauma
disease facial growth pre/post treatment ortho anteriorposteror view of paranasal sinuses, mastoid air cells, nasopharangeal soft tissue |
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Where is film placed when taking a lateral ceph?
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film is placed vertically in film cassette on left side of patients face
midsagital plane is parallel w/ film |
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How should pts teeth and lips be when taking lateral ceph?
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posterior teeth in occlusion
lips at rest |
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frankfort plane with lateral ceph
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frankfort plane parallel to floor
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where is central ray directed with lateral ceph?
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central ray directed to exteral auditory meatus and perpendicular to plane of film and midsagittal plane
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with lateral ceph can soft tissue be seeN?
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yeah if a filter is ued
wedge filter is placed over anterior side of beam at tube head or cassette filter absorbs some radiation strikin nose, lips, chin beam intensity in anterior region is reduced and soft tissue is seen on xray |
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distance between source and midsaggital plane on lateral ceph
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152 cm or 60 in
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waters projection
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occipitaomental view
used to evaluate maxillary sinus |
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what is visualized with water's projection?
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maxillary sinus
fronal sinus orbit zygomatic bone and arch nasal cavity coronoid process of mandible orbits sphenoid sinus |
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position of patient with waters projection
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chin is raised to elevate canthomeatal line 37 degrees above the horizontal plane
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x ray used to evaluate maxillary and frontal sinus
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Waters' projection
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with waters projection where is petrous portion of temporal bone visualized?
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posterior to the apex of maxillary sinus
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film and head placement with water's projection
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cassette positioned vertically
head position is midsaggital plane of head perpendicular to film plane chin is raised to elevate canthomeatal line 37 degrees above horizontal plane |
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Where is Xray source with water's projection?
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perpendicular to film plane through midsaggital plane at level of max sinus
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what does it mean if petrous portion of temporal bone lies over the apex of maxillary sinus?
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patients chin to low so must be raised further
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What xray allows you to see orbit view?
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Caldwell projection
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where is petrous portion of temporal bone seen in Caldwell projection?
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at lower border of orbit
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what is different with xray source with caldwell projection?
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patient even with tragocanthal line but xray source is 23 degrees caudal to canthomeatal line and exits the glabella
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Reverse Townes Projection indications
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visualize ramus area
Condylar neck fractures medial displacements of condyle posterolateral wall of maxillary sinus nasal septum |
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What does reverse Townes projection view eliminate/
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superimposition of masstoid and zygoma over the condylar neck bc superimposition occurs in PA view
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describe pt postition with reverse towne's projection
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head centered in front of cassette and forehead in contact with cassette
pts mouth is wide open canthomeatal line is oriented 25-30 degrees downwards |
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Xray source with reverse townes projection or townes view
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parallel with floor and directed to film in sagittal plane through occiptal bone
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Submentovertex projection
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base or full axial projection
used to visualize: base of skull curvature of mandible position of condyles sphenoid sinus zysoma zygomatic process |
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patient position with submentovertex projection
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pts head/nect extended backward w/vertex of skull on center of casette, midsagitall plane of pt's perpendicular to floor
frankfort plane vertical and parallel to vilm plane |
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Xray source for submentovertex projection
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directed from below mandible and enters midline between condyles
xray source is perpendicular to film plane |
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what is lateral jaw radiography?
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mandibular lateral oblique projection
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what replaced mandibular lateral oblique projectioin?
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pano
althought mandibular lateral oblique projection has greater detail and can be done in conventional dental xray machine with open,round cylinder |
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mandibular body projection
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broader coverage than periapical films
shows pre molar/molar region, inferior border of body of mandible |
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if pt cant open mouth which xray should be used?
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mandibular lateral oblique projection
(mandibular body projection) |
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pt position with mandibular body projection
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long axis of head tilted toward side being examined
mandible protrouded casette against patients cheek centered over 1st molar casette lower border parallel w/ inferior border of mandible and extending at least 2 cm below it pt holds the casette |
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where is xray source with mandibular body projection?
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toward first molar from a point 2 cm below angle of mandible on tube side
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what does mandibular ramus projection allow?
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view of ramus from angle of mandible to condyle
used for evaluation of 3rd molar regions of maxilla and mandible |
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where is casette and pt placed with mandibular ramus projection?
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casette placed over ramus and posteriorly extended to include condyle
lowere border parallel w/inferior border of mandible and extended at least 2 cm below the border pt head tilted toward film pt mandible protroaded |
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Xray source for mandibular ramus projection
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source directed toward center of ramus on side of interst from a point 2 cm below the inferior border of the first molar regions on the mandible on the tube side
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