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124 Cards in this Set

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What is xray film coated with?
emulsion on both sides
what does film emulsion consist of?
photosensitive and radiosensitive silver halide grains (mainly silver bromide and small amount of silver iodide)
what does silver halide crystal contains?
silver, bromide, and iodide ions
are free silver ions present in the spaces between the crystalline lattice atoms?
yes
what are large iodide ions added to crystal lattice?
to create physical distortion in regular array of silver and bromide ions to increase emulsion sensitivity
why do you want an irregular crystal lattice?
to increase speed of xray and decrease dose
What film speed uses silver iodide?
D speed
sensitivity sites
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
where does image formation start in crystal lattice?
at the latent image site
What happens at the latent image site?
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)
what begins latent image formation?
sensitivity sites
How many sensitivity sites does each silver halide crystal have?
MANY
During processing, what initiates the conversion of silver ions in the crystal into grains of metallic silver?
the developer
Describe processing
critical stage
good technique is required
processing has many steps
done in darkroom
2 types of processing
manual and automatic
4 steps of automatic processing
1. developin
2. fixation
3. washing
4. drying
6 steps of manual processing
1. wetting
2. developing
3. rinsing
4. fixation
5. washing
6. drying
Processing solutions
developer and fixer
primary function of developer
conversion of exposed silver halide into metallic silver atoms
reducing agen in developer
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
What reduces phenidone back after it has been oxidized?
hydroquine
functions of hydroquione
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-
alkali compounds or activator of developer
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
What maintains alkaline pH of developer?
buffers like sodium carbonate
preservative or antioxidant in developer
sodium sulfite

it prevents rapid oxidation of developing agent in o2 atmosphere
it extends useful life
restrainer of developer
potassium or sodium bromide

restrains development of unexposed silver halide crystals

it prevents chemical fog
primary function of fixer
removal of unexposed or undeveloped silver halide crystals and to harden and shrink the film emulsion
fixing agent or clearing agent of fixer
ammonium thiosulfate

removes unexposed silver halide grains from the film emulstion
what is acidifier of fixer?
acetic acid buffer system

promotes diffusion of ammonium thiosulfate into emulsion

removes silver thiosulfate complex of emulsion

blocks development of unexposed crystals
Perservative in fixer
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
hardener of fixer
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
composition of fixer
ammonium thiosulfate
acetic acid
sodium or ammonium sulfate
aluminum salts
result of prolonged development
darder radiographs w/ higher density
what does excessive fixation result in?
gradual loss of film density
when does washing efficiency decline?
efficiency declines when the wter temp falls below 60 F
Function of washing
aids in removal of all residual processing chemicals (thiosulfate ions and silver thiosulfate complexes) that may obscure the diagnostic info in final image
rxn of discoloration due to improper washing
thiosulfate + Ag = silver
sulfide

silver sulfide is brown
function of drying
removes moisture from film and prepares it for viewing
what does uneven drying result in?
distortion of gelatin and thus variation in density may be seen
steps of manual processing prior to processing
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
manual processing steps
wetting (30 s)
development (5 min @ 68 F)
water rinsing (30 s)
fixation (10 min)
washing (10-15 min)
drying (30 min)
recommended temp for manual processing? why?
temp of 70 degrees is recomendded

fog is minimized
contrast and density increase
optical quality
processing time is practical
temp is easily controlled
advantages of automatic processing
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
function of roller in automatic processing
transport films

massage action, uniform distribution of chemicals

uniform processing

prevent carry over of slns

processing slns and water

roller motions stirs sln
how does developer smell?
how does fixer smell?
developer is alkaline and soapy

fixer is acidic and has sharp smell
what is different about chemical is automatic x ray developing?
work at higher conc and temp
in automatic processing what is added to the developer?
gluteraldehyde (hardener)

sulfate (minimize swelling)
why should processing slns be replenished?
dev. becomes inactive w/use and by exposure to O2

fixer goes inactive too
how to replenish processing slns
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
why to change processing solutions?
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
what is used to evaluate image quality?
step wedge

to check image quality expose a film w/ step wedge when slns are changed
what does loss of step wedge indicate?
poor image quality
when can rapid processing chemicals be used?
in emergencies and endo
what is rapid processing?
more concentrated (15 s development and 15 s. fixation at room temp)
problem w/ rapid processing?
discolor over time
extraoral radiography
images made of oral and maxiofacial regions with film and xray source placed extraorally
uses of extraoral radiology
evaluation of areas not fully covered by intraoral films

visualizations of skull and facial structures
film and intensifying screens used with extraoral radiography
medium or hi speed rare earth screen film
describe medium speed film with extra oral radiography
relatively higer resolution and higher radiation dose
what do lead markers allow?
for left/ right orientation
size of skull film
8 x 10 inch

use posterior anterior view or lateral skull view
size of panoramic film
15 x 30 cm
size of lateral oblique views of mandible
5x7 inch
what uses intesifying screens?
rare earth elements
light emited by rare earth screens
60% of green portion of light wave spectrum
green sensitve film
T Mat film by Kodak

this is 2x as fast compared to Calcium Tungstate screen-film combination
Kodak's name, phosphor, and emission
name: lanex
Phosphor: Gadolinium
Emission: Green
Imation name, phosphor, and emission
name: Trimax
Phosphor: Gadolinium
Emission: Green
Sterling name, phosphor, and emission
name: Quanta
Phosphor: Yttrium
Emission: Blue and UV
How can screen films be combined to provide good soft tissue visulization?
Kodak T-Mat L film combined with Kodak Lanex
T or F: extraoral film is indirect exposure film
TRUE
how do extraoral film create image
phosphors in intensifying screens emit light when exposed to readiation

light exposes film to form an image
Types of intensifying screens
calcium tungstate intesifying screen

rare earth intensifying screen

PA
Describe calcium tungstate intensfying screen
effective dose single panoramic film: 14 microSv
Describe rare earth intensfying screen
less radiation dose

effective dose single pano film: 7 microSv
types of extraoral radiography
posterior-anterior (PA)

Lateral skull ceph

Waters projection

caldwell projection

Reverse Towne's Projection

Submentovertex (Axial)

Lateral oblique mandible projection

Pano
2 ways extraoral radiography can be made
conventional dental xray unit

advanced types of xray machine designed specifically for extraoral imaging
requirement for extraoral radiography
means of fixing tube head in standardized position

device for reproducible head positioning (cephlostat)
Frankfort plane
superior border of external auditory meatus to infraorbital rim
Canthomeatal line or Tragocanthal Line
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
Cephalometrics
technique employing oriented radiographs for purpose of making head measurements
what are cephlometrics used for?
study craniofacial growth

diagnosis

ortho treatment

evaluation of treated cases
Uses of posteroanterior cephalometric projection
evaluate skull
pathology
trauma
developmental abnormalities
asymmetrical growth
ethmoid sinuses
nasal fossa
orbits
in what direction can you view changes by reading a posterior anterior ceph?
progressive changes in mediolateral dimension
film placement with posteroanterior ceph
cassette positioned vertically in a holding device
head position when taking a posteroanterior ceph
centered in center of cassette, midsagittal plane is perpendicular to floor. franfort plane is perpendicular to film
central ray with posteroanteriior ceph
central ray directed perpendicular to film

source should be conincident with midsagittal plane of head at level of bridge of nose
source distance from midcoronal plane of pt with posteroanterior ceph
152 cm or 60 in
where is petrous ridge visualized in posteroranterior ceph?
superior border of petrous ridge seen in lower third of orbit
posterior anterior projection exposure parameters vary with what?
type of machine
source object distance
screen film combination
what is lateral ceph skull projection used for?
trauma

disease

facial growth

pre/post treatment

ortho

anteriorposteror view of paranasal sinuses, mastoid air cells, nasopharangeal soft tissue
Where is film placed when taking a lateral ceph?
film is placed vertically in film cassette on left side of patients face

midsagital plane is parallel w/ film
How should pts teeth and lips be when taking lateral ceph?
posterior teeth in occlusion

lips at rest
frankfort plane with lateral ceph
frankfort plane parallel to floor
where is central ray directed with lateral ceph?
central ray directed to exteral auditory meatus and perpendicular to plane of film and midsagittal plane
with lateral ceph can soft tissue be seeN?
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
distance between source and midsaggital plane on lateral ceph
152 cm or 60 in
waters projection
occipitaomental view

used to evaluate maxillary sinus
what is visualized with water's projection?
maxillary sinus
fronal sinus
orbit
zygomatic bone and arch
nasal cavity
coronoid process of mandible
orbits
sphenoid sinus
position of patient with waters projection
chin is raised to elevate canthomeatal line 37 degrees above the horizontal plane
x ray used to evaluate maxillary and frontal sinus
Waters' projection
with waters projection where is petrous portion of temporal bone visualized?
posterior to the apex of maxillary sinus
film and head placement with water's projection
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
Where is Xray source with water's projection?
perpendicular to film plane through midsaggital plane at level of max sinus
what does it mean if petrous portion of temporal bone lies over the apex of maxillary sinus?
patients chin to low so must be raised further
What xray allows you to see orbit view?
Caldwell projection
where is petrous portion of temporal bone seen in Caldwell projection?
at lower border of orbit
what is different with xray source with caldwell projection?
patient even with tragocanthal line but xray source is 23 degrees caudal to canthomeatal line and exits the glabella
Reverse Townes Projection indications
visualize ramus area

Condylar neck fractures

medial displacements of condyle

posterolateral wall of maxillary sinus

nasal septum
What does reverse Townes projection view eliminate/
superimposition of masstoid and zygoma over the condylar neck bc superimposition occurs in PA view
describe pt postition with reverse towne's projection
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
Xray source with reverse townes projection or townes view
parallel with floor and directed to film in sagittal plane through occiptal bone
Submentovertex projection
base or full axial projection

used to visualize:
base of skull
curvature of mandible
position of condyles
sphenoid sinus
zysoma
zygomatic process
patient position with submentovertex projection
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
Xray source for submentovertex projection
directed from below mandible and enters midline between condyles

xray source is perpendicular to film plane
what is lateral jaw radiography?
mandibular lateral oblique projection
what replaced mandibular lateral oblique projectioin?
pano

althought mandibular lateral oblique projection has greater detail and can be done in conventional dental xray machine with open,round cylinder
mandibular body projection
broader coverage than periapical films

shows pre molar/molar region, inferior border of body of mandible
if pt cant open mouth which xray should be used?
mandibular lateral oblique projection

(mandibular body projection)
pt position with mandibular body projection
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
where is xray source with mandibular body projection?
toward first molar from a point 2 cm below angle of mandible on tube side
what does mandibular ramus projection allow?
view of ramus from angle of mandible to condyle

used for evaluation of 3rd molar regions of maxilla and mandible
where is casette and pt placed with mandibular ramus projection?
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
Xray source for mandibular ramus projection
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