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107 terms

Radiology, image characterisitcs, localization technique

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radiolucent
dark or black, air space is this
radioopaque
light or white, structures are dense adn absorbe or ressit passage of xray beam, enamel, dentin, bone
the quality of dental radiographs is determined by its
image characterisitcs, ideal radiograph is not too light or too dark
diagnostic radiograph
great deal of information, exhibit proper density and contrast, have sharp outlines, are of same shape and size of object radiographed
visual characteristics
density and contrast
density
overall blackness or darkness, heavier deposits of black silver particles causes the darkness
degrees of blackness is
contrast
Influency factors
Milliamperage(mA), kVp, exposure time, and subject thickness
milliamperage
produces more x-ray that expose the film and increases film density. this is increased, density increase, the darker the image
operating kVp
increase this, increase film density by increasing the mean or average energy of x-rays adn by producing x-ray of higher energy. increase this, increase density, darker image
exposure time
increase exposure time, increases film density by increasing total number of x-ray that reach film surface. increase this, increases density, causes darker image
subject thickness
few x-rays reach film in patient with increased amount of soft tissue or thick, dense bones, less density and appears lighter. adjustments in mA, kVp, exposure time compensate for variations in size of patients and subject thickness
high contrast
very dare areas and very light areas, the two are strikingly different. black and white.
low contrast
many shades of gray.
film contrast
refers to the characterisitcs of film that influence radiographic contrast, chararateristics that influence contrast include the inherent qualities of the film and film processing
subject contrast
characteristics of teh subject that influence radiographic contrast, this is determined by thickeness adn density and composition of subject. can be altered by increasign and decreasing kVp
Only one exposure factor has direct influence on the contrast of dental radiograph, this one factor is
kVp, increasing kVp, affects film contrast, by producing higher energy x-rays. xrays with higher energy are better able to penetrate tissue. appears as varying shades of gray, low contrast. higher kvp, lower contrast, lower kvp, Higher contrast
scales of contrast
range of useful densities seen on dental radiograph. has short scale and long scale
short-scale contrast
shows only two densities areas of black and white,, lower kVp, high contrast
long scale contrast
dental radiograph that exhibits many densities or many shades of gray, has long contrast scale, higher kVp, lower contrast
stepwedge
uniform layered thickness to show long scale and short scal contrast, made of aluminum
geometric characteristics
sharpness, magification, distortion, must be minimized to produce acurate radiographic image
sharpness
refers to the capability of the x-ray film to reproduce the distinct outlines of an object. small details of an object are reproduced on dental radiograph
penumbra
fuzzy, unclear area that surrounds a radiographic image. unsharpness, or blurring, edges of radiographic image
umbra
shadow
influencing factors of sharpness
focal spot size, film composition, movement
focal spot
tungsten target of anodes, small area converts bombarding electrons into x-ray photons.
the smaller the focal spot
the sharper the image apears
the larger the focal spot
the loss of image sharpness
filim composition
the composition of the film emulsion influences sharpness. sharpness is relative to the size of the crystals found in film emulsion. faster film contains larger crystal that produce less images sharpness,
slower filim contains
smaller crystals that produce more image sharpness
movement
influences film sharpness. loss of image sharpness occurs if either the film or the patient moves during x -ray exposure
this results in unsharpness
magnification
radiographic image that appears larger than the actual size of the object it represents
influencing factors of magnification
target film distance, object film distance
target-film distance
is distance between the source of x-rays(focal spot on the tungsten target) and the film. when longer PID used, more paralllel rays from middle of xray beam strike object rather than diverging x-ray from periphery of beam.
longer PID results in less image magnification
shorter PID and target film distance results in
more image magnification
object film distance
distance between the object being radiographed (the tooth) and the dental x-ray film. tooth and film should always be placed close together as possible.
the closer the tooth to the film
less image enlargment there will be on the film.
increase in object film distance results in an
increase in image magnification, this is bad
distortion
variation in true size and shape of the object being radiographed. results from unequal magnification of different parts of the same object, improper film alignment or beam angulation
influencing factors of distortion
object film distance and x-ray beam angulation
object film distance
minimize dimensional distortion, ojbect and film must be parallel to each other, not parallel, angular relationship results,
angular relationship produces
variation of distances between the tooth adn film that results in distored image, distorted image may appear too long or too short
x-ray beam angulation
minimize dimensional distortion, xray beam must be directed perpendicular to the tooth and the film, central ray of the x-ray beam must be as nearly perpendicular to the tooth and film as possible to record adjacent structures to their true spatial relationships
to limit distortion
film and tooth are positioned parallel to each other, and xray beam is directed perpendicular to the tooth and film
to limit magnification
the longest target film distance and shortest object film distance are used
portion of a processed radiograph that appears dark or black is termed
radiolucent
portion of a processed radiograph that appears light or white is termed
radiopaque
which of the following appears most radiolucent on dental radiograph?
air space
an example of a radiopaque structure seen on dental x-ray is
bone, enamel and dentin
the overall blackness or darkness of a dental radiograph is termed
density
increasing the mA will cause
an increase in density, the film apears darker
increasing the operating kVp will cause
increase in density, film appears darker
increasing exposure time will cause
an increase in density, film appears darker
dental patient has thick soft tissues and dense bones. to compensate for this increase in subject thickness and provide a film of diagnostic density, the dental radiographer may
increase exposure time, increase mA, increase kVp
the difference in the degress of blackness between adjacent areas on a dental radiograph is term
contrast
when viewed on a light soruce, a dental radiograph that demonstrates many shades of gray is said to have
low contrast
when views on a light source, a dental radiograph that demonstrates very dark areas adn very light areas is said to have
high contrast
the one exposure fator that has a direct influence on the contrast of a dental radiograph
is kVp
the type of contrast preferred in dental radiography is
low contrast
the stepwedge is used for
demonstrations of longscale and shortscale, monitor quality control of film processing, demonstrate film densities
the capability of the x-ray film to reproduce distinct outlines of an object is termed
sharpness
the unsharpness or blurred edges seen on radiographic image is termed
penumbra
geometric characteristic that refers to a radiographic image that appears larger than its acutal size is term
magnification
a variation in the true size and shape of object being radiographed is termed
distortion
Principles of shadow casting
1. source of radiation should be as small as possible
2. tube to ojbectdistance shoudl be as great as possible
3. object to film distance should be as small as possible
4. film shoudl be parallell to the long axis of teeth
5. the central ray should be perpendicular to the film
6. the central ray should be directed between the teeth
7. the x-ray tube, patient, and film should be motionless
umbra
shadow
paralleling obeys most all principles of shadow casting except which principle?
principe #3, object to film distance should be as small as possible. this is only principle of shadow casting that bisecting technique does better
method used to locate the position of a tooth or object in the jaws
localization technique
pupose and use of localization technique
two dimensional picture of 3 dim object, depicts superior-inferior and anterior posterior relationships, but doest not depict buccal lingual relationship
localization technique can locate the following
foreign bodies, impacted tooth, unerupted tooth, retained roots, root positions, salivary stones, jaw fractures, broken needles, and instruments, filling materials
two basic technique are used to localize objects:
buccal object rule and right angle technique
what rule governs the orientation of structure portrayed in two radiographs exposed at different angulations
1st use proper technique, 2nd change verical and horizontal angulation
buccal object rule(slob)
when dental structure or obejct seen int eh second radiograph appears to have moved in the same direction as teh shift of teh PID, the structure or object in question is positioned to teh
lingual, same=lingual
when dental structure or object seen in second radiograph appears to ahve moved in direction opposite the shift of the PID, the structure or object in question is positioned to teh
buccal, opposite=buccal mostly maxillary
another rule for orientatino of structures seen in two radiographs
right angle technique
superior inferior and anterior posterior relationship for the
right angle technique
how is technique used
occlusal film (anterior posterior)is exposed directing the central ray at a right angle, or perpendicular(supeior inferior) to the film, mainly for located on mandibule
What are 3 main uses of dental radiograph
detect disease, confirm disease, legal document
filmless imaging system, method of capturing radiographic image using a sensor, breaking it into electronic pieces, and presenting and storing the image using computer
digitial radiography
Radiation then onto film, then developing process bring latent to visible, then making the radiograph is called
radiology imaging
radiation onto sensor(phosphur plate), making digital image to visible image, scanned on computer
digital imaging
the greater the pixels the greater teh
sharpening
is a solid state detector that contains silicon chip witha n electronic circuit embedded in it, is senstive to xrays or light
CDC, change coupled device. our is phosphorus
the cdc has this part instead of silver crystals
pixels
imaging is how many impulse per second compaired to conventional 60=sec
1/100 sec. 100 impulse=sec
is 50-80% less radiation
two types of digital imaging
direct and storage phsophur(indirect)
Direct uses a
CDC,
indirect uses a
PSP, storage phosphur, phot stimulate phosphur image
have wireless rare earth phosphur coated plates
indirect digital imaging
phosphur plate store the ___image
latent image
the _____stimulates the fluorescent signal which is converted into a digital image
laser scanner
measurement of the ability of digital system to capture the detail in an image
line pairs/millimeter
how are existing readiographs converted to digital image
cdc camera scans radiographs, digitizes the info, sent to computer, view on monitor or printed, archived old records
how many linepairs does digital radiograph have?
12-20 ln pairs/mm, beginning at 10lp mm, new machine 20+
digital imaging can detect how many shade of grade scale resolution
256 shades compared to 16-25 shades of radiography, and human eye of 32 shades
computer enhancements are
colorization, zoom, digital subtraction, density, decay sensor
advantages to digital imaging
superior gray scale, reduction exposure speed of viewing, decrease in equipment costs(processing), efficiency, enhancement of image, patient education tool
disavantages
cost, image quality, sensor size, infection cotnrol, legal issue, manipulated images
Legal issue in radiology laws
radiation control for health and safety act 1968
consumer patient radiation health and safety act 1981
invidual state and local laws
risk management policies and procedures
instructor's approval of radiographic selection, sign your clinic book, fill out the exposure record
informed consent of patient, dentist's authorization
standard of care is the
quality fo care that is provided by dental practioners in a similar locatily under the same or similar conditions, negligence if not follow standard of care
documentaiton
informed consent, signed treament plan, number and type of radiographs to be taken
number and type of radiographs
exposure record, treatemtn record
diagnostic information obtained, recorded by dentist, referrals indicated
ownership of radiographs
dentist or owens community college
patient may request radiographs
copy made if second copy unavailable
must be writeen in record
forward to their dentist
refusal of radiographs
patient refusal of dental radiographs, compromises the patien'ts diagnosis and treatment
the patient can not sign a relsease consent to negligent care is invalid
section instructor will assist you with any difficult clients
patient management
convey confidence, be prepared, you know what you are doing!
helpful hint to avoid gag reflex
never metion gag!! do reasure the patient, begin anterior, do suggest breathing, do try to distract the patient. do try tactile stimulation, do use topical anesthetic, avoid the palace, demonstrate placement