Radiology chapter twenty two
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. What would you like to do?
Uses of the panoramic x-ray
- evaluate impacted teeth
- evluate eruption patterns
- detect diseases, lesions, and conditions of the jaw
- examine extent of large lesions
- evaluate trauma
What should the panoramic film not be used to determine?
- diagnos caries
- periodontal disease
- periapical regions
The x ray tube moves around the patients head in one direction while the film rotates in the____________________.
allows the imaging of one layer or section of the body while blurring images from structures in other planes
The tomography image in dental radiology conforms to what?
the shape of the dental arches
the pivotal point or axis, around which the cassette carrier and x-ray tubehead rotate is termed what?
What are the 3 rotation centers?
- double-center rotation
- triple-center rotation
- moving=center rotation
does the center of rotation change as the film and tubehead rotate around the patient? What does this allow?
- the image layer to conform to the elliptical shape of the dental arches
the location and number of rotational centers influences what?
the size and shape of the focal troph
2 rotation centers, one for the right side, one for the left side
3 rotational centers, uninterrupted image
continously moving circle, uninterrupted image
a 3 dimensional curved zone in which structures are clearly demonstrated on a panoramic radiograph; used to determine where the dental arches must be positioned to achieve the clearest image
in most panoramic x-ray machines, the focal trough is__________in the anterior, and____________in the posterior
What do different panoramic x-ray machines differ in?
- number of rotation centers
- size and shape of focal trough
- type of film transport mechanism used
what are the similar components that each panoramic x ray machine have?
- x-ray tube head
- head positioner
- exposure controls
describe the collimater used in panoramic radiography.
lead plate with an opening in the shape of a narrow vertical slit
Where does the x ray beam travel in panoramic radiography?
through the narrow slit in the collimator, emerges as a narrow band and passes through the pt, then through another vertical slit in the cassette carrier
what is the main purpose of a collimator?
to reduce patient exposure to x radiation
Does the vertical angulation ever change in panoramic x ray?
the tubehead of the unit always rotates___________the pts head as the film rotates______________of the pts head.
head positioner consists of
- chin rest
- notched bite block
- forehead rest
- lateral head support or guides
Which of these is fixed and can't be moved?:
What is the purpose of the screen film?
it converts the x rays to light, and then exposes the film
What sizes are the film used in panoramic radiology available in?
what color of light does calcium tungstate screen emit? And rare earth?
Which type of intensifying screen is recommended and why?
rare earth, because it requires less x-ray exposure and is faster, so less radiation to the pt
What must you label on the casset of the panoramic film?
- left and right sides
- dentist name
- pt name
What is the purpose of placing pts teeth in the notch of the biteblock?
to align the teeth in the focal trough
Where should the pts midsagittal plane be positioned for a pano?
perpendicular to the floor
where should the pts frankfort plane be positioned for a pano?
parallel to the floor
What are 2 more common pt preparation errors in panoramic radiography?
- ghost image
- lead apron artifact
a radioopaque artifact seen on a panoramic film that is produced when a radiodense object is penetrated twice by the x ray beam, such as earings or hearing aids etc.
how does a ghost image appear on a radiograph?
indistinct, larger, and higher than its counter part, and is blurred
What will appear on the radiograph if the pts lips arent closed on the bite block?
a darke radiolucent shadow that obscures the anterior teeth
What will appear on the radiograph if the tongue is not positioned on the roof of the mouth?
a dark radiolucent shadow that obscures the apices of the maxillary teeth
What happens if the pts chin is tipped up and the frankfort plane is not parallel to the floor?
- hard palate and floor of the nasal cavity appear superimposed over the roots of the maxillary teeth
- loss of detail in the maxillary incisor region
- reverse smile line is seen on radiograph
What happens if the pts chin is tipped down and the frankfort plane is not parallel with the floor?
- mandibular incisors appear blurred
- loss of detailn in the anterior apical regions
- condyles may not be visible
- exagerated smile line
What happens if the pt is positioned anterior to the focal trough?
anterior teeth appear skinny; image is blurred
What happens if the pt is positioned posterior to the focal trough?
anterior teeth appear fat; out of focus and blurred
What happens if the pts head is not centered, midsagittal plane is not perpendicular to the floor?
the ramus and posterior teeth appear unequally magnified on the pano; the side furthest from the film appears magnified, and the side closest appears smaller
What happens if the pts spine is not strait?
the cervical spine appears on the radiograph as a radiopacity
What are the advantages of the pano?
- field size
- pt cooperation
- minimal exposure to radiation
What are the disadvantages of the pano?
- image quality
- focal trough limitations
- equipment cost
What would you like to do?
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