pano radiography Flashcards
what sensors can be used with pano?
film, pspp, and digital
purpose of this?
what is film placed in for pano
cassette, possesses intensifying screens for the film
does pspp use a cassette?
no
receptor and source movement with pano
both move extraorally opposite to one another (same movement direction rotatioanlly)
how is beam shape dif with pano?
narrow vertical beam
where does the divergence of xrays occur in the vertical plane?
at the source
horizontal vs vertical mag in pano
more magnification in horizontal due to shorter source to object distance (from rotation center) compared to vertical (from actual source)
film/pspp? digital?
how is the discrepancy between vert and horizontal mag corrected?
film/pspp: receptor moves slowly in opposite direction to cause foreshortening in horizontal deminision
digital: software can auto correct the discrepancy
focal trough/image layer
area of sharpness where vertical=horizontal magnification
what component of the pano machine helps to align jaw in focal trough?
bitestick
what qualities are best at the focal trough?
sharpness and magnification (lack of)
what is the ideal plane of the image layer
central plane
are focal troughs consistent among manufacturers?
no, may vary
trough width ant/post of arch
more narrow in anterior= less room for error here (more in posteriors)
qualities of pano images
sharpness
distortion
magnification
how is sharpness altered in pano?
based on distance from the image layer, further from this=less sharp
diagram: how is image altered?
how is distortion altered in pano?
based on distance from the focal trough
further deviation = more distortion
error?
too anterior to focal trough
error?
deviation from focal trough= fuzzy
error?
placement post to focal trough= increased hor. mag of CI
blurriness too
MAGNIFICATION FACTORS
OF PANORAMIC MACHINES
varies among manufacturers
may be dif in ant/post
magnification only applies to the central plane of the focal trough
what kinds of images can be seen with pano?
real and ghost images
REAL IMAGE
Formed when object is located
between rotation center of beam
and film/receptor.
GHOST IMAGE
Formed when object is located
between x-ray source and rotation
center of beam.
ghost images of non-midline structures?
will appear opposite to real image, higher up and blurry
PRINCIPLE ADVANTAGES OF PANORAMIC RADIOGRAPHY
- Broad anatomic region imaged
- Relatively low radiation dose
- Convenience and speed of examination
- Can be used on patients who are unable to open mouth
PRINCIPLE DISADVANTAGES OF PANORAMIC RADIOGRAPHY
- Lacks the fine anatomic detail of intraoral radiographs
- Geometric distortion
- Overlapping of contacts
