panoramic radiography Flashcards
what is panoramic radiography
shows us a picture of the entire dentition - unobstructed view if every region in every direction - dynamic movement
what is the greyscale is dependant on
the degree of absorption
what is tomography
coordinated source of movement of the image receptor and the tube
what does tomography generate
an in focus slice of anatomy
what does the technique produce
a curved in focus slice called the focal trough
what do we want the dental trough to coincide with
the entire dentition
what is the x ray source and the tube called
the gantry
what happens to the image outside the focal trough
they are blurry
what is the angle between the x ray source and the tube
8 degree angulation
how are ghost images produced
anything between the x ray source and the centre of rotation
characteristics of ghost imaged compared to the real image
larger
higher
on the opposite side
blurred (more blurred vertically than horizontally)
why is the ghost image larger
due to beam convergence
why is the ghost image higher
due to the beam angulation
how dow we get a crisp beam
with less divergence of the x ray beam
when is the image in focus
when the image receptor object distance is short
what can ghost images be formed in
earrings
tongue studs
anything situated between the x ray source and the centre of rotation
what can we also produce ghost images of
the patients normal anatomy
what is the disadvantages of panoramic
ghost images
when do positioning errors occur
when the patient isn’t found in the focal trough
what are common positioning errors
chin down
chin up
AP positioning error
rotational
what are the issues with the chin being down
extenuated smily face as the posterior teeth are higher than we expected it to be
what are the issues with the chin being up
inverted occlusal plane
grumpy face
upper incisors fall out of the focal trough-out of focus, blurred bigger
what happens if the patients teeth are too far back from the image observer
big teeth
magnified out of focus
advantages of panoramic radiography
shows the entire dentition
time efficient- takes 8-10 seconds
radiation dose may be lower than a full mouth surgery of intra oral images
well tolerated by patients
can be used eve n when patient can’t fully open mouth or pronounced gag reflex
disadvantages of panoramic
only appreciate images within the focal trough
might have overlapping of teeth- difficult to see inter proximal caries
careful patient positioning
superimposition of soft tissues and air shadows causes misinterpretation
poor resolution one detail- caries detection and imaging of fine perio tissues
long exposure susceptible to damage by movement or difficult with children
what anatomy do we see on OGP- four white lines
involves maxillary antrum post wall of the maxillary sinus floor of the max sinus hard palate zygomatic butress
key features of the zygomatic buttress
cortical curve of the buttress
