Extra-Oral Radiography Flashcards
when is a radiograph an extra oral radiograph
when the receptor is outside the mouth
what are indications for using extra oral radiographs
for people who cannot tolerate intra-oral ones
for looking at structures that aren’t dento-alveolar
what are common types of extra oral radiographs
panoramic
cephalometric
oblique lateral
skull radiographs
what does a postero-anterior x-ray mean
the beam is starting from behind the patient and passes anteriorly
what does a true radiograph mean
the angulation is perpendicular to the head
what does an oblique radiograph mean
the angulation is not perpendicular to the head
what is the mid sagittal plane
vertical line down middle of the face
what is the interpupillary line
connects both pupils
what is the frankfort plane
connects the infraorbital margin and the superior border of the external auditory meatus
what is the orbito-meatal line
connects the outer canthus and centre of external auditory meatus
what is the difference in degrees between frankfort plane and orbitomeatal line
10 degrees
why are reference lines/ planes important
if you want to take updated x-rays to compare in the future you need to be able to set up the same way
what is cephalometry
the measurement and study of the head and neck
what are the two types of cephalometry
lateral
postero-anterior
what is the most important cephalogram
lateral cephalogram
what anatomy does a lateral cephalogram capture
teeth
facial bones and soft tissues
paranasal sinuses
pharyngeal soft tissue
cervical vertebrae
when are lateral cephs usually used
assessing skeletal discrepancies when functional appliances or fixed appliances are to be used for labio-lingual movement of incisors
what do the design of cephalometry machines depend on
whether using a phosphor plate or solid state sensor
what is a cephalostat
ensures standardising of equipment and patients head
reduces magnification and distortion
ear rods and forehead support
what distance should the receptor be from the x-ray focal spot to minimise magnification
1.5m to 1.8m
what are the two solutions to viewing facial soft tissues since they show up poorly on radiographs
place aluminium wedge filter in the unit to attenuate the specific area of the beam exposing the soft tissue
use software to enhance soft tissues post exposure
what is collimation
field of view should not be larger than what is clinically required
when might you find triangular collimation
units that do not use a solid state sensor
what are examples of patient contact shielding
thyroid collar as the thyroid gland is relatively radiosensitive
what is the downside to using thyroid collar
may obscure hyoid bone and cervical vertebrae
what is CBCT
cross sectional 3D imaging but at increased radiation dose
what are advantages of CBCT
no superimposition or magnification of anatomy
images can be viewed at any angle
what is oblique lateral radiography
extra-oral radiograph provides view of posterior jaws without superimposition of contra-lateral side
what are the indications for taking an oblique lateral radiograph
similar to panoramic radiography - assessment of pathology, presence of unerupted teeth, lesions and conditions affecting jaws
what are the 4 indications for taking an extra-oral radiograph
poorly cooperative child
learning difficulties
involuntary movements
unconscious
