Extra oral views Flashcards
images relating to the mandible? 3
Poster-anterior mandible
Lateral oblique of mandible
DPT
Images relating to the maxilla and cranium ? 3
Lateral cephalogram (skull)
Occipito-mental views (face)
Sailography (imaging of salivary glands)
Terminology - views - relate to direction of the x-ray beam
PA
AP
OM
Lat
postero-anterior
antero-posterior
occipito-mental
lateral
define positioning landmarks?
imaginary lines on the side of a patients face
name the 3 positioning landmarks
radiographic baseline
frankfort plane
maxillary occlusal plane
what is the radiographic baseline?
Line from outer canthus of the eye to external auditory meatus
what is the franfort plane?
Line from inferior orbital margin to external auditory meatus
what is the maxillary occlusal plane?
Line from the ala of the nose to the tragus of the ear
which positioning landmark is red?
radiographic baseline
which positioning landmark is yellow?
maxillary occlusal plane
which positioning landmark is blue?
frankfort plane
what equipment is needed for extra oral radiography? 3
Skull unit or cephalometric unit with a high intensity, highly penetrating beam
Image receptor
- Cassette with intensifying screen and film
- Digital system cassette containing a phosphor plate
Anti-scatter grid
There is more scatter radiation in skull radiography this can add to background fog and produce a greyer image lacking in contrast
Anti-scatter grid
Stops ? scattered in the patient reaching the ? and degrading the film, only the ???? are able to get through and reach the receptor
Narrow strips of ? alternating with ?
photons
receptor
straight high energy photons
lead
plastic
this shows a scatter grid -> understand
when x-rays pass through tissues, some are scattered. what is this called?
Compton scatter
Positioning a patient for extra-oral radiography
patient relative to film
Facial views
- Radiographic baseline ?* to film
- Median sagittal plane ?* to film
45
90
positioning a patient for extra oral radiography
patient relative to film
Skull radiography
- Radiographic baseline ?* to film
90
positioning a patient for extra oral radiography
x-ray beam relative to patient
the beam can be in what 3 orientations?
postero-anterior
antero-posterior
lateral
positioning a patient for extra oral radiography
Angle of the beam relative to the patient
Most head and neck radiography requires angles to move structures out of the way of other anatomy
what is this extra oral imaging technique?
PA mandible
what is this extra oral imaging technique?
PA mandible as mandible is elongated
what is the main use of a postero-anterior mandible ragiograph?
fractures of the mandible
why is a PA mandible the preferred method of extra-oral views? 2
Reduced magnification of facial features
Reduce dose to eyes
what is the technique for taking a PA mandible?
Patient nose and forehead touching the film -> radiographic baseline 90*
Aim beam to midline (external occipital protuberance and between the eyes) of patient at height of mid-ramus
name this anatomical feature of a PA mandible
nasal septum
name this anatomical feature of a PA mandible
coronoid process
name this anatomical feature of a PA mandible
angle of mandible
name this anatomical feature of a PA mandible
shadow of spine
name this anatomical feature of a PA mandible
neck of condyle
name this anatomical feature of a PA mandible
head of condyle
name this anatomical feature of a PA mandible
mastoid process
name this anatomical feature of a PA mandible
petrous part of temporal bone
what is this extra-oral imaging technique?
Lateral oblique radiography of the mandible
why do we do lateral oblique rather than just lateral?
Superimposition of two rami make it difficult to make sense of image
what extra-oral imaging technique is useful for children who cant tolerate bitewings?
lateral oblique mandible
lateral oblique mandible is useful for
Fractures
Pathology
Assessment of wisdom teeth (though normally DPT)
Dental assessment
Caries in children who cannot tolerate bitewings
what equipment do you use for lateral oblique to query a fracture or pathology?
isoscentric skull unit
or
conventional x-ray tube (pathology)
- vertical angulation
- horizontal angulation
for lateral oblique mandibles how is a isoscentric skull unit used?
Patient supine
Rotate machine into horizontal plane
Angle 25* towards head
Get patient to tilt head towards the receptor
what is this imaging technique?
lateral oblique mandible using isoscentric skull unit
what is this imaging technique?
lateral oblique mandible using skull unit
for lateral oblique mandibles what is the technique for using a dental tube with vertical angulation?
Patient holds receptor against and parallel to the side under investigation
Tube head positioned beneath the lower border of the mandible not under examination
Aim the tube towards the teeth under investigation
Angle the tube slightly upwards
what imaging technique is this?
lateral oblique using dental tube with vertical angulation
what is this imaging technique
lateral oblique mandible using dental tube with horizontal angulation
how is a lateral oblique mandible using dental tube with horizontal angulation taken?
Patient holds receptor against and parallel to the side under investigation
Tube head aimed along occlusal plane, just below ear towards the teeth being examined
- Radiographic keyhole: triangular space between the back of the ramus and the cervical spine
name this anatomical feature of a lateral oblique mandible (skull unit)
coronoid process
name this anatomical feature of a lateral oblique mandible (skull unit)
condylar head
name this anatomical feature of a lateral oblique mandible (skull unit)
condylar neck
name this anatomical feature of a lateral oblique mandible (skull unit)
cervical spine
name this anatomical feature of a lateral oblique mandible (skull unit)
ramus of mandible
name this anatomical feature of a lateral oblique mandible (skull unit)
angle of mandible
name this anatomical feature of a lateral oblique mandible (skull unit)
hyoid
name this anatomical feature of a lateral oblique mandible (skull unit)
body of mandible
name this anatomical feature of a lateral oblique mandible (skull unit)
mental foramen
cephalometric radiography is used to view what structures?
maxilla and cranium
cephalometric radiography is useful for what?
orthodontics
pre-orthognathic surgery (jaw surgery)
cephalometric radiographs can only be taken with what?
Cephalostat unit (usually attached to DPT)
cephalometric radiographs need to be reproducible as this is important for measurements before orthodontics and surgery. how is this achieved?
patient positioned with ear rods
what are the two views for cephalometric radiography?
lateral cephalometric radiography
postero-anterior cephalometric radiography
lateral cephalometric radiography
Mid sagittal plane ? to receptor
Frankfurt plane ?
Centre of x-ray beam aimed at ?
Teeth in ?
parallel
horizontal
external auditory meatus
occlusion
what extra oral view is this?
cephalometric radiography
what extra oral view is this?
lateral cephalometric radiography
what extra oral view is this?
Posteroanterior cephalometric radiography
what is the Only procedure where give patient lead apron (thyroid shield) as exposure and dose slightly higher?
cephalometric radiography
what is used to calculate the magnification of a cephalometric radiograph for surgical planning?
placing a magnification rod or ruler on the image
cephalometric radiography
to ensure the magnification is ok we need a
? source to object distance
? object to receptor distance
long
short
how do you see soft tissues with cephalometric radiography?
an aluminium filter
Positioned over anterior face to absorb some of the x-rays, digital x-rays have software that does this automatically
Postero-anterior cephalometric radiograph
Radiographic baseline ? to floor
X-ray beam aimed at level of ?
parallel
external acoustic meatus
what extra oral view is this?
occipito-mental view
what extra oral view is this?
occipito-mental view
what is seen in an occipito-mental veiw?
facial bones
what is occipito-mental view useful for?
ruling out fracture
To see all the bones in the face have to use different angulations of the beam. Standard views are OM ?, OM ? and OM ?*
0
10
30
occipito-mental view
Positioning
Patient faces receptor with ? and ? touching
Radiographic baseline ?* to film
X-ray beamed aimed at middle through ?????
nose
chin
45
base of the nose
occipito-mental view
Increasing downwards angulation projects dense bones of skull base away from facial structures, improving the view of the zygomatic arch
Cone beam CT
3D reconstructions of anatomy that give much more information than extra-oral radiography
Should not be considered as first form of imaging for the patient as the dose is much greater
