Extra oral and other plain views Flashcards
maxillofacial views
show facial bones/skull from either a lateral or an anterior/posterior or a basal perspective (basal rarely indicated nowadays)
maxillofacial views equipment
X-ray tube-head
Cassette with film or digital –direct or indirect
Has special collimator
collimation of beam
the control of the size and shape of the X-Ray beam
* Occurs at tube head
* Want smallest size for field of view E.g. rectangle PA
To ensure correct collimation, light beam shows area on patient which will be exposed to primary beam
Central ray in middle of cross
Move the pt to be in the right position for collimator
cassette
film (1818x24 cm or 24x30 cm)
Intensifying screen - minimum speed 400
grid
comprising thin lead strips adjacent to cassette which attenuate obliquely travelling photons before they reach the film
but for same number of photons to reach film dose must be increased, otherwise insufficient blackening
anatomical planes
and radiographic positioning
enable positioning of patient relative to film and X-Ray tube
Use visible anatomical landmarks
Commonly used planes/lines:
* Frankfort plane
* Orbitomeatal line (OM line)
* Interpupillary line
* Mid-sagittal plane
anatomical planes
and radiographic positioning
enable positioning of patient relative to film and X-Ray tube
Use visible anatomical landmarks
Commonly used planes/lines:
* Frankfort plane
* Orbitomeatal line (OM line)
* Interpupillary line
* Mid-sagittal plane
commonly used planes/lines for radiographic positioning
4
- Frankfort plane
- Orbitomeatal line (OM line)
- Interpupillary line
- Mid-sagittal plane
frankfort plane
Connects orbitale (most inferior infraorbital rim) with porion (superior external auditory meatus)
* Skeletal references - select overlying soft tissue
Position horizontally for panoramic and cephalometric radiographs
orbitomeatal line
Links central part of external auditory meatus with outer canthus of eye
Differs from Frankfort plane by about 10 degrees
Much more easily visualised
Used as **radiographic baseline **
sagittal plane and inter-orbital/pupillary line
royal college of radiologists guidelines
iRefer
Making the best use of clinical radiology – referral guidelines, version 8.0.1
Overview available at: http://www.irefer.org.uk
Limited reference nowadays to plain X-ray views of the facial bones, with the availability of CT and MRI, and more recently cone beam CT, which is included in the guidelines.
About iRefer
Who should use this resource?
* GPs
* Emergency care physicians
* Doctors and other referrers
* Radiographers
* Physiotherapists
* Other healthcare professionals
* Dentists
* Medical students
iRefer categories of relevance – ENT/head and neck; trauma
lateral skull
image
Similar to Lateral ceph.
Shows lateral view of whole skull as well as facial bones and upper cervical spine
Inc all of calvarium, but not all of facial bones or any soft tissues
No cephalostat or wedge for soft tissue profile (free positioning)
lateral skull
4 indications
Fractures of skull/skull base
Facial fractures to show vertical and anteroposterior displacement (although both sides are superimposed on each other – not widely used)
Skull pathology (e.g. Pagets, myeloma)
* Pagets – bone turnover disorder, white patches
Pituitary fossa enlargement, sphenoid sinus pathology
Now increasingly replaced by CT (also detects intra-cranial abnormalities)
AP or PA?
Refers to direction of beam and therefore position of tube and image receptor (IR) relative to patient
PA posteroanterior tube posterior, IR anterior
AP anteroposterior tube anterior, IR posterior
Maxillofacial views are usually PA
Why most maxillofacial views PA?
posteroanterior
structures want to see close to IR as possible, magnified less
Reduced magnification
* Objects closer to film are magnified less than more distant objects
Dose Reduction
* Low energy photons entering back of head are attenuated before they reach radiosensitive tissues (e.g. lens)
occipitomeatal view
shows
Orbit
Frontal sinus usually asymmetrical, unique to pt
Maxillary sinus
Zygoma, zygomatic arch
Nasal septum
Coronoid process
Odontoid peg/dens of C2
occipitomeatal view
how it is taken
Orbitomeatal line at 45 degrees to image receptor (IR)
(nose-chin position)
Mid-sagittal plane perpendicular to IR
interpupillary line parallel to floor
X-Ray beam perpendicular to IR centred in midline, level with region of interest
alterations to standard (0 degrees) occiptomeatal projection
Changing angulation of X-Ray beam alters projection of bones onto radiograph
Gives better view of some areas, e.g. zygomatic arch
Gives different view of displacement, e.g. displacement at infraorbital rim in zygomatic complex fractures
PA mandible
what does it show
Good view of posterior body, angle and ramus of mandible
Superimposition of cervical spine obscures anterior mandible
Superimposition of mastoid process and zygomatic arch obscure condyle
PA mandible
indications 3
Fractures of angle, posterior body and ramus of mandible - medial and lateral displacement
* More likely when unerupted 8s
Cysts/tumours (same areas of mandible) - medial and lateral expansion/destruction
Facial deformity (often then taken in a cephalostat)
*CBCT much more information so favoured *
PA manidible
how it is taken
Orbitomeatal line perpendicular to image receptor (IR)
(forehead-nose position)
Mid-sagittal plane perpendicular to floor and IR, interpupillary line parallel to floor
X-Ray beam perpendicular to IR centred between angles of mandible
Submentovertex (SMV) shows
4
Sphenoid sinus
Maxillary sinus
Plan view of mandible, including condyle
Zygomatic arches* so thin only show at certain radiation doses when other bones are not shown
SMV how is it taken
submentovertex
Ensure no history of neck injury/disease
Extend head and neck as far as possible
Orbitomeatal line parallel to image receptor (IR)
Mid-sagittal plane perpendicular to IR and floor
Vertex of head contacts IR
Beam centred between angles of mandible
3 indications for SMV
submentovertex
Fracture of zygomatic arch
Expansion of more posterior mandible (anteriorly, true occlusal)
Cranial base pathology (now replaced by CT)
SMV to show zygomatic arch
Submentovertex
- Arch very thin, therefore normal beam too penetrating: energy and quantity need to be reduced
- Exposure factors (kV and time) reduced c.f. those to show skull
- Skull therefore underexposed appearing white
Know what would need to be moved to reposition – help surgeon plan surgery
floor of maxillary sinus seen on what views
5
Panoramic
Occipitomental
Lateral
Coronal CT/MRI
CBCT
roof of maxilary sinus seen on what views
5
Panoramic
Occipitomental
Lateral
Coronal CT/MRI
CBCT
anterior wall of maxillary sinus seen on what views
3
Lateral
Axial CT/MRI
CBCT
Possible panoramic if line above 5s
posterior wall of maxillary sinus seen on what views
4
Panoramic
Lateral
Axial CT/MRI
CBCT
medial wall of maxillary sinus seen on what views
4
Panoramic (above canine)
Occipitomental
Axial + coronal CT/MRI*
CBCT
lateral wall of maxillary sinus seen on what views
3
Occipitomental – good for intra antro pathology when no 3D imaging available (arrow)
Axial + coronal CT/MRI*
CBCT
