Facial Bones Technique Flashcards
indications for x-raying LATERAL SKULL - 3 points
as part of skeletal survey for NAI and myeloma
“shunk” series - hydrocephalus
tangential views for FB demo
3 #s for facial bones
zygomatic arch #
tripod #
orbital blow-out #
what is carried out as part of radiation protection - 6 points
ID check careful technique - avoid repeats gonad protection wherever practicable efficient collimation 28 day rule where appropriate consider alternative imaging modalities
Radiographic positioning for LATERAL SKULL - 4 points
pt seated with lateral aspect of head in contact with receptor
frontal, parietal and occipital bones in profile
EAMs superimposed - MSP parallel to receptor so no rotation
IPL at 90 degrees to receptor so no rotation
where to centre for LATERAL SKULL?
SID?
midway between the external occipital protuberance and the glabella, 5cms superior to EAM
100cm
image criteria for LATERAL SKULL - 3 points
frontal bone superiorly and anteriorly
base of skull and partial facial bones inferiorly
occipital bone posteriorly
correct positioning for LATERAL SKULL - 3 points
EAMs superimposed so no rotation
floor of anterior cranial fossa, anterior & posterior clinoid process and sella turcica = superimposed so no rotation
superimposition of tables of bone associated with frontal, parietal and occipital bones
why is a horizontal beam used?
in order to demonstrate fluid levels associated with facial bones injury
radiographic positioning OM VIEW - 6 points
pt sat facing image receptor
anterior nasal spine coincident with midline of image receptor and MSP at 90 degrees
outer canthus of the eye and EAM should be equidistant from the image receptor so no rotation
IPL should be parallel to image receptor to ensure head is not ‘canted’
raise pt’s chin to bring RBL 45 degrees to image receptor
infra-orbital margins should be aligned to the central lines of image receptor
centre to where for OM VIEW?
SID?
centre of the image detector
100cm
image criteria for OM VIEW - 3 points
superior orbital margins superiorly
distal aspect of maxillae inferiorly
parietal/temporal bones laterally
correct positioning for OM VIEW - 4 points
distance between lateral orbital borders and lateral skull borders should be equidistant so no rotation
petrous ridge to be projected inferiorly to maxillary sinuses
nasal septum should be coincident with midline of the image
inferior orbital margins should be on same horizontal plane and coincident with midline of image
radiographic positioning OM30 VIEW - 6 points
pt seated facing image receptor
anterior nasal spine coincident with midline of image receptor and MSP at 90 degrees
outer canthus of eye and EAMs should be equidistant from image receptor so no rotation
IPL should be parallel to image receptor so head not ‘canted’
raise pt’s chin so RBL 45 degrees to image receptor
upper portion of symphysis menti should be aligned to central lines of receptor
where to centre for OM30 VIEW?
SID?
more inferior than OM VIEW because a caudal angle is applied - centre to centre of image receptor
100cm
image criteria for OM30 VIEW - 3 points
superior orbital margins superiorly
mandible/mastoid air cells inferiorly
parietal/temporal bones laterally
correct positioning OM30 VIEW - 4 points
distance between the lateral orbital borders and lateral skull borders should be equidistant so no rotation
nasal septum should be coincident with midline of the image
petrous ridge to be projected well below the maxillary sinuses and orbital floor seen clearly through maxillary sinuses
symphysis menti should be coincident with midline of the image
how to assess the image
why do we image both sides of the face
ABCs
to allow for injured and uninjured sides to be compared for asymmetry and abnormalities
what are the 2 methods for analysis of facial bones
what are these?
Dolan’s lines
McGrigor’s lines
these are standardised lines that can be traced over the anatomy to look for discontinuities and abnormalities
when is a MODIFIED OM VIEW used?
what view is performed?
what is the radiographic positioning?
where pt’s arrive on trolley and horizontal beam cannot be utilised because cannot sit them in erect position
a mento-occiptal view is performed supine with vertical ray angled appropriately and centred on the anterior aspect of the pt
ideally positioning of RBL should be the same however a collar or associated injuries can make this difficult
how is the central ray angled and by how much?
what is a disadvantage of the mento-occiptal view?
is a similar approach used for an OM30 view, why/why not?
cranially and depending on how restricted the pt is at raising their chin to bring RBL 45 degrees to receptor -
the less the chin is raised, the greater the angle applied
doesn’t demonstrate fluid levels and can appear magnified/distorted but still gives preliminary diagnostic information
no because the view is too distorted
what is the radiographic positioning for a MODIFIED LATERAL VIEW - 4 points
pt has lateral aspect of face in contact with receptor
frontal bone, nasal septum, maxillae and mandible all in profile
EAMs superimposed so MSP = parallel to receptor so no rotation
IPL at 90 degrees to receptor so no rotation
where to centre for MODIFIED LATERAL VIEW?
SID?
2.5cm behind the outer canthus of the eye along the RBL
100cm
image criteria for LATERAL FACIAL BONES - 4 points
frontal bone superiorly
mandible inferiorly
soft tissues on anterior aspect of frontal/nasal/maxillae/ mandible anteriorly
anterior portion of parietal/temporal bone/c-spine posteriorly
correct positioning for LATERAL FACIAL BONES - 3 points
EAMs should be superimposed so no rotation
floor of anterior cranial fossa and sella turcica should be superimposed so no rotation
superimposition of tables of bone associated with frontal/orbital/maxillae/mandible
aim for MODIFIED SMV (SUB-MENTO VERTICAL) ‘JUG HANDLES’
radiographic positioning - 4 points
aiming to get zygoma parallel to receptor
pt supine (or erect), neck extended until zygomatic arches are parallel to receptor
EAMs equidistant from receptor so no rotation
MSP - 90 degrees to receptor
IPL - parallel to receptor
where to centre for JUG HANDLES
what can be done to visualise more of affected side
where is central ray angled
midway between EAMs ensuring angle is 90 degrees to receptor - profile of zygomatic arches seen on receptor
head may be tilted 5-10 degrees away from side under examination allowing visualisation of zygoma without superimposition of the skull or other facial bones
at 90 degrees to receptor
image criteria for JUG HANDLES - 2 points
mandibular symphysis superiorly
entirety of zygomatic arches laterally
correct positioning for JUG HANDLES - 3 points
angles of mandible should be clear of the petrous temporal bones
whole length of zygomatic arch should be demonstrated in profile
midline of the pt’s skull should be coincident with midline of the image
