Extraoral views - Lateral Ceph Flashcards
What are the principles of extra oral radiography
x ray source is outside the patient
image receptor is outside the patient
can be done using digital or phosphor options
previously indirect x ray film was used with intensifying screens
patient positioning is critical
What are the reference lines and planes
MSP (mid saggital plane)
inter-orbital/pupillary line
orbito-meatal line (OM line) = radiographic baseline (RBL):
frankfort plane
What is the orbito-meatal line
outer cants of eye to centre of EAM
What is the frankfort plane
superior border EAM to lowest point of infra-orbital rim
What is the important terminology for maxillofacial views
PA
AP
OM
SMV
What is PA
posterio-anterior (beam direction)
coming from posterior aspect and coming out the anterior
What is AP
anteroposterior
What is OM
orbitomeatal (line) and occiptomental (view)
What is SMV
submentovertex (view)
What is a true lateral radiograph
film and MSP are parallel and x ray beam is perpendicular to both
What is an oblique lateral radiograph
the film and the MSP are not parallel
the x ray beam is not perpendicular to either but oblique to both
What are the different lateral views
lateral cephalometric radiograph
lateral oblique (mandible)
bipolar (both sides on one receptor)
What is cephalometric radiography
standardized and reproducible form of skull/facial bones radiography
used extensively in ortho, orthognatic surgery and implants but for some CBCT is replaced
can be lateral or PA projections
What is a lateral cephalometric radiograph
true lateral view of facial bones, base of skull and upper cervical spine
also shows paranasal sinuses and nasopharyngeal soft tissues
What are orthodontic cephs for
patients with skeletal vertical or anterior-posterior discrepancy
requiring fixed or functional appliance therapy, for labio-lingual movement of incisors
requiring orthographic surgery in addition to orthodontics but now largely replaced by CBCT
What are the indications for lateral ceph
orthographic surgery for pre-op assessment and post-op review
implant planning - historically. used to get anterior mandible and cross sectional image
both of these are now superseded if CBCT is available
What is cephalometric analysis
often traced or digitized
reference lines and planes
direct digital techniques now available
What equipment is required for the direct or indirect digital or film in cassette
cephalostat (can be freestanding or attached)
ear rods
CCD/CMOS sensor or cassette holder (phosphor plate or intensifying screens)
What is an anti scatter grid
not used at GDHS
put infant of the receptor to absorb x rays coming in at an oblique angle but have to increase the px dose but there is no justification for this increase in radiation
How far should the source be from the patients MSP
153.4 cm (5ft) in traditional equipment
How far is the image receptor to the MSP
manufacturer dependent, fixed or adjustable
What is the effect of anode object distance on magnification
short anode object distance means more magnification
What is the collimation used in lateral ceph
height and depth of field of view or triangular
What is the effective dose for lateral ceph
- 6 with collimator
3. 0 without collimator
What are the other important equipment
nasion marker to help kepe still
magnification scale
automatic facial contour in direct digital machines or aluminum wedge filter (ideally at tube head)
height and width adjustment OR triangular lead collimator in older px
What is the positioning for a lateral ceph
hinge nasion rest up and sideways thyroid collar on Frankfort plane horizontal - use light MSP vertical and parallel to cassette MSP correct distance from cassette if adjustable teeth together - in metric occlusion or as requested ear rods in EAM - move symmetrically nasion support in place
What is oblique lateral radiography used for
extra oral view of jaws
right and left sides taken separately
limited use now due to panoramic radiographs
What are the indications for oblique lateral radiographs
generally same as for panoramic but particularly when panoramic not available or possible
