Lateral cephalometric radiograph (Lateral ceph.) Lateral Oblique (mandible) (LOJ) only one side of pt Bimolar (both sides on one receptor)

Extra Oral Views - Lateral Cephalometric Flashcards by niamh ritchie

principles of extra-oral radiography

X-ray source outside the patient
image receptor outside the patient
digital CCD/CMOS and storage phosphor options
previously indirect X-ray film used with intensifying screens
patient positioning critical
X-ray beam and image receptor related to patient

How well did you know this?

Not at all

Perfectly

reference lines and planes

mid-sagittal plane (MSP) (green)

inter-orbital/pupillary line (green)

orbito-meatal line (OM line) = Radiographic Baseline (RBL): outer canthus of eye to centre of EAM (yellow)

Frankfort Plane: superior border EAM to lowest point of infra-orbital rim

10º difference between RBL and FP

How well did you know this?

Not at all

Perfectly

4 different maxillofacial views

postero-anterior
antero-posterior
orbitomeatal (line) and occipitomental (view)
submentovertex

How well did you know this?

Not at all

Perfectly

postero-anterior (beam direction)

How well did you know this?

Not at all

Perfectly

antero-posterior

How well did you know this?

Not at all

Perfectly

orbitomeatal (line) and occipitomental (view)

back of head to chin

How well did you know this?

Not at all

Perfectly

SMV

submentovertex (view)

underneath chin to top of head

How well did you know this?

Not at all

Perfectly

2 types of lateral radiography

true

oblique

How well did you know this?

Not at all

Perfectly

true lateral radiography

film and MSP are parallel and X-ray beam is perpendicular to both

How well did you know this?

Not at all

Perfectly

Oblique lateral radiograohy

film and MSP are not parallel

X-ray beam is not perpendiculat to either, but oblique to both

less used

How well did you know this?

Not at all

Perfectly

3 lateral views

Lateral cephalometric radiograph (Lateral ceph.)
Lateral Oblique (mandible) (LOJ) only one side of pt
Bimolar (both sides on one receptor)

How well did you know this?

Not at all

Perfectly

rods position in lateral cephalometric view

rods in EAM

How well did you know this?

Not at all

Perfectly

rods position in PA cephalometric views

rods in EAM still

but pt facing image receptor - turn 90^o

How well did you know this?

Not at all

Perfectly

cephalometric radiography

Standardised and reproducible form of skull/facial bones radiography
Used extensively in orthodontics
lateral and PA projections
Orthognathic surgery – replaced by CBCT*
(Implants, but largely replaced by cone beam CT)*

How well did you know this?

Not at all

Perfectly

lateral cephalometric radiography

True lateral view of facial bones, base of skull and upper cervical spine.

Also shows paranasal sinuses and nasopharyngeal soft tissues

Whole mandible, base of skull – how the relate
Soft tissue – nose, lips, chin
Scale
Upper cervical spine
Sinus – maxillary , sphenoid and ethmoid
Pharyngeal soft tissue – posterior border and upper surface of tongue, soft palate

How well did you know this?

Not at all

Perfectly

guidelines for orthodontic radiographs

BOS Orthodontic Radiographs Guidelines, 2008 & 2015
updated in 4th re CBCT indications

ISBN 1 899297 09 X

Ref. to CBCT in 2008, Full section in 2015

pdf available on-line:

https://www.bos.org.uk/Portals/0/Public/docs/General%20Guidance/Orthodontic%20Radiographs%202016%20-%202.pdf

cephs for who?

(4)

patients with skeletal vertical or antero-posterior discrepancy – judged clinically prior
requiring fixed or functional appliance therapy, for labio-lingual movement of incisors
requiring orthognathic surgery in addition to orthodontics (if doing CBCT, don’t do both)

Flow charts pp 20 and 21 (pre-treatment) – unchanged in 2015 since previous edition (10-18years or above and below)

2 indications for lateral cephalometry

Orthognathic Surgery

Pre-op assessment and post-op review
- Neurovasxular canals
- How bones moved - success

Implant planning - historically

Anterior mandible - cross sectional image – implant should go through symphysis but actually crosses in – causing bother as alignment wrong

Both of these often superseded if cone beam CT available

cephalometric analysis

often traced or digitised
reference lines and planes
direct digital techniques now available

equipment for ceph

direct or indirect digital film in casette
distances
nasion marker
magnification scale
automatic facial contour in direct digital machines (soft tissue)
heigh and width adjustment
thyroid collar

direct or indirect digital film in cassette

for lat cephs

Cephalostat (free-standing or attached to panoramic machine)

ear rods
CCD/CMOS sensor or cassette holder (phosphor plate or intensifying screens)
- Historic - anti-scatter grid - but higher dose to patient – don’t need increased detail so not justified - not at GDH&S

distances

for lat ceph

Source to patient’s MSP - 152.4cm (5 feet) in traditional equipment

Image receptor to MSP – manufacturer dependent, fixed or adjustable

in GDH&S fixed

distance from source to pt MSP in lat ceph

152.4cm (5 feet) in traditional equipment

image receptor to MSP distance in lat cep

manufacturer dependent

can be fixed or adjustable

in GDH&S it is fixed

effect of anode-object distance on magnification

Short anode-object distance * Double images – larger is closer Long anode-object distance * Desired – reduce magnification and less different between right and left side * long reduction in object magnification* * short get considerable magnification*

collimation on lat ceph

height and depth of field of view/depth (adjust where triangle is) or adjustable, by programme or visual * shine light through to see where it is on pt * stainless steel – not able to get photons through*

collimation impact on effective dose in µSv

1. 6 – with collimator 3. 0 – without collimator * 50% substantial (smaller field of view = less dose)

colliamtion on current digital cephs in GDH&S

17cm (reduced height) covers enough for most * Larger head may need a greater height May need to increase depth e.g. prognathic mandible can expose whole face of skeleton and cranium – not needed mostly

nasion marker in lat cephs

Perspex, brings to rest on pt – keep still, scale to get magnification factor in that plane

Automatic Facial Contour in direct digital machines

for soft tissue OR aluminium wedge filter - ideally at tube head (before going through pts better than after)

how can collimation be adjusted in lat cephs

heigh and width adjustment OR triangular lead collimator in older machines

position for lateral cephs

* Select for Lateral Ceph, and press button to line up X-ray tube head and cephalostat with receptor * Hinge nasion rest up and sideways * Thyroid collar on * Prevent exposure to radiation that is not needed * Frankfort plane horizontal – use light * MSP vertical and parallel to cassette (head straight) * MSP correct distance from cassette if adjustable * Teeth together – in centric occlusion or as requested * Ear rods in EAM – move symmetrically * Nasion support in place

thyroid collar

prevent exposure to radiation that is not needed esp in growing pts

programme selection for lat cephs

according to patient’s size and clinical requirement, OR move triangular collimation adjust field of view

how to capture soft tissues in lat cephs

Automatic exposure adjustment (facial contour), OR aluminium soft tissue filter, preferably pre-patient

why have fixed distances

subsequent images will always be able to be directly comparable

oblique lateral radiography

film and MSP not parallel * X-ray beam not perpendicular to either MSP or film\* extra-oral view of jaws - right and left sides taken separately uses dental or E/O X-ray set limited use now due to panoramic radiography

indications for oblique lateral radiography

Generally same as for panoramic radiography, but particularly when: * panoramic not available or possible e.g. handicapped patient, not able to still - quicker