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BDS3 CLINICAL Radiology > Extraoral views - Lateral Ceph > Flashcards

Extraoral views - Lateral Ceph Flashcards

1
Q

What are the principles of extra oral radiography

A

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

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2
Q

What are the reference lines and planes

A

MSP (mid saggital plane)
inter-orbital/pupillary line
orbito-meatal line (OM line) = radiographic baseline (RBL):
frankfort plane

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3
Q

What is the orbito-meatal line

A

outer cants of eye to centre of EAM

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4
Q

What is the frankfort plane

A

superior border EAM to lowest point of infra-orbital rim

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5
Q

What is the important terminology for maxillofacial views

A

PA
AP
OM
SMV

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6
Q

What is PA

A

posterio-anterior (beam direction)

coming from posterior aspect and coming out the anterior

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7
Q

What is AP

A

anteroposterior

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8
Q

What is OM

A

orbitomeatal (line) and occiptomental (view)

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9
Q

What is SMV

A

submentovertex (view)

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10
Q

What is a true lateral radiograph

A

film and MSP are parallel and x ray beam is perpendicular to both

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11
Q

What is an oblique lateral radiograph

A

the film and the MSP are not parallel

the x ray beam is not perpendicular to either but oblique to both

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12
Q

What are the different lateral views

A

lateral cephalometric radiograph
lateral oblique (mandible)
bipolar (both sides on one receptor)

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13
Q

What is cephalometric radiography

A

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

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14
Q

What is a lateral cephalometric radiograph

A

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

also shows paranasal sinuses and nasopharyngeal soft tissues

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15
Q

What are orthodontic cephs for

A

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

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16
Q

What are the indications for lateral ceph

A

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

17
Q

What is cephalometric analysis

A

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

18
Q

What equipment is required for the direct or indirect digital or film in cassette

A

cephalostat (can be freestanding or attached)
ear rods
CCD/CMOS sensor or cassette holder (phosphor plate or intensifying screens)

19
Q

What is an anti scatter grid

A

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

20
Q

How far should the source be from the patients MSP

A

153.4 cm (5ft) in traditional equipment

21
Q

How far is the image receptor to the MSP

A

manufacturer dependent, fixed or adjustable

22
Q

What is the effect of anode object distance on magnification

A

short anode object distance means more magnification

23
Q

What is the collimation used in lateral ceph

A

height and depth of field of view or triangular

24
Q

What is the effective dose for lateral ceph

A
  1. 6 with collimator

3. 0 without collimator

25
Q

What are the other important equipment

A

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

26
Q

What is the positioning for a lateral ceph

A 
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
27
Q

What is oblique lateral radiography used for

A

extra oral view of jaws
right and left sides taken separately
limited use now due to panoramic radiographs

28
Q

What are the indications for oblique lateral radiographs

A

generally same as for panoramic but particularly when panoramic not available or possible

BDS3 CLINICAL Radiology (16 decks)

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