Extra-oral radiography Flashcards
name the 4 EO images that relate to the mandible
- postero-anterior mandible
- reverse townes view
- lateral oblique mandible
- DPT
name the 4 Eo images that relate to the maxilla/cranium
- lateral cephalogram
- lateral skull
- occipital-mental views 0, 10, 30 degrees
- TMJ joint views
what is PA in radiography?
postero-anterior (X-ray beam coming from post to ant)
what is AP in radiograph?
Anterior-posterior (X-ray beam coming from ant to post)
OM stands for?
Occipito-mental
LAT stands for?
lateral
name the 3 radiographic landmarks?
- radiographic baseline
- frankfort plane
- maxillary occlusal plane
what does the radiographic baseline represent?
the base of the skull
where does the radiographic baseline start and finish?
from the canthus of the eye to EAM external auditory meatus
what does the frankfort plane represent?
the anthropological base line
where does the frankfort plane begin and end?
at the IOB inferior orbital border to the upper border of the EAM
where does the maxillary occlusal plane begin and end?
the ALA of the nose to the tragus of the ear
why is there increased scatter in EO radiography?
because you must increase the field of the beam
what are the consequences of more scatter radiation? 3 things
- more background fog
- greyer image
- lacks contrast
what is the anti-scatter grid composed of?
narrow strips of lead and plastic (alternating)
what does the anti-scatter grid do?
prevents scattered photons in the patient from reaching the film
the anti-scatter grid can be … or ….
moving/oscillating OR fixed/stationary
indications to take a PA mandible are.. 3 points
- FRACTURES (shows media-lateral displacement)
- CYSTS/MALIGNANCY (causing bone destruction or media-lateral displacement
- GOOD VISUALISATION of POSTERIOR BODY of RAMUS
2 positives of PA mandible radiograph?
- reduced magnification of facial structures
2. reduced dose to eyes
For PA mandible what is the positioning landmark used and at what angle is it?
the radiographic baseline is horizontal (from the canthus of the eye to the EAM)
the 4 procedures for taking a PA mandible are…
- get pt facing film
- nose and forehead touching the film holder
- horizontal radiographic baseline
- centre of beam aimed to midline of patient at height of midline ramus of mandible
give 8 external landmarks to determine the midline
- nasal septum
- coronoid process
- mastoid process
- condyle head
- condyle neck
- angle of mandible
- petrous part of temporal bone
- shadow of spine
3 indications for taking reverse townes radiograph
- Improve visualisation of HEAD and NECK of condyle
- Trauma
- Pathology
4 point for positioning for the reverse townes
- patient facing film
- nose and forehead touching the film
- radiographic baseline horizontal (canthus of eye to EAM)
- centre of beam aimed to midline of patient and through condyles. Xray beam angled 30 degrees up
indications for an EO lateral oblique mandible radiograph 5 things
- FRACTURES of ramus, body or condyle
- PATHOLOGY such as cysts
- assessment of UPPER 8’s
- CARIES assessment for YOUNG CHILDREN that cannot tolerate bitewings
- dental assessment for SPECIAL NEEDS patients
name the 3 positions that you can take a lateral oblique mandible
- isocentric positioning using a skull unit
- dental tube with horizontal angulation
- dental tube with vertical angulation
what is the isocenteric position? to take a lateral oblique mandible
- pt supine
- machine rotated to horizontal position
- angle 25 degrees towards the head
- top of pts head tilted towards film
what is the dental tube vertical angulation? to take a lateral oblique mandible
- pt holds cassette against and parallel to the side of mouth that is getting radiographed
- X-ray tube at other side touching underneath the border of the mandible
- ## X-ray beam aimed at teeth needing radiographed and angled SLIGHTLY UPWARDS
1 positive and 2 negative points about the dental tube vertical angulation for an EO lateral oblique mandible
+ = opposite body of the mandible projected up and away from area of interest
- = vertical distortion of the teeth
- = maxillary teeth not always shown clearly
what is the dental tube - horizontal angulation also called?
radiographic keyhole
what is the dental tube horizontal angulation aiming?
horizontally, across occlusal plane
the radiographic keyhole is where in the horizontal angulation of the X-ray tube when taking a lateral oblique EO mandible view?
triangular space between the BACK OF RAMUS and the CERVICAL spine
disadvantage of horizontal angulation of the X-ray tube?
X-ray beam does not pass straight through the contact points giving crossover
In a lateral ceph, what is the xray to film distance?
1.5-2m
In a lateral ceph, what is used to have standardising positioning?
ear rods
In a lateral ceph, what are the 2 main indications?
- orthodontic assessment
- pre orthognathic surgery
In a lateral ceph, what helps to understand how much if any magnification has occurred?
the magnification rod
how to position the patient and X-ray beam for a lateral cephlogram? 5 points
- ear rods in place
- teeth in occlusion
- mid sagittal plane parallel to the image receptor
- frankfort plane horizontal (from lower border of orbit to the EAM
- centre of beam aimed at EAM
In a lateral ceph, how do you image the soft tissues with a film and digital receptor?
film = aluminium filter positioned at anterior part of face that attenuates the beam in that region.
digital = the software make it visible
how can you reduce the dose for a lateral cephlogram?
reduce the beam size which cuts out most of the skull but still showing necessary areas (mandible and maxilla)
2 main indications to take a lateral SKULL?
- pathology = pagets disease and myeloma
- trauma = fractures
which area of the skull are you aiming to see in a lateral skull view?
the vault of the skull
Give 4 main differences between lateral ceph and lateral skull
lateral ceph
- uses a cephlogram
- has an aluminium filter to see soft tissues
- patient must be in occlusion
- has a large patient to focus distance to reduce magnification
