Extra-oral radiography Flashcards
extra-oral views are mostly relating to the mandible
- postero-anterior mandible
- lateral oblique mandible
- DPT
Extra-oral views are also related to the maxilla and cranium
- lateral cephalogram (skull)
- occipital-mental views (0,10 and 30 degrees) (face)
- sialography
AP (antero-posterior)
beam is pointing to the front of the patient
PA (postero-anterior)
beam is pointing to the back of the patient
OM (occipito-mental)
beam is entering the patient at the occiput (back of head) and exiting between the mental foramina
Lateral (view taken from the side)
beam hits the side of the patient first
what is compton scattering?
when x-rays pass through tissues, some are scattered. Due to weaker x-ray photons being deviated off track as they do not possess enough radiation to pass all the way through to the receptor and make a useful interaction
why do we prefer to take a mandible film PA?
1) reduces the magnification of the facial structures on the receptor - always want the object to be as close to the receptor as possible
2) It also reduces the radiation dose to the eyes - shouldn’t have direct high energy x-ray photons straight into a patient’s eyes as the lens of the eye is quite radiosensitive
Why do we need to do an oblique mandible?
the mandible is a curved bone which makes it difficult to image in one view. In general radiography we always try to take 2 images at right angles to one another - AP or PA, and a lateral view
what are the 2 ways to take a lateral oblique mandible?
1) For an adult when you are querying a fracture or pathology in the mandible - you would use a skull unit or conventional x-ray unit
2) To visualise dental pathology - use a dental tube with either horizontal or vertical angulation
what are disadvantages with the lateral oblique mandible view?
the angulation can cause vertical distortion of the teeth, and the maxillary teeth are not always clearly shown
