Panoramic radiography Flashcards
What principles does panoramic radiography use?
Tomography
Describe the movement of the film in relation to the tube
Film and tube move in opposite directions
What is the significance of the focal trough
Objects within the focal trough are sharp on image.
Objects out with appear blurred
What are the components of the panoramic
Film within cassette
Film sensitive to light
Intensifying screens
What is the function of the intensifying screen?
Absorbs X-rays and emits light
Reduces the dose but also image clarity
What are the disadvantages of the intensifying screen?
Emits light in all directions
Image quality poorer than direct action film
What replaces the intensifying screen in digital panoramics?m
Solid state censor
What are the advantages of panoramic radiography?
Images teeth and bone with minimal discomfort
Reduced dose in comparison to full mouth PAs
What are the indications for panoramic radiography?
Assessment of unerupted teeth Evaluation of cysts and tumours Allows comparison of both sides Show heigh of mandible and ID canal Shows sinus walls
What are the main problems re. Panoramics?
Lack of fine detail
Superimposition eg. Cervical spine re. Anterior teeth
Exposure time can be up to 14 seconds
Magnification
What planes do the light beams mark?
Mid Sagital plane vertically
Frankfurt plane horizontally
What is the dose of DPT?
3.85- 30 micro sv
What is the average background radiation in the UK?
2.5 milli sv
What hard tissues structures can be seen on DPT
Teeth Mandible Maxilla Hard palate Zygomatic arches and zygoma Styloid process Hyoid bone Septum and conchae Orbital rim
What soft tissue structures can be seen on panoramic rad?
Ear lobe Nasal cartilage Soft palate Tongue Lips
Where are the main air shadows?
Between lips
Oral cavity
Oropharynx
Nasopharynx
What are ghost images?
Images of a structure on one side projected onto the other side
What are commonly seen as ghost images?
Ramus and angle
Hard palate
Foreign bodies
What happens to image quality if patient is positioned too far back?
Magnification of anterior teeth horizontally
What happens to image quality if patient is positioned too far forwards?
Magnification vertically
What happen to image in pt is position chin down
Image appears overly curved
What happens to image if pt is positioned chin up?
Flat occlusal plane
What happens to image if pt is slumped?
Spine can obscure image
Why are panoramic images not gold standard for caries diagnosis?
Poor fine detail
Over lap
Superimposition of air
