RAD03-2007 What is an X-ray image? Flashcards
What is the radiodensity like in the black areas of the X-ray?
Radiolucent
no absorption
What is the radiodensity like in the white areas of the X-ray?
Radiopaque
Total absorption
What is the radiodensity like in the grey areas of the X-ray?
Mixed
Varying absorption
What factors affect the radio density of the shadows?
Object material Object thickness Object shape X-ray beam intensity Position of object
Which materials will appear white in x-ray?
Metal
How does thickness affect the colour of the x-ray image?
Thicker objects will absorb more photons and appear white
How does x-ray beam intensity affect radio density?
As exposure increases, there is increased blackening
What happens to the image if the object position is not ideal?
Image can be foreshortened
What happens to the image if the film position is not ideal?
Image can be elongated
What happens to the image if the x-ray beam is not ideal?
Image can be distorted
What are the limitations of conventional film?
2D representations of 3D objects
Affected by exposure factors
Affected by geometric distortion
Superimposition on 2D images
What are tomographs?
Sectional radiographs that allows the analysis of the head so superimposition of 2D structures is avoided
What is a simple linear tomograph?
Moving tube head and film to produce various sections
What is the section of the patient at the centre of rotation in the simple linear tomograph?
Linear focal place or in-focus layer
Do large movements in simple linear tomographs produce thin or thick slices?
thin slice
What is a disadvantage of simple linear tomographs?
Blurring is common due to movement of equipment
What is an advantage of complex multidirectional tomographs over simple linear?
Reduced blurring as it uses a complex spiral motion instead of linear movement
What is complex multidirectional tomographs designed for?
Maxillofacial region to produce cross sections of the jaw
What are CT scans used for?
Medical images- multiple slices can be combines together to produce a 3D image
What is CBCT?
Only images the maxillofacial skeleton
How do dental panoramic radiographs work?
Tubehead and film orbit around the patient’s head.
The film comes round the front of the patient’s face and the tube head moves round the back
What are the limitations of the dental panoramic radiograph?
If the teeth are in an abnormal position, the patient cannot use both teeth in bite on the bitewing hence the tooth not within the section will be out of focus and appear blurred
Also, in order to image one side of the patient, x-ray beam has to pass through the other side of the jaws which creates a ghost shadow that are blurred
Blurred due to movement of x-ray tube head and film Poor resolution
What are examples of ghost shadows?
Mandible (L-shaped)
Cervical spine
Air space in the mouth between the tongue and hard palate
What are the limitations of digital images?
2D representations of 3D objects
Affected by geometrical distortion
Affected by software image processing
