RAD03-2007 What is an X-ray image?

Question 1

What is the radiodensity like in the black areas of the X-ray?

Answer 1

Radiolucent

no absorption

Question 2

What is the radiodensity like in the white areas of the X-ray?

Answer 2

Radiopaque

Total absorption

Question 3

What is the radiodensity like in the grey areas of the X-ray?

Answer 3

Mixed

Varying absorption

Question 4

What factors affect the radio density of the shadows?

Answer 4

Object material
Object thickness
Object shape 
X-ray beam intensity 
Position of object

Question 5

Which materials will appear white in x-ray?

Answer 5

Metal

Question 6

How does thickness affect the colour of the x-ray image?

Answer 6

Thicker objects will absorb more photons and appear white

Question 7

How does x-ray beam intensity affect radio density?

Answer 7

As exposure increases, there is increased blackening

Question 8

What happens to the image if the object position is not ideal?

Answer 8

Image can be foreshortened

Question 9

What happens to the image if the film position is not ideal?

Answer 9

Image can be elongated

Question 10

What happens to the image if the x-ray beam is not ideal?

Answer 10

Image can be distorted

Question 11

What are the limitations of conventional film?

Answer 11

2D representations of 3D objects
Affected by exposure factors
Affected by geometric distortion
Superimposition on 2D images

Question 12

What are tomographs?

Answer 12

Sectional radiographs that allows the analysis of the head so superimposition of 2D structures is avoided

Question 13

What is a simple linear tomograph?

Answer 13

Moving tube head and film to produce various sections

Question 14

What is the section of the patient at the centre of rotation in the simple linear tomograph?

Answer 14

Linear focal place or in-focus layer

Question 15

Do large movements in simple linear tomographs produce thin or thick slices?

Answer 15

thin slice

Question 16

What is a disadvantage of simple linear tomographs?

Answer 16

Blurring is common due to movement of equipment

Question 17

What is an advantage of complex multidirectional tomographs over simple linear?

Answer 17

Reduced blurring as it uses a complex spiral motion instead of linear movement

Question 18

What is complex multidirectional tomographs designed for?

Answer 18

Maxillofacial region to produce cross sections of the jaw

Question 19

What are CT scans used for?

Answer 19

Medical images- multiple slices can be combines together to produce a 3D image

Question 20

What is CBCT?

Answer 20

Only images the maxillofacial skeleton

Question 21

How do dental panoramic radiographs work?

Answer 21

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

Question 22

What are the limitations of the dental panoramic radiograph?

Answer 22

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

Question 23

What are examples of ghost shadows?

Answer 23

Mandible (L-shaped)
Cervical spine
Air space in the mouth between the tongue and hard palate

Question 24

What are the limitations of digital images?

Answer 24

2D representations of 3D objects
Affected by geometrical distortion
Affected by software image processing