Radiography

Question 1

Radiolucent definition

Answer 1

Radiolucent materials appear dark
E.g. air

Question 2

Radiopacity definition

Answer 2

Radiopaque materials appear white
E.g. bone or metal

Question 3

What color is air on radiograph

Answer 3

Black

Question 4

What color is fat on radiograph

Answer 4

dark grey

Question 5

What color is water/soft tissue/fluid on radiograph

Answer 5

Grey

Question 6

What color is bone on radiograph

Answer 6

Light grey/white

Question 7

How are x-rays produced

Answer 7

1. high voltage power supply send electric current to x-ray tube
2. Electric current causes electrons to be emitted from cathode in x-ray tube
3. Electrons are accelerated towards metal target (made of tungsten) inside x-ray tube (anode)
4. When electrons collide with tungsten they produce an x-ray
5. X-rays travel through body & some are absorbed by tissues
6. X-rays that pass through body reach detector which converts x-rays into electrical signal
7. Electrical signal is sent to computer which converts it to visual image

Question 8

Effect of increasing kV

Answer 8

Reduces difference between different structures

Question 9

Effect of decreasing kV

Answer 9

Increases difference between different structures

Question 10

Effect of increasing mAs

Answer 10

Increased plate exposure

Question 11

Effect of decreasing mAs

Answer 11

Decreased plate exposure

Question 12

How is image formed in Computed radiography

Answer 12

1. Phosphor plate held in cassette
2. Where x-rays strike plate, electrons are energised to form invisble latent image (trapped energy)
3. Cassette placed into reader & plate removed
4. Plate scanned by laser & trapped energy released as visible light
5. Light detected by photomultiplier & converted to electronic signal
6. Signal processed by computer to produce image on screen
7. Image can be manipulated post processing & stored electronically

Question 13

How is image formed in direct digital radiography

Answer 13

1. X-rays stimulate sensor panel that sends electronic signals directly to computer
2. Image can be manipulated & stored

Sensor panel can be separate or mounted in table

Question 14

Importance of positioning

Answer 14

Position part of interest as close as possible to image receptor
Position accurately with part of interest parallel to image receptor
Use standard radiographic positions

Question 15

Importance of centring

Answer 15

centre primary beam over area of interest

Question 16

Importance of collimation

Answer 16

Scattered radiation contributes to general image opacity & increases radiation hazard
Collimation reduces scatter
Collimate beam to minimum size necessary

Question 17

Importance of exposure in radiographs

Answer 17

Use correct exposure factors
Important for good density (brightness), contrast & resolution

Question 18

Importance of labeling

Answer 18

Always exposure side marker

Question 19

Importance of artefacts

Answer 19

Check there is nothing that could cause artefact
e.g. sandbags, collars etc.

Question 20

Name some positioning aids

Answer 20

Sandbags - used to keep animal in correct position
Foam wedges - keep animal in correct position/prevent movement
Lead markers - used to mark left & right sides of body