Imaging

Question 1

What are x-rays?

Answer 1

electromagnetic radiation used to create an image

Question 2

What is a radiograph?

Answer 2

the image on a display screen - a shadow picture and 2D projection

Question 3

Properties of x-rays

Answer 3

• high energy and short wavelength
• ability to penetrate materials and cause changes at atomic level
• can lead to ionisation
• no charge/mass
• invisible
• travel in straight lines

Question 4

What is ALARP?

Answer 4

radiation safety = As Low As Reasonably Practicable

• dose
• personnel
• times
• distance
• shielding

Question 5

Properties of x-ray beam

Answer 5

Quality = penetrating power of the beam

Intensity = amount of radiation in the beam

Question 6

What is the effect of changing kV?

Answer 6

• increasing kV
  = increased electron acceleration, increased energy of electrons, increased no. of x-rays
  therefore x rays = increased penetrating power therefore decreased contrast

Question 7

What is the effect of changing mA?

Answer 7

mA controls the current applied to filament

• increasing mA = increased tube current, increased no of electrons = more x rays produced
  HOWEVER
  energy of x-rays unchanged

Question 8

Effect of kV

Answer 8

quality and intensity

Question 9

Effect of mA

Answer 9

intensity only

Question 10

Computed radiography (CR)

Answer 10

• phosphor plate held in cassette
• electrons energised to form latent image (trapped energy)
• cassette placed into reader and plate removed
• plate scanned by laser and trapped energy released as visible light
• light detected by photomultiplier and converted into electronic signal
• signal processed by computer and image produced

Question 11

Direct radiography (DR)

Answer 11

• x-rays stimulate sensor panel that sends electronic signals direct to computer
• sensor panel can be separate or mounted on table

Question 12

What does Pink Camels Collect Extra Large Apples stand for?

Answer 12

Positioning
Centring 
Collimation
Exposure
Labelling
Artefacts

Question 13

Why is collimation important?

Answer 13

reduces production of scattered radiation - reducing hazard and appropriate processing of the image

Question 14

What is an optimal radiograph?

Answer 14

needs to show wide range of differentiated shades of grey

Question 15

How to limit scattered radiation?

Answer 15

• good collimation
• low kv
• use of radiographic grid if necessary

Question 16

How do you describe abnormality on a radiograph?

Answer 16

• number
• location
• size
• shape
• margination
• radiopacity
• internal architecture
• function

Question 17

What should a good radiograph look like?

Answer 17

1. accurate portrayal
2. easy perception
   
   • sharp shadows
   • range of shades of grey
3. no misleading artefacts
4. consistent results
5. no unnecessary risks

Question 18

What is different about taking radiographs on a horse?

Answer 18

need 4 standard views as the equine limb is too thick

Question 19

What preparation needs to be done before imaging?

Answer 19

try to starve cats and dogs 24 hours before abdominal radiography and allow to urinate and defaecate beforehand

Question 20

Assessing axial rotation in lateral thoracic view

Answer 20

caudodorsal rib heads should be superimposed and joined at the top