How to perform an ultrasound

Question 1

Considerations when using analgesia, sedation or anaesthesia for ultrasound

Answer 1

Drugs may affect organ perfusion and therefore appearance
Normal pain responses wont be presetn to tell where is painful

Question 2

How to make sure the sound can penetrate into the tissue best (4)

Answer 2

Clip hair
Remove dirt and skin oil using alcohol
Apply ultrasound gel
Ensure contact between transducer and skin

Question 3

When is it good to use a linear transducer

Answer 3

To get a full cross sectional image

Question 4

When is it good to use a curved transducer

Answer 4

Small contact area-> large cross section of body
E.g. when looking in between ribs

Question 5

What are gel standoffs and when are they useful

Answer 5

Placed between transducer and skin to reduce the effect of near field noise from the transducer
Useful when looking at very superficial structures such as equine tendons
Normally a siliconey block but can also use a blob of gel in places such as the eye

Question 6

How to select frequency

Answer 6

Highest frequency you can get away with for the depth or structures you need
Remember frequency governs longitudinal resolution and depth of penetration
So for:
eye- 10mHz- high resolution but poor depth of penetration
sheep PD- 3mHz- low resolution but good depth of penetration

Question 7

Which way is the leading edge conventionally directed in longitudinal or dorsal imaging

Answer 7

Cranially

Question 8

Which way is the leading edge in transverse imaging

Answer 8

to the right

Question 9

In cardiac ultrasound where is the apex of the heart normally

Answer 9

To the right

Question 10

What part of the animal is normally to the left of the screen when ultrasounding

Answer 10

Cranial or right side or proximal limb

Question 11

Steps to undertaking a systematic ultrasound examination

Answer 11

Use standard imaging views
Image in at least 2 planes
Use alternative planes if necessary
E.g. consider moving the position of the animal if gas in gut interferes
Remember the principles of “knobology” throughout the examination
Remember that artifacts are common
Use known normal / textbooks for comparison
Store images appropriately for subsequent appending to clinical records and for review

Question 12

What is time gain compensation

Answer 12

Sound is attenuated when travelling into the tissue, so LESS sound reaches deeper tissues which means they appear darker than they should
Gives tissue an even consistency
Turn up deeper gain controls to amplify more distant waves to see deeper structures in better detail