Principles of Ultrasound

Question 1

Why is ultrasonography good?

Answer 1

• Does not involve radiation
• Reveals different characteristics of tissues
• Shows internal architecture
• Excellent soft tissue details
• Real-time motion to assess organ function
• Measurements can assess structure

Question 2

Anechoic

Answer 2

○ Produce no echo
All sound passes through tissue and none is reflected back to transducer
○ Appears black
○ E.g. Fluid

Question 3

Hypoechoic

Answer 3

○ Produce little echo
Most sound passes through, some reflected back
○ Appears dark grey
○ E.g. tissues high water content
Cartilage
Muscle
Renal medulla

Question 4

Medium Echogenicity

Answer 4

○ Medium amount of sound passes through tissue
○ Appears lighter grey
○ E.g. most soft tissues
Liver
Spleen
Prostate

Question 5

Hyperechoic

Answer 5

○ Produce a lot of echo
Most sound is reflected back to transducer
○ Appears light/white
○ E.g. gas, bone, mineralised tissue

Question 6

Homogenous

Answer 6

Uniform appearance throughout tissue
Most tissue should be homogenous

Question 7

Heterogenous

Answer 7

Mixed, irregular pattern
Associated with pathology

Question 8

What environment do you need for ultrasound?

Answer 8

Dark, quiet room
Restrained animal - doesn’t have to be fully immobile

Question 9

How can you prepare for ultrasound?

Answer 9

Clip hair
Remove dirt and skin oil with alcohol
Apply ultrasound gel
Have transducer in contract with skin

Question 10

Linear transducers

Answer 10

○ Fires multiple lines or sound parallel to each other
○ Rectangular beam created
○ Requires full contact along surface of transduced
○ Rectangular cross-section of sound

Question 11

Curved transducers

Answer 11

○ Fires multiple lines of sound that diverge from each other
○ Triangular beam created
○ Requires only a small contact area
○ Good for looking between ribs

Question 12

How can you reduce near field ‘noise’?

Answer 12

Need to make transducer further away from superficial structures
Used gell Standoff between skin and transducer
Commonly used when imaging equine tendons

Question 13

What is an ideal frequency?

Answer 13

High as possible with depth of structure
High frequency - good resolution, poor depth

Question 14

Orientations of transducer

Answer 14

Longitudinal
Transverse
Dorsal/frontal

Question 15

Which side is cranial on the screen?

Answer 15

SHOULD be the left (notch on thumb cranial)

Question 16

Which side of animal is on the left of screen?

Answer 16

Right hand side

Question 17

What settings do you adjust before placing transducer on animal?

Answer 17

Approximate depth
overall gain and power set to mid/low values

Question 18

What settings do you adjust when placing transducer on animal?

Answer 18

Adjust depth so organ fills screen
Adjust focal zone to middle of organ

Question 19

What does low gain look like?

Answer 19

Image too dark

Question 20

What does high gain look like?

Answer 20

Bright image