Ultrasound

Question 1

Explain simply how ultrasound works?

Answer 1

• Electric field applied to piezoelectric crystal in the transducer causes it to vibrate, generating ultrasound waves.
• When sound wave encounters a change in tissue type/density, some waves are transmitted on, others are reflected.
• These reflected waves are detected and used to generate an image.
• The time it takes for the ultrasound waves to return are used to calculate depth.

Question 2

Bright white on image represents _________

Answer 2

structures that a have reflected a lot of sound wave energy e.g. periosteum of bones, aponeurosis, nerve and tissue interfaces between muscle groups

Question 3

Darker areas on image represent __________

Answer 3

structures that have reflected the sound wave energy poorly e.g. fluid filled structures such as arteries appear black

Question 4

4 ways you can control the ultrasound probe?

Answer 4

Pressure
Rotation
Alignment
Tilt

Question 5

Describe how changing pressure can change the image?

Answer 5

Too little pressure loss of contact

Too much obliterate some structures such as veins

Question 6

Describe how changing rotation can change the image?

Answer 6

change it to a sideways vs vertical view

Question 7

Describe how alignment can change the image?

Answer 7

you want to align the ultrasound with the structures of interest, you will see what is the range of the probe so moving the probe to anatomically where the structure will be will allow you to see it

Question 8

Describe how tilt can change the image?

Answer 8

change tilt depending on structure you are looking at

sound waves are best reflected if they are perpendicular to the structure

Question 9

What is the doppler effect and why is it useful?

Answer 9

The frequency of transmitted sound is altered as it is reflected from a moving object. Can be used to examine flow, for example in a blood vessel.

Question 10

What must be used between the skin and the probe?

Answer 10

acoustic coupling gel

Question 11

The marker on the side of the probe corresponds to a _________________

Answer 11

marker onscreen to aid orientation

Question 12

Describe how bones appear on ultrasound?

Answer 12

Hyperechoic periosteum with acoustic shadow below.

Bright white

Question 13

Explain what is meant by hyperechoic, hypoechoic and anechoic?

Answer 13

hyperechoic - more echoic than normal so appears very bright as reflecting back lots of sound
hypoechoic- less echoic so appears darker
anechoic - doesn’t reflect sound so appears black

Question 14

Describe how arteries appear on ultrasound?

Answer 14

Anechoic, pulsatile, usually round

Question 15

Describe how veins appear on ultrasound?

Answer 15

Anechoic, non-pulsatile, compressible

Question 16

Describe how nerves appear on ultrasound?

Answer 16

Variable appearance. Generally circular or oval, with a hyperechoic outline and speckled interior. More proximal nerves, have a predominantly hypoechoic interior because they contain less connective tissue.

Question 17

Describe how tendons appear on ultrasound?

Answer 17

Can be difficult to differentiate from nerves. Follow their course, a nerve will still stay round or oval; a tendon blends into the muscle proximally and becomes more prominent distally.

Question 18

Describe how muscles appear on ultrasound?

Answer 18

Hypoechoic mass. May have visible striae or hyperechoic fascia.

Question 19

3 types of artefact that may be produced on ultrasound scan?

Answer 19

acoustic shadowing, post-cystic enhancement, reverberation

Question 20

Describe acoustic shadowing?

Answer 20

when an acoustically opaque structure (eg bone, heavily calcified vessel) is in the line of the ultrasound beam, a dark shadow appears behind/deep to it

Question 21

Describe post-cystic enhancement?

Answer 21

inappropriately bright area behind/deep to a fluid filled structure

Question 22

Describe reverberation?

Answer 22

commonly occurs where there is a strongly reflecting interface close to and parallel to the transducer, often a needle, vessel wall or muscle fascia.

Question 23

How does air appear on ultrasound?

Answer 23

It doesn’t appear well, lots of reflections and artefacts