Ultrasound

Question 1

How does ultrasound work?

Answer 1

Electric field applied to crystal in transducer causes it to vibrate and generate sound waves. These sound waves encounter tissue and different density/type causes some waves to transmit on and others to reflect. Reflected waves detected and used to generate image

Question 2

How is depth calculated in ultrasound?

Answer 2

By calculating the time it takes for the ultrasound waves to return

Question 3

Why are higher frequency ultrasound waves only used to examine relatively superficial structures?

Answer 3

Because the waves they produce have a shorter wavelength. This means they produce better image resolution but only at small depth

Question 4

What is the Doppler effect?

Answer 4

Frequency of transmitted sound is altered as it is reflected from a moving object so can be used to examine flow e.g. blood

Question 5

Colour Doppler - use BART to determine flow. What does this stand for?

Answer 5

Blue - Away

Red - towards

Question 6

What are 4 basic movements that help optimise image in ultrasound?

Answer 6

Pressure
Align (slide)
Rotate
Tilt

Question 7

How does bone appear on ultrasound?

Answer 7

Hyperechoic periosteum with acoustic shadow below (basically white with dark bit underneath)

Question 8

How do arteries and veins appear on ultrasound?

Answer 8

Artery: anechoic, pulsatile, usually round
Vein: anechoic, non-pulsatile, compressible

Question 9

How do nerves appear on ultrasound?

Answer 9

Variable - generally circular or oval with a hyperechoic outline and speckled interior

Question 10

More proximal nerves have a predominantly hyperechoic interior in ultrasound. Why is this?

Answer 10

Because they contain less connective tissue

Question 11

Tendons and nerves can be difficult to differentiate. How can you do this?

Answer 11

Nerves tend to stay oval/circular however if you follow path of tendon it will blend into muscle proximally and become more prominent dismally

Question 12

How do muscles appear on ultrasound?

Answer 12

Hypoechoic mass, may have visible striae or hyperechoic fascia

Question 13

What are three artefacts in ultrasound?

Answer 13

Acoustic shadowing
Post-cystic enhancement
Reverberation

Question 14

What is acoustic shadowing and what two structures can it happen with?

Answer 14

Acoustic shadowing is when an acoustically opaque structure is in line of the ultrasound beam and so a dark shadow appears deep to it
Two structures: bone, heavily calcified vessel

Question 15

What is post-cystic enhancement?

Answer 15

Inappropriate bright area behind/deep to a fluid filled structure e.g. large blood vessel or cyst

Question 16

What is reverberation?

Answer 16

Lines reflected from a strongly reflected interface close to and parallel to the transducer often a needle, vessel wall or muscle fascia