Vascular Book: How, Why, When

Question 1

What is the equation relating speed, frequency and wavelength?

Answer 1

c = lambda * f

Question 2

What are typical frequencies of US probes?

Answer 2

2 - 15 mHz

Question 3

What is the speed of sound in air?

Answer 3

330 m/s

Question 4

What is the sound of ultrasound in soft tissue?

Answer 4

1540 m/s

Question 5

How many wave cycles do pulsed ultrasound typically contain?

Answer 5

1 - 3 cycles

Question 6

How do you calculate distance travelled by the ultrasound beam?
(Equation)

Answer 6

d = (t * c) / 2

Question 7

Describe how sound signals can be broken down into their components?

Answer 7

Signals are composed of sine waves of varying frequencies

Question 8

How does change in acoustic impedance impact reflection?

Answer 8

The greater the acoustic impedance difference at the boundary, the stronger the reflection at the boundary

Question 9

What is attenuation?

Answer 9

Loss of energy from ultrasound as it passes through tissue

Question 10

What is the attenuation coefficient of water?

Answer 10

0.2

Question 11

What is the attenuation coefficient of fat?

Answer 11

60

Question 12

What is the attenuation coefficient of blood?

Answer 12

20

Question 13

What is the attenuation coefficient of muscle?

Answer 13

160

Question 14

What is the attenuation coefficient average of soft tissue?

Answer 14

70

Question 15

How many piezoelectric elements do transducers usually comprise?

Answer 15

128

Question 16

What is the typical range of amplitudes that can be displayed by an ultrasound scanner?

Answer 16

20dB

Question 17

How are US beams steered away from perpendicular to the transducer?

Answer 17

They introduce timing delays between consecutive transducer elements causing interference between wavelets
- NOTE this also allows focusing of the beam