Principles of ultrasound physics and equipment

Question 1

what is a wave

Answer 1

a mode of energy transfer from one place to another

Question 2

what happens in longitudinal waves

Answer 2

particles move with a direction of travel

Question 3

what is a sound wave

Answer 3

longitudinal waves that travel through a medium

Question 4

what are ultrasound waves

Answer 4

very high frequency sound waves

Question 5

what frequency are audible waves

Answer 5

20-20,000 Hz

Question 6

what frequency are ultrasound waves

Answer 6

between 1-30 MHz

Question 7

what is a wavelength

Answer 7

distance between consecutive wave crests or similar points on a wave

Question 8

what is frequency (3 points)

Answer 8

1) number of cycles per second
2) measured in Hertz (Hz)
3) frequency affects penetrative power of the ultrasound beam

Question 9

the higher the frequency…

Answer 9

less penetration power but more resolution

Question 10

4 ways that sound is affected by tissue

Answer 10

1) reflection
2) attenuation
3) speed
4) absorption

Question 11

when does reflection occur

Answer 11

when there is a difference in 2 types of tissue

Question 12

what happens during attenuation

Answer 12

energy is lost as sound propagates through the tissue

Question 13

what does speed depend on

Answer 13

the nature of the tissue

Question 14

what happens during absorption

Answer 14

some ultrasound energy is converted into heat

Question 15

How is an ultrasound image formed? 6 steps

Answer 15

1) transducer
2) Piezoelectric crystals
3) conversion of energy
4) sound attenuated, reflected and absorbed by tissue
5) reflected sound converted to electrical signals
6) grey scale image is formed

Question 16

what is a B-mode image

Answer 16

a grey scale image

Question 17

how is a B-mode image produced

Answer 17

by the piezoelectric effect

Question 18

what is the piezoelectric effect

Answer 18

the conversion of electrical pulses to mechanical vibrations and the conversion of returned mechanical vibrations back into electrical energy

Question 19

how is a Doppler image produced

Answer 19

utilises the Doppler principle

Question 20

what is the Doppler principle

Answer 20

the change in observed frequency of the sound wave which occurs due to the relative motion between observer and source

Question 21

Doppler imaging includes (3 types)

Answer 21

1) colour Doppler
2) power Doppler
3) spectral Doppler imaging

Question 22

what is colour Doppler (2 things)

Answer 22

1) shows direction of blood flow

2) different colour indicates different direction of flow

Question 23

what is power Doppler (3 things)

Answer 23

1) uses colour to indicate flow
2) non directional
3) can pick up very low velocities

Question 24

what is spectral Doppler

Answer 24

indicates direction and velocity of flow

Question 25

ultrasound safety (2 things)

Answer 25

1) no evidence of harm by ultrasound

2) there are thermal and mechanical effects

Question 26

what must thermal indices and mechanical indices be

Answer 26

kept at recommended levels

Question 27

clinical examples of ultrasound uses

Answer 27

1) obstetrics
2) gynaecology
3) general;abdo,superficial,paed
4) vascular
5) musculoskeletal
6) heart
7) emergency point of care