Basics

Question 1

Longitudinal wave:

Answer 1

particles of a medium are in a direction parallel to the wave propagation.

Question 2

Mechanical wave:

Answer 2

a wave that requires a medium to travel

cannot propagate in a vacuum

Question 3

Acoustic variable:

Answer 3

pressure, temperature, density, and particle motion (oscillation)
all of these variables change as an acoustic wave passes through a medium

Question 4

The number of cycles per second:

Answer 4

freq

Question 5

Unit for frequency:

Answer 5

MHz

Question 6

Unit for period:

Answer 6

us

Question 7

Unit for wavelength:

Answer 7

mm

Question 8

What is propagation speed determined by?

Answer 8

density and stiffness

mm/us

Question 9

Sound travels faster in lung than liver. True or false.

Answer 9

False– sound travels faster in stiffer material

Question 10

If you double the frequency, what happens to the wavelength?

Answer 10

halves it

Question 11

As imaging depth increase, what happens to the PRF?

Answer 11

decreases

Question 12

What happens to the PRP when the imaging depth is increased?

Answer 12

increases

Question 13

The max variation that occurs in an acoustic variable:

Answer 13

amplitude

Question 14

Power relationship to amplitude?

Answer 14

power ∝ amplitude^

2

Question 15

Units of intensity?

Answer 15

W/cm^2

Question 16

Units for power?

Answer 16

Watts

Question 17

Intensity relationship to amplitude?

Answer 17

Intensity ∝ amplitude^2

If amplitude doubles, then the intensity quadruples

Question 18

Intensities in US range from?

Answer 18

1-50mW/cm^2

Question 19

Intensities have both a peak value and an average value. The intensity of the sound beam as it
travels through a medium varies across the beam (spatial intensity) and with time (temporal
intensity).

Answer 19

Didn’t know this, thought it’d be good info to know lolz.

Question 20

Spatial peak is the intensity where?

Answer 20

at the center of the beam

Question 21

Spatial average is intensity where?

Answer 21

averaged throughout the beam

Question 22

Temporal peak:

Answer 22

is the max intensity in the pulse

Question 23

Temporal average:

Answer 23

intensity averaged over one of-off beam cycle.

takes into account the intensity at the beginning of one pulse to the beginning of the next

Question 24

Pulse average:

Answer 24

intensity averaged over the duration of the single pulse

Question 25

What’s the highest intensity?

Answer 25

SPTP

Question 26

What’s the lowest intensity?

Answer 26

SATA

Question 27

What’s the major source of attenuation in soft tissues?

Answer 27

absorption

Question 28

Diffuse scattering is what? What’s an example of it?

Answer 28

redirection of the sound beam after it strikes rough or small boundaries. (when the wavelength is larger than the reflecting surface)
liver parenchyma and RBC’s are examples.

Question 29

The attenuation coefficient is approximately _______ of the operating frequency of the transducer.

Answer 29

1/2

so for every 1cm per MHz, there is approx 0.5dB of attenuation

Question 30

In oblique incidence. what 2 angles are equal?

Answer 30

angle of incidence and angle of reflection

Question 31

What is the range equation?

Answer 31

relationship between the round trip travel time of the pulse and the distance to the reflector.

Question 32

Piezoelectric effect is voltage applied to the crystal. True or false.

Answer 32

False– that is reverse.

It is the physical compression on the crystal that generates a potential difference