Basic US Physiology

Question 1

what will increase the speed of sound transmitting through a medium? what doesn’t change the speed?

Answer 1

increasing the stiffness of the medium
Decreasing the density of the medium (DD)

frequency and wave does not matter for speed of transmission

Question 2

Is sound wave longitudinal or transverse

Answer 2

longitudinal

Question 3

What happens to sound waves in a vaccum

Answer 3

it cannot propagate in a vacuum

Question 4

What property of sound stays constant with increasing depth

Answer 4

frequency, pulse duration, period and axial resolution

velocity also does not change if the medium is homogenous

Question 5

What happens with amplitude with increasing depth

Answer 5

decreases (attenuates)

Question 6

How do you calculate power?

Answer 6

amplitude squared

Question 7

How do you calculate intensity

Answer 7

Intensity = Power / cross-sectional area of the beam

(as the beam diameter increases past the focal point and the power decreases with depth, both cause intensity to decrease)

Question 8

As sound wave travels from soft tissue to air, what happens? (wavelength, velocity, power and amplitude)

Answer 8

wavelength decreases
velocity decreases
amplitude increases
power increases

does not change: freq & pulse duration

Question 9

speed =

Answer 9

wavelength x frequency

Question 10

what is the velocity of sound in soft tissue?

Answer 10

1540 m/s (1.54 mm/micro sec)

Question 11

Calculate depth by using time an ultrasound wave comes back to a probe

Answer 11

depth = [time in flight (ms) / 2 ] x velocity of sound through a specific medium

Question 12

What is pulse repetition period (PRP) in ultrasound

Answer 12

the amount of time from the start of one pulse to the start of another pulse. Includes pulse duration and “listening time”. PRP can be adjusted by sonographer, adjusted for depth of view.

Deeper imaging = longer PRP

Question 13

What is attenuation

Answer 13

DECREASE of amplitude and intensity of ultrasound waves as they travel through tissue

Attenuation is increased with higher FREQUENCY of sound (attenuation = frequency squared)

Question 14

If you want to ultrasound higher depth, do you want higher or lower frequency?

Answer 14

lower frequency

because attenuation affects higher frequency waves more than lower frequency (at the expense of lower spatial resolution)