Ultrasound Physics and Principles

Question 1

What is sound?

Answer 1

it is a longitudinal, mechanical wave that require a medium for transmission

Question 2

longitudinal waves vibrate in which direction?

Answer 2

in the direction they are moving (propagate)

Question 3

transducer frequency for USG procedures vary because of

Answer 3

structure depth, structure location, and composition of surrounding tissue

Question 4

frequency

Answer 4

cycles/second

Question 5

wavelength

Answer 5

(meters/cycle) = (meters/sec) / (cycles/sec)

Question 6

propagation velocity

Answer 6

(meters/sec) = (meters/cycle) x (cycles/sec)

Question 7

high frequency transducers are considered

Answer 7

> or equal to 7 MHz

Question 8

low frequency transducers are considered

Answer 8

1-5 MHz

Question 9

high frequency vs low frequency

Answer 9

high frequency

• more cycles per second
• higher resolution images
• increased attenuation
• imaging limited to shallow structures

low frequency

• fewer cycles per second
• lower resolution images
• less attenuation
• imaging deeper structures possible

Question 10

a high frequency transducer is typically used for vascular access because:

a. the sound beam has increased attenuation
b. there are fewer cycles per second
c. it generates a high resolution image
d. imaging deep structures is possible

Answer 10

c. it generates a high resolution image

Question 11

propagation velocity for soft tissue (average)

Answer 11

1,540 m/s

Question 12

the less dense the medium, the ____ sound travels

Answer 12

slower

Question 13

true or false: all frequencies travel at the same speed through the same medium

Answer 13

true

Question 14

which of the following statements regarding sound is faster?

a. sound requires a medium to propagate
b. hertz = cycles/sec
c. the higher the frequency, the shorter the wavelength
d. sound travels through all tissue at 1540/sec
e. all statements are correct

Answer 14

e. all statements are correct

Question 15

which zone of the ultrasound beam has the best resolution?

Answer 15

focal zone

Question 16

which zone has the poorest resolution?

Answer 16

far field/ fraunhofer zone

Question 17

which zone has decent resolution?

Answer 17

near field/fresnel zone

Question 18

which technique allows US systems to send and receive echoes?

Answer 18

pulse-echo technique

Question 19

brightness results from the differences in

Answer 19

acoustic impedance between adjacent tissues

Question 20

doppler is dependent on the angle of

Answer 20

insonation

Question 21

which of the following statements regarding doppler ultrasound is incorrect?

a. doppler is nore used to create an image
b. the optimal angle of insonation is 60 degrees
c. either the sender or the receiver must be moving
d. colors depicted with doppler indicate flow, but not direction
e. all of the above are correct

Answer 21

d. colors depicted with doppler indicate flow, but not direction