Test 2

Question 1

If the intensity of the beam is 20 mW/cm^2

Answer 1

3dB

Question 2

What are three names for normal incidence?

Answer 2

Right angle
Orthogonal
Perpendicular

Note: Not 45 degrees

Question 3

What is the property of a medium that provides a measure of resistance to sound passing through the medium?

Answer 3

Acoustic impedance

Question 4

What causes refraction at a tissue interface?

Answer 4

Change in propagation speed

Question 5

What happens to the intensity if the amplitude is increased by a factor of 3?

Answer 5

Intensity is increased by a factor of 9.

Note: amplitude multiplied by itself = the amount of intensity

Question 6

The intensity of an ultrasound beam is 1000 mW/cm^2. You increase the power by 40 dB. What is the new intensity of the beam?

Answer 6

10,000,000 mW/cm^2

Question 7

With absorption, acoustic energy is converted to:

Answer 7

Heat

Question 8

Acoustic impedance is expressed in which unit?

Answer 8

Rayl

Question 9

What is the amount of transmission expected from a soft tissue / air interface

Answer 9

1% or less.

Question 10

If the intensity transmitted at a boundary 40% what is the intensity reflection coefficient?

Answer 10

0.6

Question 11

What is something that would cause a strong echo at an interface?

Answer 11

A great change in impedance

Question 12

True/False

Lower frequency transducers perform better when using harmonics

Answer 12

True

Question 13

What is the angle at which there is a 100% internal reflection and no transmission?

Answer 13

Critical angle

Question 14

Which interaction is responsible for the internal texture of organs in the ultrasound image?

Answer 14

Scattering

Question 15

What is the best estimate of how much a 8 MHz beam will be reduced if it travels a total of 5 cm in soft tissue?

Answer 15

20 dB

Question 16

Determine the percentage of transmitted power at an interface between the two media if the acoustic impedance of the first medium in 3 MRayls and the acoustic impedance of the second medium is 2 MRayls

Answer 16

96%

Question 17

(Typed)

One advantage of using harmonics is that the (blank) resolution is improved.

Answer 17

Lateral

Question 18

What is the expected attenuation of a 5 MHz sound beam that has returned from a soft tissue target 6cm away?

Answer 18

30 dB

Question 19

True/False:

Frequency and propagation speed are indirectly related

Answer 19

False

Note: there is NO relationship between frequency and propagation speed

Question 20

Which of the following has the correct relationship to an increase in stiffness?

Answer 20

Increased propagation speed

Question 21

An increase in the frequency from 2MHz to 4MHz will have the greatest effect on which type of interface?

Answer 21

Rayleigh scatterer

Question 22

True/False:

Attenuation always results in a decibel loss

Answer 22

True

Question 23

How are frequency and attenuation related?

Answer 23

Directly related

Question 24

What is the attenuation coefficient of a 6MHz probe traveling 2cm?

Answer 24

3 dB/cm

Question 25

What is the half value layer for a 12MHz transducer?

Answer 25

0.5 cm

Question 26

You had an initial intensity of 10,000 mW/cm^2. You are scanning with a 4 MHz transducer and the beam had a total path length of 10 cm. What is the final intensity of your beam?

Answer 26

100mW/cm^2

Question 27

What term describes the distance between the compression zones?

Answer 27

Wavelength

Question 28

What does Snell’s law predict?

Answer 28

Beam direction transmitted through an interface

Question 29

With a specular reflector, the angle of reflection equals:

Answer 29

Angle incident

Question 30

The angle of incidence is equal to 90 degree. The acoustic impedance of medium one equals four rayls and the propagation speed of medium one equals 1.54 mm/microseconds. The acoustic impedance of medium two equals four rayls and the propagation speed of medium two equals 1.45 mm/microseconds. What is the IRC? (%)

Answer 30

0%

Question 31

In DMS, what will happen to the wavelength if the frequency doubles?

Answer 31

It will be halved

Question 32

True/False: Scattering reflectors are angle dependent

Answer 32

False Note: Scattering reflectors (non-specular) are frequency dependent; not angle dependent.

Question 33

Rank the propagation speeds of the following mediums from fastest to slowest: fast, blood, soft tissue

Answer 33

Blood, Soft tissue, Fat

Question 34

True/False: Tissue harmonics are present at the transducer face and near field so artifacts are reduced in these areas

Answer 34

False

Question 35

List all the components that go into beam attenuation. (What are the different things that happen to the beam?) You must list all of them to get credit.

Answer 35

Reflection Refraction Transmission Absorption