Chapters 6-11 Review Questions Flashcards
(54 cards)
1
Q
Which of the following does NOT affect impedance? A. stiffness B. density C. propagation speed D. frequency E. all of the above affect impedance
A
D. frequency
2
Q
Normal incidence, same impedance. What will occur? A. no reflection will occur B. a small reflection will occur C. all the sound will be transmitted D. a large reflection will occur
A
C. all the sound will be transmitted
3
Q
What are the units of impedance? A. rayls B. dB/cm C. m/s D. Ohms
A
A. rayls
4
Q
With absorption, acoustic energy is converted to what? A. mechanical energy B. electrical energy C. heat D. total absorption
A
C. heat
5
Q
The intensity transmission coefficient at the interface between two structures equals 1%. What is the intensity reflection coefficient?
A
99%
6
Q
What must be present for sound reflection to occur at the interface of two structures?
A
a difference in acoustic impedance of the media
7
Q
what is an example of specular relection?
A
a renal capsule
8
Q
Which of the following adjustments would reduce attenuation? A. increase receiver gain B. decrease transmit power C. increase dynamic range D. decrease frequency E. decrease focusing
A
D. decrease frequency
Attenuation is determined by two factors:
* path length
* frequency
{ frequency & attenuation are directly related}
9
Q
Reflection of the sound beam from a large interface with a rough surface is called: A. specular reflection B. diffuse reflection C. scattering D. absorption
A
B. diffuse reflection
10
Q
The angle of sound transmission at an interface with oblique incidence and different propagation speeds describes what?
A
Snells law
11
Q
The attenuation of ultrasound propagating through soft tissue is approximately \_\_\_\_\_\_ dB/cm/MHz. A. 0.5 B. 2 C. 1.5 D. 1.54
A
A. 0.5
12
Q
During an abdomen exam, you would most expect to encounter refraction in this view: A. transverse view of the pancreas B. sagittal view of the aorta C. sagittal view of the liver D. transverse view of the gallbladder
A
D. transverse view of the gallbladder
13
Q
Sound may be attenuated by all of the following EXCEPT: A. reflection B. scattering C. conversion of sound to heat D. absorption E. compression
A
E. compression
14
Q
The term for reflection from a large smooth interface is.. A. diffuse reflection B. specular reflection C. refraction D. scattering
A
B. specular reflection
15
Q
During an aorta exam, 40% beam-to-vessel incidence is…
A
oblique
16
Q
Which is true regarding the effect of frequency on Rayleigh scattering?
A. rayleigh scattering and frequency are inversely related
B. scattering intensity is proportional to frequency squared
C. The are completely unrelated
D. scattering intensity is proportional to frequency raised to the 4th
A
D. scattering intensity is proportional to frequency raised to the 4th
17
Q
An echo from which sound reflectors is most dependent on the angle of incidence? A. scattering B. diffuse reflection C. attenuation D. specular reflection
A
D. specular reflection
18
Q
In soft tissue, sound travels to a reflector and back to the transducer in 52usec. How deep is the reflector? A. 4 cm B. 8 cm C. 3 cm D. 2 cm
A
A. 4 cm
13 uses per 1 cm { 13 X 4 = 52}
19
Q
In soft tissue, the time it takes to receive an echo from interface 2.0 cm into the body is ... A. 13 usec B. 1.3 usec C. 39 usec D. 26 usec
A
D. 26 usec
20
Q
What is the curie temp? A. 300 C B. 129 F C. 300 F D. 600 C
A
A. 300 degrees celsius
21
Q
If the transducers Q - factor is low, the bandwidth will be.. A. narrow B. high C. wide D. low
A
C. wide
22
Q
In pulsed wave imaging, what helps to establish the primary frequency of the acoustic energy discharged by the transducer
A
??
23
Q
Damping of the transducer oscillations will:
decrease the ________ and decreases the ______
A
decreases the pulse duration and decreases the quality factor
24
Q
The purpose of the damping material is to {decrease/increase} the number of cycles in the pulse.
A
Decrease
25
```
The matching layer of the transducer is designed to ..
A. optimize the pulses
B. reduce reflectivity
C. create shorted pulses
D. reduces "ringing"
```
B. reduce reflectivity
26
What helps to determine the frequency of the acoustic wave produced by a CW transducer?
The frequency of the electrical signal exciting the PZT crystal
27
The property of certain material to create a voltage ..
piezoelectric effect
28
```
What transducer component is designed to control PZT element ringing?
A. matching layer
B. the case
C. backing material
D. the wire
```
C. backing material
29
What is the optimal thickness for the matching layer?
one-fourth the wavelength
30
What is the optimal thickness for the active element?
one-half the wavelength
31
The PZT crystal of a transducer typically have a higher impedance than that of skin {T/F}
TRUE
32
```
Which of the following actions will cause a PZT crystal to lose its special properties?
A. breaking it in pieces
B. exposing it to high temperatures
C. exposing it to electrical current
D. exposing it to low pressures
```
B. exposing it to high temperatures
33
What is the formula for bandwidth?
bandwidth= highest frequency - lowest frequency
34
What is the formula for Q-factor?
Q-factor= main frequency/bandiwdth
35
```
Which properties of the PZT crystal of an imaging transducer results in the highest frequency?
A. thin, high propagation speed
B. thick, slow propagation speed
C. thin, slow propagation speed
D. none of the above
```
A. thin, high propagation speed
36
Which crystal would you use for the lowest frequency?
A. 6 mm thick, 4 cm diameter, 4.0 mm/us propagation speed
B. 8 mm thick, 2 cm diameter, 2.0 mm/us propagation speed
C. 4 mm thick, 9 cm diameter, 5.0 mm/us propagation speed
D. 2 mm thick, 6 cm diameter, 6.0 mm/us propagation speed
B. 8 mm thick, 2 cm diameter, 2.0 mm/us propagation speed
The frequency is the lowest when the crystal is thick and its propagation speed is low. The diameter of the active element does NOT affect the frequency of the pulse.
37
The Q value is principally a function of what?
resonant frequency and bandwidth
38
```
Where is the point of maximum intensity in a sound beam?
A. the fresnel zone
B. the fraunhofer zone
C. the focal point
D. the near zone
```
C. the focal point
39
Constructive and destructive interference sound waves from each individual sound source of a transducer is known as what?
Huygens principle
40
Increasing the transducer diameter has what affect?
increases the near zone length
41
What should you do to obtain the best lateral resolution for a given transducer?
use the MAXIMUM number of transmit focal zones
42
Which statement is NOT true regarding lateral resolution?
A. it is equal to the beam width
B. it is improved by focusing
C. It is also known as azimuthal resolution
D. it remains constant throughout scanning depth
D. it remains constant through out scanning depth
43
```
What is the minimum beam diameter for an unfocused disc transducer?
A. 3 X the disk diameter
B. 2 X the disk diameter
C. equal to the disc diameter
D. 1/2 the disk diameter
E. 1/4 the disk diameter
```
D. 1/2 the disk diameter
44
How is the beam focused with a single element transducer?
A. electronic phasing transmit
B. dynamic aperture
C. delay lines upon receive
D. curved element
E. single element transducer can not be focused
D. curved element
45
Which unfocused transducer would provide the longest near zone length for a superficial study?
*** 10 MHz, 6 mm diameter
*** 10 MHz, 6 mm diameter
46
```
Which will produce a long fresnel zone?
A. increased crystal diameter
B. decreased crystal diameter
C. higher frequency
D. none of the above
```
A. increased crystal diameter
47
```
Which of the following probes creates a beam with the shallowest focus?
A. 4mm diameter, 4 MHz
B. 6 mm diameter, 8 MHz
C. 4 mm diameter, 2 MHz
D. 5 mm diameter, 8 MHz
```
C. 4mm diameter, 2 MHz
Shorter focal lengths are associated with small diameter, low frequency probes.
48
```
Which focusing technique is different from the others?
A. lens
B. curved crystal
C. fixed
D. phased
```
D. phased
49
All of the following occur with focusing except?
A. lower intensity at the focus
B. shorter near zone length
C. more compact focal zone
D. smaller beam diameter at the end of the near zone
??
50
```
Which is internal focusing?
A. lens
B. curved
C. electronic
D. fixed
```
B. curved
51
Which term means adjustable focusing or multi focusing?
phased array
52
Which technique is consistent with variable or multi focusing?
electronic
53
```
Which imaging modality places dots of dissimilar gray scale on the display?
A. A-mode
B. I-mode
C. B-mode
D. M-mode
```
C. B-mode
54
```
To which of the following do the x-axis of a B-mode, the Y-axis of an M-mode and the x-axis of an A-mode all relate?
A. depth of view
B. go time
C. echo amplitude
D. time of flight
```
D. time of flight
