問題一覧
1
Axial resolution affects structures that are
positioned along the scan beam
2
The diameter of a disc-shaped, unfocused piezoelectric crystal is 1 cm. What is the best estimate for the minimum lateral resolution of the US system?
5 mm
3
Lateral resolution is equal to ____.
Beam width
4
Which of the following determine the spread of a sound beam in the far field? A. crystal thickness and impedance B. speed of sound in ceramic and frequency C. frequency of sound and density of the ceramic D. diameter of ceramic and frequency of sound
diameter of ceramic and frequency of sound
5
Which of the following transducers has the best axial resolution?
2.6 MHz & 2 cycles per pulse
6
Which situation produces the best axial resolution?
4 MHz with 2 cycles per pulse
7
When using standard ultrasonic imaging instrumentation, lateral resolution has a higher numerical value than the axial resolution.
True
8
Axial resolution
is affected by wavelength
9
With a specific ultrasound system and transducer, the system’s axial resolution is invariant, and the sonographer can do nothing to improve it. A. True B. False
True
10
What will lower the value of an ultrasound system's lateral resolution?
use an acoustic lens
11
Which of these techniques is consistent with variable or multifocusing?
electronic
12
Two ultrasound systems are identical except for the pulse repetition period (PRP) of the emitted pulse. Which system will have the deeper focus?
their foci will be at the same depth
13
Wavelength has the greatest effect on
axial resolution
14
One way that a sonographer can alter the axial resolution achieved during an exam is to adjust the maximum imaging depth. A. True B. False
False
15
The near zone length should be kept as short as possible.
False
16
Which of the following transducers will have the poorest axial resolution?
1.7 MHz & 5 cycles per pulse
17
When using an instrument typical of today's imaging devices, a higher frequency transducer is likely to improve axial resolution. A. True B. False
True
18
The focus of an ultrasound beam is the location where the ____.
optimum transverse resolution is
19
Frequency and focal depth are _____ related. A. Directly B. Inversely C. Reciprocally D. Not
Directly
20
Which of the following determine the focal length of a sound beam? A. crystal thickness and impedance B. speed of sound in ceramic and frequency C. frequency of sound and density of the ceramic D. diameter of ceramic and frequency of sound
diameter of ceramic and frequency of sound
21
Which of these terms means adjustable focusing or multi-focusing?
phased array
22
Which of the following determines the frequency of sound created by a pulsed wave transducer? A. crystal thickness and impedance B. speed of sound in ceramic and diameter C. speed of sound and density of the ceramic D. thickness and speed of sound in the ceramic
thickness and speed of sound in the ceramic