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18 Cards in this Set

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  • Back
The ability to image accurately is what?
Resolution
The ability to display two structures that are very close together when the structures are parallel to the beam's main axis (one in front of the other)
Axial Resolution
Axial Resolution: Units?
Distance (mm, cm, etc)
Axial Resolution: Determined by what?
Spatial Pulse Length
(which, in turn, is determined by both the source and the medium)
Axial Resolution: Adjustable?
No
Other names for axial resolution include what? (hint: LARRD)
Longitudinal
Axial
Range
Radial
Depth
What is the relationship between the numerical value of the axial resolution and the image quality?
Inversely related
(low #s > shorter pulses > better img)
What are two properties of a transducer with improved axial resolution?
1. Less Ringing
2. Higher Frequency
When there are few cycles in a pulse, this results in less what?
Ringing
How is ringing prevented in modern transducers?
Backing material will dampen the ringing
Superior axial resolution is composed of what type of pulses?
High Frequency (short wavelength)
The following factors affect axial resolution in what way?
- shorter SPL
- shorter pulse duration
- higher freqs / shorter wavelength
- fewer cycles/pulse (less ringing)
Improved Axial Resolution
The more cycles in a pulse, the ___ the numerical value of the range resolution is
Greater
If a new pulsed transducer has many more cycles in its pulse, the image accuracy ___
Degrades
___ frequency transducers generally have the best range resolution
High
Which of the following transducers has the poorest axial resolution?
A. 1.7 MHz and 4 cycles/pulse
B. 2.6 MHz and 3 cycles/pulse
C. 1.7 MHz and 5 cycles/pulse
D. 2.6 MHz and 2 cycles/pulse
C
In soft tissue, a 3 cycle, 1 MHz pulse has a pulse length of 4.5 mm. What is the axial resolution?
A. 3 mm
B. 1 mm
C. 2.25 mm
D. 1.54 mm
C
Which of the following transducers has the best axial resolution?
A. 1.7 MHz and 4 cycles/pulse
B. 2.6 MHz and 3 cycles/pulse
C. 1.7 MHz and 5 cycles/pulse
D. 2.6 MHz and 2 cycles/pulse
D