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18 Cards in this Set
- Front
- Back
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The ability to image accurately is what? |
Resolution
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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)
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Axial Resolution
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Axial Resolution: Units?
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Distance (mm, cm, etc)
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Axial Resolution: Determined by what?
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Spatial Pulse Length
(which, in turn, is determined by both the source and the medium) |
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Axial Resolution: Adjustable?
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No
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Other names for axial resolution include what? (hint: LARRD)
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Longitudinal
Axial Range Radial Depth |
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What is the relationship between the numerical value of the axial resolution and the image quality?
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Inversely related
(low #s > shorter pulses > better img) |
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What are two properties of a transducer with improved axial resolution?
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1. Less Ringing
2. Higher Frequency |
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When there are few cycles in a pulse, this results in less what?
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Ringing
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How is ringing prevented in modern transducers?
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Backing material will dampen the ringing
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Superior axial resolution is composed of what type of pulses?
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High Frequency (short wavelength)
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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
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The more cycles in a pulse, the ___ the numerical value of the range resolution is
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Greater
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If a new pulsed transducer has many more cycles in its pulse, the image accuracy ___
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Degrades
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___ frequency transducers generally have the best range resolution
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High
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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
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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
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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
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