SPI practice exam 1 Flashcards
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*note:
- signal to noise ratio: measure of how strong a signal is relative to the background noise
- The ratio of the signal amplitude to the noise amplitude
_ The higher the SNR (signal to noise ratio), the better the image is
*To improve SNR at depth:
- use a TDR designed for penetration
- use lower frequency
- move focus down deeper
- turn off dynamic frequency
- turn off harmonics *harmonics are best at the midfield, not with the depth
- use different imaging plane
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\*\*\*
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PRF
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\*increased image quality but decrease frame rate
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C
\*dynamic aperture is a type of receive focusing. the technique uses more crystals to receive deeper reflections than to receive shallow reflection.
It will reduce lobe artifact
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Air, blood, liver, bone
\*the more dense an object or media the higher the acoustic impedance levels
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\*The timed voltages produced in a **convex** shape will create wider beam.
\*If the voltages are timed to stimulate the elements in a **concave** pattern, a focused beam is produced.
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\*spatial compounding can be used to image noise and clutter
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\*the speed of sound through fat is slower than soft tissue thus the reflections take longer to return to the TDR.
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\*the speed of sound through fat is slower than soft tissue thus the reflections take longer to return to the TDR.
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PRF should be adjested
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\*Decreasing the dynamic range will increase the contrast of the image, causing the posterior shadowing to be more prominent
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output power
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C: VBF allows for improved lateral resolution without degrading temporal resolution
VBF
* very fast FR
* use receive focusing to improve detail resolution across the whole image \*No transmit focusing is needed