Week 15 Pulsed Echo Instrumentation Part 2 Flashcards
What are the order of Receiver Operations?
- Amplification
- Compensation
- Compression
- Demodulation
- Reject
Is amplification adjustable?
Yes
How are the signals processed with Amplification?
All signals are treated identically.
What effect does amplification have on an image?
Entire image gets brighter or darker
Is Compensation adjustable?
Yes
How are the signals processed with Compensation?
Signals treated differently based on reflector depth.
What effect does compensation have on an image?
Image will be uniformly bright from top to bottom.
Is Compression adjustable?
Yes
How are the signals processed with Compression?
Signals are treated differently depending on the strength.
What effect doe compression have on an image?
Changes gray scale mapping
Is Demodulation adjustable?
No
How are the signals processed with demodulation?
Prepares electrical signals to be suitable for display.
What are the effects of demodulation on an image?
NONE
Is reject or suppression
or threshold adjustable?
Yes
How are the signals processed with reject?
Only weak signals are affected: Strong signals remain unchanged.
What are the effect of reject on an image?
Weak echoes appear or are eliminated from an image.
What are the units of Amplification?
Db
What is the typical value of amplification?
60-100 Db
Output power:
- Changes brightness of the entire image
- alters signal-to-noise ratio
- alters patient exposure
- bioeffect concerns
- Decreases this first if image is too bright
Receiver Gain:
- Changes brightness of entire image.
- Does not affect signal-to-noise ratio
- Does not change patient exposure
- No bioeffect concerns
- Increase this first if image is too dark.
What are the 2 ways Demodulation forms more suitable displays on a monitor?
- Rectification
- Smoothing
What is Rectification?
Converts all negative voltages into positive voltages.
What is smoothing or enveloping?
Places a smooth line around the “bumps” and evens them out.
What is the purpose of preamplification?
process of improving the signal quality before amplification.
Which receiver function will provide this image with equal brightness?
compensation
“Compensation” receiver function is needed to ______.
correct for attenuation
Another name for TGC’s are ______.
swept gain
compensation
depth gain compensation
What could happen if the gain is not optimized appropriately throughout the image?
deeper structures may not be seen
Which receiver function is important for seeing differences in weak reflections.
compression
Due to ALARA which would you use first to decrease the energy emitted?
output power
