2 Ch 14: Pulsed Echo Instrumentation Flashcards
What are the two major functions of the u/s system?
- preparation and transmission
2. reception
This u/s component transforms electrical energy into acoustic energy. During reception it converts the returning acoustic energy into electrical energy.
transducer
The u/s component creates and controls the electrical signals sent to the transducer that generates sound pulses.
pulser and beam former
The u/s component determines the amplitude, pulse repetition period, and pulse repetition frequency.
pulser
This u/s component determines the firing delay patterns for phased array systems.
beam former
This u/s component transforms the electrical signals from the transducer into a form suitable for display.
receiver
This u/s component presents processed data.
display
This u/s component archives the u/s studies.
storage
This u/s component maintains and organizes the proper timing and interaction of the system’s components.
master synchronizer
T/F? The pulser functions during reception.
FALSE, during transmission
Synonyms for pulser voltage?
- output gain
- acoustic power
- pulser power
- energy output
- transmitter output
- power
- gain
Is the pulser voltage adjustable by the sonographer?
yes
Can output power alone make an image of uniform brightness from top to bottom?
nope
This is loosely defined as a random and persistent disturbance that obscures or reduces a signal’s clarity.
noise
This is a comparison of the meaningful information in an image compared to the amount of contamination.
signal-to-noise ratio
When the signal-to-noise ratio is high, the signal is much ___ than the noise and the image is of ___ quality.
stronger, high
When the signal-to-noise ratio is low, the signal is much ___ and the image is of ___ quality.
lower, low
How does transducer output affect noise?
Increasing power output also increases signal-to-noise ratio.
The ___ determines the time between one voltage spike and the next (PRP).
pulser
The beam former adjusts electrical spike voltages to reduce lobe artifacts in a process called…
apodization
Modern beam formers use advanced microprocessor technology called a…
digital beam former.
What are the advantages of a digital beam former?
- softward programming
- extremely stable
- versatile
The ___ protects the receiver components from the signals that are created for pulse transmission and directs the electrical signals from the transducer to the appropriate electronic and processing components.
switch
The ___ prepares the information contained in minuscule signals for eventual display on the system’s monitor.
receiver
What is the order of receiver operations?
- amplification
- compensation
- compression
- demodulation
- reject
During ___, each electronic signal returning from the transducer is made larger.
amplification
T/F? Each signal undergoes an equal amount of amplification.
true
T/F? Amplication alone can make an image of uniform brightness from top to bottom.
FALSE, cannot
Is amplification adjustable by the sonographer?
yes
Amplification is measured in units of…
decibels (dB)
What’s a typical value for amplification?
60-100 dB
This is the process of improving the quality of a signal before it is amplified.
preamplification
Preamplification occurs where?
in the transducer itself
The receiver corrects for attenuation with a process called…
compensation
T/F? Compensation creates an image that is uniformly bright from top to bottom.
true
Is compensation adjustable by the sonographer?
yes
Synonyms for compensation?
- time-gain compensation (TGC)
- depth gain compensation (DGC)
- swept gain
The depth at which variable compensation begins is known as the….
delay.
Compensation corrects for the effects of increasing attenuation that result from increasing path length in the region of the…
slope.
Reflections are maximally compensated by the u/s at the region of the…
knee.
This region indicates the maximum amount of compensation that the receiver can provide.
far gain
T/F? Compression is performed twice.
true
This keeps the electrical signal levels within the accuracy range of the system.
compression
This keeps an image’s gray scale content within the range of detection by the human eye.
compression
Is compression adjustable by the sonographer?
yes
Synonyms of compression?
log compression, dynamic range
Compression is reported in units of…
decibels (dB)
This is a two-part process that changes the electrical signals within the receiver into a form more sutiable for display ona monitor.
demodulation
This converts all negative voltages into positive voltages.
rectification
This places a smooth line around the ‘bumps’ and evens them out.
smoothing or enveloping
Is demodulation adjustable by the sonographer?
nope
How does demodulation effect the image?
Trick question! It doesn’t.
This allows the sonographer to control whether low-level gray scale information within the data will appear on the displayed image.
reject
Synonyms for reject?
threshold or suppression
Is reject adjustable by the sonographer?
yes
How does reject effect the image?
It effects only low-levels echoes, not bright echoes.
Systems with ___ use only the high frequency part of the reflected pulse’s bandwidth to create the superficial portion of the image.
dynamic frequency tuning
This affects image brightness by altering the strength of the sound pulse that the transducer sends to the body.
output power
Increasing output power improves the ___ because the meaningful diagnostic echoes become stronger while the noise level remains unchanged.
signal-to-noise ratio
This alters the strength of the voltages in the receiver that the transducer created during reception.
receiver gain (amplification)
T/F? Increasing amplification does not alter the signal-to-noise ratio.
true, both signals and noise are treated identically
Patient exposure to sound energy is affected by alteration in ___ but not by changes in ___.
output power, amplification
ALARA stands for…
As Low As Reasonably Achievable
If the image is too dark, first increase the ___ which does no increase patient exposure.
receiver gain
If the image is too bright, first decrease the ___ which decreases patient exposure.
output power
