Ch. 14 Pulsed Echo Instrumentation Flashcards
Pulsed Echo ultrasound system has two major functions:
- The preparation and transmission of electrical signals to the transducer, which creates the sound beam.
- The reception of electrical signals from the transducer, with subsequent processing into clinically meaningful images and sounds.
The _____________ and _________________ of electrical signals to the transducer, which creates the sound beam.
The Preparation and transmission of electrical signals to the transducer, which creates the sound beam.
The ___________________________ of electrical signals from the transducer, with subsequent processing into clinically meaningful images and sounds.
The Reception of electrical signals from the transducer, with subsequent processing into clinically meaningful images and sounds
ultrasound systems contain these six major components:
- transducer
- pulser and beam former
- reciever
- display
- storage
- master synchronizer
_____________________: during transmission, this transforms electrical energy into acoustic energy. During reception, it converts the returning acoustic energy into electrical energy.
Transducer : during transmission, this transforms electrical energy into acoustic energy. During reception, it converts the returning acoustic energy into electrical energy.
_______________ and ______________________: creates and controls the electrical signals sent to the transducer that generate sound pulses. The ______________________ determines the amplitude, pulse repetition period, and pulse repetition frequency. While the _________________________ determines the firing delay patterns for phased array systems.
Pulser and Beam Former : creates and controls the electrical signals sent to the transducer that generate sound pulses. The Pulser determines the amplitude, pulse repetition period, and pulse repetition frequency. While the Beam Former determines the firing delay patterns for phased array systems.
____________________________ : transforms the electrical signals from the transducer (produced by the reflected signal) into a form suitable for display.
Reciever : transforms the electrical signals from the transducer (produced by the reflected signal) into a form suitable for display.
______________________ : presents processed data. This may be a flat screen monitor, a transparency, a spectral plot, or a variety of other formats.
Display : presents processed data. The display may be a flat screen monitor, a transparency, a spectral plot, or a variety of other formats.
_____________________ : archives the ultrasound studies. Typically these devices (or media) include computer hard drives, CD, DVD, videotape, magneto-optical discs, paper printouts, photographs, and USB drives.
Storage : archives the ultrasound studies. Typically these devices (or media) include computer hard drives, CD, DVD, videotape, magneto-optical discs, paper printouts, photographs, and USB drives.
_________________________________ : maintains and organizes the proper timing and interaction of the system’s components.
Master Synchronizer : maintains and organizes the proper timing and interaction of the system’s components.
The ____________ creates electrical signals that excite the transducer’s PZT crystals and create sound beams
The Pulser creates electrical signals that excite the transducer’s PZT crystals and create sound beams
The pulser functions during ________________________
The pulser functions during transmission
True or False: Changes in pulser voltage modify the brightness of the entire image displayed on the systems screen
True
Changes in the pulser voltage modify the ______ of the image.
higher voltage (output) = _______________ image
lower voltage (output) = ______________ image
Changes in the pulser voltage modify the brightness of the image
higher voltage (output) = brighter image
lower voltage (output) = darker image
When the pulser voltage is low, the active element vibrates (more,less) forcefully, transmits (stronger,weaker) sound beams into the body, reflected echoes are (stronger, weaker) and the entire image is (brighter, darker)
less; weaker; weaker; darker
When the pulser voltage is high, the active element vibrates (more, less) forcefully, transmits (stronger, weaker) sound beams into the body, reflected echoes are (stronger, weaker) and the entire image is (brighter, darker)
more; stronger; stronger; brighter
output gain, acoustic power, pulser power, energy output, transmitter output are also known as for …
Pulser voltage
Can transducer output be adjusted by the sonographer?
Yes
As long as image quality is optimal, (lower, higher) pulser voltage is desirable
lower
__________________ is loosely defined as a random and persistent disturbance that obscures or reduces a signals clarity.
Noise is loosely defined as a random and persistent disturbance that obscures or reduces a signals clarity
A comparison of the meaningful information (signal) in an image, compared to the amount of contamination (noise)
Signal to Noise ratio
When the signal-to-noise ratio is ____________, the signal is much stronger than the noise and the image is of high quality.
When the signal-to-noise ratio is high, the signal is much stronger than the noise and the image is of high quality.
When the signal-to-noise ratio is ___________, the strength of the signal is closer to the strength of the noise and the image is of less quality.
When the signal-to-noise ratio is low, the strength of the signal is closer to the strength of the noise and the image is of less quality.
As the sonographer increases output power, the signal-to-noise ratio _________________. (increases, decreases)
increases
increasing output power is the most common way to ___________________ the signal-to-noise ratio
increasing output power is the most common way to improve the signal-to-noise ratio
The pulser also determines the time between one voltage spike and the next known as _____________________
The pulser also determines the time between one voltage spike and the next known as Pulse repetition period or PRP
If the pulser determines PRP, what else does it determine?
PRF (PRF and PRP are reciprocals)
PRP determines the:
maximum imaging depth (depth of view)
When the PRP is short, the PRF is __________ and the system spends (more,less) time listening?
When the PRP is short, the PRF is high and the system spends less time listening
When the PRP is long, the PRF is _____________ and the system spends (more,less) time listening?
When the PRP is long, the PRF is low and the system spends more time listening
Can a sonographer change the depth of view?
yes
Shallow imaging = __________ listening, _____________ PRP, ______________ PRF and _________________ duty factor
Shallow imaging =
less listening
shorter PRP
higher PRF
higher duty factor
Deep imaging = ___________ listening, _____________ PRP, _______________ PRF, ________________ duty factor
Deep imaging =
more listening
longer PRP
lower PRF
lower duty factor
The __________________________ functions with array transducers during transmission and reception
The Beam Former functions with array transducers during transmission and reception
The beam former also adjusts electrical spike voltages to reduce lobe artifacts in a process called …
The beam former also adjusts electrical spike voltages to reduce lobe artifacts in a process called Apodization
Modern beam formers use advanced microprocessor technology and produce signals in digital format. This device is called ______________________________
Digital Beam Former
The beam former has a special “transmit-recieve” _____________ that is important during transmission and reception
The beam former has a special “transmit-recieve” switch that is important during transmission and reception
A ____________________ is made up of a single PZT elements in the transducer, the electronics in the beam former/ pulser, and the wire that connects them
A Channel is made up of a single PZT element in the transducer, the electronics in the beam former/ pulser, and the wire that connects them
The number of elements in an array transducer that can be excited is determined by the number of ______________________
The number of elements in an array transducer that can be excited is determined by the number of channels
Most systems have between __ and ___ channels.
32-256 channels
What are the 5 operations that must be performed in the appropriate order for the system to function properly
- amplification
- compensation
- compression
- demodulation
- reject
The first function of the receiver is ________________________, also called …
The first function of the receiver is Amplification, also called receiver gain
All electrical signals in the receiver gain are affected ________________________ by amplification
All electrical signals in the receiver gain are affected identically by amplication
True or False: the entire image is made brighter or darker when the sonographer adjusts receiver gain
true
Amplification (does, does not) improve signal-to-noise ration, since both signal and noise are amplified equally
does not
True or False: Amplification alone can make an image of uniform brightness from top to bottom
false
Can a sonographer alter the amplification?
yes
Amplification is measured with units of ______________, which are _______________ units of measure
Amplification is measured with units of decibels, which are relative units of measure
Typical values of amplification:
60-100 db
The process of improving the quality of a signal before it is amplified:
preamplification
Preamplification occurs ____ to the transducer and often within the transducer itself.
Preamplification occurs close to the transducer and often within the transducer itself
The second function of the receiver is ___________________________
The second function of the receiver is compensation
Without compensation, the ultrasound image would become progressively _________________ with increasing depth
Without compensation, the ultrasound image would become progressively darker with increasing depth
The receiver corrects for attenuation with a process called:
compensation
Compensation creates an image that is:
uniformly bright from top to bottom
Can the sonographer adjust compensation?
yes
Compensation is measure in units of:
decibels
Compensation treats echoes differently, depending upon:
the depth from which they arise
Three identical masses located in the body at depths of 2cm, 4cm, and 6cm will produce reflections with different strengths. The echo will be the ________ (strongest,weakest) from the mass of 2cm and the _________ (strongest, weakest) from the mass at 6cm
Three identical masses located in the body at depths of 2cm, 4cm, and 6cm will produce reflections with different strengths. The echo will be the strongest from the mass of 2cm and the weakest from the mass at 6cm
Time gain compensation (TGC), depth gain compensation (DGC), and swepth gain are all AKA’s for ..
Compensation
At superficial depths, reflections undergo a small, constant amount of compensation called
The near gain
The depth at which variable compensation begins is known as _____________
The depth at which variable compensation begins is known as delay
At the depth of the _______________, reflections are maximally compensated by the ultrasound system
At the depth of the knee, reflections are maximally compensated by the ultrasound system
The third function of the receiver is ______________________
The third function of the receiver is compression
The ___________________ indicated the maximum amount of compensation that the receiver can provide
The far gain indicated the maximum amount of compensation that the receiver can provide
Compression is produced twice. First, compression keeps the electrical signal within the accuracy range of the systems electronics and second, keeps an images ________________________ content within the range of detection by the human eye
Compression is produced twice. First, compression keeps the electrical signal within the accuracy range of the systems electronics and second, keeps an images gray scale content
Humans can distinguish approximately (20, 30, 40) shades of grey.
20
In the region of the _________, compensation corrects for the effects of increasing attenuation that result from increasing path length.
In the region of the slope, compensation corrects for the effects of increasing attenuation that result from increasing path length
What allows us to visualize different tissues within 20 gray shades?
Compression
Can a sonographer adjust compression?
yes
Compression is expressed in units of:
decibels
Log compression where small differences in _____________ signals are displayed and seen as different gray scale levels
Log compression where small differences in weak signals are displayed and seen as different gray scale levels
Why is log compression important in clinical ultrasound?
most meaningful back scattered signals from biological tissues are very weak and sonographer must be able to see differences in the weak signals
The fourth function of the receiver is ________________________
demodulation
Demodulation is a process of
converting the voltage delivered to the receiver from one form to another
Demodulation is a two-part process:
- rectification (converts all neg voltages into pos voltages)
- smoothing or enveloping (places a smooth line around the “bumps” and evens them out)
Is demodulation adjustable by the sonographer?
No
demodulation effect on image?
none; just changes the form of the electrical signal so that it is appropriate for the system’s display
The fifth function of the Receiver is:
Reject
Reject allows the sonographer to control whether ________-level gray scale information within the data will appear on the displayed image
*Rejection does not affect bright echoes
Reject allows the sonographer to control whether low-level gray scale information within the data will appear on the displayed image
Can Reject be adjusted by the sonographer
Yes
Reject effect on image:
affects low-level signals on the image, regardless of their location
What is the difference between output power and receiver gain?
Output power affects image brightness by altering the strength of the sound pulse that the transducer sends to the body - increasing output power improved the signal-to-noise ratio
receiver gain (amplification) alters the strength of the voltages in the receiver that the transducer created during the reception
Patient exposure to ultrasound is affected by:
alterations in output power but not not by changed in amplification
ALARA Principle (As Low As Reasonably Achievable)
Radiographic principle that dictates the use of every method available to reduce radiation exposure to the patient in order to minimize risks and adverse consequences of ionizing radiation
According to the ALARA principle, if the image is too dark increase the (receiver gain, output power) first.
receiver gain
According to the ALARA principle, if the image is too bright decrease the (receiver gain, output power)
output power
