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82 Cards in this Set

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  • Back
Which system component can transform electrical energy into acoustic energy during transmission and acoustic energy into electrical energy during reception?
Transducer
Which system component determines amplitude, pulse repitition period/frequency?
Pulser
Which system component determines the firing delay pattern for phased array systems?
Beam Former
Which system component transforms the electrical signals from the transducer into a form suitable for display?
Receiver
Which system component presents processed data?
Display
Which system component archives ultrasound studies?
Storage
Which system component maintains and organizes the proper timing and interaction of the system's components?
Master Synchronizer
Does the pulser function during transmission or reception?
Transmission
What control does a sonographer use to modify pulser voltage?
Output Gain
(aka, acoustic power, pulser power, energy output, transmitter output, power)
Increasing pulser voltage (gain) will have what effect on the image?
Increases Brightness
What is the relationship between pulser voltage and returning echo strength?
Direct Relationship
Attempts to standardize output gain has resulted in what two measurements appearing onscreen?
Thermal Index (TI)
Mechanical Index (MI)
Random and persistent disturbance that obsures or reduces the clarity of a signal is called what?
Noise
A comparison between the amount of meaningful information and contamination in an image, is called what?
Signal-to-Noise Ratio
To improve image quality, what type of signal-to-noise ratio is desired?
High Signal-to-Noise Ratio (improves image quality)
What is the relationship between output power/gain and signal-to-noise ratio?
Direct Relationship
What is the most common method of overcoming noise? Why?
Increase output power/gain. That increases the signal-to-noise ration since noise is generally constant
In addition to controlling the strength of the transmitted sound wave, the pulser also determines the time between one voltage spike and the next, called what?
Pulse Repitition Period

(PRF is also determined, since PRP & PRF are reciprocals)
Changing the PRP/PRF (controlled by the pulser), directly affects what?
Depth of View
Identify the depth of imaging:
- short listening time
- short PRP
- higher PRF
Shallow Imaging
Identify the depth of imaging:
- longer listening time
- long PRP
- lower PRF
Deep Imaging
During transmission, this part receives the single electrical spike from the pulser and distributes it to the active elements of a phased array transducer
Beam Former
During transmission, the beam former adjusts electrical spike voltages in all types of transducers to prevent what?
Prevent Side/Gradient Lobes
(aka Apodization)
During reception, the beam former also varies the number of crystals used in order to control what?
Dynamic Aperture
What are three advantages of digital beam formers?
1) Software (easy updates)
2) Stable (no mechanical parts)
3) Versatile (can use transducers with a wide range of frequencies)
This component protects the delicate receiver components from the high voltage signals created during pulse creation. It also directs low voltage signals from the transducer to the appropriate processing components within the system.
Switch
A single crystal, the beam former/pulser electronics, and the wire connecting them is called what?
Channel
What are the five operations that must be performed during reception?
1. Amplification
2. Compensation
3. Compression
4. Demodulation
5. Reject
The first function of the receiver is to take each signal returning from the transducer and make them equally larger. What is this called?
Amplification
Does amplification improve signal-to-noise ratio? why or why not?
No, because both signal and noise are amplified equally
Does amplification affect the amount of patient exposure to ultrasound energy?
No, because only returning signals are amplified
AMPLIFICATION: units?
Decibels / dB
(the final signal leaving the receiver is compared to the initial signal strenth entering the receiver)
What is a synonym for amplification?
Receiver Gain
The process of improving signal quality before it is amplified is called what?
Pre-amplification
Where does pre-amplification occur within the ultrasound system?
As close to the crystals as possible, often within the transducer itself
What is the role of pre-amplification in processing signals from the transducer during reception?
Preventing electronic noise from contaminating the tiny (yet meaningful) electrical signals created by the transducer's crystals
The second function of the receiver is to correct for attenuation by creating an image uniformly bright from top to bottom. Signals are thus treated differently based on reflector depth. What is this called?
Compensation
What are synonyms for compensation?
TGC (Time Gain Compensation)
DGC (Depth Gain Compensation)
COMPENSATION: units?
Decibels / dB
An echo with three masses at 2cm, 4cm, and 6cm depths will appear progressively darker. How does compensation address this issue?
Compensation produces an image of uniform brightness from top to bottom
On a TGC curve, what does the X axis and Y axis represent?
X=TGC (amount of compensation)
Y=depth
At superficial depths, reflections undergo a small, constant amount of compensation. What is this called?
Near Gain
The depth at which compensation begins is called what?
Delay
Compensation corrects attenuation effects over path lengh. What is this area called?
Slope
The depth at which max compensation is used
Knee
The maximum amount of compensation that the receiver can provide is called what?
Far Gain
You are using a 4 MHz transducer and are given a new one to use. The new TGC slope is to the lower left of the old one. Is the new transducer frequency higher or lower than the old one?
The new transducer is less than 4 MHz since it is imaging deeper (y=depth)
You are using a 4 MHz transducer and are given a new one to use. The new TGC slope is to the upper right of the old one. Is the new transducer frequency higher or lower than the old one?
The new transducer is more than 4 MHz since it is imaging shallower (y=depth)
The third function of the reciever is to keep grayscale content within the range of detection of the human eye & electrical signal levels within the accuracy range of the system's electronics. Signals are thus treated differently based on strength. This is called what?
Compression
What are synonyms of compression?
Log Compression
Dynamic Range
COMPRESSION: units?
Decibels, dB
Why is log compression clinically important?
Most meaningful backscattered signals from biologic tisues are very weak and we must be able to see differences in these weak reflections
The fourth function of the receiver is a two-part process that changes the electrical signals within the receiver into a form for suitable for CRT display
Demodulation
Converting all the negative voltages into positive voltages is called what?
Rectification
Does demodulation have a visible effect on the image?
No, it simply modifies the signal so it can be fully displayed on a monitor
This, part of demodulation, eliminates the small bumps in the voltage signal
Smoothing
Enveloping
The fifth function of the receiver allows us to choose whether or not to display low-level (weak signal) grayscale information; strong signals remain unchanged
Reject
What are synonyms for reject?
Threshold
Suppression
What type of reflections does reject affect?
Low-level signals, regardless of location
Bright signals are not affected
Which receiver function is NOT adjustable by the sonographer?
Demodulation
As a result of damping, sound pulses used for imaging contain a wide range of frequencies. This is called what?
Wide Bandwidth
Using the high frequency portion of the pulse to create the shallow images, and the low frequency portion to create the deep images, is called what?
Dynamic Frequency Tuning
What is the difference between output gain and receiver gain?
Output Gain - improves signal-to-noise ratio, possibility of more bioeffects
Receiver Gain - does not (both are amplified equally), no risk of additional bioeffects
What does ALARA stand for?
As Low As Reasonably Achievable
What does ALARA principle mean?
Choose settings that will maximize image quality while minimizing patient ultrasound exposure
In harmony with the ALARA principle, what is the first thing to do if the image is too dark?
Try increasing receiver gain
In harmony with the ALARA principle, what is the first thing to do if the image is too bright?
Try decreasing output gain
Which gain (output or receiver) does the following:
- changes brightness of entire image
- alters signal-to-noise ratio
- alters patient exposure
- has bioeffect concerns
Output Power/Gain
Which gain (output or receiver) does the following:
- changes brightness of entire image
- does not affect signal-to-noise ratio
- does not change patient exposure
- no bioeffect concerns
Receiver Gain
Which of the following is best when only deep reflectors are displayed, not shallow ones?
A. adjust compensation
B. use higher frequency transducer
C. decrease output power
D. adjust the reject level
A
Which of the following is best when the image is saturated (too bright everywhere)?
A. decrease the amplification or gain
B. use a higher frequency transducer
C. decrease the output power
D. adjust the reject level
C
Which of the following is best when the image displays only bright reflectors but no weak reflectors throughout the image?
A. increase overall gain
B. use higher frequency transducer
C. increase the output power
D. adjust the reject level
D
Which of the following is best when the image displays only shallow reflectors but no deep reflectors?
A. adjust compensation
B. use a higher frequency transducer
C. increase the power output
D. adjust the reject level
A
All of the following are components of an ultrasound system except:
A. transducer
B. pulser
C. alternator
D. synchronizer
E. display
F. receiver
C
This type of pulser generates a constant electrical signal in the form of a sine wave:
A. pused wave, array
B. continuous wave
C. pulsed wave, single crystal
B
This type of pulser generates a single electrical spike, which ultimately creates a single sound pulse:
A. pulsed wave, phased array
B. continuous wave
C. pulsed wave, single crystal
C
This type of pulser generates numerous electrical spikes, which ultimately create a single sound pulse:
A. pulsed wave, phased array
B. continuous wave
C. pulsed wave, single crystal
A
The acoustic power of a sound beam emitted from a transducer is determined by the ___ of the pulser's crystal:
A. PRF
B. frequency
C. voltage
D rectification
C
All of the following are functions of the receiver except:
A. demodulation
B. amplification
C. suppression
D. attenuation
D
Place these functions in the order in which the system performs them:
A. reject
B. demodulation
C. amplification
D. compression
E. compensation
C, E, D, B, A
(hint: alphabetical order)
T/F: Amplification processes all reflected signals in a similar manner
T
T/F: Compensation processes all reflected signals in a similar manner
F