8.PULSE ECHO INSTRUMENTATION Flashcards
1
Q
Name the components of an ultrasound system?
A
The components of an ultrasound system are transducer, pulsar, receiver, scan converter, display, and master synchronizer.
2
Q
What is the Master Synchronizer?
A
Answer: Master Synchronizer is a component of ultrasound machine which maintains and organizes the proper timing and interaction of all components of the ultrasound machine so that ultrasound system can operate as a single integrated system.
3
Q
What is an ultrasound transducer?
A
The ultrasound transducer is a part of ultrasound machine. It contains a piezoelectric material which converts electrical energy into acoustic energy during the transmission phase, and converts acoustic energy into electrical energy when the echoes return to the transducer after traveling in the body during reception phase.
4
Q
What is Channel?
A
Answer: A channel in ultrasound system consists of a single crystal, the beam former, pulsar electronics, and the wire connecting them.
5
Q
What is a receive channel?
A
Answer: Each active element in an ultrasound transducer is connected to an amplifier and processing chain. The amplifier and processing chain are collectively known as the receive channel. There are 256-512 active receive channels are present in ultrasound systems. The benefits of more receive channels in ultrasound systems is greater processing flexibility.
6
Q
What is Switch?
A
Answer: Switch in ultrasound system protects the delicate receiver components from the high voltage signals created during pulse creation.
It directs low voltage signals from the transducer to the appropriate processing components within the system.
7
Q
What is interpolation?
A
Answer: Fill in Interpolation is a technique in which made up pixels are used to fill the areas between the scan lines where there is no information available.
8
Q
What is frequency compounding?
A
Answer: Frequency compounding is the technique of imaging with multiple frequencies and averaging them out. Frequency Compounding improves contrast resolution and reduces speckle which improves the image
quality.
9
Q
What is Dynamic Frequency Tuning?
A
Answer: Dynamic frequency tuning is a technique in which high frequency portion of the ultrasound pulse is used to create images from the shallow depths, and the low frequency portion of the ultrasound pulse is used to create the images from the greater depths.
10
Q
All of the following are components of an ultrasound system except?
a. transducer
b. pulsar
c. alternator
d. synchronizer
e. display
f. receiver
A
Answer: c. alternator
Alternator is not the component of the ultrasound machine.
The components of an ultrasound system are transducer, pulsar, receiver, scan converter, display, and master synchronizer.
11
Q
What does the output power control?
A
Answer: Output power is the amount of voltage applied to the piezoelectric element to produce an ultrasound pulse. Output power controls the amplitude of the voltage that excites the piezoelectric crystals.
12
Q
What is the relationship between pulsar voltage and the returning echo-strength and increasing pulsar voltage will have what effect on the image?
A
Answer: There is a direct relationship between pulsar voltage and the returning echo strength. By increasing the pulsar voltage increases the strength of the returning echo signal and increases the brightness of the image.
13
Q
What is the range of pulsar output voltage which excites a piezoelectric crystal in the ultrasound transducer?
A
Answer: The strength of pulsar output voltage that excites the piezoelectric crystals ranges from 1-300 volts and lasts less than 1 microsecond.
14
Q
What is the range of input voltage signal to the receiver of an ultrasound system?
A
Answer: The signal produced by the transducer upon receiving the returned echoes and sent to the receiver of the ultrasound system is extremely small and is in the micro volt to milli volt range.
15
Q
What determines the strength or intensity of the ultrasound wave?
A
Answer:**The output power generated by pulsar determines the strength or intensity **of the ultrasound wave produced by the transducer The greater the strength of electrical signal from the pulsay that excites the piezoelectric crystal, the greater the intensity of the ultrasound wave produced
16
Q
Can the sonographer change the output power?
A
Answer: The sonographer can increase or decrease the strength of output power from the pulsar. The different names used for output power control are output gain; transmit output, acoustic power, pulsar power, and energy output.
17
Q
What two measurements are used to standardize the output gain?
A
Answer: Thermal index and mechanical index are the two measurements used to standardize the output gain.
18
Q
What does ALARA principle mean?
A
Answer: The ALARA stands for As Low As Reasonably Achievable and is related to the output power.
During the exam, the sonographer should use minimum possible output power to obtain the images. Sonographer should choose settings that will maximize image quality while minimizing patient exposure to high ultrasound
19
Q
Following ALARA principle, what is the fist thing to do it the
image is too dark?
A
Answer: Try increasing receiver gain first
If the image is too dark, first try to increase the receiver gain. In most of the cases, the image will become bright and will be able to see structures.
20
Q
Following the ALARA principle, what is the first thing to do if the image is too bright?
A
Answer: Try decreasing output gain
If the image is too bright, first try to decrease the output gain. Decreasing the output gain will decrease the risk of possible bioeffects.
21
Q
What is the difference between Output Gain and Receiver Gain?
A
Answer: Output Gain is the amount of voltage applied to the piezoelectric crystal to produce an ultrasound pulse. The strength of the ultrasound wave produced depends upon the strength of the voltage applied to excite the crystal. The stronger the voltage applied the stronger will be the ultrasound wave produced. Output gain improves the signal to noise ratio.
increasing the output gain increases the risk of potential bioeffects.
Receiver Gain increases the strength of the small electric voltages received from the transducer to a level suitable for further processing. In amplification process all electrical signals are amplified equally, that’s why amplification or receiver gain increases the brightness of the entire image There is no risk of bioeffects by increasing the receiver gain.
22
Q
What happens by changing the output power gain?
A
Answer: Changing output power gain does the following:
* changes brightness of entire image
* alters signal-to-noise ratio
* has bioeffect concerns
23
Q
What happens by changing the receiver gain?
A
Answer: Changing receiver gain does the following:
* changes brightness of entire image
* does not affect signal-to-noise ratio
-no bioeffect concerns
24
Q
What is a Pulsar?
A
Answer: Pulsar is a component of ultrasound machine which determines amplitude, pulse repetition period and pulse repetition frequency of ultrasound waves. The pulsar functions during transmission.
25
What are the functions performed by the pulsar?
Answer: The following are the functions performed by the Pulsar:
* generates the electrical signals which are applied to thepiezoelectric elements
* controls the timing of electrical signals
* controls the strength and amplitude of the electrical signal
* determines the pulse repetition period
* determines the pulse repetition frequency
26
What control does a sonographer use to modify pulsar voltage
Answer: The sonographer uses output gain control to change pulsar voltage The output gain control is **also known as power, output, transmitter output, acoustic power, pulsar power, and energy output.**
27
What is the relationship between pulsar voltage and the returning echo strength?
Answer: **There is a direct relationship between pulsar voltage and the returning echo strength**.
Increasing the pulsar voltage increases the strength of the returning echo signals and increases the brightness of the image.
Decreasing the pulsar voltage decreases the strength of the returning echo signal and decreases the brightness of the image.
28
How does the pulsar determines the pulse repetition period?
Answer: The pulsar determines the time between one voltage spike and the next which is called pulse repetition period.
**Timing the Next Pulse**:
**The pulsar delays the next voltage spike until all returning echoes from the first pulse are received**.
**This delay determines the PRP (the time interval between two pulses).**
29
What type of pulsar **generates a constant electrical signal** in the form of a sine wave?
Answer: **In continuous wave transducer**, the pulsar generates electrical signals continuously and produces continuous sound waves.
30
What type of pulsar generates a single electrical spike, which creates a single sound pulse?
Answer: In pulsed wave transducers, the pulsar generates a single electrical spike, which creates a single sound pulse.
31
What type of pulsar generates numerous electrical spikes which create a single sound pulse?
Answer: In phased array transducers, the pulsar generates numerous electrical spikes, which create a single sound pulse.
32
What is Beam Former?
Answer: Beam Former is a component of ultrasound machine. Beam Former receives the electrical voltages from the pulsar during transmission and distributes it to the active elements of a phased array transducer.
33
What are two important functions of the beam former?
Answer: Beam former creates the appropriate **phase delays and pulse sequencing** to **create the transmit beam** and also creates the appropriate **phase delays and pulse sequencing** to **create the receive beam.**
Beam former also determines the firing delay patterns in phased array transducers for steering and focusing of the ultrasound beam.
34
How does the beam former works during transmission?
Answer: During transmission, beam former receives the electrical voltage from the pulsar and distributes it to the active elements of a phased array transducer.
During transmission, the beam former. also adjusts electrical voltages to different PZT crystals to prevent side lobes and grating lobes. It is also called apodization.
35
How does the beam former works during reception?
Answer: During reception, the beam former creates time delays for dynamic receive focusing It also varies the number of crystals used and controls dynamic aperture.
36
What are the advantages of digital beam formers?
Answer: The advantages of digital beam former are:
* no mechanical parts needed
* it is software programming and can be updated easily
* it can be used with wide range of frequencies
37
What is Dynamic Aperture?
Answer: The beam former varies the number of crystals used in order to control Dynamic Aperture during reception.
38
What is Apodization?
Answer: During transmission the beam former adjusts electrical voltages in phased array transducers to prevent grating lobes and side lobes. This process is called Apodization.
39
What is Noise?
Answer: **Noise is low level signals that degrade the image.** Noise is random and persistent disturbance that obscures or reduces the clarity of a signal.
40
What is the most common method of overcoming noise?
Answer: **The noise can be reduced by increasing the output power**. The signal to noise ratio increases by increasing the output power. Increasing the output power also increases the risk of exposure to possible bioeffects.
41
What is Signal to Noise Ratio?
Answer: A ratio between original signal and the degraded signal is called signal to noise ratio.
**Signal to Noise Ratio is a comparison between the amount of meaningful information and contamination in an image.**
It is the amplitude of the signal divided by the amplitude of the noise.
42
To improve image quality, what type of signal-to-noise ratio is desired?
Answer: To improve image quality, high Signal-to-Noise Ratio is desired.
43
How signal to noise ratio can be improved?
Answer: The signal to noise ratio can be improved by:
* using a lower frequency transducer
* moving transmit focus deeper
* using a larger aperture transducer
* using a different imaging plane
* maneuvering to remove attenuators such as lungs and gas
* using an endocavity probe
44
What is the relationship between output power gain and signal to noise ratio?
Answer: There is a direct relationship between output power gain and signal to noise ratio. Increasing the output power increases the signal to noise ratio and is a common method of overcoming noise. High signal to noise ratio improves the image quality.
45
What is apparent SNR?
Answer: When the overall gain is increased, the signal and noise are amplified by the same amount, which gives the appearance of improved signal to noise ratio also called apparent SNR
46
What is noise floor?
Answer: Noise floor is the amplitude level below which the signals are not detected because of the presence of noise. **The lower the noise floor the smaller the signals that can be detected**
47
What is electronic noise?
Answer: The random signals caused by electric amplification of small returning echoes are called electronic noise. Electronic noise is caused by random excitations of electrons within the electronics.
48
What does electronic noise look like in Doppler spectrum, or 2D image?
Answer: The electronic noise looks like random white speckles with high receiver gain in Doppler spectrum, or 2D image.
49
50
What is electrical interference?
Answer: **Electrical interference occurs when the transducer receives energy from other electrical devices or electromagnetic waves such as radio transmission.**The electrical interference can be carried through the air or from the power supplying the system.
51
How does electrical interference look like in the image?
Answer: The electrical interference looks like a bright flashlight down the middle of an image or a barber pole flashing on the image.
52
How does electrical interference appear on spectral Doppler spectrum?
Answer: The electrical interference appears on spectral Doppler as bright white horizontal or zigzag lines in the spectrum called Doppler tones.
53
What is Coded Excitation?
Answer: **Coded excitation uses a series of pulses and gaps rather than a single pulse.** It is a sophisticated form of transmission in which the driving voltage pulses have intrapulse variations in amplitude, and frequency.
**The advantage of coded excitation is that it improves the signal to noise ratio which improves the image quality.**
What It Does:
✔ Uses a series of pulses & gaps instead of a single pulse.
✔ Pulses have changes in amplitude & frequency (like Morse code).
✔ Improves image quality by enhancing signal strength.
54
What is a Receiver?
Answer: Receiver is the electronic component of ultrasound machine **which processes the electrical signals received from the transducer during the reception phase.** The electronic signals produced by returning sound waves are weak.The receiver increases the strength of these weak electrical signals, processes them and transforms them into a suitable form for display as an ultrasound image.
**Receiver is also known as signal processor**.
55
What are the five functions performed by the receiver during reception phase?
Answer: The five functions performed by the receiver during reception phase are;
1. amplification
2. compensation
3. compression,
4. demodulation
5. reject
All these five functions of the Receiver should be performed in the **proper order** i.e. amplification, compensation, compression, demodulation, and rejection.
56
What are the five functions performed by the receiver during reception phase?
Answer: The five functions performed by the receiver during reception phase are **amplification, compensation, compression, demodulation, and reject.**
All these five functions of the Receiver should be performed in the proper order i.e. amplification, compensation, compression, demodulation, and rejection.
57
All of the following are functions of the receiver except.
* suppression
* attenuation
* demodulation
* amplification
Answer: b. attenuation
attenuation is not the function of the receiver.
58
Place these functions of the receiver in the order?
a) compensation
b) demodulation
c) compression
d) amplification
e) reject
Answer: d, a, c, b, e
The functions performed in the order are amplification, compensation, compression, demodulation and reject.
59
What is Amplification?
Answer: Amplification is the first function of the receiver. **The returning echo signals are very weak and produce very weak electrical signals.**
*Amplification increases the strength of these electrical signals* received in the transducer to a level suitable for further processing. All electrical signals are made larger equally in the amplification process. Amplification is also called **overall gain** or **receiver gain**
60
What is the effect of amplification on signal to noise ratio?
Answer: **The amplification does not affect the signal to noise ratio because** the returning echo signals and noise are amplified equally.
61
Does amplification improve signal to noise ratio?
Answer: **The amplification does not improve the signal to noise ratio.** Both returning echo signals and noise are amplified equally.
**The signal to noise ratio is improved by increasing the output power**
62
Does amplification increase the risk of patient exposure to ultrasound energy?
Answer: **Amplification does not increase the risk of patient exposure to ultrasound energy.** Only the returning echo signals are amplified in the receiver, therefore patient is not exposed to bioeffects of ultrasound energy.
63
What is the typical value for amplification of a signal received by the receiver?
Answer: The signals that first reach the receiver are extremely weak. The amplification of these signals by **receiver ranges from 50 to 100 decibels.**
This amplification prepares the signal for further processing by the receiver and other ultrasound system components.
64
Can a sonographer adjust the receiver gain?
Answer: **The sonographer can increase or decrease the receiver gain.** This determines the overall brightness of the image during an exam.
65
What is Pre-Amplification?
Answer: Pre amplification is the process of improving signal quality before it is amplified.
**Pre amplification prevents electronic noise from contaminating the small signals received by the transducer.** Pre amplification is **performed close to the crystal** within the transducer during reception.
66
An image on an ultrasound system displays echoes from structures in all regions very bright Which ultrasound machine control will help to decrease the overall brightness of the image?
Answer: Decrease the overall amplification or gain.
**When the amplification or overall gain is set too high the ultrasound system is not able to distinguish between large amplitude and low amplitude echoes and all structures are displayed too bright**. By decreasing the overall gain you
67
What is Compensation?
Answer: Compensation is the second function of the receiver. Its function is to compensate for the **loss of echo strength** caused by the depth of the reflector and create an image which is uniformly bright from top to bottom. **The signals are treated differently based on reflector depth.Compensation is also** called **Time Gain Compensation (TGC)**or **Depth Gain Compensation (DGC)**
The unit for compensation is Decibels (dB)
68
What is the effect of compensation on the image?
Answer: TGC compensates for attenuation. The purpose of compensation is to **produce images of uniform brightness from top to bottom or from near field to far field**. Compensation treats echoes differently, depending upon the depth from which they return.
69
Describe the process of compensation?
Answer: The process of adjusting for attenuation is called compensation.
The ultrasound waves become weaker as they travel deep in the body.
The sound waves reflected from the deeper regions of body are weak and have low intensity therefore, the echoes returning from greater depths have lower amplitude than those returning from shallow depths. This process is called attenuation. The process to compensate for the loss of echo strength caused by the depth of the reflector is called compensation.
**The amplitude of received weak echo signals is increased in the receiver which makes these signals suitable for further processing in ultrasound machine to create an image.**
70
What is the function of TGC control?
Answer: The time gain compensation (TGC, DGC) control adjusts for the attenuation of sound as it propagates through the body.
71
What control will you use when only deep reflectors are displayed, not shallow ones on the image?
a) adjust compensation
b) use higher frequency transducer
c) decrease output power
d) adjust the reject level
Answer: a. adjust compensation
**Increase the time gain compensation (TGC) in the shallower region.**
When the structures at shallower depths are nod displayed that means
TGC is set too low for that region. The time gain compensation (TGC) or depth gain compensation (DGC) adjusts the brightness of echoes reflected from structures at different depths. **Increasing the TGC gain in that area will make structures visible at shallower depths.**
72
What control will you use when only shallow reflectors are displayed but no deep reflectors on the image?
a) use a higher frequency transducer
b) increase the power output
c) adjust compensation
d) adjust the reject level
Answer: c. adjust compensation
Increase the time gain compensation (TGC) in the deeper region.
The echoes of structures located in deeper regions are not displayed due to attenuation of sound wave while it travels in the body. When the structures at greater depths are not displayed that means TGC is set too low for that region. Increasing the TGC gain in that area will make weak reflectors visible.
73
Q471. The echoes from three structures located at 2 cm, 4 cm, and 6 cm depths appear progressively darker. How does compensation will help to fix this problem?
Answer: Time Gain Compensation (TGC) will amplify weak and low intensity echoes returning from structures at 4 cm and 6 cm depths so that they can appear as bright as similar structures located at 2 cm depth.
Compensation produces an image of uniform brightness from top to bottom.
74
When performing an ultrasound exam why the sonographer needs to use the TGC?
Answer: TGC is needed to amplify weak and low intensity echoes returning from deeper structures so that they can appear as bright as similar structures located at more shallow depths.
75
When TGC is adjusted which component in the ultrasound
system implements the changes?
Answer: Receiver
When TGC is adjusted the receiver in the ultrasound system implements
the changes.
76
On a TGC curve, what does the X axis and Y axis represent?
X axis represents amount of compensation
Y axis represents depth
77
The reflections at superficial depths undergo a small amount of compensation. What is this called on TGC curve?
Answer: Near Gain
The ultrasound waves at superficial depths attenuate less and need small amount of compensation. On TGC curve this is called near gain.
78
On TGC curve the depth at which compensation begins is called what?
Answer: Delay
On TGC curve, the depth at which compensation begins is called delay.
This is the region of minimum amplification. and is associated with area close to the transducer. **The low frequency transducers are more likely to have longer delay in the TGC curve.** A long delay in TGC curve is consistent with less compensation in the area close to the transducer.
79
Transducer A has frequency of 5 MHz and transducer B has frequency of 2.5 MHz. Which transducer will have longer delay in TGC curve?
Answer: Transducer B will have longer delay in TGC curve.**The low frequency transducers are more likely to have longer delay in the TGC curve.** A long delayin TGC curveshows **lesscompensation**needed in the area close to the transducer.
80
As the ultrasound wave travels in the body, it becomes weaker. Compensation increases the strength of returning weak ultrasound waves. What is this area called on the TGC curve?
Answer: Slope
On TGC curve, the area where compensation corrects for attenuation is called slope.
81
The depth at which maximum compensation is used, what is this area called on TGC curve?
Answer: Knee
On TGC curve, the area where maximum compensation is used is called
knee.
82
The area where maximum amount of compensation is used is called what on TGC curve?
Answer: Far Gain
On TGC curve, the area where maximum amount of compensation is used is called far gain.
83
During an exam, sonographer is using a 5 MHz transducer and is given a new transducer to use. The new TGC slope is to the lower left of the old slope. The frequency of new transducer is higher or lower than the old one.
Answer: The frequency of new transducer is less than 5 MHz
By using a lower frequency transducer, the ultrasound beam undergoes less attenuation. Therefore, less TGC will be needed to compensate for the attenuation. On the diagram, the TGC curve will be shifted downward and to the left.
84
During an exam, sonographer is using a 5 MHz transducer and is given a new one to use. The new TGC slope is to the upper right of the old one. The frequency of new transducer is higher or lower than the old one.
Answer: The frequency of new transducer is more than 5 MHz
By using a higher frequency transducer, the ultrasound beam undergoes more attenuation. Therefore, more TGC will be used to compensate for attenuation. On the diagram, the TGC curve will be shifted upward and to the right.
85
In what region of the ultrasound beam TGC is most effective to improve image quality?
TGC is most effective in focal zone area of ultrasound beam in improving image quality. Compensation for attenuation in focal zone area will help to produce superior quality images with detailed information.
86
What does the far gain setting on a TGC curve represents?
Answer: The far gain setting on a TGC curve represents the maximum compensation that a reflected ultrasound wave undergoes during the compensation process.
87
What is Compression?
Answer: Compression is the third function of the receiver.
**Compression decreases the dynamic range **of the electrical signals by decreasing the **difference between the smallest and largest electrical voltages passing through the system**.Compression keeps electrical signals within the operating range of the ultrasound system electronics.
Compression is done without altering the relationships between the voltages. The largest electrical voltages stay largest, and smaller electrical voltages remain smallest. Electrical signals are treated differently based on strength.
Compression also changes the gray scale mapping and keeps gray scales within the range of what we can see. **Compression decreases the dynamic range of the signals and increases the image contrast.**
88
What is the function of compression?
Answer: The function of compression is to **keep electrical signal levels within the range of the electronics of the ultrasound system** and**keep grayscale content within the range of detection of the human eye.**
89
What is Dynamic Range?
Answer: **Dynamic Range is the ratio of the largest to the smallest signal strength** or amplitude of a component such as transducer, receiver, scan converter, or display. It is the ratio between the largest signal amplitudes and the smallest signal amplitudes processed by a device.
**The dynamic range of a signal decreases the more it is processed and is expressed in units of decibels.**
90
What are the different types of dynamic range?
Answer: The different types of dynamic range are input dynamic range, output dynamic range, display dynamic range, and gain dynamic range.
91
What is input dynamic range?
Answer: The ratio of the maximum input signal to the minimum input signal is called input dynamic range. Input dynamic range is the range of the signal amplitudes a system can receive and process without causing harmonic distortion.
92
What is output dynamic range?
Answer: The ratio of the maximum output signal to the minimum output signal is called output dynamic range.
93
What is the default dynamic range?
Answer: The input dynamic range is the default dynamic range.
94
Which component of the ultrasound system has the largest dynamic range?
Answer: Within different components of the ultrasound system, the amplifier has the largest dynamic range.
95
Which component of the ultrasound system has the lowest dynamic range?
Answer: Within different components of the ultrasound system, the display has the lowest dynamic range.
96
What does the**dynamic range of the receiver** of an ultrasound
system refers to?
Answer: **The dynamic range of the receiver** of an ultrasound instrument refers to**the range of echo signal amplitudes that can be processed without distortion.**
97
What is a bit?
Answer: A bit is the smallest amount of computer memory, A group of bits is assigned to each pixel to store the gray scale color for that pixel. The more bits per pixel, the more shades of gray.
98
How to calculate the number of shades of gray in a pixel?
Answer: The number of shades of gray in a pixel can be calculated by the following formula.
To calculate the number of shades of gray in a pixel, multiply 2 by as many times as there are bits in a pixel.
1 bit per pixel = 2 shades (white and black)
2 bits per pixel = 2 x 2 = 4 shades of gray
3 bits per pixel = 2 x 2 x 2 = 8 shades of gray
4 bits per pixel = 2 x 2 x 2 x 2 = 16 shades of gray
8 bits per pixel = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 shades of gray
99
What will result in **the greatest number of shades of gray** in a digital image display?
Answer: **Large pixels with many bits per pixel will result in the greatest number of shades of gray in a digital image display**.
The more bits per pixel the more shades of gray.
100
What is the largest number of shades of gray that can be stored with 4 bits in a pixel?
Answer: A maximum of 16 shades of grav can be stored with 4 bits in a pixel.
To calculate the number of shades of gray in a pixel, multiply 2 by as many times as there are bits in a pixel.
There are 4 bits in this pixel, therefore, multiply 2 by itself 4 times.
Shades of gray = 2 x 2 x 2 x 2 = 16 shades of gray
A pixel with 4 bits will have 16 shades of gray.
101
Two ultrasound systems are used in an ultrasound exam.
System A has been assigned 8 bits per pixel; the System B has been assigned 4 bits per pixel. Which ultrasound system will have the ability to display more shades of gray?
Answer: The ultrasound system A will have the ability to display more shades of gray.
**The more bits per pixel the more shades of gray**. The pixels with more bits per pixel will result in the greatest number of shades of gray in a digital image display.
102
What happens when number of bits assigned to a pixel is increased in an image?
Answer: As the number of bits assigned to a pixel are increased in a digital image, **the number of shades of gray that can be viewed in an image increase**.
103
Can the gray scale be changed by the sonographer?
Answer: True.
The gray scale can be changed by the sonographer.
**Compression changes the gray scale mapping**. Compression keeps electrical signals within the operating range of the ultrasound system electronics and the gray scale within the range of what we can see.
**Compression can be adjusted by sonographer therefore gray scale can be changed by the sonographer**.
104
What is Bistable?
Answer: A video display with the **ability to show only black and white colors** is called bistable.
105
What is Demodulation?
Answer: Demodulation is the process **which changes the shape of the electrical signal** from one form to another which is more suitable for display. Demodulation is the function of the receiver.
Demodulation is done in two steps. These steps are called **rectification**, and **smoothing**
106
Can a sonographer adjust the demodulation in an ultrasound machine?
Answer: Demodulation is the function of the receiver which is set by the manufacturer in the ultrasound machine and **cannot be changed by the sonographer.**
107
What is rectification?
Answer: Converting all the negative voltages into positive voltages is called rectification.
108
Does demodulation have a visible effect on the image?
Answer: **No. demodulation does not have a visible effect on the image**.
simply modifies the signal so it can be displayed on a monitor
109
What is smoothing or enveloping?
Answer: The smoothing or enveloping is a part of demodulation. It eliminates the small bumps in the electrical signals.
110
Which receiver function is not adjustable by the sonographer?
Answer: Demodulation
Demodulation is the function of the receiver which is set by the manufacturer in the ultrasound machine and cannot be changed by the sonographer.
111
What is Reject?
Answer: The process of **removing low amplitude signals** from further processing by an ultrasound system is called Reject.
Reject removes low level signals which can degrade the image regardless of the location. **Strong signals are not affected** and remain unchanged. The other names used for reject are **threshold** and **suppression**.
**The sonographer can adjust the reject level during the exam**.
112
What is the function of Rejection?
Answer: **Rejection suppresses low level noise signals produced by the body, transducer, cable, or system electronics**. It does not affect the strong or bright signals.
Rejection sets threshold below which signals will not be visible on the display.
113
What is the balance for reject?
Answer: The balance for reject is pushing the noise floor as low as possible while preserving the required **signal input dynamic range**.
114
An image on an ultrasound system, displays only echoes arising from bright reflectors at all depths. **Weak reflectors are not visible on the image anywhere**. Which ultrasound machine control adjustment will make **weak reflectors visible**?
Answer: **Lower the reject level**
The ultrasound system rejects all low-level echoes from the entire image when the reject level or **threshold is set too high**. Only strong reflections will be displayed on the image. By lowering the reject level or threshold the ultrasound system will process low level echoes which will appear on the image.
115
Which of the following is best when the **image displays only bright** reflectors but **no weak reflectors throughout the image**?
a) use higher frequency transducer
b) increase overall gain
C) adjust the reject level
d) increase the output power
Answer: c. adjusts the reject level
116
Name the three different kinds of video displays and monitors used with ultrasound machines?
Answer: CRT, LCD, and DLP are the three different kinds of video displays and monitors used with ultrasound machines.
CRT stands for Cathode Ray Tube which up until few years ago was the most common monitor used in ultrasound systems.
LCD stands for Liquid Crystal Display
DLP stands for Digital Light Processing Chips
117
How the charged particles emitted by the electron gun in cathode ray tube are steered?
Answer: The negatively charged particles emitted by the electron gun in cathode ray tube are steered by sending the charged particles through a time varying magnetic field so that they sweep across the front screen and produce an image.
118
How is an image produced in a CRT display?
Answer: The inner surface of a CRT monitor is coated with a phosphorous material that glows when struck by electrons. This allows producing the image on CRT monitor.
A color CRT monitor has three different phosphorous coatings on the screen. Each phosphorous coating produces different color when struck by the electrons and produces a color image.
119
What are the advantages of LCD monitors?
Answer: The advantages of LCD monitors are that they are much lighter and more flexible. The LCD monitors are also larger in size. The matte finish reduces glare.
120
What does NTSC stand for and what is the NTSC standard for black and white monitors?
Answer: The NTSC stands for the National Television Standards
Committee which sets US standards.
The NTSC standard for black and white interlaced monitors is 525 horizontal lines and 30 frames per second for.
Color was added to the NTSC standard. Adding color takes longer to create a frame which drops the frame rate to 29.97 Hz.
121
How many horizontal scan lines make up a picture on a standard television monitor in United States?
Answer: A standard television picture consists of 525 horizontal scan lines in United States. The electron beam is rapidly steered across the face of a CRT monitor from top to bottom and from left to right and paints an
image.
122
How is the data processed in the standard television for real time display?
Answer: An interlaced display is used in standard television in United States. The interlaced display consists of an odd field which consists of lines 1, 3, 5... And an even field which consists of lines 2, 4, 6 .... The image consists of one odd field and one even field which are painted on screen in order. A total of 30 frames are displayed in one second. Each frame consists of one odd field and one even field; therefore, 60 fields are displayed in one second.
123
What is an A-mode display?
Answer: **A-Mode is also called Amplitude Mode**. The returning echoes are presented as an upward deflection. The **upward** deflection is proportional to the **amplitude or strength** of the returning echo. The location of the **peak** represents reflector **depth and depends on the go-return time** of the ultrasound pulse.
**A-Mode is used in ophthalmology for measuring depth.**
124
What is a B-mode display?
Answer: B-Mode is also called Brightness Mode. The **returning echoes are presented as dots of varying brightness** on the line of travel of the transmitted ultrasound pulse. **The position of the dot on the display is related to the depth of the reflector.** The brightness of the dot is proportional to the strength of the returning echo.
**B-mode serves as the basis for gray scale imaging and is used to create two dimensional images.**
125
In B-mode display what does z-axis represents?
Answer: **Z-Axis represents the amplitude of returning echoes and is measured by echo strength**.
The brightness of the spot is proportional to the strength of the returning echo. The stronger the returning echo, the brighter the spot.
126
What is an M-mode display?
Answer: M-mode is also called motion mode. **M-Mode displays the one-dimensional** recording of the moving position of reflectors with respect to time.
In M-mode, the position of the **reflector is represented on x-axis** and the **time is represented on the Y-axis.**
127
What is a scan converter?
Answer: A scan converter is an electronic component of the ultrasound system.
The scan converter converts analog signals to digital signal, then store these digital signals in its memory. After storing in the memory, process and convert these digital signals again into analog signals to be displayed as an image on a display.
128
What is analog to digital conversion?
Answer: Analog to digital conversion is a process by which **analog signals are converted to digital signals**. During reception phase, the signals produced by the transducer are analog signals. The computer in ultrasound machine can process only digital signals; therefore, analog signals are first converted into digital signals. The analog to digital scan converter converts analog signals to digital signals.
129
What is digital to analog conversion?
Answer: Digital to analog conversion is the process by which **digital signals are converted into analog signals**. The image is stored in the digital memory as numbers. But these numbers cannot be viewed unless they are converted back to an image. The digital to analog converter converts-these stored numbers bäck to analog signals which can be displayed on the monitor.
130
Which component of the ultrasound system stores digital echo
signal information?
Answer: Scan converter
The function of scan converter is to convert analog signals to digital signals, then store these digital signals in its memory.
131
Which component of the ultrasound system contains the memory bank?
Answer: Scan converter
In ultrasound system the scan converter contains the memory bank. The role of scan converter is image storage and scan conversion.
132
In an analog scan converter, which component stores the image data?
Answer: dielectric matrix
Analog scan converter uses the panel called dielectric matrix to store image information. It divides picture into a 1000 x 1000 matrix. It stores image brightness values as electrical charges.
133
What is preprocessing?
Answer: The signal processing that occurs before the image data is stored in the scan converter is called preprocessing. **Preprocessing cannot be changed after the image is acquired.**
134
During ultrasound exam when does the preprocessing occurs?
Answer: Preprocessing is the manipulation of **the data before storage in the memory** by the receiver.
135
What are the different names of preprocessing functions?
Answer: **time gain compensation (TGC), write magnification**, log
Compression are the examples of preprocessing **Edge
enhancement, pixel interpolation, persistence, spatial compounding, panoramic imaging**, and 3-D are all preprocessing functions.
136
What is post processing?
Answer: Any changes made after the image data is stored in the scan converter, is called post processing. Post processing is done in scan converter.
137
During ultrasound exam when the postprocessing occurs?
Answer: Post processing is done after the image is stored in scan
A converter. Post processing is performed after the data is acquired.
138
What are the different names of postprocessing functions?
Answer: **Read magnification, freeze-frame, contrast variation**, and black and white inversion are the names of different postprocessing functions.
139
What are names of the post processing system controls which are user controlled?
Answer: **Compression, grayscale, dynamic range, post processing curves or maps**, and **contrast** are the names of the post processing system controls which are user controlled.
140
What is Write Magnification?
Answer: Write magnification is a preprocessing function of the receiver in which area of interest in the image is **enlarged before it is stored** in the pocial resoluiemory. The data originally in the scan converter, before zoom is
discarded. **The same numbers of pixels appear** in the original region of interest and the **zoomed image which increases the pixel density and image quality of the zoomed area.**
141
What is Read Magnification?
Answer: Read magnification is a postprocessing function and is **done after the image is stored in the memory**.
The data originally in the **scan same pixel
converter**, before zoom remains intact. **No new information is acquired**. On the screen, the **pixels in the zoomed area appear larger than those in the region of interest**. The same numbers of ultrasound pulses are used
to create the original region of interest and the zoomed image.
142
What allows for scrolling back in time, freezing data, and placing calipers?
Answer: Data storage in digital format in the memory allows for scrolling back in time, freezing data, and placing calipers.
143
What is a Pixel?
Answer: A Pixel is the smallest element of a picture. The more pixels in an image, the greater the detail will be in the image.
144
What improves it, number of pixels per inch are increased.
Answer: Spatial Resolution
Better spatial resolution is obtained with more pixels in the image matrix, regardless of whether the scan converter is digital or analog.
Spatial resolution is related to the quality or detail of the image. It is the ability of the system to distinguish closely spaced objects. The numbers of pixels per inch determine the detail that a digital picture can demonstrate. The more pixels per inch, the better is the spatial resolution. The fewer pixels per inch, the lesser the detail.
145
Two ultrasound systems are used to perform an ultrasound exam. System A has 1,000,000 pixels in the image. System B has 500,000 pixels in the image. Which ultrasound system has better ability to display more details in an image?
Answer: System A will have better ability to display more detail in an image which is called spatial resolution. The better spatial resolution is obtained with more pixels in the image matrix. System A has more pixels in the image than system B.
146
What does electronic noise look like in color Doppler?
Answer: The electronic noise looks like random color pixels where there is no flow in color Doppler.
