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Ultrasound Physics > 12 Pulsed Echo Instrumentation > Flashcards

12 Pulsed Echo Instrumentation Flashcards

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0
Q

Describe the ultrasound system.

A

The entire device that produces sound beams, retrieves the echoes and produces visual images and audio signals

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1
Q

What is the information processed by the ultrasound system?

A

Time of flight
Strength of reflection
Direction
Frequency (for Doppler)

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2
Q

List the six interconnected components of an ultrasound system.

A 
Master synchronizer
Transducer
Pulser
Receiver
Display
Storage
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3
Q

What does the master synchronizer do?

A

Communicates with all of the individual components of the ultrasound system
Organizes and times their functions, so as to operate as a single integrated system

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4
Q

What does a transducer do for an ultrasound system?

A

Converts electrical into acoustic energy during transmission

Converts returning acoustic into electrical energy during reception

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5
Q

What does a pulser do?

A

Controls the electrical signals sent to the active elements for sound pulse generation
Determines the pulse repetition period, PRF, and pulse amplitude
Creates the firing pattern for phased array systems, beam former

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6
Q

What does a receiver do for an ultrasound system?

A

The electronics associated with processing the electronic signal produced by the transducer during reception and producing a picture on a display device

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7
Q

What is the display device for an ultrasound system?

A

The device associated with the presentation of processed data for interpretation

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8
Q

What is the storage for an ultrasound system?

A

Any number of devices and media that are used to permanently archive the US data

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9
Q

What do the pulser signals depend upon?

A

System and transducer

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10
Q

What are the different pulser modes?

A

Continuous wave
Pulsed wave, single crystal
Pulses wave, arrays

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11
Q

What type of wave occurs with continuous wave pulser modes?

A

Constant electrical signal in the form of a sine wave

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12
Q

What does a pulsed wave, single crystal pulser mode create?

A

Short duration electrical spike, 1 electrical spike per US pulse

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13
Q

What does a pulsed wave, arrays pulser mode create?

A

Many elements fired for each ultrasound pulse

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14
Q

What is transducer output?

A

Output gain, acoustic power, pulser power, energy output, transmitter output

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15
Q

What is the effect upon the image if the transducer output is changed?

A

Affects brightness of the entire image

The strength of every pulse transmitted to the body changes

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16
Q

What is the signal-to-noise ratio?

A

Meaningful portion of the data versus inaccurate portion of the data

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17
Q

What is the signal-to-noise ratio when a high-quality image I s created?

A

High signal to noise ratio

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18
Q

What is the signal-to-noise ratio when an image is degraded?

A

Low signal-to-noise ratio

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19
Q

What is the overall function of the receiver?

A

Boosts the strength of the signals returning from the transducer, processes them and prepares them for display

20
Q

What is the order of the functions of a receiver?

A

Amplification, compensation, compression, demodulation, rejection

21
Q

What is the purpose of amplification?

A

Increases the strength of all electrical signals in the receiver prior to further processing

22
Q

Can the amplification be adjusted by the sonographer?

A

Yes

23
Q

What is the effect of amplification upon an image?

A

Every signal is treated identically, thus, amplification changes the brightness of the entire image

24
Q

What does a preamplifier do to the signal?

A

Alters the signal before it is amplified, often performed in the probe

25
Q

What is the purpose of compensation?

A

Used to create image of uniform brightness from top to bottom

26
Q

What is the effect of compensation upon the image?

A

Makes all echoes from similar reflectors appear identical regardless of their depth

27
Q

Can compensation be adjusted by the sonographer?

A

Yes

28
Q

How is TGC and frequency related?

A

More TGC is used with higher frequency because of more attenuation

29
Q

What will you adjust if you cannot see reflectors in the near field or far field on your image?

A

TGC

30
Q

What is the purpose of compression on an image?

A

Keeps signals within the operating range of the system’s electronics and the grayscale within the range of what the human eye can see
Decreases the dynamic range of the signals

31
Q

What is the effect of compression upon an image?

A

Changes the grayscale mapping

32
Q

Can compression be adjusted by the sonographer?

A

Yes

33
Q

How are decibels affected by compression?

A

They add or subtract

34
Q

What is the purpose of demodulation?

A

Changes the signal’s form to one more suitable for display

35
Q

Can demodulation be adjusted by the sonographer?

A

No, it is done automatically

36
Q

What are the 2 steps of demodulation?

A

Rectification – corrects for or eliminate negative voltages

Smoothing – putting an envelope around the bumps to even them out

37
Q

What is the purpose of rejection?

A

Displays low-level echoes only when they are clinically meaningful
Low-level noise is eliminated in images

38
Q

What is the effect of rejection upon an image?

A

Affects only low-level signals everywhere on the image, but does not affect bright echoes

40
Q

Can rejection be adjusted by the sonographer?

A

Yes

41
Q

What are contrast agents?

A

Micro-bubbles of gas entrapped in a shell

42
Q

What allows contrast agents to be seen?

A

Different acoustic fingerprint

Large impedance difference between contrast agents and biologic tissues and creates strong reflections

43
Q

What are requirements for contrast agents?

A 
Safe
Strong reflector of US
Long persistence
Small enough to pass through capillaries
Metabolically inert
44
Q

What adjustments alter brightness of the entire image?

A

Output power or Receiver gain

45
Q

What is output power?

A

Affects brightness by adjusting the strength of the sound waves sent to the body from the transducer and affects patient exposure

46
Q

What is degraded when the image is too bright from high output power?

A

Lateral and longitudinal resolution

47
Q

What is receiver gain?

A

Affects brightness by changing the amplification of the electronic signals after returning to the receiver

48
Q

What is ALARA?

A

As Low As Reasonably Achievable

Minimize patient exposure

Ultrasound Physics (20 decks)

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