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Physics 2 > Chapter 14 > Flashcards

Chapter 14 Flashcards

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1
Q

what are the 2 major functions of the US system?

A

1) preparation and transmission of electrical signals to the transducer (creates the sound beam)
2) reception of electrical signals from the transducer, with subsequent processing into clinically meaningful images and sounds

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2
Q

what are the 6 major components of the US system?

A

transducer, pulser and beam former, receiver, display, storage, and major synchronizer

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3
Q

during transmission the ______ transforms electrical energy into acoustic energy, during reception it converts the returning acoustic energy into electrical energy

A

transducer

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4
Q

the ______ determines the amplitude, pulse repetition period, and pulse repetition frequency, while the ______ determines the firing delay patterns for phased array systems. together they create and control the electrical signals sent to the transducer that generate sound pulses

A

pulser, beam former

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5
Q

______ transforms the electrical signals from the transducer into a form suitable for display

A

receiver

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6
Q

______ presents precessed data, may be a flat screen monitor, a transparency, a spectral plot, or a variety of other formats

A

display

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7
Q

______ archives the US studies, typical devices include computer hard drives, CD, DVD, videotape, magneto-optical discs, paper printouts, photographs, and USB drives

A

storage

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8
Q

______ maintains and organizes the proper timing and interaction of the systems components

A

master synchronizer

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9
Q

the ______ creates electrical signals that excite the transducers PZT crystals and create sound beams, functions during transmission

A

pulser

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10
Q

what is the range of the magnitude of the pulsers electrical voltage spikes?

A

near 0 to approximately 100 volts (can be adjusted by the sonographer)

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11
Q

what happens when you change the pulser voltage? what happens when it is low compared to high?

A

modifies brightness of the entire image displayed on the systems screen
low voltage vibrates gently, and a week sound beam is transmitted into the body and image is dark
high voltage vibrates forcefully, and transmits stronger sound beams into the body and image is brighter

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12
Q

what are the terms used to describe pulser voltage?

A

output gain, acoustic power, pulser power, energy output, transmitter output, power, or gain (this term is vague and should be avoided)

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13
Q

______ pulser voltages are desirable because they decease transmitted acoustic energy and minimize patient exposure to ultrasonic energy and likelihood of bioeffects

A

lower

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14
Q

______ is loosely defined as a random and persistent disturbance that obscures or reducers a signal’s clarity, contaminates images with low-level, undesirable information

A

noise

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15
Q

______ is a comparison of the meaningful information (signal) in an image, compared to the amount of contamination (noise)

A

signal-to-noise

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16
Q

what happens when the signal-to-noise ratio is high or low?

A

high-the signal is much stronger than noise and the image is of high quality
low-the strength of the signal is closer to the strength of the noise, the image contains a larger amount of visible contamination, an has less diagnostic value

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17
Q

when transducer output is ______, noise is more likely to degrade the image, as the sonographer ______ output power, the signal-to-noise ratio does the same.

A

low, increases

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18
Q

______ output power is the most common way to improve the signal-to-noise ratio

A

increasing

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19
Q

the pulser determines the time between one voltage spike and the next, the ______

A

pulse repetition period (reciprocals to PRF) also determines the maximum imaging depth

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20
Q

when the PRP is short, the PRF is ______, and the system spends less time listening (superficial imaging)

A

high

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21
Q

when the PRP is long, the PRF is ______ and the system listens for a longer time (deeper imaging)

A

low

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22
Q

______ is a sophisticated electronic device that receives the pulser’s single electrical spike and distributes it to the numerous active elements of an array transducer

A

beam former

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23
Q

______ is when the beam former adjusts electrical spike voltage to reduce lobe artifacts

A

apodization

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24
Q

during ______, the beam former establishes the correct time delays used for dynamic receive focusing

A

reception

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25
Q

the beam former controls ______ by varying the number of PZT crystals used during both reception and transmission

A

dynamic aperture

26
Q

what is the technology that the beam former uses to produce signals in digital format called?

A

digital beam former

27
Q

what are the advantages of the digital beam former?

A

the system updates require only software programming and are more flexible, extremely stable, versatile (can use transducers with a wide range of frequencies)

28
Q

during pulse creation the voltage from the US system to the transducer are very ______, during reception the voltages from the transducer back to the US system are extremely ______

A

high, low

29
Q

the ______ protects the delicate receiver components from the powerful signals that are created for pulse transmission, it also directs the electrical signals from the transducer to the appropriate electronic and processing components within the US system

A

switch

30
Q

a ______ is made up of a single PZT element in the transducer, the electronics in the beam former/pulser, and the wire that connects them

A

channel

31
Q

what determines the number of elements in an array transducer that can be excited simultaneously?

A

the number of channels in the US system: most have between 32 to 256 channels

32
Q

the ______ prepares the information contained in the minuscule signals that return to the transducer for eventual display on the system’s monitor

A

receiver

33
Q

what 5 operations must be preformed for the system to function properly?

A

amplification, compensation, compression, demodulation, and reject

34
Q

in the ______ process, each electronic signal returning from the transducer is made larger (each signal undergoes an equal amount of this)

A

amplification (also known as receiver gain)

35
Q

why is amplification required?

A

because the electrical signals are to low to be displayed on the monitor

36
Q

what happens when the sonographer adjusts the receiver gain?

A

the entire image is made brighter or darker (receiver gain is affected identically by amplification)

37
Q

can amplification alone make an image uniform brightness from top to bottom?

A

no, it does not improve signal to noise ratio either

38
Q

what are the measurements and typical value of amplification?

A

decibels; from 60-100 decibels

39
Q

______ is the process of improving the quality of a signal before it is amplified

A

preamplification (occurs close to the PZT, often within the transducer)

40
Q

what is preamplification designed for?

A

prevent electronic noise from contaminating the tiny electrical signals created by the transducers active elements during reception

41
Q

______ is the process where the receiver corrects for attenuation, creates an image with uniform brightness from top to bottom

A

compensation (without it the images will get darker with deeper depth)

42
Q

what are the units for compensation?

A

decibels

43
Q

what are the synonyms for compensation?

A

TGC, depth gain compensation (DGC), and swept gain

44
Q

what is the order that the TGC goes in as it gets deeper?

A

near gain, delay, slope, knee, far gain

45
Q

______ keeps the electrical signal levels within the accuracy range of the systems electronics

A

(first) compression

46
Q

______ keeps an image’s gray scale content within the range of detection by the human eye

A

(second) compression

47
Q

humans can distinguish around ______ shades of gray, and compression allows us to visualize different tissues within these gray shades

A

20

48
Q

what are the synonyms for compression?

A

long compression or dynamic range

49
Q

what are the units for compression?

A

decibels

50
Q

______ compression is an adjustable compression where small differences in weak signals are displayed and seen as different gray shade levels (a wide range of strong signals are all displayed as bright white)

A

log

51
Q

why is log compression important?

A

most meaningful backscattered signals from biologic tissues are very weak and the sonographer must be able to see differences in these weak reflections

52
Q

______ is a two-part process that changes the electrical signals within the receiver into a form more suitable for display on a monitor (changes the form)

A

demodulation (only process not adjustable)

53
Q

______ converts all negative voltage into positive voltage, it corrects for, or eliminates, negative voltage

A

rectification

54
Q

______ (or enveloping) places a smooth line around the “bumps” and evens them out

A

smoothing

55
Q

______ allows the sonographer to control whether low-level gray scale information within the data will appear on the displayed image

A

reject (its desirable to display low-level reflections but noise should not appear)

56
Q

what are the synonyms for reject?

A

threshold or suppression

57
Q

as a result of damping, sound pulses used for imaging contain a wide range of frequencies and are described as ______ or ______

A

wide bandwidth or broadband

58
Q

systems with dynamic frequency tuning use only the high frequency part of the reflected pulses bandwidth to create the ______ of the image because higher frequency sound has superior axial resolution

A

superficial portion

59
Q

______ affects image brightness by altering the strength of the sound pulse that the transducer sends to the body

A

output power

60
Q

______ alters the strength of the voltage in the receiver that the transducer created during reception

A

receiver gain (also called amplification)

61
Q

patient exposure to sound energy is affected by alterations in ______ but not by changes in ______

A

output power, amplification

62
Q

the ______ principle states that when modification to either output power or receiver gain can improve the images diagnostic quality, the first and best choice is the one that will minimize the patients US exposer

A

ALARA

Physics 2 (11 decks)

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