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Sonography Exam review > cram cards > Flashcards

cram cards Flashcards

1
Q

acoustic variables include

A

pressure
density
distance (particles in motion)

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2
Q

sound frequency is determined by __________and is ____________ within given medium

A

the source, constant

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3
Q

the speed of sound in a given medium is determined by

A

stiffness and density

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4
Q

US machines assume the speed of sound in the human body to be

A

1540 m/sec

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5
Q

in addition to its Doppler capabilities, continuous wave US may also by used to produce images , T or F?

A

False

US must be pulsed to create images

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6
Q

Pulse repetition frequency (PRF) is limited by

A

imaging depth

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7
Q

Duty factor (DF) is the percentage of time that the US system is producing sound T or F?

A

True

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8
Q

which type of resolution is determined by the SPL (spatial pulse length)

A

axial resolution

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9
Q

the go return time to a reflector located 1cm from the transducer is

A

13 microseconds

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10
Q

as sound propagates through soft tissue, the lower the frequency, the greater the attenuation?

A

False

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11
Q

Which of the following are components of attenuation?

a. absorption
b. scattering
c. frequency
d. a and b
e. a, b, and c

A

d. attenuation is affected by frequency, but it is not one of its components

components are; absorption, scattering and reflection

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12
Q

T or F

echoes from specular reflectors are weaker, or lower in amplitude than echoes returning from Rayleigh scatteres?

A

False
Echoes from specular reflectors (irregular interfaces) are about 1000x stronger!
Rayleigh scattering: sound is scattered in all directions (red blood cells -particles smaller than wavelength)

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13
Q

attenuation coefficient for soft tissues is

A

.5dB/cm/MHz

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14
Q

T or F

adequate penetration of the US beam to the region of interest outweighs the desire for high resolution images

A

True

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15
Q

T or F

a transducer is a device that converts one form of energy to another

A

True

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16
Q

which of the following may be found in all transducers?

a. piezoelectric crystal
b. backing layer
c. scan converter
d. a and b
e. a, b, and c

A

d. a and b

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17
Q

the purpose of the backing material is to reduce

A

ringing

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18
Q

the optimal frequency at which a transducer operates is its resonance frequency, which is determined by :

a. backing layer
b. thickness of the crystal
c. matching layer

A

b.thickness of the crystal

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19
Q

for CONTINUOUS wave US the acoustic frequency is determined by the ______________ applied

A

electrical frequency of the exciting voltage applied by the machine to the crystal

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20
Q

For PULSED US the PRF is determined by _____ the frequency of the US is determined by __________

A

number of electrical pulses applied by the US machine to the crystal

thickness of the crystal and propagation speed of crystal

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21
Q

T or F

the range of frequencies contained in a pulsed US wave is called the transducer’s resonance frequencies

A

False

it is called the bandwith

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22
Q

T or F

for continuous wave, transducer frequency is determined primarily by the thickness of the crystal

A

False (true for pulsed US)

frequency is determined by the electrical frequency of voltage

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23
Q

T or F
generally, poorly dampened crystals produce long pulses with narrow frequency bandwidths, while highly dampened crystals produce short pulses with wide frequency bandwidths

A

True

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24
Q

A-mode display represents echoes as

A

spikes rising up from a time-distance baseline

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25
Q

T or F

B-mode provides the operator with a better temporal resolution than A-mode?

A

False

M-mode. takes a B-mode scan line and moves it across the display screen; it is the only mode that provides information regarding the position of reflectors with respect to time

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26
Q

which of the following transducer types are capable of electronic focusing and beam steering?

a. linear sequential array
b. linear phased array
c. annular array
d. all of the above

A

b.

-only array transducers can be focused electronically
- only phased array can be electronically steered
(may no longer hold true- Cross beam??/)

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27
Q

the effective beam forming surface of the transducer is known as the

a. beam profiler
b. ultrasonic fear
c. aperture
d. lens

A

c. aperture

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28
Q

the near zone is called?

a. Fraunhofer zone
b. Fresnel zone
c. transition point
d. none of the above

A

b. Fresnel zone

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29
Q

T or F
NFL (near field length increases as
1. transducer frequency increases
2. transducer diameter decreases

A
  1. T

2. F

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30
Q

lateral resolution is equal to

A

beam width

**axial resolution Far exceeds lateral resolution

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31
Q

the TGC is a component of which of the following

a. transmitter
b. receiver
c. scan converter
d. none of the above

A

b. receiver

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32
Q

the scan converter may also by referred to as

A

image memory or storage

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33
Q

Axial resolution is determined by

A

spatial pulse length

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34
Q

T or F

Preprocessing functions occur after the image is stored in memory and include all receiver functions

A

False

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35
Q

Doppler shift is defined as

A

reflected frequency minus incident frequency

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36
Q

Horizontal accuracy of the US system is dependent on the proper function of the system’s

A

position encoder

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37
Q

which factors contribute to possible bioeffects?

a. degree of power output
b. degree of sound beam focusing
c. degree of system gain
d. a and b

A

d, a and b

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38
Q

the highest beam intensity is

A

SPTP

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39
Q

which of the following imaging modalities exhibits the lowest SPTA acoustic output values?

a. color flow Doppler
b. M-mode
c. B-scan imaging
d. pulsed doppler

A

c. B- scan imaging

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40
Q

the primary reason the Doppler angle (cos0) is applied to the Doppler equation is :

A

to estimated flow velocity

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41
Q

wider beam aperture results in ________ (more/less) directional beam and (more/less) divergent beam

A

more directional
less divergent

more intense

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42
Q

the shape of the US beam is called the

A

beam profile

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43
Q

frequency is

A

of cycles per second

  • determined by the source
  • constant in given medium
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44
Q

period is

A

time required to complete one ocillation

reciprocal of frequency

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45
Q

Wavelength is

A

distance over which one cycle occurs

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46
Q

wave equation

A

Speed of sound
WL= ————————–
frequency

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47
Q

wavelength is __________ proportional to the speed of sound

A

directly

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48
Q

wavelength is _________ proportional to frequency

A

indirectly

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49
Q

Propagation speed is determined by medium’s stiffness; increased stiffness will _________ speed,

A

increase

50
Q

increased density will

A

decrease speed

51
Q

Amplitude is

A

max variation from the baseline

52
Q

Amplitude is determined by

A

determined by the source
(the voltage applied to transducer)

decreases as sound s travel through tissue
affects power and intensity

53
Q

intensity is

A

concentration of power in the US beam

  • determined by the source
  • decreases as sound travels through tissue
intensity= power/ beam area
I= watts/cm^2
54
Q

power is

A

proportional to amplitude squared

55
Q

wavelength is affected by source or medium

A

both

56
Q

near zone length=

A 
              6
57
Q

larger crystal diameter= _________________ near zone length

A

longer

58
Q

higher transmitter frequency = ____________ near zone length

A

longer

59
Q

focusing is defined as the process of _________ beam width to improve lateral resolution

A

reducing

focusing is mainly effective in the near zone

60
Q

what are the two methods of focusing a US beam?

A

-mechanical focusing
(external)
for higher frequencies; lenses ans mirrors
(internal)
shaping and curving crystal for 5MHz and lower

-electronic focusing

61
Q

beam focusing improves ___________ resolution and system __________

A

lateral

sensitivity

62
Q

spatial resolution is

A

axial and lateral

63
Q

axial resolution is determined by

A

SPL
axial res. =_______________
2

frequency is important, because wavelength varies with frequency

64
Q

lateral resolution results in ___________ echoes being detected, it is equal to _______________

A

separate

beam width

65
Q

which is better axial or lateral resolution?

A

axial resolution is better at all frequencies

66
Q

Doppler effect is a

A

change in sound frequency, because of motion between sound source and receiver. Positive (moving towards) negative (moving away)

67
Q

Doppler: Flow towards the transducer has an ___________ frequency, flow away from the transducer has a ______ frequenct

A

increased

decreased

68
Q

Doppler shift frequencies fall into what range

A

-10 KHz to 10 KHz

69
Q

Doppler shift is

A

reflected frequency - incident frequency

70
Q

Doppler equation

A

Doppler shift = received frequency - source frequency

71
Q

in order to calculate blood cell velocity the Doppler __________must be known

A

angle

72
Q

the magnitude of the Doppler shift depends on its

A

angle

73
Q

clinically useful Doppler angles

A

30- 60 degrees

74
Q

Doppler angle = 0 (cos 1) = >

A

maximum Doppler shift occurs

75
Q

Doppler angle= 90 ( cos 0) =>

A

no detectable Doppler shift

76
Q

in order to determine the velocity of RBC, three bits of information need to be known

A

Speed of sound C
tramsmitted sound frequency
Doppler angle

77
Q

types of Doppler

A

continuous wave Doppler
pulsed wave Doppler
color flow Doppler
Power Doppler

78
Q

relationship of PRF to PRP?

A

reciprocals

79
Q

PRF definition

A 
# of US pulses generated by the transducer per second
  (4-10KHz)

controlled by pulser (sound source)

80
Q

what limits PRF?

A

image depth - go-return time

81
Q

PRP includes both the pulse duration and the

A

echo reception time

82
Q

PRF and PRP are controlled and influenced by

A

operator, sound source (not the medium)

83
Q

Duty factor is

A

% of time the US machine is producing a pulse

DF= pulse duration / PRP

84
Q

SPL determines what kind of resolution?

A

axial

85
Q

SPL is determined by what?

A

sound source and medium

is not adjustable

86
Q

SPL formula

A

wavelength x # of cycles in a pulse

87
Q

Range equation

reflector distance

A

1.54mm/us x go return time
________________________________
2

88
Q

to calculated the go return time to a reflector in 1cm distance formula

A

time (usec)= reflector distance (mm) / 0.77(mm/usec)

time= 13 usec to reflector and back

89
Q

attenuation is

A

decrease in amplitude and intensity

90
Q

units of attenuation

A

dB, always negative when referring to attenuation

91
Q

3 components of attenuation

A

absorption
scattering
reflection

the greater the frequency the greater the attenuation

92
Q

absorption is

A

dissipation of sound energy into other forms of energy , mainly heat

makes up 70% of attenuation coefficient

93
Q

doubling of frequency ________ the absorption

A

doubles

94
Q

Reflection occurs ar

A

interface

part of the energy is reflected, part of it is transmitted into the second medium

95
Q

Refraction is

A

bending or change in direction of the transmitted soiund wave at interface.
wavelength may change to accommodate new speed of sound

96
Q

Snell’s law

A

when sound strikes at oblique incidence;
if medium2 has a higher speed of sound than medium 1, then the angle of transmission is greater than the angle of incidence. and vice versa

97
Q

scattering

A

reflection of US wave at

  1. rough or irregular interfaces (diffuse scattering, or reflection)
  2. reflectors smaller than wavelength (Rayleigh scattering)
98
Q

attenuation coefficient

A

amount of attenuation per cm

unit; dB/cm

99
Q

attenuation coefficient in soft tissue is

A

0.5dB/cm/MHz or half the frequency

100
Q

attenuation formula

A

attenuation= path length x attenuation coefficient

attenuation increases with frequency and path length

101
Q

bandwidth

A

difference between highest and lowest frequency emitted by transducer

102
Q

SPL is _________ related to bandwidth

A

inversely

poorly dampened crystals have long pulse length and narrow bandwidth

103
Q

A-mode

A

-first form of echo display
-hardly used anymore (ophthalmic, , )
-series of spikes
y= strength (amplitude)
X= distance from transducer

104
Q

B-mode (brightness)

A
  • basis of all US today
  • strength of echo displayed as brightness on monitor

positioning encoder allows the creation of a 2D image (B scan)

105
Q

M mode

A

-the only mode that provides information of position with respect to time
-uses one B-mode scan line
Y= depth
X= time
- used in echocardiography

106
Q

Hugen’s principle

A

each particle on the surface of a transducer can be considered a small separate sound source

107
Q

US system components

A
  • transducer
  • transmitter (pulser)
  • receiver
  • detector
  • scan converter
  • display
108
Q

transmitter (pulser, sounder) is responsible for

A

exciting piezoelectric crystal

109
Q

receiver is responsible for _______echoes;

4 components

A

returning

MAIN PROFILER-amplification (system gain)
TGC- compensation
SIGNAL PROCESSOR- compression (compresses ans balances dynamic range)
VIDEO AMPLIFIER- demodulation (converts voltages to video signal)

110
Q

the imaging effect of changing the overall Gain control is the same as increasing the output gain by the same factor, but it

A

doesn’t have the increased exposure effect

111
Q

the typical dynamic range of signals sent to the scan converter is about

A

40dB (monitor; 20dB)

112
Q

scan converter is also called

A

image memory or storage

does not produce a visible image

113
Q

transducer array types

A

linear (rectangular images)
Convex (curved, trapezoid)
annular (ring) pie shaped

114
Q

power
typical power output?

in pulsed wave doppler mode?

A

20-100mW

up to 2,000mW

115
Q

US beam can be described in both (time and space)

A

Spatial -space

Temporal -time

116
Q

with a focused transducer, SP intensity is always _________ than in an unfocused transducer, why?

A

Higher because of a small beam area

117
Q

Temporal average intensity is greatly affected by

A

PRF

if PRF increases DF increases and TA will ve higher

118
Q

highest intensity

A

SPTP

119
Q

Lowest intensity

A

SATA

120
Q

highest acoustic power during

A

color flow imaging

121
Q

AIUM stands for

A

American institute for ultrasound in medicine

Sonography Exam review (4 decks)

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