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Spring: Physics > final pt 2 > Flashcards

final pt 2 Flashcards

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1
Q

Empirical approach

A

searches for a relationship between exposure and response

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2
Q

Contrast: shrinking and swelling

A

bubbles shrink when exposed to compression and they expand when exposed to rarefaction

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3
Q

What is the primary investigative technique of epidemiology?

A

reviewing data from patients

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4
Q

What is the intensity most related to tissue heating?

A

thermal mechanism (TI)

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5
Q

Bioeffects study in nonliving things:

A

In vitro

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6
Q

What type of transducers cause the least amount of temp elevation in tissues?

A

(gray scale imaging)

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7
Q

The possibility of patient or technologist shock:

A

cracked transducer housing and frayed wires

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8
Q

When is it safe to perform an US?

A

when the benefits outweigh the risks

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9
Q

Electronic component used for gray scale imaging:

A

scan converters

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10
Q

Know all the preprocessing functions:

A

TGC

log compression(dB)

write magnification

persistence

spatial compounding

edge enhancement

fill-in interpolation

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11
Q

Know all the processing functions:

A

any change after freeze frame

black/white inversion

read magnification

contrast variation

3-D rendering

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12
Q

What function steers the scan lines in different directions?

A

sloped pattern in phased array transducer

(spatial compounding?)

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13
Q

Advantages of PACS systems:

A

instant access to archived studies

no degradation of data

ability to electronically transmit images and reports to remote sites

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14
Q

Signal from the transducer to the receiver:

A

pulser-determines amp

beam former-firing patterns

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15
Q

Know the requirements for contrast agents:

A

safe

metabolically inert(metabolized throughout system, then removed)

long lasting

strong reflector of US

small enough to pass through capillaries

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16
Q

Harmonics vs fundamental frequencies

A

fundamental-initial freq of probe

harmonics-double the fundamental freq

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17
Q

Acceleration and deceleration of velocities from cardiac contraction:

A

pulsatile

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18
Q

Acceleration and deceleration of velocities from respiration:

A

phasic

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19
Q

Flow pattern with normal physiological states:

A

laminar

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20
Q

Reynolds number for turbulent flow:

A

> 2,000

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21
Q

What are the effects of a stenosis?

A

change in flow direction

increased velocity as vessel narrows

turbulence downstream from the stenosis

pressure gradient across the stenosis

loss of pulsatility

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22
Q

Know hydrostatic pressure at all locations:

A

Supine- all numbers are 0

ankle- 100mmHg

knee- 75mmHg

waist- 50mmHg

mid chest- 0mmHg

top of head- -30mmHg

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23
Q

What is it referred to when the vessel collapses (venous)?

A

coaptation

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24
Q

Venous flow in the leg decreases, what is the patient doing?

A

inspiration

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25
Q

What is the Doppler shift when source and receiver are moving apart?

A

negative Doppler shift

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26
Q

What is the typical range of Doppler shift?

A

20Hz to 20,000Hz (range of audible sound)

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27
Q

Phenomenon with high velocities appear negative:

A

aliasing

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28
Q

Five ways to eliminate aliasing:

A

adjust the scale to its maximum (increase Nyquist limit)

select a new ultrasonic view with a shallower sample volume (increases Nyquist limit)

select a lower freq transducer (decreases Doppler shift)

use baseline shift (aliasing remains but display is more appealing)

use continuous wave Doppler (never aliases, but range ambiguity)

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29
Q

Horizontal access of the Doppler spectrum:

A

time

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30
Q

What is Doppler shift inversely related to?

A

propagation speed

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31
Q

Basic Doppler system just identified a freq shift:

A

(Power Doppler?)

32
Q

Know traveling towards the transducer and away (Doppler shifts)

A

towards- positive (arteries)

away- negative (veins)

33
Q

Primary advantage of pulsed wave

A

range resolution (being able to select the exact location where velocities are measured)

34
Q

Primary advantage of continuous wave

A

ability to accurately measure very high velocities

35
Q

What is the limitation for color Doppler imaging?

A

no measurement of velocity or direction

lower frame rate

more time needed to acquire data

reduced frame rate

decreased temporal resolution

36
Q

What is the area of interrogation for Doppler?

A

sample volume or gate

37
Q

What method will have increased sensitivity to low flow states?

A

Power Doppler

(color Power Doppler?)

38
Q

Portions of the image that are brighter than surrounding tissues:

A

hyperechoic

39
Q

Structures without echoes

A

anechoic

40
Q

similar echo characteristics

A

isoechoic (homogeneous?)

41
Q

Know the cause for artifacts

A

violation of assumptions

equipment malfunction or poor design

the physics of ultrasound

operation error

42
Q

Which artifact has multiple equally spaced parallel lines?

A

reverbations

43
Q

Which artifact is unrelated to the US pulse?

A

refraction

(enhancement?)

44
Q

Which artifact produces an image with incorrect number of reflectors?

A

side lobe artifacts, grating lobe, refraction

45
Q

Two distinct reflectors, one is an artifact, one is deeper than the other:

A

mirror image

46
Q

What is the artifact if they are side by side?

A

side lobe, grating lobe, refraction

(lateral resolution?)

47
Q

Which artifact creates only one reflection from two reflectors?

A

Axial resolution

48
Q

What are lobes created by array transducers called?

A

grating lobes

49
Q

Refraction at the edge of circular structure:

A

edge shadow (shadowing by refraction)

50
Q

What is it called when there is too much gain in the focal zone?

A

focal enhancement

51
Q

Which artifact occurs when you see reflectors at incorrect depths?

A

speed error or range ambiguity

52
Q

a grainy appearance

A

speckle

53
Q

What artifact occurs when your PRF is too high?

A

range ambiguity

54
Q

What artifact is found only with Doppler?

A

crosstalk

55
Q

Know about tissue equivalent phantom:

A

similar to soft tissue

speed of sound

attenuation

scattering characteristics

echogenicity

56
Q

Know about informed consent:

A

autonomy

57
Q

Know about gold standard:

A

a perfect technique, for ex MRI or angiography, that we deem 100% accurate to which our US results are compared

(all tests confirm the same result: MRI, CT, Xray, US)

58
Q

Ability to position echoes in their correct position along a distance perpendicular to the sound

A

(lateral resolution?)

59
Q

Stratigically located pin cysts in masses, what kind of phantom?

A

tissue equivalent phantom

60
Q

Know the intensity imits for unfocused and focused transducers:

A

unfocused- 100mw/cm2

focused- 1w/cm2

61
Q

Know the appropriate way to introduce yourself to the patient:

A

first action when sonographer enters the room

state your name and what type of exam you are performing

62
Q

Use of more active elements to receive reflections with a greater time of flight:

A

dynamic apeture

63
Q

Lateral resolution improves with what?

A

multi-focusing

(narrower beam, smaller field of view)

64
Q

Know all about temporal resolution

A

depends on frame rate, “real time movie”, depth and # of pulses

65
Q

Know all about spatial resolution

A

more pixels= more detail ^ line density

66
Q

Know all about contrast resolution

A

more shades of gray= better contrast resolution

67
Q

Know how to calculate the time it takes to make a single image when given the frame rate

A

Tframe= number of pulses * PRP

68
Q

Imaging depth is 15cm, with 100 lines. The number of pulses making up the scan is what?

A

100

69
Q

Of the receiver functions, which one treats the signal differently due to depth of the reflector?

A

TGC (compensation)

70
Q

Output power vs receiver gain

A

output power:

changes brightness of entire image, alters signal-to-noise, alters patient exposure, bioeffect concerns, decrease this first if image is too bright

receiver gain:

changes brightness of entire image, does not affect signal-to-noise ratio, does not change patient exposure, no bioeffect concerns, increase this first if image is too dark

71
Q

Mechanical transducer

A

1 crystal

fan shape (secter)

entire image lost

focusing- fixed lens

steering- mechanical

72
Q

Linear sequential (switched)

transducer

A

120-250 crystals

rectangle shaped

drop out (drop down)

focusing-electronic: curved elements and external lens

steering- electronic: phasing

73
Q

Linear phased array transducer

A

200 crystals

sector shape

poor steering and focusing

focusing- electronic: curved elements and external lens

steering- electronic: phasing

74
Q

convex sequential transducer

A

over 200 crystals

blunted sector shape

drop out of image

focusing- electronic: curved elements and external lens

steering- electronic: phasing

75
Q

vector transducer

A

200 crystals

flat top sector (trapezoid)

poor steering and focusing

focusing- electronic: curved elements and external lens

steering- electronic: phasing

76
Q

3D/4D

A

over 200 crystals

rectangle shape/checkerboard shape

drop down

focusing- electronic: both in lateral and thickness

steering- electronic: phasing

77
Q

annular phased transducer

A

5 crystals- in concentric rings

sector shape

horizontal drop out

focusing- electronic: multiple zones

steering-mechanical: motor physically moves the ringed-element array

Spring: Physics (10 decks)

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