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Spring: Physics > final pt 2 > Flashcards

final pt 2 Flashcards

(77 cards)

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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
What is the Doppler shift when source and receiver are moving apart?
negative Doppler shift
26
What is the typical range of Doppler shift?
20Hz to 20,000Hz (range of audible sound)
27
Phenomenon with high velocities appear negative:
aliasing
28
Five ways to eliminate aliasing:
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)
29
Horizontal access of the Doppler spectrum:
time
30
What is Doppler shift inversely related to?
propagation speed
31
Basic Doppler system just identified a freq shift:
(Power Doppler?)
32
Know traveling towards the transducer and away (Doppler shifts)
towards- positive (arteries) away- negative (veins)
33
Primary advantage of pulsed wave
range resolution (being able to select the exact location where velocities are measured)
34
Primary advantage of continuous wave
ability to accurately measure very high velocities
35
What is the limitation for color Doppler imaging?
no measurement of velocity or direction lower frame rate more time needed to acquire data reduced frame rate decreased temporal resolution
36
What is the area of interrogation for Doppler?
sample volume or gate
37
What method will have increased sensitivity to low flow states?
Power Doppler (color Power Doppler?)
38
Portions of the image that are brighter than surrounding tissues:
hyperechoic
39
Structures without echoes
anechoic
40
similar echo characteristics
isoechoic (homogeneous?)
41
Know the cause for artifacts
violation of assumptions equipment malfunction or poor design the physics of ultrasound operation error
42
Which artifact has multiple equally spaced parallel lines?
reverbations
43
Which artifact is unrelated to the US pulse?
refraction (enhancement?)
44
Which artifact produces an image with incorrect number of reflectors?
side lobe artifacts, grating lobe, refraction
45
Two distinct reflectors, one is an artifact, one is deeper than the other:
mirror image
46
What is the artifact if they are side by side?
side lobe, grating lobe, refraction (lateral resolution?)
47
Which artifact creates only one reflection from two reflectors?
Axial resolution
48
What are lobes created by array transducers called?
grating lobes
49
Refraction at the edge of circular structure:
edge shadow (shadowing by refraction)
50
What is it called when there is too much gain in the focal zone?
focal enhancement
51
Which artifact occurs when you see reflectors at incorrect depths?
speed error or range ambiguity
52
a grainy appearance
speckle
53
What artifact occurs when your PRF is too high?
range ambiguity
54
What artifact is found only with Doppler?
crosstalk
55
Know about tissue equivalent phantom:
similar to soft tissue speed of sound attenuation scattering characteristics echogenicity
56
Know about informed consent:
autonomy
57
Know about gold standard:
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
Ability to position echoes in their correct position along a distance perpendicular to the sound
(lateral resolution?)
59
Stratigically located pin cysts in masses, what kind of phantom?
tissue equivalent phantom
60
Know the intensity imits for unfocused and focused transducers:
unfocused- 100mw/cm2 focused- 1w/cm2
61
Know the appropriate way to introduce yourself to the patient:
first action when sonographer enters the room state your name and what type of exam you are performing
62
Use of more active elements to receive reflections with a greater time of flight:
dynamic apeture
63
Lateral resolution improves with what?
multi-focusing (narrower beam, smaller field of view)
64
Know all about temporal resolution
depends on frame rate, "real time movie", depth and # of pulses
65
Know all about spatial resolution
more pixels= more detail ^ line density
66
Know all about contrast resolution
more shades of gray= better contrast resolution
67
Know how to calculate the time it takes to make a single image when given the frame rate
Tframe= number of pulses \* PRP
68
Imaging depth is 15cm, with 100 lines. The number of pulses making up the scan is what?
100
69
Of the receiver functions, which one treats the signal differently due to depth of the reflector?
TGC (compensation)
70
Output power vs receiver gain
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
Mechanical transducer
1 crystal fan shape (secter) entire image lost focusing- fixed lens steering- mechanical
72
Linear sequential (switched) transducer
120-250 crystals rectangle shaped drop out (drop down) focusing-electronic: curved elements and external lens steering- electronic: phasing
73
Linear phased array transducer
200 crystals sector shape poor steering and focusing focusing- electronic: curved elements and external lens steering- electronic: phasing
74
convex sequential transducer
over 200 crystals blunted sector shape drop out of image focusing- electronic: curved elements and external lens steering- electronic: phasing
75
vector transducer
200 crystals flat top sector (trapezoid) poor steering and focusing focusing- electronic: curved elements and external lens steering- electronic: phasing
76
3D/4D
over 200 crystals rectangle shape/checkerboard shape drop down focusing- electronic: both in lateral and thickness steering- electronic: phasing
77
annular phased transducer
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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