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Flashcards in final pt 2 Deck (77):
1

Empirical approach

searches for a relationship between exposure and response

2

Contrast: shrinking and swelling

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

 

3

What is the primary investigative technique of epidemiology?

reviewing data from patients

4

What is the intensity most related to tissue heating?

thermal mechanism (TI)

5

Bioeffects study in nonliving things:

In vitro

 

6

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

(gray scale imaging)

7

The possibility of patient or technologist shock:

cracked transducer housing and frayed wires

8

When is it safe to perform an US?

when the benefits outweigh the risks

9

Electronic component used for gray scale imaging:

scan converters

10

Know all the preprocessing functions:

TGC

log compression(dB)

write magnification

persistence

spatial compounding

edge enhancement

fill-in interpolation

11

Know all the processing functions:

any change after freeze frame

black/white inversion

read magnification

contrast variation

3-D rendering

12

What function steers the scan lines in different directions?

sloped pattern in phased array transducer 

(spatial compounding?)

13

Advantages of PACS systems:

instant access to archived studies

no degradation of data

ability to electronically transmit images and reports to remote sites

14

Signal from the transducer to the receiver:

pulser-determines amp

beam former-firing patterns

15

Know the requirements for contrast agents:

safe

metabolically inert(metabolized throughout system, then removed)

long lasting

strong reflector of US

small enough to pass through capillaries

16

Harmonics vs fundamental frequencies

fundamental-initial freq of probe

harmonics-double the fundamental freq

17

Acceleration and deceleration of velocities from cardiac contraction:

pulsatile

18

Acceleration and deceleration of velocities from respiration:

phasic

19

Flow pattern with normal physiological states:

laminar

20

Reynolds number for turbulent flow:

> 2,000

21

What are the effects of a stenosis?

change in flow direction

increased velocity as vessel narrows

turbulence downstream from the stenosis

pressure gradient across the stenosis

loss of pulsatility

22

Know hydrostatic pressure at all locations:

Supine- all numbers are 0

ankle- 100mmHg

knee- 75mmHg

waist- 50mmHg

mid chest- 0mmHg

top of head- -30mmHg

23

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

coaptation

24

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

inspiration

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