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SPI > Chapters 13-17 > Flashcards

Chapters 13-17 Flashcards

1
Q

What is harmonics?

A

multiples of the transducer frequency

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2
Q

Where are harmonics created?

A

In the tissues

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3
Q

What creates harmonics?

A

non-linear behavior

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4
Q

Where does sound move slightly faster?

A

in regions of compression (higher pressure)

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5
Q

where does sound travel slightly slower?

A

in regions of rarefraction (lower pressure)

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6
Q

what is the major disadvantage of pulse invertion imaging?

A

the frame rate is half that of fundamental imaging

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7
Q

What does pulse inversion do?

A

degrades temporal resolution while improving spatial resolution

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8
Q

What is brightness related to?

A

the brilliance of an image

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9
Q

What does contrast determine?

A

the range of brilliancies that are displayed (Bistable images are high contrast)

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10
Q

Analog (real world)

A

a variable attains a continuum of values

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11
Q

what is a pixel?

A

the smallest element of a digital picture

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12
Q

what does pixel density improve?

A

spatial or detail resolution

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13
Q

what is spatial resolution related to?

A

the number of lines per frame (more lines, better spatial resolution)

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14
Q

what do more bits per pixel give you?

A

more shades of gray and more contrast resolution

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15
Q

what is a byte?

A

a group of 8 bits

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16
Q

preprocessing

A

TGC, log compression, write magnification, fill-in interpolation, persistance, spatial compounding

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17
Q

how can write magnification improve temporal resolution?

A

if imaging is shallower

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18
Q

fill in interpolation improves what?

A

spatial or detail resolution

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19
Q

how is artifact created?

A

by the interference effects of scattered sounds, both constructive and destructive

20
Q

how are scan lines steered?

A

by the transducer in different directions or views

21
Q

dynamic apeture

A

optimizes lateral resolution @ all depths

22
Q

edge enhancement

A

increases the contrast @ a boundary; ideally suited to distinguish interfaces

23
Q

where does coded excitation take place

A

in the pulser

24
Q

rendering

A

creates an element of realism to a 3D or 4D image

25
Q

what is dynamic range?

A

the ratio of the largest to the smallest signal strength that each component processes, the number of choices

26
Q

PACS

A

Picture Archiving and Communication Systems

27
Q

DICOM

A

Digital Imaging and Communications in Medicine

28
Q

NAS

A

Network storage devices

29
Q

what are two types of laminar flow?

A

plug and parabolic, found in normal physiologic states

30
Q

turbulence

A

may be identified as spectral broadening

31
Q

units of viscosity

A

poise

32
Q

what causes increased blood viscosity?

A

increased hematocrit or hemoglobin

33
Q

what does anemia reduce?

A

viscosity because blood is thinner

34
Q

where does velocity change @?

A

@ a stenosis

35
Q

where in a stenosis is pressure lower?

A

@ the point of maximum narrowing

36
Q

what are the units of electrical resistance?

A

Ohms

37
Q

what are the resistance vessels in the circulation?

A

arterioles

38
Q

what does valsalva accomplish?

A

increases pressure in the thorax and reduces all venous flow

39
Q

what is a positive doppler shift?

A

when source and receiver are approaching each other, reflected frequency is higher than transmitted frequency

40
Q

Units of Doppler shift?

A

Hertz, cycles per second

41
Q

what are the typical values of Doppler shift?

A

20 Hz- 20KHz

42
Q

Doppler shift =

A

2 x reflector speed x incident frequency x cos (angle) /propagation speed

43
Q

what must be known in order to accurately determine velocity?

A

the angle between the directions of flow and the sound beam

44
Q

what does doppler measure?

A

velocity, not speed

45
Q

what does the magnitude of shift depend upon?

A

the cosine of the angle between the sound beam & the direction of motion

SPI (3 decks)

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