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Physics 2 > Chapter 10 > Flashcards

Chapter 10 Flashcards

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1
Q

______ is the ability to create accurate images

A

resolution

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2
Q

______ describes one measure of the detail found in an image

A

axial resolution (measures in mm), it is also called longitudinal, range, radial, or depth resolution

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3
Q

axial resolution measures the ability of a system to display two structures that are very close together when the structures are ______ to the sound beams main axis

A

parallel

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4
Q

axial resolution is related to the ______

A

spatial pulse length (determined by both sound source and the media)

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5
Q

______ pulses improve axial resolution, and is also related to pulse duration

A

short

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6
Q

what is the typical values for axial resolution?

A

0.1 to 1 mm, lower numerical values indicate shorter pluses and improve image accuracy

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7
Q

to remember axial resolution synonyms use LARRD, which means

A

Longitudinal, Axial, Range, Radial, Depth

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8
Q

what is the equation for axial resolution?

A 
axial resolution (mm) = spatial pulse length (mm) / 2
In soft tissue it is 0.77 x # cycles in phase / frequency (MHz)
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9
Q

what are the two ways that short pulses are created?

A

less ringing and higher frequency

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10
Q

one way to reduce ringing is to ______ the crystals after it has been excited by an electrical signal from the system

A

dampen

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11
Q

if the pulse is short because there are few cycles in the pulse its known as _____

A

less ringing

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12
Q

is the pulse is short because each cycle in the pulse has a short wavelength its known as ______

A

higher frequency sound

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13
Q

what all is the axial resolution associated with?

A

shorter spatial pulse length, shorter pulse duration, higher frequencies, fewer cycles per pulse, and lower numerical value

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14
Q

______ is the ability to distinctly identify two structures that are vary close together when they are side by side or perpendicular to the sound beams main axis

A

lateral resolution (mm or cm)

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15
Q

what is the lateral resolution determined by?

A

width of the sound beam

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16
Q

______ beams have better resolution

A

narrower; beam diameter varies with depth and lateral resolution changes with depth

17
Q

to remember the synonyms for lateral resolution use LATA which means?

A

Lateral, Angular, Transverse, Azimuthal

18
Q

Lateral resolution is best at the _____, where the beam is narrowest

A

focus

19
Q

what is the equation for lateral resolution?

A

lateral resolution (mm) = beams diameter (mm)

20
Q

axial resolution is better that lateral resolution because ultrasound pulses are ______ than they are wide

A

shorter; thus the numerical value is less

21
Q

when two side-by-side reflectors are closer to each other than the width of the beam, only ______ reflection is observed on the image

A

one

22
Q

______ frequencies improve both lateral and axial resolutions

A

higher

23
Q

______ is improved in the entire image with higher frequency because shorter pulses are associated with high frequency sound.

A

axial resolution

24
Q

______ is improved by high frequency only in the far field because high frequency pulses diverge less in the far field

A

lateral resolution

25
Q

changes with depth, smallest diameter crystals are best in near field, largest diameter and highest frequency is best in far field

A

lateral resolution

26
Q

same at all depths, does not change, shortest pulses are best in far and near fields

A

axial resolution

27
Q

what are the three methods of focusing?

A

external focusing (with a lens), internal focusing (with a curved active element), and phased array focusing (with the electronics of the ultrasound system)

28
Q

______, also called conventional or mechanical focusing, includes both external and internal techniques

A

fixed focusing

29
Q

with external focusing a ______ is placed in front of the piezoelectric material

A

lens

30
Q

as the arc of the lens becomes more prominent, the degree of focusing ______ and the beam narrows in the focal zone

A

increases

31
Q

with internal focusing a ______ concentrates that sound energy into a narrower or tighter beam (most common form of fixed focusing)

A

curved piezoelectric crystal

32
Q

as the curvature of the PZT becomes more pronounced, the degree of focusing ______

A

increases

33
Q

______ means adjustable or multiple focusing

A

phased array

34
Q

in phases array transducers, the systems ______ focus the sound beam

A

electronics

35
Q

what is the effects of focusing the sound beam?

A

beam diameter in near field and focal zone is reduced, focal depth is shallower, beam diameter in the far zone increases, and focal zone is smaller

Physics 2 (11 decks)

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