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Physics > 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 
_ measures the ability of a 
system to display two structures that are 
very close together when the structures 
are parallel to the sound beam’s 
main axis. (one in front of the other)
A

Axial resolution

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3
Q

_ answers the question: What is the minimum distance that two
structures positioned front-to-back can be
apart and still produce two distinct echoes on
an ultrasound image?

A

Axial resolution

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4
Q

Axial resolution is usually measured in

A

units of distance such as mm

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5
Q

Axial resolution is related to

A

SPL and pulse duration

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6
Q

_ pulse improve axial resolution

A

Shorter

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7
Q

Is axial resolution adjustable? Why/why not?

A

No, SPL for a transducer is fixed, you cannot change the axial resolution.

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8
Q

Typical value for axial resolution

A
  1. 1-1mm (for class)

0. 05-0.5mm (for SPI)

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9
Q

For axial resolution, _ numerical values indicated shorter pulses and _ image accuracy

A

Lower

Improve

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10
Q

Axial resolution AKA

A 
LARRD
Longitudinal
Axial
Range
Radial
Depth
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11
Q

Image quality is better when axial

resolution has a _ numerical value.

A

Lower

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12
Q

The mathematical description of axial

resolution is:

A

Axial resolution= SPL/2

Axial resolution= wavelength x # of cycles in pulse/2

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13
Q

Axial resolution is determined by

A

Pulse length

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14
Q

_ pulses yield improved axial resolution

A

Shorter

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15
Q

A short pulse is created in 2 ways:

A
  1. Less ringing

2. Higher frequency

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16
Q

A pulse is _ if there are few cycles in the

pulse.

A

Short

17
Q

Crystal dampening creates shorter pulses by

A

reducing the ringing of the crystal after it has

been excited by an electrical signal.

18
Q

A pulse is _ if each cycle in the pulse has a short

wavelength.

A

Short

19
Q

Shorter wavelengths are characteristic of

A

Higher frequency sound

20
Q

Pulses made of _ frequency cycles have better axial resolution

A

Higher

21
Q

Better axial resolution is associated with:

A 
Shorter SPL
Shorter pulse duration
Higher frequencies (shorter wavelength)
Fewer cycles per pulse (less ringing)
lower numerical values
22
Q 
Which is the best and worst axial resolution:
A. 12 MHz; 6 cycles/pulse
B. 12 MHz; 3 cycles/pulse
C. 4 MHz; 8 cycles/pulse
D. 4 MHz; 2 cycles/pulse
A

Best: B
Worst: C

23
Q 
The ability to distinctly identify two 
structures that are very close together 
when they are side by side, or 
perpendicular, to the sound beam’s 
main axis.
A

Lateral resolution

24
Q

_ resolution answers the question:
◦ What is the minimum distance that two structures
positioned side-by-side can be apart and still produce
two distinct echoes on an ultrasound image?

A

Lateral

25
Q

Lateral resolution is measured in units of

A

Distance

mm, cm

26
Q

Lateral resolution: _ numbers are preferable since they

indicate more accurate images

A

Smaller

27
Q

Lateral resolution is determined by

A

The width of the sound beam

28
Q

_ beams have better lateral resolution

A

Narrow

29
Q

Beam diameter varies with _; lateral resolution varies with

A

Depth

Depth

30
Q

Lateral resolution AKA

A 
LATABP
Lateral
Angular
Transverse
Azimuthal
Beam width variation
Point spread artifact
31
Q

Lateral Resolution is best at

A

the focus

where the beam is the narrowest.

32
Q

Lateral resolution=

A

beam diameter

33
Q

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

A

only one

34
Q

Lateral resolution is degraded/worse in

A

the far field

Physics (25 decks)

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