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Sonography > Ch. 10 physics: Axial and Lateral Resolution > Flashcards

Ch. 10 physics: Axial and Lateral Resolution Flashcards

1
Q

A systems ability to distinguish between two structures that are lying close together.

A

Resolution

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2
Q

The ability of a system to accurately display two very close structures that are parallel to the axis of the sound beam.

A

Axial Resolution

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3
Q

Represents 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

LARRD

A

Longitudinal

Axial

Range

Radial

Depth

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5
Q

Shorter pulses have __________ axial resolution

A

Improved

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6
Q

How are shorter pulses are created?

A

Less ringing

Higher frequency

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7
Q

Is the axial resolution adjustable or non adjustable?

A

Not adjustable
Pulse length is fixed

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8
Q

What is the clinical range of axial resolution?

A

0.1 - 1.0mm

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9
Q

The ability to separate structures parallel to the ultrasound beam.

A

Axial Resolution

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10
Q

Formula for axial resolution and spatial pulse length.

A

axial resolution (mm) = spatial pulse length (mm) / 2

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11
Q

formula for axial resolution and wavelength.

A

Axial resolution (mm) = wavelength (mm) x # cycles in pulse / 2

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12
Q

Formula for axial resolution in soft tissue.

A

Axial resolution (mm) = 0.77 x # cycles in pulse / frequency (MHz)

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13
Q

True or false:
A pulse is longer if there are fewer cycles in the pulse

A

false
the pulse is shorter

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14
Q

If a pulse is shorter with fewer cycles, this is known as…

A

Less ringing

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15
Q

With fewer cycles in the pulse length, axial resolution …..

A

improves

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16
Q

A pulse is short if each cycle in the pulse has a …..

A

Short wavelength

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17
Q

High frequency and having shorter wavelengths =

A

Better axial resolution

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18
Q

Better Axial Resolution is Associated with:

A

Shorter spatial pulse length

Shorter pulse duration

Higher Frequencies (shorter wavelengths)

Fewer cycles per pulse (less ringing)

Lower numerical values

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19
Q

With axial resolution, Wavelength = ½ the PZT thickness, which means ….

A

thinner crystals equal shorter wavelengths resulting in higher frequency

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20
Q

Thinner crystals means

A

Fast

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21
Q

Thicker crystals means

A

Slow

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22
Q

True or False:
Higher frequency is associated with shorter pulse length.

A

True

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23
Q

True or False:
Fewer pulses per cycle will improve axial resolution.

A

True

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24
Q

Which of the following choices would have the best axial resolution?

12 MHz, 2 cycles per pulse

6 MHz, 2 cycles per pulse

12 MHz, 4 cycles per pulse

6 MHz, 4 cycles per pulse

A

6 MHz, 2 cycles per pulse

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25
Q

The ability to distinctly identify two structures that are very close together when they are perpendicular to the sound beams main axis.

A

Lateral Resolution

26
Q

Lateral resolution is also known as LATA, which means….

A

Lateral

Angular

Transverse

Azimuthal resolution

27
Q

Lateral resolution is measured in …..

A

Distance (mm, cm)

28
Q

Lateral resolution is determined by

A

Beam width

29
Q

Lateral resolution changes with ______ due to _____

A

Depth
divergence of the sound beam

30
Q

When two side-by-side reflectors are closer together than the beam’s diameter, only ______ reflection is seen on the image

A

one

31
Q

For lateral resolution, image is accuracy is best at _________

A

the focus

32
Q

the beam in lateral resolution is the narrowest at ________

A

The focus

33
Q

The structures located closer together than the beams diameter at the depth they are located, appear as one structure instead of ________

A

two

34
Q

Higher frequencies improve both _______ and _____________

A

axial

Lateral resolution

35
Q

Axial is improved in the entire image with

A

shorter pulses

36
Q

Lateral is improved in the far field with

A

Less divergence

37
Q

Results in a narrower beam, improving lateral resolution

A

focusing the beam

38
Q

What are the types of focusing?

A

Fixed, Conventional, or Mechanical

39
Q

How do you focus externally?

A

with a lens

40
Q

How do you focus internally?

A

with a curved active element

41
Q

How is Phased array focused?

A

with the electronics of the ultrasound system

42
Q

Phased array is adjustable or not adjustable?

A

adjustable

43
Q

A fixed focusing technique where a lens is placed in front of the PZT

A

External focusing

44
Q

As the arc of the lens becomes more prominent in external focusing, ……

A

the degree of focusing increases and the beam narrows

45
Q

The PZT is curved, concentrating its energy and creating a narrow beam, improving the beams focus and is the most common form of fixed focusing used. Is this internal focusing or external focusing?

A

Internal focusing

46
Q

What type of focus is achieved through phased array transducers?

A

Electrical focusing

47
Q

What does phased array mean?

A

Adjustable or multiple focusing

48
Q

What kind of transducers use phased array?

A

Multi-element transducers only

49
Q

True or false:
Electronic focusing allows the sonographer the ability to alter the beams focus.

A

True

50
Q

How can the Sonographer alter the electronic focus?

A

By beam steering

51
Q

What are the 4 modifications a sound beam goes through to be electronically focused?

A

The beam diameter in the near field and the focal zone narrows

Near zone length is reduced

The beam diameter beyond the focal zone widens

Size of the focal zone is reduced

52
Q

Where is the lateral resolution better in the beam?

A

Where it is narrow

53
Q

If the transducer crystal diameter is 10 cm, what is the lateral resolution at the focus?

A

5cm
remember the lateral resolution = beam diameter

The beam diameter is ½ the crystal diameter at the focus.

54
Q

Which of the following transducers have the poorest axial resolution?

2.5 MHz and 2 cycles/pulse

3 MHz and 4 cycles/pulse

2.5 MHz and 4 cycles/pulse

3 MHz and 2 cycles/pulse

A

2.5 MHz and 4 cycles/pulse

55
Q

In soft tissue, a 4 cycle, 2MHz pulse has a pulse length equal to 6 mm. What is the axial resolution?

A

3 mm
the axial resolution = ½ the spatial pulse length

56
Q

A transducer with more cycles per pulse will have greater/lower axial resolution?

A

Lower

57
Q

Which of the following terms does not belong with the others?

Longitudinal

Range

Azimuthal

Radial

A

Range

58
Q

What is the most common form of fixed focusing?

A

internal

59
Q

What is electronic beam focusing called?

A

Phased

60
Q

Single crystal transducers are always (fixed/phased) focusing?

A

Fixed

Sonography (39 decks)

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