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Ultrasound Physics > Chapter 12 Two-Dimensional Imaging > Flashcards

Chapter 12 Two-Dimensional Imaging Flashcards

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1
Q

What transducer has the following characteristics:

  • contains a single, circular, disc-shaped active element
  • image shape is fan or sector-shaped
  • crystal moves with motor
  • mechanical steering
  • fixed focusing
  • damaged PZT = no image
A

Mechanical Transducers

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2
Q

Modern transducers are called ________ and contain multiple active elements.

A

Arrays

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3
Q

An array comprises a single slab of PZT cut into a collection of seperate pieces called _________.

A

elements

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4
Q

A combination of the active element, wire, and system electronics is called?

A

channel

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5
Q

Types of Array Transducers?

A

Linear
Annular
Convex

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6
Q

Active elements arranged in a straight line is what type of array transducer?

A

Linear

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7
Q

Elements arranged as circular rings with a common center is what type of array transducer?

A

Annular

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8
Q

Active elements arranged in a bowed or arched line. Also called curved, or curvilinear array transducer?

A

Convex

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9
Q

What transducer has the following characteristics:

  • narrow rectangle elements
  • 100 to 300 active elements on face
  • fan or sector-shaped image created
  • no moving parts
  • steered and focused with phasing
  • electronic focusing
  • damaged PZT = steering or focusing is off
A

Linear Phased Array

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10
Q

What always means “adjustable” or “multi-focus”?

A

Phased Array

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11
Q

How many elements are excited in a phased array probe during a single sound pulse?

A

All elements

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12
Q

The sound beam is directed downward when the spike line is _____________.

A

horizontal

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13
Q

The sound beam is steered is the spike line has a ________.

A

slope

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14
Q

The time differences between many wavelets create a single unified sound beam is also called?

A

phase delays

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15
Q

__________ ________ is achieved electronically without any moving parts in the transducer.

A

Beam steering

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16
Q

The electronics within the ultrasound system that create electrical patterns is called?

A

beam former

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17
Q

When a spike pattern is a straight line, an __________ sound beam is created?

A

unfocused

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18
Q

What happens when the spike line is curved?

A

The sound beam is focused

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19
Q

To determine beam steering, draw a line from the far ______ to the far _____ spike. The direction of steering is ___________ to this line.

A

left to right

perpendicular

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20
Q

What happens when the spike curve is curved outward or in a D-shape?

A

Defocused sound beam, has no application in diagnostic imaging.

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21
Q

Slope = _________

A

Steering

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22
Q

Curvature = ___________

A

Transmit focusing

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23
Q

In multifocusing three beams are created, what will the pattern with the greatest curvature create, and the pattern with the least curve?

A

Greatest curvature = shallowest focus

Least curvature = deepest focus

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24
Q

As the transducer listens for reflections, what happens to the delay patterns during receive-focusing?

A

Change continuously

25
Q

Can the sonographer control the dynamic receve focusing?

A

NO, the system does it automatically

26
Q

With dynamic receive focusing, focusing may also occur during…?

A

Reception

27
Q

How do you determine if the beam is focused?

A

if the spike line is curved

28
Q

How do you determine if the beam is steered?

A

if the spike line has a slope

29
Q

What transducer has the following characteristics:

  • Disc-shaped elements
  • multiple rings with common center
  • Image shape is sector
  • multiple transmit focal zones
  • mechanical steering
  • electronic focusing
  • damaged PZT = portion of image lost horizontal
A

Annular Phased Arrays

30
Q

What transducer has the following characteristics:

  • large acoustic footprint
  • rectangle elements
  • 120 to 250 rectangular-shaped strips of PZT
  • image shape is rectangle
  • electronic steering
  • electronic focusing
  • damaged PZT = portion of image lost where crystal is out
A

Linear Sequential Array

31
Q

With linear sequential arrays, Electronic transmit focusing is achieved with a _________ excitation pattern of the active element.

A

curved

32
Q

___________ ____________ is achieved dynamically by introducing electrical delays in the signals returning from the transducer.

A

Receive focusing

33
Q

Can linear sequential array transducers steer sound beams electronically?

A

Yes, creating a parallelogram shaped image instead of rectangle shape.

34
Q

What transducer has the following characteristics:

  • array has bowed or curved shape
  • 120 to 250 rectangle pzt
  • image shape is blunted sector
  • some but not all crystals fired simultaneously
  • focused electronically
  • damaged PZT = one section of pzt out, same section of picture out
A

Convex, Curved, or Curvilinear Array transducers

35
Q

What transducer has the following characteristics:

  • rectangle shaped elements
  • 120 to 250 pzt
  • electronic steering and focusing
  • image shape is trapezoidal
  • damaged PZT = poor steering and focusing
A

Vector Arrays

36
Q

A __________ array is a combination of linear sequential and linear phased array technologies.

A

Vector

37
Q

Technology where sloped phase delay patterns can electronically steer the sound beams in different directions is called?

A

vector or virtual sector

38
Q

What is the synonym for slice thickness?

A

Elevational Resolution

39
Q

Elevational Resolution depends on?

A

Transducer style

40
Q

Elevational Resolution is created by?

A

structures that lie above or beneath the image plane

41
Q

What shape of active element creates the thinnest ultrasound slices and the best elevational resolution?

A

Disc-shaped crystals

42
Q

What transducers have the best elevational resolution?

A

Mechanical and annular phased array

43
Q

The elevational resolution is identical to the ________ ___________ with disc-shaped active elements.

A

lateral resolution

44
Q

What determines elevational resolution is phased array, linear array, and convex array transducers?

A

These array probes have rectangular-shaped active elements placed side by side. With phasing, the beam is focused or narrowed only side to side in the imaging plane, but not above and below. This narrowing improves lateral resolution but does not affect slice thickness.

45
Q

What newer types of transducers have improved slice thickness?

A

1 1/2-D Array transducers

46
Q

What is 4-D?

A

Real time 3-D imaging

47
Q

__________ creates an image from 3-D data acquired during the ultrasound exam. It provides an element of realism to the image.

A

Rendering

48
Q

Single element transducers create what kind of lobes?

A

Side lobes

49
Q

Side lobes are created more in the _____ field.

A

far

50
Q

Side lobes ________ lateral resolution.

A

degrade

51
Q

Grating lobes are created by?

A

Array transducers

52
Q

Grating lobes are created in the?

A

Near and far field

53
Q

Side lobes bring back ________ information

A

reflective

54
Q

Grating lobes are undesirable because?

A
  1. degrade lateral resolution
  2. reduce image quality
  3. create artifacts
55
Q

Modern transducers are designed to reduce the strength of side and grating lobes. How is this accomplished?

A

by a process called apodization, which is exciting crystals inner first and weakening the signal as it moves to the outer crystals

56
Q

What is subdicing?

A

it reduces grating lobes by grouping the crystals.

57
Q

A technique called _________ __________ can be used to make a sound beam narrow over a greater range of depths and thus optimize lateral resolution.

A

Dynamic aperture

58
Q

When the ultrasound system changes the number of crystals along the face of the probe, that is being used to transmit pulses ans receive reflections, is called?

A

Variable Aperture, or dynamic aperture

Ultrasound Physics (7 decks)

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