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Physics SON-111AB-2B1 > Transducers and Beams > Flashcards

Transducers and Beams Flashcards

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1
Q

Aperture

A

The size of a source of ultrasound

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2
Q

Apodization

A

The non-linear excitation of crystal elements

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3
Q

Axial Resolution

A

The ability of the system to accurately display 2 objects very close together that are parallel to the beams main axis

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4
Q

Array

A

Collection of active Elements in a transducer

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5
Q

Axial

A

Along the axis of the beam

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6
Q

Beam

A

description of the width of a pulse as it travels away from the transducer

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7
Q

Composite

A

Acoustic impedance of composite piezoelectric elements is closer to that of soft tissue, so matching is easier and more efficient with these transducers

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8
Q

Convex array

A

Crystals arranged in an arc; sector shape format

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9
Q

Crystal

A

piezoelectric element or active element

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10
Q

Curie point

A

Temperature point at which transducer crystals lose their piezoelectric properties

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11
Q

Damping

A
  • Placed behind the active element

- Reduces the “ringing” of the pulse

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12
Q

Detail resolution

A

Determined by the transducer

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13
Q

Dynamic focusing

A

focusing the beam by altering the electric stimulation of various transducer elements either singly or in groups

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14
Q

Element

A

A single piece of PZT has been cut into many small pieces

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15
Q

Elevational resolution

A

“Slice Thickness” Thickness of the sound beam

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16
Q

Far zone

A

“Fraunhofer Zone”

  • The part of the beam after the focus
  • Sound beam is Diverging
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17
Q

Focal length

A

distance from the transducer to the center of the focal region

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18
Q

Focal region

A

An area with multiple focal zones

19
Q

Focal zone

A

Area surrounding the Focal point where the best image is achieved

20
Q

Focus

A

Concentrates the sound energy into a narrower beam. The best image resolution is at the focus

21
Q

Grating lobes

A
  • “an artifact”
  • From an Array Transducer (Multiple Elements)
  • Weaker then the central beam
  • Can produce extra echoes on an image if they hit a strong reflector
  • A line of band of echoes in an anechoic structure
22
Q

Lateral

A

Scan plane width or beam diameter

23
Q

Lateral resolution

A

The ability of a system to accurately display 2 closely objects perpendicular to the beams main axis, also known as transverse resolution

24
Q

Lead zirconate titanate

A

PZT (most often used in diagnostic US transducers)

25
Q

Lens

A

Used to improve image resolution by reducing the beam width of the transducer

26
Q

Linear

A

Arranged in or extending along a straight or nearly straight line

27
Q

Linear array

A

“Sequential” or “Switched” array

28
Q

Linear phased array

A

Linear sequenced with phased focal control

29
Q

Linear sequenced array

A

Rectangular in shape with a fixed focus and no electrical steering

30
Q

Matching layer

A

Reduces the Impedance differences between the transducer

31
Q

Natural focus

A
  • Ultrasound beam from a flat aperture will get narrow and then spread out within and angle range
  • The depth where beam is most narrow is the natural focus of the aperture
32
Q

Near zone

A
  • “Fresnel’s Zone”
  • The area between the transducer and the focal point
  • The part where the sound beam is converging
33
Q

Operating frequency

A

Element thickness: the operating frequency of a transducer is such that thickness is equal to one half the wavelength in the transducer element material

34
Q

Phased array

A

flat arrangement of elements typically smaller footprint than linear probe, which produces a sector field of view

35
Q

Piezoelectricity

A

When voltage is applied to these materials, they change shape and vibrate

36
Q

Probe

A

an instrument that is used especially for examining parts of the body

37
Q

Resolution

A

Ability to image accurately

38
Q

Resonance frequency

A

The operating frequency of a transducer, also known as the natural frequency

39
Q

Sector

A

Curvilinear array transducers; The area between an arc and two radii of a circle

40
Q

Side lobes

A

A line of band of echoes in an anechoic structure “an artifact”

41
Q

Transducer

A

converts one form of energy to another

42
Q

Vector array

A

Combination of phased array electronics and linear sequential array probes to provide electronic steering and multiple focal zones

43
Q

Phased linear array

A

small surface area that touches skin (compact footprint, square shape about 1cm on each side); no moving parts and electronically steered

Physics SON-111AB-2B1 (5 decks)

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