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SON-111 Physics > Transducers and Beams > Flashcards

Transducers and Beams Flashcards

1
Q

Aperture

A

size of the source

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2
Q

Apodization

A

technical term for changing the shape of an electrical signal

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3
Q

Array

A
  • an ordered arrangement

- the active elements are arranged in an array in the transducer

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4
Q

Axial

A
  • or anterior to posterior is one dimension
  • relating to an axis
  • along the axis of the ultrasound beam
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5
Q

Axial Resolution

A
  • The minimum distance 2 structures are separated from front to back or anterior to posterior, and still be distinguished as separate by the ultrasound machine
  • along the axis of the ultrasound beam
  • Perpendicular to scan plane width
  • Determines section thickness artifact
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6
Q

Beam

A

in pulsed ultrasound, a description of the width of the pulse as it travels away from the transducer

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7
Q

Composite

A
  • man made

- made up of various parts or elements

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8
Q

Convex Array

A

crystals are arranged in an arc

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9
Q

Crystal

A

main component of the transducer

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10
Q

Curie point

A
  • temperature at which the crystals must not be heated above
  • if heated above the Curie point they will loose their piezoelectric properties
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11
Q

Damping

A
  • shortens SPL and pulse duration
  • improves image quality
  • compare to covering a bell with your hand as it is ringing
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12
Q

Detail/Spatial Resolution

A

the machines ability to see and differentiate structures and represent them as anatomically correct on the image

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13
Q

Dynamic Focusing

A
  • improves accuracy of image

- causes the focus of the beam to become narrower

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14
Q

Element

A

-component used in the transducer (natural/man made) that vibrates and in turn transfers the sound wave to create the image

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15
Q

Elevational resolution

A

Perpendicular to the depth and beam scan direction

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16
Q

Far Zone/ Fraunhofer Zone

A
  • region that lies beyond the distance of one near zone length
  • place where the beam begins to diverge
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17
Q

Focal length

A

the distance between the center of a lens or curved mirror and its focus

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18
Q

Focal Region

A

the area of focus

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19
Q

Focal zone

A

area of highest, most uniform beam intensity

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20
Q

Focus

A
  • the center of interest or activity

- the anatomy of interest should lie in the focus

21
Q

Grating lobes

A
  • a result of substancial acoustic energy directed outward, but not along the main axis of the sound beam
  • most common with linear array transducer
22
Q

Lateral

A

or side to side is a second dimension

23
Q

Lateral/transverse resolution

A
  • min distance that 2 structures can be separated and still show 2 separate echos on the screen
  • perpendicular to beam path
24
Q

Lead Zirconate Titanate (PZT) or barium

A

element in transdcuer

25
Lens
a piece of glass or other transparent substance with curved sides for concentrating or dispersing light rays
26
Linear
arranged in or extending along a straight or nearly straight line
27
Linear array
- produce sound waves parrallel to each other and produces a rectangular image - elements arranged in a line
28
Linear phased array
elements are still arranged in a line but the array is very small
29
Linear sequenced array
- Multiple elements arranged in a line - Elements are fired in sequence - Image consists of parallel scan lines - Rectangular image shape - Conventional focusing - NO Beam Steering
30
Matching Layer
- reduces reflections at transducer - tissue interface - also called impedance matching layer - usually 1/4 the wavelength of the US beam
31
Natural focus
- 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
Near zone
area between the transducer and the focus
33
Operating frequency
- also called resonant frequency - transducer frequency depends on 1. the thickness of the crystal 2. speed of sound in the crystal
34
phased array
- also called linear phased, or electronic sector | - elements are still in a line but the array is very small
35
Phased linear array
- also called linear phased, or electronic sector | - elements are still in a line but the array is very small
36
Piezoelectricity
- when a mechanical force or pressure is applied to certain materials a voltage is created
37
Probe
device that converts one from of energy into another
38
Resolution
accuracy of an image
39
Resonance Frequency
- operating frequency of the transducer | - natural frequency of vibration determined by the physical parameters of the vibrating object
40
Sector
Produces a fan like image that is narrow near the transducer and increase in width with deeper penetration
41
Side lobes
Although the main ultrasound beam is central, multiple beams are projected out from the transducer in a diverging manner (side lobes)
42
Transducer
device that converts one from of energy into another
43
Vector array
Combination of phased array electronics and linear sequential array probes to provide electronic steering and multiple focal zones
44
Vector
``` Size May be small Crystals 120-250 Image Trapezoid Steering Electronic Focusing Electronic ``` Damage Vertical line signal dropout
45
Convex Sequential
``` Size Long / Curved Crystals 120-250 Image Blunted Sector Steering Electronic Focusing Electronic ``` Damage Vertical line signal dropout
46
Linear Sequential
``` Size Long / Linear Crystals 120-250 Image Rectangle Steering Electronic Focusing Electronic Damage Vertical line signal dropout ```
47
Annular Phased
``` Size Small Crystals Circular / Bull’s eye Image Sector Steering Mechanical Focusing Electronic from multi focal zones ``` Damage Horizontal band of signal dropout
48
Linear Phased
``` Size Small Crystals 100-300 Image Sector Steering Electronic Focusing Electronic Damage Bad Steering and focusing ```

SON-111 Physics (5 decks)

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