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SON-111 Physics > Transducers and Beams > Flashcards

Transducers and Beams Flashcards

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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
Q

Lens

A

a piece of glass or other transparent substance with curved sides for concentrating or dispersing light rays

26
Q

Linear

A

arranged in or extending along a straight or nearly straight line

27
Q

Linear array

A
  • produce sound waves parrallel to each other and produces a rectangular image
  • elements arranged in a line
28
Q

Linear phased array

A

elements are still arranged in a line but the array is very small

29
Q

Linear sequenced array

A
  • 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
Q

Matching Layer

A
  • reduces reflections at transducer
  • tissue interface
  • also called impedance matching layer
  • usually 1/4 the wavelength of the US beam
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

area between the transducer and the focus

33
Q

Operating frequency

A
  • also called resonant frequency
  • transducer frequency depends on
    1. the thickness of the crystal
    2. speed of sound in the crystal
34
Q

phased array

A
  • also called linear phased, or electronic sector

- elements are still in a line but the array is very small

35
Q

Phased linear array

A
  • also called linear phased, or electronic sector

- elements are still in a line but the array is very small

36
Q

Piezoelectricity

A
  • when a mechanical force or pressure is applied to certain materials a voltage is created
37
Q

Probe

A

device that converts one from of energy into another

38
Q

Resolution

A

accuracy of an image

39
Q

Resonance Frequency

A
  • operating frequency of the transducer

- natural frequency of vibration determined by the physical parameters of the vibrating object

40
Q

Sector

A

Produces a fan like image that is narrow near the transducer and increase in width with deeper penetration

41
Q

Side lobes

A

Although the main ultrasound beam is central, multiple beams are projected out from the
transducer in a diverging manner (side lobes)

42
Q

Transducer

A

device that converts one from of energy into another

43
Q

Vector array

A

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

44
Q

Vector

A 
Size		May be small
Crystals		120-250
Image		Trapezoid
Steering		Electronic
Focusing	           Electronic

Damage Vertical line
signal dropout

45
Q

Convex Sequential

A 
Size		Long / Curved
Crystals		120-250
Image		Blunted Sector
Steering		Electronic
Focusing	Electronic

Damage Vertical line
signal dropout

46
Q

Linear Sequential

A 
Size		Long / Linear
Crystals		120-250
Image		Rectangle
Steering		Electronic
Focusing	Electronic
Damage		Vertical line
 				signal dropout
47
Q

Annular Phased

A 
Size			Small
Crystals			Circular / Bull’s eye
Image			Sector
Steering			Mechanical
Focusing		           Electronic from 
					multi focal zones

Damage Horizontal band
of signal dropout

48
Q

Linear Phased

A 
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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