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ultrasound > oct 17 > Flashcards

oct 17 Flashcards

1
Q

converts one form of energy to another

A

transducer

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2
Q

convert electric energy into ultrasound energy, and vice versa

A

ultrasound transducers

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3
Q

to press

A

piezo

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4
Q

electron, organic plant resin that was used in early studies of electricity

A

amber

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5
Q

results in the production of a pressure when an applied voltage deforms these materials.

A

piezoelectricity

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6
Q

used commonly as materials in the production of modern ultrasound transducer elements

A

lead zirconate titanate

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7
Q

ceramics often are combined with a nonpiezoelectric polymer to create materials called

A

piezo-composite

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8
Q

take the form of disks.

A

single-element transducers

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9
Q

contain numerous elements that have a rectanguar shape

A

linear array transducers

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10
Q

refers to the piece of piezoelectric material that converts electricity to ultrasound, and vice versa

A

transducer element aka piezoelectric element

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11
Q

Elements, with their associated case and damping and matching materials, are called

A

transducer assembly
probe
scan head
or
transducer

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12
Q

produces a two- or three-cycle ultrasound pulse

A

single-cycle driving voltage

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13
Q

typically 5 to 30 cycles, are used for Doppler techniques

A

loner-driving voltages

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14
Q

preferred, or natural, frequency of operation for the element

A

operating frequency (sometimes called resonance frequency)

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15
Q

Operating frequency is determined by the following:

A
  • The propagation speed of the element material (ct).
  • The thickness (th) of the transducer element
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16
Q

Typical diagnostic ultrasound elements are ___mm thick and have propagation speeds of ___ mm/μs

A

0.2 to 1 mm, 4 to 6 mm/μs

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17
Q

higher frequency

A

better detail resolution

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18
Q

lower frequency

A

degradation in resolution

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19
Q

quicker, more convenient, and more cost-effective than changing of transducers

A

push-button frequency switching

20
Q

in which echoes of twice the frequency sent into the body are received to improve the image.

A

harmonic imaging

21
Q

mixture of metal powder and a plastic or epoxy resin, is attached to the rear face of the transducer elements to reduce the number of cycles in each pulse

A

Damping (also called backing) material

22
Q

equal to period multiplied by number of cycles in the pulse

A

pulse duration

23
Q

reduces pulse duration and spatial pulse length and improves resolution

A

damping

24
Q
  • reduces the time that the bell rings after the tap
  • also reduces the loudness of the ringing
A

rubber

25
Q

reduces the ultrasound amplitude and thus decreases the efficiency and sensitivity (ability to detect weak echoes) of the system (an undesired effect)

A

damping material

26
Q

composites and damping material ___ pulses and ____ resolution

A

shorten, improve

27
Q

facilitate the passage of ultrasound across the transducer-skin boundary

A

matching layer and coupling media

28
Q

applied to the skin before transducer contact. This eliminates the air layer and facilitates the passage of sound into and out of the tissue

A

coupling medium

29
Q
  • designed to enter the body via the vagina, rectum, esophagus, or a blood vessel (catheter mounted type)
  • allow the transducer to be placed closer to the anatomy of interest, thus avoiding intervening tissues and reducing the sound transmission path length
A

invasive transducers

30
Q

refers to the width of a pulse as it travels away from the transducer

A

beam

31
Q

The width in the scan plane determines the ____, whereas the width perpendicular to the scan plane determines the extent of the section thickness artifact.

A

lateral resolution

32
Q
  • additional beams
  • source of artifacts
A

side lobes

33
Q

region extending from the element to a distance of one near zone length is called the

A

near zone, near field, or Fresnel zone

34
Q
  • determined by the size and operating frequency of the element
A

Near-zone length (NZL; also called nearfield length)

35
Q

Near-zone length increases with increasing frequency or element size, which is also called

A

aperture

36
Q

The region that lies beyond a distance of one near-zone length is called

A

far zone, far field, Fraunhofer zone

37
Q

What is somewhat surprising but true is that even in the case of this flat, unfocused transducer element, there is some beam narrowing. This narrowing is sometimes called

A

natural focus

38
Q

size of a source of ultrasound

A

aperture

39
Q

distance from the transducer to the center of the focal region

A

focal length

40
Q

distance between equal beam widths that are some multiple (e.g., ×2) of the minimum value (at the focus)

A

focal zonelength aka depth of field in photography

41
Q

wave length decreases, frequency ____

A

increases

42
Q

thinner elements yield? higher or lower frequency

A

higher

43
Q

pulse duration is equal to

A

period multiplied by number of cycles in the pulse

44
Q

increase in frequency or in aperture
______ the near-zone length

A

increases

45
Q

At a sufficient distance from the transducer, an increase in frequency or transducer size can _____ the beam diameter

A

decrease

ultrasound (8 decks)

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