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Physics Vocabulary > Physics 111 Chapter 3 Transducers > Flashcards

Physics 111 Chapter 3 Transducers Flashcards

1
Q

Thinner elements operate at __________ frequencies

A

Higher

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2
Q

The beam diameter is ___________ the diameter of the transducer element at a distance of two near zone lengths

A

Equal to

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3
Q

Linear phased array transducer, the elements measure the width of about

A

One quarter the wavelength

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4
Q

Focusing of the sound beam is achieved within

A

The fresnel zone

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5
Q

Utilizing multiple focal zone simultaneously increases image detail resolution and degrades

A

Temporal resolution

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6
Q

What happens to the near zone length if the aperture decreases

A

Decreases

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7
Q

In the linear array transducer the pulses travel in

A

straight lines

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8
Q

What is the impedance of the matching layer

A

an intermediate value between the transducer element and tissue

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9
Q

The ability to display moving structures in real time is termed

A

Temporal resolution

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10
Q

What is the material of the transducer that reduces the number of cycles produced in a pulse

A

Backing or damping material

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11
Q

If the sector width is increased by a factor of 2, what happens to the frame rate?

A

Decreases by a factor of 2

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12
Q

The sonographer is most likely to miss something changing quickly in time when

A

Using five focal zones

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13
Q

What are the three aspects of imaging resolution?

A

Detail
Contrast
Temporal

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14
Q

What is the cause of poor elevation resolution?

A

Too large of a beam width in the elevation plane

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15
Q

Where should the focal zone be located for the best lateral resolution?

A

At or just deep to the reflectors to be resolved

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16
Q

What is elevation resolution?

A

The ability to accurately differentiate between two structures in the slice-thickness plane

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17
Q

How can radial resolution of a transducer be maximized?

A

By using the thickest possible damping layer during transducer contruction

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18
Q

What is the best angular resolution

A

At the natural focus

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19
Q

What are the major limiting factors of temporal resolution?

A

Depth
Sweep angle
Line density
Pulse repetition frequency

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20
Q

What is the main disadvantage of continuous (Pedof) transducers?

A

Depth ambiguity

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21
Q

What does the term phased excitation mean

A

The electrical impulse to each element in the crystal array is excited at a slightly different time, resulting in a summated wave that has a wave front with varied direction and focal depth

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22
Q

____________ transducers do not utilize electronic steering

A

Mechanical sector

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23
Q

What is the shape of the footprint produced by a curved sequential array transducer?

A

Smaller convex near field and larger convex far field

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24
Q

In a linear array transducer, what function utilizes electronic steering

A

Color doppler

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25
Which type transducer can produce a vector or trapezoid shaped image
Linear array
26
How does a linear sequential array transducer produce its characteristic image shape?
By sequencing
27
What is the effect of increasing the thickness of the damping material in transducer design?
It acts to decrease the spatial pulse length, increasing bandwidth, resulting in better axial resolution
28
What is considered a disadvantage of the damping material in a pulsed wave transducer?
Decreased sensitivity
29
What is the purpose of damping material in a pulsed wave transducer?
It decreases the spatial pulse length of the pulse, leading to improved axial resolution
30
What are two things that contribute to the efficient transmission of sound from the transducer into the patient
Matching layer Gel
31
What part of the transducer provides protection from electric shock and reduces the effects of electrical interference
Transducer housing
32
What is the formula for the quality factor
operating frequency/bandwidth
33
What is constructive interference?
It occurs when in phase waves meet; the amplitude of the two waves are added to form one large wave
34
What happens to the signal strength of an ultrasound wave during constructive interference?
It increases
35
What type of interference pattern will result in the resultant wave having an amplitude of 0?
Out of phase, destructive interference
36
How is the piezoelectric property instilled in a man-made crystal material?
The crystal is heated to 328 to 365 degrees C in the presence of a magnetic field and then cooled
37
Coupling medium is applied to the transducer-tissue boundary to
Increase transmission of the sound wave
38
Arrays are operated in two ways, called
Sequencing Phasing
39
The transducer element converts _________to ________ and vice versa
electricity; ultrasound
40
The transducer has an impedance ______ times that of tissue
20
41
The linear image consist of _________ scan lines
verticle
42
Another name for the Fresnel Zone is
The near zone
43
In a single-element transducer, additional beams not included in the ultrasound beam are called
side lobes
44
Lateral resolution is equal to
Beam width
45
The useful frequency range for most diagnostic applications is
2-20 MHz
46
Factors that determine axial resolution
number of cycles in the pulse and wavelength
47
What is the purpose of the matching layer?
Reduces reflection of ultrasound at the element
48
What principle states that some materials produce a voltage when deformed by an applied pressure
Piezoelectric principle
49
Electric ___________ applied to the transducer are converted to ultrasound
voltages
50
Sequenced, phased, and vector are types of
Operations
51
_____________ resolution relates more directly to transducers
Detail
52
The critical temperature an ultrasound transducer cannot exceed is called
the curie point
53
______________ is attached to the rear face of the transducer element
Damping
54
Ultrasound transducers operate according to
The piezoelectric principle
55
Shortening the pulses in diagnostic ultrasound broadens the
bandwidth
56
Which image format would be similar to that of convex array except that the footprint is smaller?
Vector
57
Partial - volume artifact is also called
section thickness artifact
58
The near zone length is determined by the size and the ____________ ___________ of the element
operating frequency
59
Intravascular imaging generally utilizes a frequency range
up to 50 MHz
60
Linear and convex are types of ___________ arrays
assembly
61
Increasing the transducer frequency _______________ the maximum imaging depth
decreases
62
The purpose of the coupling medium is to
facilitate passage of ultrasound into human tissue
63
Invasive transducers utilize ___________ wavelengths
smaller
64
Without compensation the ultrasound transducer would cause about __________ of the emitted intensity to be reflected at the skin boundary
80%
65
In the curved array, the pulses travel
out in different directions
66
Electronic scanning is performed by
array transducers
67
Phasing can
focus the beam improve the image quality steer the beam
68
The dimension perpendicular to the scan plane is called the
section thickness
69
Arrays have additional beams resulting from their multi-element structure called
Grating lobes
70
___________ is a combination of linear and phased array operations
Vector
71
With phasing, the reception beam is _________________ and dynamically ___________
steered; focused
72
If the aperture increases, the near zone length
increases
73
What is axial resolution
the minimum separation necessary to resolve reflectors along the scan line
74
The distance from the transducer to the center of the focal region is called the
focal length
75
What determines the beam width at the focus
Aperture, focal length, and wavelength
76
What is achieved within the Fresnel zone?
Focusing of the sound beam
77
Improvements in Principle 2 virtual beam forming include reduced section thickness, which improves_________________ ______________.
Elevational resolution
78
Continuous wave transducers have ____________ ___________ because energy is not lost to damping material
Higher efficiencies
79
Axial resolution is often normally __________________ than lateral resolution
better
80
Focusing in the section thickness plane reduces
section thickness artifact
81
Various formulations of ____________ ____________ ____________ are commonly used in modern day transducers
lead zirconate titanate
82
Beam width can be reduced by focusing to improve
lateral resolution

Physics Vocabulary (6 decks)

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