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CORE EXAM > Physics 2 - Module 1 & 3 > Flashcards

Physics 2 - Module 1 & 3 Flashcards

1
Q

Most common material used to for the transducer crystal

A

PZT

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2
Q

Occurs when a mechanical pressure deforms the crystal, changing the orientation of the dipoles, and produces a small electrical voltage

A

Piezoelectric effect (direct)

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3
Q

Occurs when an electrical voltage changes the orientation of the dipoles, causing the crystal to expand and contract

A

Reverse piezoelectric effect (indirect)

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4
Q

Which mode of vibration is most desirable?

A

Thickness

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5
Q

What is the Currie temperature for PZT?

A

350

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6
Q

The frequency at which the crystal likes to ring at. It is determined by the crystal material and thickness. AKA fundamental frequency

A

Resonant frequency

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7
Q

Frequency determined by the AC voltage sent to the crystal. If the voltage is altered, the crystal is forced to ring at a frequency different then the fundamental

A

Driving frequency

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8
Q

The frequency you are using to scan

A

Operating frequency

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9
Q

Two times the resonant frequency

A

2nd harmonic

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10
Q

How to determine the thickness of the crystal

A

=1/2 wavelength

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11
Q

How does crystal thickness affect frequency?

A

Thicker crystal = lower frequency

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12
Q

What is the purpose of the backing/damping material?

A

Reduce the SPL which will improve axial resolution. Absorb sound so that reflections don’t occur from behind the crystal.

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13
Q

What else does the damping material do that is not a good thing?

A

Reduces the amplitude therefore reducing sensitivity

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14
Q

As we increase the amount of damping material, what happens to the length of the pulse?

A

It becomes shorter

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15
Q

What is the Z value of the damping material?

A

Similar to the crystal for absorption to occur

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16
Q

How to have a probe that is capable of 2D and doppler? (2-3 cycles per pulse vs. minimum of 4)

A

Dynamic damping

17
Q

What does the matching layer do?

A

Has a Z value between that of the skin and the crystal to help sound get into the patient.

18
Q

What is the thickness of the matching layer?

A

1/4 wavelength

19
Q

How is bandwidth related to SPL and resolution?

A

The wider the bandwidth, the shorter the SPL and the better the resolution.
A wider bandwidth also means more frequencies to choose from

20
Q

Is low Q factor good or bad?

A

It is good.

21
Q

Using nanosecond time delays to change when the voltage excites the crystal.

A

phasing

22
Q

What is the purpose of phasing?

A

Controls the beam and allow for focusing and steering

23
Q

What is segmental sequencing?

A

Firing groups of crystals at a time so that information is not missed.

24
Q

How to correct for grating lobes?

A

Apodization

25
Q

The voltages to the crystals are gradually weakened from the inside out

A

Apodization

26
Q

Near fields have __________ beams due to interference between the wavelets and far fields have ________ beams.

A

Non-uniform, uniform

27
Q

Grating lobes are a result of what kind of vibration?

A

Length and width vibration resulting in crosstalk

28
Q

Equal to 2 NZL’s

A

Usable beam shape

29
Q

What happens to the NZL as the frequency or diameter of the crystal increases?

A

It also increases

30
Q

What happens to the angle of divergence in the far field if the frequency or diameter of the crystal increases?

A

It decreases

31
Q

Increasing the delays in transmit focusing does what to the focus?

A

Increases it

32
Q

Bringing received echoes into phase so that they don’t cancel each other out.

A

Dynamic receive focus

33
Q

What determines the width of the beam?

A

Aperture, frequency, distance from transducer face

CORE EXAM (6 decks)

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