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Physics Review Questions > Review Questions > Flashcards

Review Questions Flashcards

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1
Q

True or False?

The PRF and frequency are unrelated

A

True

PRF is determined by depth.
Frequency is determined by characteristics of Tx.

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2
Q

Typical value for DF%/Duty cylce?

A

.002 - .005

or .2% - .5%

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3
Q

What is the value of DF% in CW?

A

1.0 or 100%

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4
Q

What is the value of DF% in Pulsed US?

A

less than 100%

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5
Q

Decibel notation is a _____ between two numbers

a. difference
b. sum
c. product
d. ratio

A

d. ratio

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6
Q

Which of the following reports the RELATIVE strength of an US wave?

a. db
b. watts
c. W/cm2
d. pascals

A

a. dB

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7
Q

The factors that determine Attenuation?

A

pathlength and frequency of sound

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8
Q

Diffuse Reflection / Backscatter

A

Sounds reflects in many different directions.

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9
Q

What is the uniform dispersion of a sound wave in may different dir3ections after striking a very small particle?

A

Rayleigh Scattering

The redirection of an acoustic wave in many different directions as a result of striking a small particle.

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10
Q

Rayleigh scattering is related to

A

frequency ^4

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11
Q

As a pulse passes through ST, a certain amount of acoustic energy remains in the tissue as heat. What is this constituent called?

A

Absorption

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12
Q

The amount of attenuation per cm that a sound wave undergoes

A

Attenuation coefficient

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13
Q

T/F? Attenuation and PS are unrelated?

A

True.

Attenuation is WEAKENING of the beam as is travels, nothing to do with speed.

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14
Q

“Z” equation

A

Z (Rayls) = density (kg/cm3) x PS (m/s)

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15
Q

The range of impedance in ST?

A

1.5 - 2.5 million Rayls

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16
Q

Units of Intensity Transmission Coefficient?

A

no units. its a %

ITC%

17
Q

_________ cycles and ______ frequency

give the best AXIAL resolution

A

few cycles and high frequency

18
Q

How thick is the ACTIVE ELEMENT of a 3MHz pulsed wave transducer?

A

half the wavelength of the sound wave in the PZT

19
Q

The main purpose of the Tx’s case is

A

to protect the patient from shock

to protect the internal components of the Tx

20
Q

Which component of the Tx is made from a slab of Epoxy impregnated with Tungsten filaments

A

the Dampening material/ Backing material

21
Q

What is the thickness of the MATCHING LAYER of a 2MHz pulsed wave Tx

A

1/4 the Wavelength of the sound in the matching layer

22
Q

T/F The backing material helps decrease the PRP achieved at a given imaging depth.

A

False, the PRP is UNRELATED to backing material

PRP is determined by depth

23
Q

T/F The backing material helps to decreased the Duty cycle at a particular PRF

A

True

The backing material shortens the DF (talk time)

24
Q

T/F Backing material decreases the PD

A

True

25
Q

T/F The backing material decreases the Quality factor

A

True

26
Q

The SPL decreases with more backing material

A

True

27
Q

Backing material consequences:

A

decreases sensitivity, decreases QFactor and increases bandwidth

28
Q

Which properties of the PZT of a CW Tx result in high emitted acoustic wave frequency?

a. thin, high PS
b. thick, slow PS
c. think, slow PS
d. none of the above

A

d. none of the above

CW frequency is determined by ONLY the frequency of the electrical signal that excites the PZT.

29
Q

What helps determine the Frequency of the sound produced by the Tx of a CW US system?

A

The ultrasound system

30
Q

With PULSED wave imaging, what helps to establish the primary frequency of the acoustic energy discharged by the transducer?

a. PZT diameter
b. PZT thickness
c. dampening material
d. US system electronics

A

b. PZT thickness

and PS of PZT

31
Q

The best estimate of PS of a PZT?

  1. 2 mm/us
  2. 0 m/s
  3. 0 mm/us
  4. 0 km/sec
A

About 3 to 5 times greater than PS of ST so…
range typically 4-8 km/sec

ST if 1.54 mm/us

32
Q

Which properties of an imaging Tx result in the highest emitted frequency?

A

thin crystals, fast PS

33
Q

T/F In CW The higher the frequency of a sound wave, the shorter the length of the near zone?

A

FALSE

The higher the frequency, the deeper the focus

34
Q

T/F In CW, the greater the diameter of the PZT, the longer the near zone?

A

TRUE

35
Q

For a DISC SHAPED PZT crystal producing continuous sound, which design will create a beam with the shallowest focus?

A

smaller diameter and low frequency

36
Q

for a DISC SHAPED PZT crystal producing Continuous sound, which design will create the deepest focus?

A

large diameter, high frequency

Physics Review Questions (1 decks)

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