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Ambers Physics 1 > Pulsed Ultrasound > Flashcards

Pulsed Ultrasound Flashcards

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1
Q

Describe pulsed ultrasound

A
  • a master synchronizer sends and electronic signal to a pulse
  • the transducer must pause (listen) after transmitting
  • the crystal can not transmit and receive at the same time
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2
Q

In pulsed ultrasound the pulse can be generated in two ways describe these ways.

A

1- electrical output from generator is gated to apply rapidly alternating voltage to crystal

2- charged capacitor is discharged through crystal which is stimulates to vibrate at resonance frequency (not common)

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3
Q

What are the 5 wave parameters of pulsed sound

A 
Pulse duration
Spatial pulse length
Pulse repetition frequency
Pulse repetition period
Duty factor
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4
Q

The time it takes for one pulse to occur is called?

A

Pulse duration (PD)

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5
Q

What is the formula for PD?

A

PD = T times cycles in a pulse

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6
Q

What does the pulse duration NOT include and what are the units it is measured in?

A

PD does not include the dead time

Usually measured in microsecond (us)

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7
Q

If frequency was increased what would happen to the pulse?

A

The pulse would decrease, go down (it would get shorter)

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8
Q

The length of the pulse is called ?

A

SPL

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9
Q

What is the formula for SPL? And what is it usually measured in?

A

SPL = wavelength times cycles in a pulse

Typically measured in millimeters (mm)

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10
Q

Cycles in a pulse is also known as ?

A

Ring down

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11
Q

If frequency is increased what happens to the spatial pulse length?

A

Increasing frequency will decrease the wavelength which will result in the SPL being decreased as well

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12
Q

If frequency (wavelength) decreases the SPL, what else will decrease the SPL?

A

Decreasing the ring down (number of cycles in a pulse ) will also decrease the SPL

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13
Q

Decreasing the SPL does what to our image on the screen?

A

Improves the image resolution

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14
Q

The number of pulses emitted in one second is called what?

A

Pulse repetition frequency (PRF)

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15
Q

Ultrasound probes typically emit how many pulses per second?

A

Few thousand pulses per second

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16
Q

What affects pulse repetition frequency?

A

Depth!!

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17
Q

If depth is decreased, what will happen to the PRF?

A

The PRF will be increased.

Half the distance, now the sound is being reflected back quicker so it can send out another wave sooner

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18
Q

What is the time from the beginning of one pulse to the beginning of the next called?

A

Pulse repetition period (PRP)

19
Q

PRP is another way of expressing the —— calculated in the range equation.

A

Time (there and back)
D D
PRP = —— T = ——
C C

20
Q

What is the relationship between PRF and PRP

A

Reciprocals
1 1 C D
PRF = —— PRP = —— PRF = —— PRP = ——
PRP PRF D C

21
Q

What is the fraction of time that a pulsed ultrasound if on, expressed as a percentage?

A

Duty factor (DF)

22
Q

Continous wave is on what percent of the time?

A

100%

23
Q

A higher PD and PRF does what to the DF?

A

This increases the DF because there is less “listening” time,
pulse length goes up

24
Q

What is the equation for DF as a percentage?

A

PD
DF = ——— times 100
PRP

25
Q

Sound velocity is dependent on the medium it travels through. What two characteristics of the medium determine the velocity?

A

Density

Compressability

26
Q

The mass of a medium per unit volume….concentration of matter is called ?

A

Density

27
Q

If ONLY density increases (all other factors are constant) what will happen to the velocity?

A

The velocity will decrease.

More mass requires more energy for particle motion

28
Q

What has a greater transfer of energy, something more stiff or something less stiff?

A

More stiff!!

Think of people putting hands against one another and having floppy arms versus locked arms

29
Q

Indicating the fractional decrease in volume when pressure is applied to the material is known as?

A

Compressibility

30
Q

The more dense the material (less compressible) results in a decreased or increased sound velocity?

A

Increased

31
Q

The easier it is to compress a material the higher or slower the velocity ?

A

Slower

32
Q

The reciprocal of compressibility is known as ?

A

Bulk modulus (stiffness)

33
Q

If bulk modulus (stiffness) is increased, what happens to compressibility and velocity?

A

Bulk modulus increases
Compressibility decreases
Velocity increases

34
Q

The ability of an object to return to its original shape and volume after a force is no longer acting on it is referred to as?

A

Elasticity

35
Q

Does ultrasound cause elastic deformations by separation and compression or molecules?

A

Yes it sure does

36
Q

What is the dominant factor, stiffness or density?

A

Stiffness baby

37
Q

If only the density increases then the velocity in that medium

A

Decreases

38
Q

If compressibility increases then stiffness is

A

Decreasing

39
Q

If stiffness increases then the velocity

A

Increases

40
Q

Does Temperature effect the speed of sound?

A

Yes

41
Q

If temperature increases the velocity of sound will

A

Increases as well

42
Q

How is a pulsed system different then a continous wave system ?

A

Pulsed - one crystal to send THAN listen

Continous - two crystals, send and listen at same time

43
Q

How does pulse repetition frequency relate to the operating frequency of the probe?

A

NOT RELATED jokes on ya

44
Q

Is pulsed ultrasound or continous wave ultrasound capable of obtaining an image.

A

Pulsed

Ambers Physics 1 (7 decks)

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