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Physics Final Flashcards > Pulse-Echo Instrumentation > Flashcards

Pulse-Echo Instrumentation Flashcards

1
Q

True or False: A lower frequency probe requires greater compensation than a higher frequency probe

A

False

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2
Q

If a reflector is sitting twice as far away from the transducer, what effect will this have on the time-of-flight of the sound pulse

A

Doubled

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3
Q

Post processing of the image occurs

A

after the A/D converter & storage but before display

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4
Q

What are the two steps of demodulation?

A

Rectification/smoothing

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5
Q

An ultrasound machine is operating in the harmonic mode. The fundamental frequency is 4 MHz. What is the transmitted frequency

A

4 MHz

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6
Q

What control could you adjust to improve the signal to noise ratio on the image

A

Power

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7
Q

True or False: The scan converter is the part of the US system that contains the memory bank

A

True

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8
Q

True or False: When the sonographer is operating the ultrasound machine in continuous wave, the electrical frequency equals the ultrasound frequency.

A

True

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9
Q

Which operator control adjusts the dynamic range of the displayed echoes

A

Compression

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10
Q

The elimination of voltages that do not exceed a certain level is: ( affects all low levels everywhere on the image)

A

Rejection

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11
Q

Compare and contrast pre processing and post processing.

  • At what stage during the imaging process does each one manipulate the data?
  • What are the other names for these 2 things?
A
  • Pre-processing is before scan converter memory (before image is frozen).
  • Pre-processing may apse be termed: persistence, panoramic imaging, spatial compounding , 3D processing.
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12
Q

Explain the role of the Piezoelectric Effect in creating diagnostic images. How does it play a role in both transmit and receive modes? At what point does the piezoelectric effect occur during the entire imaging process?

A

Piezoelectric effect refers to applying an electric field to a crystal, which causes realignment of the internal dipole structure resulting in the crystal to lengthen or contract. The process converts electrical energy into kinetic or mechanical energy.The reverse of the piezoelectric effect converts kinetic or mechanical energy, due to crystal deformation, into electrical energy. Together, this works to send out sound waves as well as receive them in order to display a final image on our screen. The piezoelectric effect occurs when the charge balance within a material’s crystal lattice is disturbed.

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13
Q

A pulse is emitted by a transducer and is traveling in soft tissue. The go-return time, or time-of-flight, of a sound pulse is 52 microseconds. What is the reflector depth?

A

4cm

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14
Q

When you adjust the TGC what component of the ultrasound system implements the changes?

A

Receiver

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15
Q

You are scanning an abdomen and your entire image is too dark. In order to lighten your image what control will you use and why? Be sure to include the control that you will NOT use in your explanation.

A

I would use the TGC because it is used to make an image uniformly bright from top to bottom. I could also use the overall gain because that would increase the amplification at all depths making the entire image brighter. I would not change the dynamic range.

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16
Q

The distance to a reflector is doubled. The time-of-flight for a pulse to travel to the reflector and back is:

A

2 times

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17
Q

Explain how A-mode graphing of information relates to B-mode graphing of information. In other words:

  • What type of information can A-mode and B-mode display
  • And on which axis does each mode display this information?
A
  • A-mode can display a precise measurement of distances between the probe & the reflector. B-mode can display the brightness of the returning echo.
  • The reflector depth in A-mode is measured by the X-axis. The amplitude strength in B-mode is measured by the Z-axis.
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18
Q

The x-axis of a M-mode measures what?

A

Time

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19
Q

What function of the receiver converts electrical signals from radiofrequency form to video form

A

Demodulation

20
Q

The range equation describes the relationship between what 3 things?

A

sound wave, time of flight, reflector depth, return of wave

21
Q

What does the range equation allow the machine to do?

A

Allows us to determine the distance/reflector depth by pulse travel time.

22
Q

What is the range equation? (write it out)

A

Depth (mm) = velocity of sound x time of flight (µs)/2

23
Q

What is the 13 microsecond rule?

A

for every 13 microseconds of go return time the object creating the reflection is 1 cm deeper

24
Q

A sound pulse emitted from a transducer travels in a ultrasound phantom and after reflecting off a pin, returns to the transducer in 52 microseconds. Answer the following 2 questions:
A. How deep is the pin?
B. What was the distance traveled

A
  • 4cm

- 8cm

25
Q

When only bright reflecting objects and nothing else is displayed on the ultrasound machine, the sonographer should

A

Adjust the reject level

26
Q

Explain the relationship between dynamic range and compression

A

The more compressed, the narrower the dynamic range therefore there is more contrast to an image. The less compressed, the wider the dynamic range therefore there is less contrast to an image.

27
Q

True or False: The pulser generates the voltages that drive the transducer.

A

True

28
Q

This transforms the electrical signals into a form more suitable for display

A

Receiver

29
Q

True or False: A-mode scanning represents the depth of the signal in the horizontal dimension.

A

True

30
Q

What is ‘signal’

A

The “signal” is the meaningful portion of the data received. What the sonographer is trying to measure.

31
Q

What is ‘noise’?

A

The “noise” is the inaccurate portion of that data that degrades the quality of the information received. Any unwanted signal.

32
Q

What is the signal to noise ratio?

A

Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels. A measure of how strong a signal is relative to the background noise.

33
Q

How do we know when we have a good signal to noise ratio (how can we look at an image and tell the SNR is good)?

A

when we achieve a smooth image.

34
Q

What is the advantage of having a good signal to noise ratio?

A

Having more diagnostic images due to the meaningful portion of data being higher than the inaccurate portion of the data degrading the information.

35
Q

True or False: Rectification is the process of turning positive voltages into negative voltages.

A

False

36
Q

Explain how sound is created.

A

Sound waves exist as variations of pressure in a medium such as air. They are created by the vibration of an object, which causes the air surrounding it to vibrate. The vibrating air then causes the human eardrum to vibrate, which the brain interprets as sound.

37
Q

What type of wave is sound?

A

Longitudinal

38
Q

Explain how sound is transmitted.

A

Sound is transmitted by the vibration of atoms in the air.

39
Q

Why can sound not travel in a vacuum?

A

There are not atoms to vibrate to carry the sound waves. It needs a medium to travel through.

40
Q

Through what type of a medium does sound travel the fastest?

A

Solids

41
Q

The ultrasound machine transmits a pulse with a fundamental frequency of 4 MHz. When the sonographer switches to the harmonic mode, what will the harmonic frequency be?

A

8 MHz

42
Q

The amplitude of the reflection represented on a B-mode image is on the:

A

z-axis

43
Q

An ultrasound machine is operating in the harmonic mode. The harmonic frequency is 8 MHz. What is the transmitted frequency?

A

4 MHz

44
Q

True or False: Harmonic frequency characteristics occur due to non-linear behavior.

A

True

45
Q

What effect will you detect in the image if you increase the threshold control?

A

Decreased appearance of weak echo signals

46
Q

Preprocessing functions may be defined as:

A

A function that is performed before the echo data are stored in memory

47
Q

The range equation represents the relationship of the distance of the reflector to _______ and
_________.

A

time-of-flight, propagation speed

Physics Final Flashcards (6 decks)

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