Pulse-Echo Instrumentation

Question 1

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

Answer 1

False

Question 2

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

Answer 2

Doubled

Question 3

Post processing of the image occurs

Answer 3

after the A/D converter & storage but before display

Question 4

What are the two steps of demodulation?

Answer 4

Rectification/smoothing

Question 5

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

Answer 5

4 MHz

Question 6

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

Answer 6

Power

Question 7

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

Answer 7

True

Question 8

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

Answer 8

True

Question 9

Which operator control adjusts the dynamic range of the displayed echoes

Answer 9

Compression

Question 10

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

Answer 10

Rejection

Question 11

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?

Answer 11

• Pre-processing is before scan converter memory (before image is frozen).
• Pre-processing may apse be termed: persistence, panoramic imaging, spatial compounding , 3D processing.

Question 12

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?

Answer 12

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.

Question 13

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?

Answer 13

4cm

Question 14

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

Answer 14

Receiver

Question 15

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.

Answer 15

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.

Question 16

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

Answer 16

2 times

Question 17

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?

Answer 17

• 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.

Question 18

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

Answer 18

Time

Question 19

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

Answer 19

Demodulation

Question 20

The range equation describes the relationship between what 3 things?

Answer 20

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

Question 21

What does the range equation allow the machine to do?

Answer 21

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

Question 22

What is the range equation? (write it out)

Answer 22

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

Question 23

What is the 13 microsecond rule?

Answer 23

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

Question 24

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

Answer 24

• 4cm

- 8cm

Question 25

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

Answer 25

Adjust the reject level

Question 26

Explain the relationship between dynamic range and compression

Answer 26

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.

Question 27

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

Answer 27

True

Question 28

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

Answer 28

Receiver

Question 29

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

Answer 29

True

Question 30

What is 'signal'

Answer 30

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

Question 31

What is 'noise'?

Answer 31

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

Question 32

What is the signal to noise ratio?

Answer 32

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.

Question 33

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)?

Answer 33

when we achieve a smooth image.

Question 34

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

Answer 34

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

Question 35

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

Answer 35

False

Question 36

Explain how sound is created.

Answer 36

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.

Question 37

What type of wave is sound?

Answer 37

Longitudinal

Question 38

Explain how sound is transmitted.

Answer 38

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

Question 39

Why can sound not travel in a vacuum?

Answer 39

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

Question 40

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

Answer 40

Solids

Question 41

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?

Answer 41

8 MHz

Question 42

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

Answer 42

z-axis

Question 43

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

Answer 43

4 MHz

Question 44

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

Answer 44

True

Question 45

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

Answer 45

Decreased appearance of weak echo signals

Question 46

Preprocessing functions may be defined as:

Answer 46

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

Question 47

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

Answer 47

time-of-flight, propagation speed