12 Pulsed Echo Instrumentation

Question 0

Describe the ultrasound system.

Answer 0

The entire device that produces sound beams, retrieves the echoes and produces visual images and audio signals

Question 1

What is the information processed by the ultrasound system?

Answer 1

Time of flight
Strength of reflection
Direction
Frequency (for Doppler)

Question 2

List the six interconnected components of an ultrasound system.

Answer 2

Master synchronizer
Transducer
Pulser
Receiver
Display
Storage

Question 3

What does the master synchronizer do?

Answer 3

Communicates with all of the individual components of the ultrasound system
Organizes and times their functions, so as to operate as a single integrated system

Question 4

What does a transducer do for an ultrasound system?

Answer 4

Converts electrical into acoustic energy during transmission

Converts returning acoustic into electrical energy during reception

Question 5

What does a pulser do?

Answer 5

Controls the electrical signals sent to the active elements for sound pulse generation
Determines the pulse repetition period, PRF, and pulse amplitude
Creates the firing pattern for phased array systems, beam former

Question 6

What does a receiver do for an ultrasound system?

Answer 6

The electronics associated with processing the electronic signal produced by the transducer during reception and producing a picture on a display device

Question 7

What is the display device for an ultrasound system?

Answer 7

The device associated with the presentation of processed data for interpretation

Question 8

What is the storage for an ultrasound system?

Answer 8

Any number of devices and media that are used to permanently archive the US data

Question 9

What do the pulser signals depend upon?

Answer 9

System and transducer

Question 10

What are the different pulser modes?

Answer 10

Continuous wave
Pulsed wave, single crystal
Pulses wave, arrays

Question 11

What type of wave occurs with continuous wave pulser modes?

Answer 11

Constant electrical signal in the form of a sine wave

Question 12

What does a pulsed wave, single crystal pulser mode create?

Answer 12

Short duration electrical spike, 1 electrical spike per US pulse

Question 13

What does a pulsed wave, arrays pulser mode create?

Answer 13

Many elements fired for each ultrasound pulse

Question 14

What is transducer output?

Answer 14

Output gain, acoustic power, pulser power, energy output, transmitter output

Question 15

What is the effect upon the image if the transducer output is changed?

Answer 15

Affects brightness of the entire image

The strength of every pulse transmitted to the body changes

Question 16

What is the signal-to-noise ratio?

Answer 16

Meaningful portion of the data versus inaccurate portion of the data

Question 17

What is the signal-to-noise ratio when a high-quality image I s created?

Answer 17

High signal to noise ratio

Question 18

What is the signal-to-noise ratio when an image is degraded?

Answer 18

Low signal-to-noise ratio

Question 19

What is the overall function of the receiver?

Answer 19

Boosts the strength of the signals returning from the transducer, processes them and prepares them for display

Question 20

What is the order of the functions of a receiver?

Answer 20

Amplification, compensation, compression, demodulation, rejection

Question 21

What is the purpose of amplification?

Answer 21

Increases the strength of all electrical signals in the receiver prior to further processing

Question 22

Can the amplification be adjusted by the sonographer?

Answer 22

Yes

Question 23

What is the effect of amplification upon an image?

Answer 23

Every signal is treated identically, thus, amplification changes the brightness of the entire image

Question 24

What does a preamplifier do to the signal?

Answer 24

Alters the signal before it is amplified, often performed in the probe

Question 25

What is the purpose of compensation?

Answer 25

Used to create image of uniform brightness from top to bottom

Question 26

What is the effect of compensation upon the image?

Answer 26

Makes all echoes from similar reflectors appear identical regardless of their depth

Question 27

Can compensation be adjusted by the sonographer?

Answer 27

Yes

Question 28

How is TGC and frequency related?

Answer 28

More TGC is used with higher frequency because of more attenuation

Question 29

What will you adjust if you cannot see reflectors in the near field or far field on your image?

Answer 29

TGC

Question 30

What is the purpose of compression on an image?

Answer 30

Keeps signals within the operating range of the system's electronics and the grayscale within the range of what the human eye can see Decreases the dynamic range of the signals

Question 31

What is the effect of compression upon an image?

Answer 31

Changes the grayscale mapping

Question 32

Can compression be adjusted by the sonographer?

Answer 32

Yes

Question 33

How are decibels affected by compression?

Answer 33

They add or subtract

Question 34

What is the purpose of demodulation?

Answer 34

Changes the signal's form to one more suitable for display

Question 35

Can demodulation be adjusted by the sonographer?

Answer 35

No, it is done automatically

Question 36

What are the 2 steps of demodulation?

Answer 36

Rectification – corrects for or eliminate negative voltages | Smoothing – putting an envelope around the bumps to even them out

Question 37

What is the purpose of rejection?

Answer 37

Displays low-level echoes only when they are clinically meaningful Low-level noise is eliminated in images

Question 38

What is the effect of rejection upon an image?

Answer 38

Affects only low-level signals everywhere on the image, but does not affect bright echoes

Question 40

Can rejection be adjusted by the sonographer?

Answer 40

Yes

Question 41

What are contrast agents?

Answer 41

Micro-bubbles of gas entrapped in a shell

Question 42

What allows contrast agents to be seen?

Answer 42

Different acoustic fingerprint | Large impedance difference between contrast agents and biologic tissues and creates strong reflections

Question 43

What are requirements for contrast agents?

Answer 43

``` Safe Strong reflector of US Long persistence Small enough to pass through capillaries Metabolically inert ```

Question 44

What adjustments alter brightness of the entire image?

Answer 44

Output power or Receiver gain

Question 45

What is output power?

Answer 45

Affects brightness by adjusting the strength of the sound waves sent to the body from the transducer and affects patient exposure

Question 46

What is degraded when the image is too bright from high output power?

Answer 46

Lateral and longitudinal resolution

Question 47

What is receiver gain?

Answer 47

Affects brightness by changing the amplification of the electronic signals after returning to the receiver

Question 48

What is ALARA?

Answer 48

As Low As Reasonably Achievable | Minimize patient exposure