Chapter 14 Pulsed Echo Instrumentation

Question 1

What are the 2 major functions of ultrasound systems?

Answer 1

preparation and transmission (electrical signals to the transducer which creates a sound beam)

reception (receives electrical signals from the transducer; which processes images into clinically meaningful images and sounds)

Question 2

The ___________ of electrical signals to the transducer, which creates a sound beam.

Answer 2

preparation and transmission

Question 3

The __________ of electrical signals from the transducer, with subsequent processing into clinically meaningful images and sound.

Answer 3

reception

Question 4

What are the six major components of ultrasound systems?

Answer 4

1. Transducer
2. Pulser and beam former
3. Receiver
4. Display
5. Storage
6. Master Synchronizer

Question 5

Transforms electrical energy into acoustic energy. During reception, it converts the returning acoustic energy into electrical energy. This describes?

Answer 5

Transducer

Question 6

The component of the ultrasound system that creates and controls the electrical signals sent to the transducer that generate sound pulses.

Answer 6

Pulser and Beam Former

Question 7

The _______ determines the amplitude, pulse repetition period, and the pulse repetition frequency.

Answer 7

pulser

Question 8

The _______ determines the firing delay patterns for phased array systems.

Answer 8

beam former

Question 9

The component that transforms the electrical signals from the transducer (produced by the reflected sound) into a form suitable for display.

Answer 9

Receiver

Question 10

What component of the ultrasound system presents the processed data?

Answer 10

Display

Question 11

What component of the ultrasound system archives the ultrasound studies?

Answer 11

Storage

Question 12

The component of the ultrasound system that maintains and organizes the proper timing and interaction of the system’s components.

Answer 12

Master Synchronizer

Question 13

When does the pulser function?

Answer 13

during transmission

Question 14

When the pulser is set to a low voltage the image tends to be ________.

Answer 14

darker

Question 15

When the pulser voltage is high, the image tends to be _______.

Answer 15

brighter

Question 16

What are the synonyms for pulser voltage (transducer output)?

Answer 16

output gain
acoustic power
pulser power
energy output
transmitter output
power
gain (don't use this one cause its to vague)

Question 17

Can the sonographer adjust transducer output?

Answer 17

yes

Question 18

Changes in transducer output affect the brightness of ___________.

Answer 18

entire image

Question 19

defined as a random and persistent disturbance that obscures or reduces the clarity of a signal. contaminates images with low level undesirable signals

Answer 19

noise

Question 20

What is signal to noise ratio?

Answer 20

comparison of the meaningful info (signal) in an image, compared to the amount of contamination (noise)

Question 21

When the signal to noise ratio is ______, the signal is much stronger than the noise and the image is of high quality.

Answer 21

high

Question 22

A ______ signal to noise ratio results in poor image quality.

Answer 22

low

Question 23

Increasing output power is the most common way to __________ the signal to noise ratio.

Answer 23

improve (increase)

Question 24

PRP and PRF are ________.

Answer 24

reciprocals

Question 25

- Shorter listening time - shorter pulse rep. period (PRP) - higher PRF All of these will result in shallow or deep imaging?

Answer 25

Shallow imaging

Question 26

- longer listening time - longer pulse rep. period (PRP) - lower PRF All of these result in shallow or deep imaging?

Answer 26

Deep Imaging

Question 27

The beam former adjusts electrical spike voltages to reduce lobe artifacts in a process called ___________.

Answer 27

apodization

Question 28

Modern beam formers use advanced microproessor technology and produce signals in digital format. This state of the art device is called?

Answer 28

digital beam former

Question 29

made up of a single active element, the electronics in beam former/pulser and the wire that connects them.

Answer 29

channel

Question 30

most systems have between ___ to ___ channels

Answer 30

32 to 256

Question 31

Order of receiver operations

Answer 31

1. Amplification 2. Compensation 3. Compression 4. Demodulation 5. Reject

Question 32

What is amplification?

Answer 32

(aka: receiver gain) 1st function of receiving- each signal returning from the transducer is made larger; each signal undergoes equal amount of amplification

Question 33

Is amplification adjustable by sonographer? And what is the effect on image?

Answer 33

yes; the entire image is made brighter or darker.

Question 34

What are the units and typical values for amplification?

Answer 34

decibels; 60 to 100 dB

Question 35

The process of improving the quality of a signal before it is amplified. occurs as close to the pzt as possible, often within the transducer

Answer 35

preamplification

Question 36

What is compensation?

Answer 36

TGC settings (aka: time-gain compensation, depth gain compensation DGC, and swept gain) 2nd function of receiving- prevents the image from becoming progressively darker with increasing depth

Question 37

With the TGC curve, what does the x-axis and y-axis represent?

Answer 37

x-axis: the amount of compensation | y-axis: reflector depth (starting at skin level)

Question 38

At superficial depths, reflections undergo a small, constant amount of compensation called the?

Answer 38

near gain

Question 39

The depth at which variable compensation begins is known as the?

Answer 39

delay

Question 40

In the region of the _______, compensation corrects for the effects of increasing attenuation that result from increasing path length.

Answer 40

slope

Question 41

At the depth of the _______, reflections are maximally compensated by the ultrasound system.

Answer 41

knee

Question 42

The _______ indicates the maximum amount of compensation that the receiver can provide.

Answer 42

far gain

Question 43

What is compression?

Answer 43

3rd function( aka: log compression, dynamic range)- keeps image grayscale content within the range of detection of the human eye

Question 44

Why is log compresion important

Answer 44

clinically important because most meaningful backscattered signals from biologic tissues are very weak and the sonographer must be able to see differences in these weak reflections

Question 45

Is compression adjustable by sonographer?

Answer 45

yes

Question 46

What is demodulation?

Answer 46

4th function- 2 part process that changes the electircal signals within the receiver into a form more suitable for display on monitor

Question 47

One of the two-part process of demodulation: | converts all negative voltages into positive voltages. It corrects for, or eliminates, negative voltages.

Answer 47

Rectification

Question 48

One of the two-part process of demodulation: | places a smooth line around the "bumps" and evens them out.

Answer 48

smoothing (or enveloping)

Question 49

Is demodulation adjustable by the sonographer?

Answer 49

no

Question 50

What is reject?

Answer 50

``` 5th function (aka: threshold, suppression)- allows sonographer to control whether low level grayscale info within the data will appear on the displayed image Most systems have 2 levels of reject; one that is built into the design of the system(cannot be changed), the other is user adjustable Affects low level echos only, not high level echos ```

Question 51

what is the difference between output power and receiver gain? why is it important to appreciate this difference?

Answer 51

output power affects image by adjusting the sounds strength on transmission receiver gain (amplification) alters the sound strength during reception pt exposure to sound energy is affected by alterations in output power, but not by amplification

Question 52

What is ALARA?

Answer 52

As Low As Reasonably Achievable