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Flashcards in The System Deck (42):
0

What does the computer processor in the system keep track of?

time of flight

strength of the echo

direction the echo is coming from

frequency

1

a system produces ________ _________ from the echo ________ received from the transducer

visual displays

voltages

2

What is the definition of a system?

entire device that produces the beams

retrieves the echoes

produces the visual images and audio signals

3

What are the parts of the system?

transducer

master synchronizer

pulser and beam former

receiver

display

storage

all electronics and software

4

Each crystal has a ______ called a ______

wire

channel

5

What is transducer output?

determined by the excitation voltage of the pulser

piezoelectric element vibrates with a magnitude of pulser voltage

6

increasing the output by 3dB does what to the intensity?

doubles it

7

What are the synonyms of the transducer output?

output gain

pulser voltage

acoustic power

pulser power

energy output

transmitter output

transmit power

different manufacturers use different titles for the same idea

8

How do you adjust the transducer output?

by changing the power

9

If you make the power higher what happens to the picture?

you get a brighter picture

improves the signal to noise ratio (less fuzziness)

changes every pulse into the body

10

What is the Master Synchronizer?

communicates with all components

organizes and times functions

prepares components to operate as a single integrated system

11

What instructs the pulser to send an electrical signal to the transducer?

master synchronizer

brain or manager of the system

12

Where is the pulser?

IN the beam former (aka: transmitter)

13

What does the pulser do?

pulse delays - phasing - focus and steer

transmit receive switch

converters

echo delays

summer - adder of signal compnents

14

What does the beam former do?

creates electrical spikes (pulses)

rocks the PZT

15

When does the beam former function?


electronics in the US machine that creates the electrical spikes/pulses that go through the wire and rock the PZT

functions during transmission

receives the timing signal from the master ad produces and electrical voltage (10-500 volts)

communicates with the receiver at the moment the element is excited

16

Who drives the transducer?

the Beam Former

17

If you have a low voltage PZT what happens to the output signal

does not vibrate as much - weak output signal

high voltage = PZT vibrates more - strong output signal

18

What does the beam former determine?

PRF/ PRP

firing and time delays

Pulse Amplitude

19

How does the beam former work in a CW transducer?

constant electrical signal

electrical frequency = ultrasound frequency

20

how does the beam former work in CW, PW single crystal, and PW phased arrays?

CW: constant electrical signal (electrical frequency = US frequency)

PW Single: one electrical spike per pulse

PW Phased: one electrical spike per fired element therefore many spikes (patterns changes)....beam former creates delays

21

who is in charge of apodization?

the beam former

adjusts the voltages to reduce grating lobe artifacts

22

if you have shallow scanning pulses what happens to PRP and PRF?

short PRP

higher PRF

23

What is coded excitation?

driving voltage forms (happens in the beam former)

24

What does the Processor do?

continues to process the signals

Master synchronizer > Beam former > Processor

25

Who does the processor send the signal to?

the receiver (found IN the processor)

26

What does the receiver do?

takes the weak signals from the transducer and converts them and boosts the strength of the signal

receives and processes the echo info

master > beam former > processor >receiver

27

What are the five functions of the receiver?

amplification

compensation

compression

demodulation

rejection

must be in order

28

in the receiver what does amplification do?

increasing the strength of all electrical signals in the receiver

receiver/overall

increases or decreases the strength of all returning echoes*

29

what is a dB?

ratio of output electrical strength to input electrical strength of the amplifier

*

30

What does NOT change the signal to noise ratio(power)?

amplification

31

In the receiver there is compensation. What does it do?

makes all echoes from similar reflectors appear identical regardless of depth

TGC - DGC - Swept gain (sonographer adjusted)

32

Why is compensation needed?

due to the effects of attenuation

33

Higher frequency = ________ attenuation? what do you do with TGC?

greater .... more TGC

lower frequency = < attenuation needs less TGC

34

In the receiver you have compression. What does it do?

decrease the difference between large and small amplitudes

(adjusted with the dynamic range/compression button) aka: gray scale mapping

35

in the receiver there is a demodulator. What does it do?

demodulation or detection changes the signal's form

cannot be changed by the sonographer

rectification (turns negative voltages into positive)

smoothing or enveloping (put an envelope around the bumps to even them out)

prepares the signal for display

36

in the receiver there is a rejection function. What does it do?

displays low level echoes only when clinically meaningful

aka: suppression, threshold

affects all low level signal and throws them out

can be controlled by the sonographer (reject, threshold, suppression button)

37

What are harmonics?

creating an image from sound reflected at twice the fundamental frequency

done in the processor

non linear behavior

38

What happens to the frequency when you put harmonics on?

it multiples the fundamental frequency

39

What components do you adjust to yield a good representation image?

adjust the overall gain (amplification)

and then TGC (compensation)

40

What does compensation do?

provides equal amplitude for all similar structures regardless of depth

compensation - dB

41

continue from slide

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