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Beam former Flashcards

1
Q

number of cycles per second is called?

A

Frequency

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2
Q

number of pulses per second?

A

PRF

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3
Q

Number of pulses per scan line?

A

ensenble length

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4
Q

ensemble length on dopper?

A

3-30

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5
Q

ensemble length on 2D?

A

1

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6
Q

of cycles in a pulse on 2D and doppler?

A

2D- 2-3

Doppler- 5-30

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7
Q

what affects PRF in B-mode?

A

penetration/ depth

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8
Q

grating lobes are produced by?

A

arrays

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9
Q

3 ways to fix grating lobes?

A
  1. apodization
  2. THI
  3. subcidy
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10
Q

what affects NZL?

A
  • frequency

- aperture sizer/ diameter

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11
Q

U/S systems are what kind of system?

A

pulse-echo systems

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12
Q

u/s systems determine what?

A

strength and location of echo-generating site

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13
Q

the location of an echo is determined by? (2)

A
  • arrival time (depth)

- direction of returning echoes

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14
Q

4 main sections of intrument?

A

1- beam former
2- signal processor
3. image processor
4. display

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15
Q

what 8 things are involved in the beam former?

A

1) Master Synchronizer*
2) Pulser
3) Pulse delays
4) Transmit/Receive Switch
5) Amplifiers
6) Analog-to-Digital Converters
7) Echo delays
8) Summer

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16
Q

beam former involves?

A
  • transmission and reception
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17
Q

what are transmission channels?

A
  • each path to each individual element is a channel
18
Q

what are reception channels?

A
  • each path from each individual element
19
Q

beam former- components of transmitter? (4)

A
  • master synchronizer
  • pulser
  • pulse delays
  • T/R switch
20
Q

beam former- components of receiver? (4)

A
  • amplifier (TGC, overall gain)
  • analog-to-digital converters
  • echo delays
  • summer
21
Q

what is the master synchronizer?

A
  • coordinated the entire system
  • tells pulser when to fire
  • T/R switch functions
22
Q

master synchronizer prevents?

A
  • range ambiguity (incorrect placement of echo along scan line)

AKA echo-misplacement

23
Q

what is the pulser?

A
  • produces electric voltages that drive the transducer
24
Q

operating frequency range?

A

from 2-20 MHz

25
PRFvolt= PRFpulse what are the typical values for 2D?
4- 15 kHz
26
PRF?
- operator controlled in doppler - automatic in grey scale - depth of image will determine PRF
27
PRF is limited by?
depth
28
what is the pulser?
- all echoes from one pulse must be received before the next pulse is emitted
29
pulser- deeper images?
- echoes take longer to return | - decreased PRF and FR and Temp. res
30
Beam former- What happens if we go over 77 cm/ms?
- range ambiguity
31
What happens to the PRF in 2D if depth is increased by 4 x?
- PRF must drop 4x to prevent range ambiguity
32
Pulser can be controlled in terms of?
power output
33
transmission channels typically there are how many?
64, 128, 192
34
Pulse delays?
- involved in sequencing arrays | - multiple blocks of sound, each producing a scan line
35
what instument of the beam former is involved in phasing?
pulse delays
36
how much time is between element firings?
< 1 microsecond delays between element firings
37
what can pulse delays affect?
Can affect our near zone length (natural focus) Can affect our beam width at the focus How does this affect our image? Lateral resolution
38
pulse delays are involved in?
- dynamic aperture control - apodization - coded excitation
38
pulse delays are involved in?
- dynamic aperture control - apodization - coded excitation
39
dynamic aperture control ?
pulser + pulse delays - decided the width of our aperture
40
apodization?
Decreasing the strength to outer elements | Reduction of grating lobes in arrays
41
Coded excitation allows for? (5)
``` multiple foci spatial compounding increased penetration ↑ contrast resolution B-flow imaging ```

PHY (5 decks)

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