Review 1 - Beam Former Flashcards
what is the ultrasound instrument composed of?
beam former
signal processor
image processor
display
list the functions of the beam former P(3) Amp A/c(1) ED(1)
Pulser
- generating voltages that drive the transducer
- determining PRF, coding, frequency, and intensity
- scanning, focusing and apodizing the transmitting beam
Amplifier
- Amplifying echo voltages
- Compensating for attenuation
A/C - digitizing the echo voltage stream
Echo Delays
-directing, focusing and apodizing the reception beam
Which part of the beam former does the pulser perform (3)
generates voltage pulses,
sets PRF controls
controls power
how many cycles are produced by the electric voltages?
2-3 cycles/pulse
what determines the frequency of the resulting US pulse? (2)
frequency of the voltage pulse
transducer element thickness
How does the imaging depth affect the pulser and PRF?
for deeper imaging, echoes take longer to return to the transducer, thus forcing a reduction in the PRF and the frame rate
why is there a limit to PRF
all echoes from one pulse must be received before the next pulse is sent or there will be misplacement (range ambiguity)
why are pulse delays required?
pulse delays required for arrays, sequencing phasing /steering, electronic focusing aperture control
what is coded excitation?
CE uses a series of pulses and gaps rather than a single pulse to produce a scan line
what does the decoder do?
It recognizes and disassembles the coded sequence in the returning echoes
stack up the individual pulses in the sequence to make a short, high intensity echo out of them
what is a transmission channel?
each transmission element and its delays
why are transmission channels required?
for a more precise control over the beam characteristics
max number of beam channels
number of elements in the transducer
T/R switch
directs voltage pulses and delays to transduer (transmission)
directs echo voltages from transducer to amplifer (reception)
US PRF = to
voltage PRF of pulser
