Lecture 2 Flashcards
Diagnostic ultrasound systems are ______ systems
Pulse echo
Diagnostic ultrasound systems determines
Echo strength and location of echo generating sites
Echo strencth is shown by
Brightness
Location of object is determined by
Arrival time and direction of returning echoes
The ultrasound instrument consists of 4 main section s
Beam former
Signal processor
Image processor
Display
What is the beam former
Where it all begins
Works with the transducer
Are we working with sound or voltage at the beam former
Voltage
Instruments of beam former
Master syncronizer Pulser Pulse delays Transmit/recieve switch Amplifiers Analog-to-diigital converters Echo delays Summer
Beam former involves _______ and ______. It is divided into these 2 channels
Transmission and reception
Each path to each individual element is a
Transmission channel
Each path from each individual element is a.
Reception channel
Components of transmitter (4)
Master synchronizer
Pulser
Pulse delays
Transmit/recieve switch
Components of receiver (4)
Amplifier
Analog-to-digital
Echo delays
Summer
What does the master synchronizer do (4)
Coordinates the entire system
Tells the pulser when to fire
Transmission/ receiver functions
Waits for echo to come back before firing the next pulse
Why does the master synchronizer wait for the echo to come back before firing the next pulse
Prevents range abuguity artifacct
This is the incorrect placement of echo along scan line
What does the pulser do
Produces electric voltages that drive the transducer
Pulser is ____ cycle of voltage of desired ______
Single
Frequency
What is the to the electric voltage sent from the pulser?
The transducer produces ultrasound pulse
What is the fundamental frequency eequal to
Resonance=operating= transmit freq
Fundamental frequency ranges from ___-____ MHz
2-20MHz
PRFvoltage of the pulse is equal to _______ becuase
PRF pulse
Becuase for each pulse one US pulse is generated
PRPvoltage of pulser =
PRPpulse
Unit for frequency of pulser
MHz
Unit for PRF of pulser
kHz
Typical values of PRF in greyscale 2D
4-15kHz
Typical values of PRF in doppler
5-30
PRF is operator control in
doppler
In greyscale imaging PRF is
Automatic
Depth of image will determine PRF (indirect control)
PRF is limited by
Depths
PRF is always less than
77kHz
All echoes from one pulse must be recieved before
The next pulse is emitted
Three qualities of deeper images
Echoes take longer to return
PRF is decreased
Frame rate is decreased
Instrument automatically achieves _____ PRF
Highest
The power or strength of the beam entering the tissue is closely related to
Intensity
Stronger the voltage= stronger
Pulse
What happens if we go over 77cm/ms
We would get echo misplacement/range ambuguity artifact
What happens to the PRF in 2D if the depth is increased by 4X
It will decrease by 4X
Pulser can be controlled by
Output dial on some machine
Displayed in dB/%
