pulse echo tecnique 1

What does a pulse echo instrument or US unit takes

Takes the following information known about reflections, and turns it into a visual display.

What are three thing thing pulse echo instrument detect ?

Strength of the reflection

Direction of the reflection

Arrival time of the reflection

Components of a pulse echo system included

With beam former

Signal processor

Image processor

Display

What is pulser ?

Produces electric voltage pulses that drive the transducer and tell them receiver and memory when the pulses are produced?

What does pulser determines

PRF: depending on how many times it fires, how many pulses we get.

PRP: which relates to the PRF

Pulse amplitude: the stronger the voltage sent to I the crystal, the higher the a

Voltages pulses produced by the pulser=

US pulses from the transducer

The greater the voltage amplitude

The greater the amplitude and intensity of the US pulse.

For array transducers, the pulser and the beam former control the following.

sequencing

•phasing ( firing elements

•steering

•transmit focusing( when you can move your focal zone around)

•dynamic aperture ( changing the tire or the element to change the focal zone)

•apodization ( remove grading lobes)

what is a transducer use for for ?

converts voltage pulses from the pulser into US pulses

 •receives reflection or echoes and converts echo information back into voltage pulse information

What is a signal processor (receiver)

receiver processes voltage information coming from the transducer for the memory and display

What is first receiver functions and what does it do?

Amplification:

conversion of small voltages into larger ones for further processing & storage

•making the signals returning from the transducer larger

•operator adjustable – overall gain

What is the second receiver function and what does it do?

equalizes the differences in returning echo information due to depth and attenuation

 

•operator adjustable – TGC

What is the third receiver function and what do it do)

Compression

process of decreasing the differences between the smallest and largest amplitudes

 

•Dynamic Range

•ratio in dB of largest power to smallest power that the system can handle

 

•operator adjustable – , compression, log compression or dynamic range control

What is the fourth Demodulation?

process of converting the voltages to another form for easier processing

 

•done by rectification and smoothing

 

•not operator adjustable

What is the fifth receiver function

Rejection

eliminates the smaller amplitude voltage pulses produced by weak reflectors or electronic noise

 

•sometimes operator adjustable – suppression, rejection or threshold control

What is ADC?

Analog to digital converter

What does Scan converter do ?

formats echo data into image form for processing, storage and display

 

•properly locates each series of echoes corresponding to scan lines to build a frame

 

•rapid repetitive process to produce a sequence of frames stored in the memory and presented on the display