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 things pulse echo instrument detect ?

Strength of the reflection

Direction of the reflection

Arrival time of the reflection

Components of a pulse echo system included

Signal processor

Image processor

beam former

Display

Produces electric voltage pulses that drive the transducer and tell the receiver and memory when the pulses are producer

Pulser

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 amplitude

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?

Compensation

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

What is ADC

analog to digital converter

What is scan converter

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

What is Image processor (memory)

converts the digitized, filtered, detected & compressed scan line data into images

 

•processed before and after storage in the image memory

 

What is Preprocessing?

functions performed on the image data before it is stored in the memory

•includes:

•pixel interpolation

•persistence

•panoramic imaging

•spatial compounding

•3D acquisition

What does pixel interpolation?

Assigns a brightness value to missing pixels based on average brightness of adjacent pixels

What does persistence

•averages several frames together

•reduces speckle

What does panoramic imaging do

•image with a wider field of view than an individual frame from the transducer

 

What do a spatial compounding do?

•scan lines are directed in multiple positions

What is a volume imaging

•acquire 2D slices then process as 3D volumes

•manual acquisition

•automated mechanically scanned transducer

•electronic scanning

What is a presentations?

•surface rendering

•2D slices through the 3D volume

•transparent views

What does a memory do

•storing an image in memory allows display of a single image (freeze-frame)

 

•a large memory capacity which can store many images for display is cineloop

 

What does a digital memory do

Computer memory which stores numbers

•each memory board consists of pixels

•usually 512 x 512

•binary number system

•if the memory is made up of a single matrix board, each pixel can store a 1 or 0 (on or off)

•one board = bistable imaging