Pulse Echo System 1

Flashcards based on Pulse Echo System lecture notes.

What is the function of a Pulse Echo System?

Takes information about reflections and turns it into a visual display

What three things do pulse echo instruments detect?

Strength, direction, and arrival time of the reflection

What are the components of a pulse echo system?

Beam former, signal processor, image processor, display

What is the function of the Pulser?

Produces electric voltage pulses that drive the transducer

What does the pulser determine?

PRF, PRP, and pulse amplitude

What increases the amplitude and intensity of the US pulse?

The greater the voltage amplitude

What do the pulser and beam former control for array transducers?

Sequencing, phasing, steering, transmit focusing, dynamic aperture, apodization

What is the function of the Transducer?

Converts voltage pulses into US pulses, and receives/converts echo information back into voltage pulses

What are the five functions of the signal processor (receiver)?

Amplification, compensation, compression, demodulation, and rejection

What is Amplification?

Conversion of small voltages into larger ones

What is amplification operator adjustable as?

Overall gain

What is Compensation?

Equalizes differences in returning echo information due to depth and attenuation

What is compensation operator adjustable as?

TGC (Time Gain Compensation)

What is Compression?

Decreasing the differences between the smallest and largest amplitudes

What is dynamic range?

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

What is compression operator adjustable as?

Compression, log compression, or dynamic range control

What happens when changing the compression to a lower decibel setting?

Reduces dynamic range and removes weak echoes and noise

What is Demodulation?

Converting the voltages to another form for easier processing

How is demodulation done?

Rectification and smoothing

Is demodulation operator adjustable?

Not operator adjustable

What is Rejection?

Eliminates smaller amplitude voltage pulses produced by weak reflectors or electronic noise

What is rejection sometimes operator adjustable as?

Suppression, rejection, or threshold control

What does ADC stand for and do?

Converts analog signals to digital signals

What does the Image Processor (Memory) do?

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

What does the Scan Converter do?

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

What is Preprocessing?

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

What does pixel interpolation do?

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

What does persistence do?

Averages several frames together, reduces speckle

What is panoramic imaging?

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

What is spatial compounding?

Scan lines are directed in multiple positions

What is volume imaging?

Acquire 2D slices then process as 3D volumes

What does storing an image in memory allow for?

Display of a single image

What is cineloop?

A large memory capacity, which can store many images for display

What is Digital Memory?

Computer memory which stores numbers

What does each memory board consist of?

Pixels

What is one board equal to?

Bistable imaging

What is the formula for calculating the number of gray shades?

2^n = # of gray shades (n is the # of bits)

Digital memory is considered what?

Discrete ( meaning whole numbers only!)

What are the advantages of digital memory?

Stable, fast & accurate, low maintenance, postprocessing

What does the DAC do?

Converts digital data from the memory to analog voltages for the display

What is Spatial Resolution?

The ability of the memory matrix to distinguish between information on closely spaced pixels

What determines the finer spatial resolution?

The more pixels

What is Contrast Resolution?

Ability to distinguish between echoes of slightly different amplitude or intensity

What means better contrast resolution?

More shades of gray

What is Postprocessing?

Everything done with echoes after stored in the memory

What is B (background) Color?

Color is used to demonstrate various echo intensities

What happens during write zoom?

Added scan lines provide more detail

What happens during read zoom?

No new lines, image is blown up

What is a flat panel display?

Backlighted liquid crystal display (LCD)

What is the typical matrix size of a flat panel display?

1024 x 768