Pulse-Echo Instrumentation Flashcards
Where the action originates.
It consists of a pulser; pulse delays; transmit/receive switch, amplifiers, analog-to-digital converters, echo delays, and a summer.
Functions:
-Generating voltages that drive the transducer
-determining pulse repetition frequency, coding, f, and intensity;
-scanning, focusing, and apodizing the transmitted beam;
-amplifying the returning echo voltages
-compensating for attenuation;
digitizing the echo voltage stream;
directing, focusing, and apodizing the reception beam
Beam Former
Number of images that are generated each second
Frame Rate
Driving voltage-pulse forms;
This accomplishes functions such as:
- multiple transmission foci;
-separation of harmonic echo Bandwidth from transmitted pulse bandwidth;
-increased penetration;
reduction of speckle with improved contrast resolution;
coded excitation
The conversion of the small voltages received from the transducer elements to larger ones suitable for further processing and storage
Amplification
The ratio of amplifier output to electric power input
Gain
Equalizes differences in received echo amplitudes caused by different reflector depths
Compensation
Also called: Time Gain Compensation (TGC)
and Depth Gain Compensation
Allows adjustment of gain laterally across the image
Lateral Gain Control
The first word means ‘proportional’ and the other word means ‘in the form of discrete numbers’
Analog-to-digital
i.e the echo voltage has been proportional to the echo pressure
Convert the analog voltages representing echoes to numbers for digital signal processing and storage
Analog-to-digital Converter
- Determines how many shades of gray are displayed in an image;
- The ratio of the largest to the smallest amplitude or power that a system can handle;
- Demonstrates contrast or shades of gray.
Dynamic Range (The higher the dynamic range the more shades of gray demonstrated; Smaller dynamic range setting gives a higher contrast image)
-Decreases the difference between the largest and the smallest voltages or echo amplitudes;
Compression
Also called Log Compression on Acuson XP or Dynamic Range on some equip
Makes image suitable for display;
Also called Detection;
Conversion of echo voltages from radio frequency (RF) to video form;
Retains the actual amplitudes of the echo voltages;
Demodulation
Scan conversion
Image Processor
Image processing done before echo data are stored in image memory Persistence Panoramic imaging Spatial compounding 3D processing
Pre Processing
(after scan converter memory)
Gray scale
Color scale
Post Processing
Enables the image data to be viewed on video monitors
Scan Converter
converts the acquired signals to the format needed by the video monitor
Temporarily stores images during scanning, for viewing and recording
Image Memory
Averaging of sequential frames together to get a smoother image
Persistence
Averaging of frames that view anatomy from different angles
Spatial Compounding
Picture Archiving and Communications Systems
PACS
the ability to distinguish closely timed events as separate events; and to correctly display rapidly moving structures
Temporal Resolution
As frame rate increases, temporal resolution improves
number of focuses x lines per frame x frame rate
PRF
A device which takes a digital value and outputs a voltage which is proportional to the input value.
Digital-to-analog Converter
An electronic circuit that has two stable states;
or as an adjective: (of a system) having two stable states
Bistable
