Test 3 Flashcards
What are the 7 components of an imaging system?
Pulser, Beam Former, Transducer, Receiver, Display, Memory, Master Synchronizer
Beam Former
Calculates all phasing (time delays for electronic steering/focusing)
Pulser
Distributes electrical voltage to transducer to produce an echo
Pulser & scan converter
Tells scan converter that contact has been made, time of flight timer starts
Pulser & CW
Sets frequency, controls PRP, PRF, amplitude of pulse
Pulser & PW
Freq. dependent on thickness & speed of crystal
Acoustic Power aka
Output power, transmit, output, energy output, output gain
Receiver Functions
Amplification, Compensation, Compression, Demodulation, Rejection
Amplification
Small voltages boosted to be stronger, controlled by gain
Preamplification
Clips large voltage spikes or amplifies very weak signals
Compensation
aka TGC, swept gain, depth gain
Compensates for attenuation due to depth; helps create uniform echogenicity
Compression
aka log compression, dynamic range
Ratio of the greatest to smallest amplitude the instrument can handle. Squeeze signal amplitudes into a narrower range
Dynamic range relationships
Inverse to compression. More compression = lower dynamic range = less shades of grey; less compression = higher dynamic rance = more shades of grey
Dynamic range of instruments
Transducer/receiver: 100-200
Memory: 40-45
Display/printer: 20-30
Demodulation
Change voltages into another form
- Rectification: Turn negative amplitudes to positive
- Smoothing: Avg. of signals
NOT user adjustable!
Rejection
aka suppression, threshold, filter, wall filter
Suppress/eliminate small voltage amplitudes to reduce noise. Filter key
Scan Converter
aka memory
Storage of memory from receiver; analog/digital
Analog
Infinitely variable; Great resolution but unstable
Digital
Discreet binary numbers stored in RAM; stable storage
Bit
Smallest form of memory; on/off
8 bits = 1 byte
More bits increase contrast resolution (more shades of grey)
Pixel
Picture element, smallest form of picture.
Voxel in 3D
More pixels increase spatial resolution
Preprocessing (7 examples)
Available as image is live, before storage in memory
Ex. TGC, dynamic range, RES/Write Zoom, persistence, edge enhancement, smoothing, fill in interpolation
RES/Write Zoom
Rescans the ROI w/ more scan lines to improve spatial resolution