Ch. 4 Vocab Flashcards
Beam former
the part of an instrument that accomplishes electronic beam scanning, apodization, steering, focusing and aperture with arrays. Imaging depth (cm) x PRF (kHz)77 (cm/ms)
Frame rate
the number of frames of echo information stored each second.
Signal
information-bearing voltages in an electric circuit; an acoustic, visual, electric or other conveyance of information. The physical representation of a message or information.
Noise
a random and persistent disturbance that obscures or reduces a signals’ clarity.
Coded excitation
a sophisticated form of transmission in which the driving voltage pulses have intrapulse variation in amplitude, frequency and/or phase.
Contrast resolution
the ability of a gray-scale display to distinguish between echoes of slightly different intensities.
Channel
an independent signal path consisting of a transducer element, delay, and possibly other electronic components.
Amplification
the process by which small voltages are increased to larger ones.
Compensation
equalization of received echo amplitude differences caused by different attenuations for different reflector depth. (TGC or DGC)
Gain
ratio (in decibels) of amplifier output to electric power input.
T/R switch
directs the driving voltages from the pulser and pulse delays to the transducer during transmission and then directs the returning echo voltages from the transducer to the amplifiers during reception.
Compression
reduction in differences between small and large amplitudes.
Demodulation
conversion of voltage pulses from radio frequency to video form.
Reject
eliminates the smaller amplitude voltage pulses produced by weaker reflections or electronic noise.
Bandpass filter
filter that passes a range of frequencies (its bandwidth) and rejects those that are above and below the acceptance bandwidth.
DAC
a device that converts a number to a proportional voltage amplitude.
ADC
a device that converts voltage amplitude to a number.
Radio frequency (RF)
voltages representing echoes in cyclic form.
Dynamic range
ratio of largest to smallest power that a system can handle; ratio of the largest to the smallest intensity of echoes encountered. Unit dB
Image processor
an electronic device that manipulates and prepares images for visual presentation.
Image memory
the part of the image processor where echo information is stored in image format.
Scan converter
an electronic device that reformats echo data into an image form for image processing, storage and display.
Preprocessing
signal and image processing accomplished before storage in the memory.
Postprocessing
image processing done after storage in the memory.
Pixel
picture element; the unit into which imaging information is divided for storage and display in a digital format.
Pixel interpolation
a method that improves image quality accomplished by filling in missing pixels.
Persistence
averaging sequential frames together.
Panoramic imaging
an expansion of the field of view beyond the normal limits of a transducer scan plane.
Spatial Compounding
averaging of frames that view the anatomy from different angles.
Elastography
imaging tissue stiffness by tracking movement under mechanical stress.
Volume imaging
3D imaging.
Bit
binary digit. n=number of bits; # of shades of gray=2ⁿ
Freeze-frame
constant display of one of the frames in memory.
Cine-loop
sequential display of all the frames stored in memory at a controllable frame rate.
Bistable
having two possible states (on or off; black or white.)
Binary Number
a number expressed in the binary numeral system, or base-2 numeral system, which represents numeric values using two different symbols: typically 0 (zero) and 1 (one).
Write Zoom
Acoustic
is a preprocessing technique that is used during data acquisition, before storage in the memory when the system scans only the ROI and writes new data into the scan converter.
Read Zoom
Non-Acoustic
is a postprocessing technique that occurs after data is stored in the memory when the system reads and displays only the original data without rescanning the ROI.
B Color= B Scale
is a form of postprocessing ability that improves contrast resolution by assigning colors, rather than gray shades, to different echo strengths.
Spatial Resolution
the ability to distinguish two points as separate in space (it is determined by many factors, including line density, AR and LR).
A-mode
a display presentation of echo amplitude versus depth.
B-mode
mode of operation in which the display presents a spot of appropriate brightness for each echo received by the transducer.
M-mode
B-mode presentation of changing reflector postion (motion) versus time.
Display
a device that represents a visual image derived from voltages received from the image processor (or memory or scan convertor.)
CRT
a display device that produces an image by scanning an electron beam over a phosphor-coated screen.
Flat-panel display
a back-lighted rectangular matrix of thousands of liquid crystal display (LCD) elements.
Frame rate
a number of frames of echo information stored each second.
Refresh rate
the number of times each second that information is sent from the image to the display. Or: the number of times per second that a computer monitor redraws the information found in memory.
Temporal resolution
the ability of a display to distinguish closely spaced events in time and to present rapid moving structures correctly. Improves with increased frame rate.
PACS
the system that provides means for electronically communicating images and associated information to work stations and devices external to the sonographic instrument, the examing room and even the building in which the scanning is done.
