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Physics 111 > Ch. 4 Vocab > Flashcards

Ch. 4 Vocab Flashcards

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1
Q

Beam former

A

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)

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2
Q

Frame rate

A

the number of frames of echo information stored each second.

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3
Q

Signal

A

information-bearing voltages in an electric circuit; an acoustic, visual, electric or other conveyance of information. The physical representation of a message or information.

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4
Q

Noise

A

a random and persistent disturbance that obscures or reduces a signals’ clarity.

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5
Q

Coded excitation

A

a sophisticated form of transmission in which the driving voltage pulses have intrapulse variation in amplitude, frequency and/or phase.

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6
Q

Contrast resolution

A

the ability of a gray-scale display to distinguish between echoes of slightly different intensities.

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7
Q

Channel

A

an independent signal path consisting of a transducer element, delay, and possibly other electronic components.

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8
Q

Amplification

A

the process by which small voltages are increased to larger ones.

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9
Q

Compensation

A

equalization of received echo amplitude differences caused by different attenuations for different reflector depth. (TGC or DGC)

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10
Q

Gain

A

ratio (in decibels) of amplifier output to electric power input.

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11
Q

T/R switch

A

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.

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12
Q

Compression

A

reduction in differences between small and large amplitudes.

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13
Q

Demodulation

A

conversion of voltage pulses from radio frequency to video form.

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14
Q

Reject

A

eliminates the smaller amplitude voltage pulses produced by weaker reflections or electronic noise.

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15
Q

Bandpass filter

A

filter that passes a range of frequencies (its bandwidth) and rejects those that are above and below the acceptance bandwidth.

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16
Q

DAC

A

a device that converts a number to a proportional voltage amplitude.

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17
Q

ADC

A

a device that converts voltage amplitude to a number.

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18
Q

Radio frequency (RF)

A

voltages representing echoes in cyclic form.

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19
Q

Dynamic range

A

ratio of largest to smallest power that a system can handle; ratio of the largest to the smallest intensity of echoes encountered. Unit dB

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20
Q

Image processor

A

an electronic device that manipulates and prepares images for visual presentation.

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21
Q

Image memory

A

the part of the image processor where echo information is stored in image format.

22
Q

Scan converter

A

an electronic device that reformats echo data into an image form for image processing, storage and display.

23
Q

Preprocessing

A

signal and image processing accomplished before storage in the memory.

24
Q

Postprocessing

A

image processing done after storage in the memory.

25
Q

Pixel

A

picture element; the unit into which imaging information is divided for storage and display in a digital format.

26
Q

Pixel interpolation

A

a method that improves image quality accomplished by filling in missing pixels.

27
Q

Persistence

A

averaging sequential frames together.

28
Q

Panoramic imaging

A

an expansion of the field of view beyond the normal limits of a transducer scan plane.

29
Q

Spatial Compounding

A

averaging of frames that view the anatomy from different angles.

30
Q

Elastography

A

imaging tissue stiffness by tracking movement under mechanical stress.

31
Q

Volume imaging

A

3D imaging.

32
Q

Bit

A

binary digit. n=number of bits; # of shades of gray=2ⁿ

33
Q

Freeze-frame

A

constant display of one of the frames in memory.

34
Q

Cine-loop

A

sequential display of all the frames stored in memory at a controllable frame rate.

35
Q

Bistable

A

having two possible states (on or off; black or white.)

36
Q

Binary Number

A

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).

37
Q

Write Zoom

Acoustic

A

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.

38
Q

Read Zoom

Non-Acoustic

A

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.

39
Q

B Color= B Scale

A

is a form of postprocessing ability that improves contrast resolution by assigning colors, rather than gray shades, to different echo strengths.

40
Q

Spatial Resolution

A

the ability to distinguish two points as separate in space (it is determined by many factors, including line density, AR and LR).

41
Q

A-mode

A

a display presentation of echo amplitude versus depth.

42
Q

B-mode

A

mode of operation in which the display presents a spot of appropriate brightness for each echo received by the transducer.

43
Q

M-mode

A

B-mode presentation of changing reflector postion (motion) versus time.

44
Q

Display

A

a device that represents a visual image derived from voltages received from the image processor (or memory or scan convertor.)

45
Q

CRT

A

a display device that produces an image by scanning an electron beam over a phosphor-coated screen.

46
Q

Flat-panel display

A

a back-lighted rectangular matrix of thousands of liquid crystal display (LCD) elements.

47
Q

Frame rate

A

a number of frames of echo information stored each second.

48
Q

Refresh rate

A

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.

49
Q

Temporal resolution

A

the ability of a display to distinguish closely spaced events in time and to present rapid moving structures correctly. Improves with increased frame rate.

50
Q

PACS

A

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.

Physics 111 (6 decks)

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