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Physics > Chapter 15 > Flashcards

Chapter 15 Flashcards

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1
Q

scan converter

A

stores echo data signals in preparation for display

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2
Q

writing

A

The process of putting echo data signals into the scan converter/storage

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3
Q

reading

A

The process of taking the echo data signals from the scan converter/storage to display

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4
Q

Analog Scan Converters

A

They made gray scale display possible
Analog Signals consist of an unlimited continuous stream of values

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5
Q

dielectric storage matrix

A

a checkerboard of silicon wafers i.e., “electron buckets”

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6
Q

Limitations of dielectric storage matrix on the display:

A

Image fade: stored charges dissipate over time
Image flicker: caused from switching between read and write modes
Instability: image quality effected by heat and humidity
Deterioration: image degrades as device ages

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7
Q

digital scan converters

A

amplitude of the analogue voltage signal is determined, converted to digital (binary digit), and stored

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8
Q

“Digitizing”

A

analogue to digital conversion

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9
Q

Advantages to digital scan converters

A

Uniformity: consistent grayscale quality
Stability: image does not fade or drift
Durability: performance not affected by age or heavy use
Speed and Accuracy: nearly instant and error free processing
Digital data is less susceptible to contamination

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10
Q

Digital Scan Converter (memory board)

A

is set up in a computer monitor scan format (a matrix/checkerboard set up)
Rectangular series of columns and rows
Each square is a “Pixel” (picture element)

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11
Q

Pixels are at least

A

1024 x 768

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12
Q

bits

A

0 and 1 are binary digits

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13
Q

element at each pixel location can only operate in two conditions

A

1 = “on”
0 = “off”

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14
Q

bistable display

A

black and white imaging

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15
Q

A bit

A

is the smallest amount of computer memory

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16
Q

byte

A

A group of 8 bits

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17
Q

Two bytes or 16 bits

A

is a word of computer memory

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18
Q

A kilobyte

A

1000 bytes (1024) or 8000 (8192) bits

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19
Q

Preprocessing

A

Manipulation of the data during the “writing” process

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20
Q

Postprocessing

A

Manipulation of the data during the “reading” process

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21
Q

Types of Processing

A

Time gain compensation (generally pre)
Compression (generally pre)
Grayscale Maps (pre or post)
Magnification known as “zoom”

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22
Q

Write Magnification

A

the ROI is rescanned, and all pixels are devoted to the region of interest = preprocessing
Known as “RES”

23
Q

Read Magnification

A

The system reads and displays the data pertaining to the ROI
post processing

24
Q

Edge enhancement (generally pre)

A

Boundaries in memory are identified and the contrast between the adjacent pixels is enhanced (one slightly brightened while the other is slightly darkened)

25
Q

Fill-in Interpolation (pre)

A

assigns an amplitude value to a missed pixel based on an average of amplitudes of adjacent pixels

26
Q

Temporal Compounding/Averaging (pre)
AKA: Persistence

A

Averaging of sequential frames to produce one frame that is entered into the scan converter
Disadvantage = reduced frame rate and temporal resolution; therefore, most effective with static or slow-moving structures

27
Q

Speckle

A

grainy tissue texture caused when small wavelets interfere

28
Q

Panoramic imaging (pre)

A

Produces an image that has a wider field of view than what is available on an individual frame
done on static organs

29
Q

Spatial Compounding/Compound Imaging (pre)

A

Averaging of sequential frames to produce one frame that is entered into scan converter

30
Q

Three-Dimensional Imaging

A

Many 2D scans are built into a 3D volume of echo information stored in sophisticated memory = preprocessing

31
Q

Black white inversion (generally post)

A

a white on black image is turned into a black on white

32
Q

B color/colorize/ tinting/chromatization (typically post)

A

assigns a color instead of a shade or gray to amplitudes pulled from scan converter to display

33
Q

Frequency Compounding (pre)

A

Reflected signal is divided into sub bands of limited frequencies
A frame is created from each sub band
The frames are then averaged and entered in the scan converter

34
Q

Coded Excitation in Pulser /Beam Former (pre)

A

Pulse is made into an “ensemble pulse”
a decoder rebuilds or “stacks” the ensemble parts into one short high intensity pulse (“pulse compression”)

35
Q

B-flow imaging

A

grey scale imaging of blood flow

36
Q

Elastography/Elastogram = emerging modality

A

The stiffness data as well as the ultrasound reflections are represented in

37
Q

Strain

A

When hit by a force (sound wave) tissue deforms relative to its stiffness

38
Q

Fusion Tool in Volumetric Imaging

A

Allows you to merge real time ultrasound with a previously acquired CT, PET, MR or US Data Set

39
Q

Computer CRT

A

cathode ray tube
digital to analog conversion takes place
a glass vacuum tube shaped like a funnel

40
Q

Color Computer CRTs include

A

three cathodes and thousands of groups of tiny red, green, and blue phosphor dots inside the face of the screen

41
Q

Liquid Crystal Displays (LCD)

A

Most common flat panel ultrasound system display
Can operate with analog or digital signals
A rectangular matrix of thousands of liquid crystal elements
Advantages: lighter, slimmer, less power consumption and heat generation

42
Q

Display controls

A

Display needs to be calibrated in each new ambient light or the recorded study will present differently than when the images were acquired

43
Q

The contrast button

A

sets monitor gray scale range
Adjust it to achieve graduation of gray shades

44
Q

The brightness button

A

sets monitor brightness
adjust to ensure only the 16th gray scale bar is black – melting into or non distinguishable from the background

45
Q

May have one monitor control knob

A

offers various contrast/brightness combinations
Settle on one that achieves appropriate contrast and brightness

46
Q

Paper (stored static)

A

Images written on paper by automated pen writers
Images exposed onto photographic paper

47
Q

Magnetic Media

A

Dynamic and static images stored on video tape

48
Q

Optical Media

A

Standard: floppy disks (early) then CD, DVD, Flash drive
Limited capacity
Loss of echo data (highly compressed)
Specialized Disks specific to the ultrasound system
Limited capacity
Maintain echo data (less compression)
Require special reader for playback

49
Q

Ultrasound System Hard Drive

A

Capacity for several weeks of studies
Maintained echo data (no compression)
Physician would have to read and interpret study on the ultrasound system – impractical

50
Q

PACS System – solved all problems

A

Stands for Picture Archiving and Communication System
-a digital ultrasound lab in which images and reports are digitized and stored on a large specialized computer network
Advantages:
Instant access to archived studies
Studies viewed quickly
Practical high-capacity long term storage (servers)
Maintained echo data (minimal compression)
Store and forward telemedicine = the ability to view from remote sites

51
Q

DICOM = Digital Imaging and Communication (not computer) in Medicine

A

is a set of rules that describes the means of formatting and exchanging medical images and associated information.
It ensures that all devices on the network will work together to share, manage, and distribute images regardless of the manufacturer

52
Q

Lossless compression

A

eliminates redundant data only and does not alter the image (ideal)

53
Q

Lossy compression

A

eliminates redundant and similar data and does alter the image (more practical)

Physics (25 decks)

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