test 3- image processor and display ppt Flashcards by Miss Nancy

Converts the signal from the
signal processor into images

IMAGE PROCESSOR

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IMAGE PROCESSOR FUNCTIONS

◼ Scan conversion

◼ Preprocessing
* RES (Regional Expansion Selection)
* Persistence (frame-averaging)
* Pre-processing (edge enhancement
* Panoramic imaging (free-style, siescape, etc.)
* Spatial compounding (SonoCT, etc.)
* 3D processing

Storing image frames in memory
* Cine-Loop

Postprocessing
* Gray-scale (contrast assignment)
* Color-scale (color map assignment)
* B-color
* Zoom

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preprocessing functions

RES (Regional Expansion Selection)
Persistence (frame-averaging)
Pre-processing (edge enhancement
Panoramic imaging (free-style, siescape, etc.)
Spatial compounding (SonoCT, etc.)
3D processing

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postprocessing functions

Gray-scale (contrast assignment)
Color-scale (color map assignment)
B-color
Zoom

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“_____________” is the display of a
single frame out of the sequence.

Freeze-frame

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◼ Image frame is divided into
_______________

pixels

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how many pixels in image frame

◼ Usually in 512 X 512
checkerboard format

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what does pixel mean

PIcture ELement

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weak reflections are stored as ___________ numbers

small

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boards are stacked to get grey

on/off for each board gets white or black

mix the colors together to get grey

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how many bits are in a byte

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bits mean

Binary digIT

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Smallest amount of digital computer
memory (memory element)

bit

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how to find binary number

-use the number
- go to the first number that can subtract from the bits in the chart
- since it can be subtracted a 1 is assigned
- keep moving right trying to subtract what is left each time

assign a 0 if it can’t be subtracted and a 1 if it can

you can add up all the number that 1 is listed under to get the number you started with

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◼ Four bit (binary digit) memory,
each pixel has four bits
associated with it
◼ 4 bits(boards)=2^4
◼ 2x2x2x2=16

This would allow 16 shades of
gray…we can factor up to 15
with 4 boards and if we turned
them all off we would have
0000 which make up the 16th
shade (white)

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MEMORY TODAY
◼ Usually 256 x 512 or 512 x 512
pixels with 8 boards
◼ Provides over 250,000 pixels
with 256 shades of gray
demonstrated

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◼ Proper memory location for each
echo is determined by

The the beam direction (which crystal
received sound right to left)
and echo arrival time (depth, go-return
time)

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The ability to distinguish with
different brightness, echoes
that are slightly different in
intensity

CONTRAST RESOLUTION

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Analog signals from the transducer are changed into digital
form and stored in the computer memory. The digital signals
are converted back into analog form for display on a standard
television screen.

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Increases the resolution
by reassigning pixel data to a
smaller area

RES

same amount of pixels in a zommed area

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Serves as WRITE magnification

RES

Frame averaging
Serves to “smooth” the image
Reduces noise by averaging successive frames
Decreases temporal resolution (motion will
cause blurring)

PERSISTENCE

is the ability of a display
to distinguish closely spaced events in time
and to correctly present rapidly moving
structures.

Temporal Resolution

(High/low) persistence should be used on structures that are not in motion and are not being scanned rapidly

high

* (Higher/Lower) persistence should be used on structures that are in motion or when scanning rapidly (minimizes blurring)

lower

PANORAMIC IMAGING: 2 other names

* “Freestyle” or “Siescape”

* Means of providing larger cross- sectional area (as with the old static-B imaging mode * Achieved by “dragging out” the image; new scan-lines are added to a frame while the transducer is scanned across the tissue

PANORAMIC IMAGING:

◼ SPATIAL COMPOUNDING: aka

* “SonoCT”

* Scan-lines are directed in multiple directions by phasing so that structures are interrogated from multiple, overlapping directions * Sequential frames are averaged, improving the quality

SPATIAL COMPOUNDING

* Determines the number value assignment * Can be adjusted to make minor changes in brightness-level assigned to certain echoes * Allows for selective/edge enhancement

EDGE

◼ GRAY-SCALE MAPPING: * Determines the assignment of specific display brightness’ to numbers derived from memory * Used to change the contrast of an image “Contrast Enhancement” * Most machines will allow operator to change the Gray-scale curve * Higher contrast better for anechoic structures ie. GB, Bladder, & vascular structures * Lower contrast better for organs

1 of the post processing controls

* Some systems have the ability to present different echo intensities in various colors rather than gray shades * Allows the operator to “perceive” more information, as the eye can differentiate more shades of color than gray

B Color

Magnifies an image after storage in memory by enlarging the pixels

zoom Each pixel in the ROI (region of interest) is magnified. This makes for a grainy image.

elevision monitor is a _____________________________ in which a particular electron beam scanning format is used

cathode-ray tube

Generates a sharply focused beam of electrons that produces a spot of light on a phosphor- coated screen within the tube ◼ Spot can be moved across, or up and down the screen in a specific pattern “interlaced”

CATHODE-RAY TUBE (CRT)

Between memory and display, there is a ____________________

digital to analog converter (DAC)

CRT DISPLAY ◼ Usually displayed as ___________ horizontal lines that produce one frame

525

Higher frame rates allow improved imaging of rapidly moving structures (__________________)

(temporal resolution)

Refresh rates on display are usually higher as well (______________ frames per second)

60 frames per second

ACCRONYM FOR PACS

Picture Archiving and Communications System ◼ Image is shared following DICOM (digital imaging and communications in medicine) standard

which house and subdivision Output power

pulser, beam former

which house and subdivision Frequency selection if multihertz capable

pulser, beam former

which house and subdivision Depth selection (affects PRF)

(beam former)

which house and subdivision Focus and steering

pulse delays, beam former

which house and subdivision Overall gain

(amplification), beam former

which house and subdivision Time-Gain compensation

(compensation)

which house and subdivision Log compression

(rejection),

which house and subdivision Persistence

(preprocessing),

which house and subdivision RES

(preprocessing), image processing

which house and subdivision Edge

(edge enhancement)

which house and subdivision Cine-loop

(scan converter)

which house and subdivision Gray-scale assignment

(post-processing; contrast)