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SIDI > CR & DR > Flashcards

CR & DR Flashcards

1
Q

WHAT IS DIGITAL IMAGING?

A

Acquisition of images to a computer rather than to film.

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2
Q

HOW IS DATA STORED USING DR?

A

Pixels/voxels

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3
Q

WHAT IS A BYTE?

A

Represents one character, digit or value.

Computers understand 0 or 1

1 Byte = 8 Bits
1 Kilobyte = 1024 Bytes
1 Megabyte = 1 Million Bytes
1 Gigabyte = 1 Billion Bytes

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4
Q

WHAT IS A PIXEL?

A

Arranged in a matrix

CR is at least 512 x 512

More modern systems are at least 1024 x 1024

4096 x 4096 is being developed

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5
Q

WHAT IS A VOXEL?

A

Product of the pixel area and slice thickness

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6
Q

WHAT IS THE DIGITAL GRAYSCALE?

A

Bit depth = shades of grey in the image

8 Bit = 256
10 Bit = 1024
12 Bit = 4096

Increase in Bits = an increase in shades of grey

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7
Q

WHAT IS A CCD?

A

Charged Couple Device

Used in indirect digital conversion

Converts light into electric signal

Involves image stitching pixels

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8
Q

WHAT ARE DIGITAL DETECTORS MADE FROM?

A

Amorphous Silicone (a-Si)

This converts x-rays into light photons

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9
Q

WHAT IS A TFT?

A

Thin Film Transistor

Converts light captured within the pixels into an electric signal

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10
Q

WHAT IS a-SE

A

Amorphous Selenium

Converts X-rays to a hole pair electron

Electron is driven into a pixel where TFT converts it into an electric signal

Temperature dependent (not too hot and not too cold

Sharper image due to no phosphor = no light scattering

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11
Q

WHAT IS CAD?

A

Computer Aided Detection

Picking up what we may miss by eye

Available in Mamo and developing in other clinical processes

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12
Q

WHAT ARE THE COMMON PRESET DIGITAL FUNCTIONS?

A

Pre-set processing algorithms

Brightness and contrast controls

Annotation

Rotation/Flip/Zoom

Shuttering

Measurements

Magnification

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13
Q

WHAT IS CR?

A

Techniques capturing images using storage phosphors within imaging plate

Phosphors cause the release of energy when exposed to infrared light.

Photo-stimulable luminescence occurs

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14
Q

WHAT IS PHOTO-STIMULABLE LUMINESCENCE?

A

Energy stored in the form of light

Intensity is proportional to number of x-ray photons absorbed by storage phosphor

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15
Q

EQUIPMENT INVOLVED IN THE USE OF CR

A

X-ray unit

Phosphor Cassette

Cassette reader

Review work station (monitor)

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16
Q

STRUCTURE OF THE IMAGING PLATE

A

210 micrometer phosphor layer

Phosphor layer is made of barium Flurohalide

Within the phosphor layer there are conduction and valance bands along with F traps

Light Reflection layer

Conductive Crystal layer reducing electrostatic charges, absorbs light increasing sharpness

Light shielding layer made of carbon

Barcode label providing serial number

17
Q

WHAT ARE THE SEQUENCE OF EVENTS IN THE USE OF CR?

A

Barium flurohalide compounds are energised and release electrons when exposed to x-rays

Electron are trapped in F centres

After exposure to laser electrons are released from the F centres

Electrons are energised and emit light photons within 7 milliseconds

Light is detected by photomultiplier converting the signal into a time series

The signal is amplified and converted to a digital signal used ACD converter

Exposure to visible light erases the cassette

18
Q

WHAT IS AN EXPOSURE INDICATOR?

A

Number displayed indicating exposure to the imaging plate

19
Q

WHAT ARE THE DIFFERENT TYPES OF EXPOSURE INDICATORS?

A

KODAK - Exposure index (EI)
Every 300=change in exposure X2

AGFA - Log Median Value (LgM)
Every 0.3=change in exposure X2

Fuji - Sensitivity Number (S)
Every 100=2 X exposure

20
Q

CR CHARACTERISTIC CURVE

A

Very wide latitude

Less radiograph repeats

21
Q

WHAT ARE THE ISSUES RELATED TO USING DR?

A

Poor technique

Lack of understanding if exposure values

Using incorrect exposure factors

22
Q

What is QDE/DQE?

A

Quantum Detector Efficiency

Measure of efficiency of converting x-rays to useful image signal

Higher QDE = Lower patient Dose

23
Q

Advantages of CR

A

Can salvage up to 500% over exposure and 80% under exposure

Reduction in exposure factors without loss of image quality

Ability to view the same image in more than one place

Allow post processing features

Not as expensive as DR

Used with present X-ray equipment

SIDI (8 decks)

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