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Sciences Fall '13 > Ch. 31 Computed Radiography > Flashcards

Ch. 31 Computed Radiography Flashcards

1
Q

PSL

A

Photostimulable Luminescence

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2
Q

PSP

A

Photostimulable Phosphor

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3
Q

SPS

A

Storage Phosphor Screen

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4
Q

IP

A

Imaging Plate

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5
Q

SP

A

Storage Phosphor

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6
Q

PMT

A

Photomultiplier Tube

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7
Q

PD

A

Photodiode

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8
Q

Computed Radiography was developed in the early 80s by?

A

Fuji

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9
Q

What are the 5 layers of the PSP plate?

A
  1. Protective Layer
  2. Phosphor Layer
  3. Support Layer
  4. Conductor Layer
  5. Light Shielding Layer
    different than our book pg.596
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10
Q

What are the 2 types of phosphor layers and which one is more effective?

A

Conventional Powder PSP and Needle PSP.

Needle PSP is better

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11
Q

X-ray interaction with a photostimulable phosphor results in excitation of electrons into what state?

A

Metastable State

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12
Q

When metastable electrons return to their ground state this is emitted.

A

Visible Light

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13
Q

When fluorohalides luminesce they do not release all the energy absorbed in the incident beam. Some light is emitted with the interaction, but the phosphor retains energy in the form of what?

A

Latent Image

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14
Q

The latent image is created by energy transfers during what interactions?

A

Photoelectric

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15
Q

Photoelectrons produced, excite low energy electrons to create holes in the crystal phosphor these holes are what?

A

The latent image

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16
Q

Trapped signal will occur exponentially overtime through spontaneous phosphorescence, this is called?

A

Fading

17
Q

A typical imaging plate will lost about ____ of the stored signal between 10 minutes to 8 hours after an exposure and more slowly afterwards.

A

25%

18
Q

A computed Radiography Reader is comprised of what modules?

A

Mechanical, optical and computer modules.

19
Q

What are the 2 main mechanical features of the CR?

A
  1. Drive Mechanism

2. Oscillating Mirror

20
Q

This is a mechanical feature of CR readers that moves the IP along the long axis of the plate and is a slow scan.

A

Drive mechanism

21
Q

This is a mechanical feature of CR readers that deflects the laser back and forth across the IP and is a fast scan.

A

Oscillating Mirror

22
Q

After the imaging plate has been inserted into the cassette reader it is opened and the imaging plate is removed and advanced between the roller drive system. A laser beam that has been directed through a focusing lens scans the plate in a raster pattern. When the laser strikes the surface of the plate, light is emitted and channeled up to the Photo Multiplier tube. The PMT sends the analog signal to the analog to digital convertor ADC , which sends the digital signal to the computer for processing and display. This is what process?

A

Readout Process

23
Q

What is a raster pattern?

A

A scan of horizontal scanning lines traced by the electron beam. Scans reading across back and forth line by line.

24
Q

What are the 5 optical features of CR reader?

A
  1. Laser
  2. Beam Shaping Optics
  3. Light Collecting Optics
  4. Optical Filters
  5. Photodetector
25
Q

This is a source of stimulating light in a CR reader that spreads as it travels and is focused onto the reflector by a lens that keeps beam diameter small at less than 100um.

A

Laser beam

26
Q

The laser beam size in a CR reader is critical for ensuring what?

A

High spatial resolution.

27
Q

The laser light in a CR reader frees trapped electrons which return to lower energy states releasing what color photons?

A

blue-purple light photons

28
Q

What are the 2 techniques to speed up a readout with the laser in a CR reader?

A
  1. Read light from PSP line by line to increase data acquisition
  2. Use dual sided PSP that is scanned on both sides which creates increased spatial resolution.
29
Q

This type of tube performs a point by point readout along the laser line.

A

PMT

30
Q

Each line laser scanned is equal to what?

A

One line spacing or pixel dimension

31
Q

ADC converts infinite ranges of values into discrete values stored as what?

A

Digital Code

32
Q

PIxel depth is equal to what?

A

Number of density values

33
Q

Proper filtering improves signal to noise ratio. Why is this important?

A

The lower the signal to noise ratio then there is more noise present and the information needed in an image is not present. A high signal to noise ratio is what is desired.

34
Q

A computer control is an output analog signal from PMT that is processed for what 3 things?

A
  1. Amplitude
  2. Scale
  3. Compression
35
Q

What does the ADC do to the analog signal?

A

It is digitized or sampled and quantized.

36
Q

This determines the location and size of the of the PSL signal from a specific area of the detector and measures the light intensity.

A

Sampling

37
Q

This determines that average value rounding the grey scale up or down of the signal amplitude within the sample area. You end up with an image full of numbers.

A

Quantizing

Sciences Fall '13 (7 decks)

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