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Radiation Therapy Physics 2 > Radiation Imaging PPT > Flashcards

Radiation Imaging PPT Flashcards

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1
Q

Faithfully reproducing the object’s structure and tissues

A

Quality

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2
Q

4 quality characteristics:

A

Spatial Resolution

Contrast Resolution

Noise

Artifacts

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3
Q

ability to distinguish two separate objects and visually distinguish them from one another

A

resolution

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4
Q

Spatial resolution is defined by ___

A

line pairs/mm

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5
Q

property of being noticeably different

A

contrast

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6
Q

large density difference between lines

A

high contrast

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7
Q

unwanted, non-useful signal obscures (hides) the useful signal

A

noise

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8
Q

4 categories of noise:

A
  1. Graininess
  2. Structure mottle
  3. Quantum mottle
  4. Scatter Radiation
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9
Q

___ pixel size = More detail = ___ noise

A

Smaller, less

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10
Q

Irregular arrangement of spots or patches

A

mottle

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11
Q

2 types of mottle:

A
  1. structure mottle
  2. quantum mottle
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12
Q

What type of mottle?

Spots/smears - similar to graininess; structure of intensifing screen; dependent on imaging system

A

structure mottle

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13
Q

What type of mottle?

Random nature of radiation interaction with detector. Dependent on number of photons (quanta).

A

qunatum mottle

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14
Q

More quant (photons), ___ quantum mottle

A

less

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15
Q

Type of mottle that looks like a photo taken with poor lighting.

A

quantum mottle

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16
Q

____ mottle happens when x-ray is cut short (not enough photons)

A

quantum

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17
Q

___ “fogs” the image

A

scatter radiation

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18
Q

In scatter radiation, the image improves if you ___.

A

Move the image detector closer to the patient.

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19
Q

irregularity on an image that is not caused by the proper shadowing of tissue by the primary x-ray beam

A

artifact

20
Q

3 types of artifacts:

A
  1. Image Detector Artifacts
  2. Software Artifacts
  3. Object Artifacts
21
Q

____ artifacts: problems with image receptor, including, Dirt, Scratches, Pixel malfunction, Ghost images

A

image detector

22
Q

software artifacts can result from problems with: (3)

A
  1. range/scaling
  2. image compression
  3. window and level
23
Q

Solution to image compression software artifact:

A

lossless compression (all data is retained, redundant data is compressed)

24
Q

3 types of object artifacts:

A
  1. Patient Positioning
  2. Collimator
  3. Backscatter
25
Q

Magnification problem: ___ detail.

A

loses (gets mottled, so quality decreases)

26
Q

Mag factor equation:

A

𝑀𝐹= (𝐼𝑚𝑎𝑔𝑒 𝑆𝑖𝑧𝑒)/(𝑂𝑏𝑗𝑒𝑐𝑡 𝑆𝑖𝑧𝑒)

27
Q

MF = SID/SOD, what are SID and SOD

A

SID = source to image distance SOD = source to object distance

28
Q

Mag factor: Near Objects appear ___, while Far Objects appear ____

A

larger, smaller

29
Q

This image illustrates what?

A

Closer objects appear larger and far objects appear smaller

30
Q

This image illustrates what?

A

Closer images appear larger and far images appear smaller

31
Q

What are the solutions for distortion from magnification? (2)

A
  1. adjust distance to detector
  2. adjust source to object distance
32
Q

This illustrates the geometric factor ___ that depends on ___. What is the solution?

A

distortion, thickness, reduce distance to detector

33
Q

Geometric factors affecting imaging quality: (3)

A
  1. magnification
  2. distortion
  3. focul spot blur
34
Q

This illustrates the geometric factor ___ that depends on ___. What is the solution?

A

distortion, position, get multiple image angles

35
Q

This illustrates the geometric factor ___ that depends on ___. What is the solution?

A

distortion, position, get multiple image angles

36
Q

This illustrates the geometric factor ___ that depends on ___. What is the solution?

A

distortion, position, get multiple image angles

37
Q

The best position to resolve geometric distortion is at __.

A

isocenter

38
Q

This image illustrates the geometric factor ___. What is the solution?

A

focal spot blur, small source size, patient close to imager

39
Q

Patient factors in imaging quality: (2)

A

Contrast

Motion

40
Q

The thicker the patient, the __ scatter you will get.

A

more

41
Q

What is the solution for patient thickness?

A

Increase the dose to the detector

42
Q

Solution for patient motion artifacts causing blurred image: (4)

A
  1. shorten imaging time (may be moving bc of pain)
  2. restrict pt motion
  3. image detector close to pt
  4. gating
43
Q

This picture illustrates a ___ image, due to ___.

A

blurred, patient motion

44
Q

EPID is located?

A

mounted on gantry head

45
Q

EPID uses ____ technology, is a ___ detector and is ___-based.

A

amourphous Si, digital, video

Radiation Therapy Physics 2 (9 decks)

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