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Radiology > Digital Imaging Receptors > Flashcards

Digital Imaging Receptors Flashcards

1
Q

Film screen radiology (FSR)

A

Also called “flat films”

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2
Q

Flat panel detectors

A
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3
Q

What are reasons film is being replaces with digital? (5)

A
  1. Less retakes
  2. Lower long term costs
  3. Storing images is easier & less costly
  4. Electronically send images
  5. Images can be manipulated to show other pathology
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4
Q

Two types of digital imaging receptors

A
  1. CR - Computed radiography
  2. DR - Direct digital radiography
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4
Q

What is the difference with DR and film?

A

It’s the image receptor!

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5
Q

Computer radiography (CR): Cassette info

A
  1. CR contains a phosphor plate in it’s cassette instead of a film sheet like analog.
  2. The CR receptor includes a cassette w/imaging plate (IP)
  3. IP absorbs transmitted x-rays to produce the latent image
  4. During absorption, a luminescence is released as part of the photoelectric effect
  5. Phosphor layer is composed of barium fluorohalide crystals doped with europium
  6. This layer receives transmitted x-rays & holds the latent image until it’s processed
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6
Q

Photoelectric effect (3)

A
  1. X-ray photons usually carry enough energy to ionize an atom in their path.
  2. Ionization means that an atom has temporarily released an orbiting electron.
  3. This atom is now a positive ion. The ejected electron is held in a higher energy state until it’s released through processing.
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7
Q

What is PACS as an acronym?

A

PACS
- Picture - viewing at workstations
- Archiving - images short/long term
- Communication - local or wide area networks
- System - use with HIS, other equipment

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8
Q

What does PACS do? (3)

A
  1. Once an image is made, it’s sent to PACS
    - Image is also sent elsewhere as offsite storage
  2. Then image can be pulled up & viewed
  3. Method that allows storing, retrieving, distributing throughout your hospital or the internet
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9
Q

What is DICOM acronym?

A

Digital Imaging and Communications in Medicine

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10
Q

What does DICOM do?

A
  1. Imaging standard that allows multiple pieces of medical equipment to communicate
  2. Essentially all PACS and almost all equipment speak to DICOM now
  3. DICOM doesn’t effect image quality!
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11
Q

Computed radiology:
Once a scan is complete from the cassette, how does it get “wiped?”

A
  • The imaging plate (IP) is exposed to a bright light before it’s returned into the cassette and ready for more services
  • This erases any excess energy left in the IP after the previous exposure
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12
Q

T/F: Digital rad has a wide latitude

A

True!

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13
Q

T/F: kVp has no effect on image quality with DR

A

True

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14
Q

T/F: DR can get both bone and soft tissue in the same exposure

A

True

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15
Q

What does scatter do to the image?

A

FOGS IT and exposes anyone in proximity

15
Q

What is Compton’s effect?

A

AKA “scatter”
- When the xray beam interacts with the patient, some of the beams are deflected
- Photons that were directed toward the patient interact with outer shell electrons and change directions

16
Q

Four ways to reduce scatter?

A
  1. Collimate the light to reduce the area of exposure
  2. Reduce kVp by 15% and double the mAs to reduce scatter. As kVp increases, so will the scatter.
  3. Add a grid to the exam
  4. Air gap techniques: works better in human med than vet med
17
Q

What are grids?

A
  1. They are composed of tiny lead lines embedded in either plastic or aluminum.
  2. The lines are positioned so that X-ray beams pass between the lines
  3. Scatter will be impacted by the lead lines
18
Q

Should the mAs be slightly increased when using a grid?

A

Yes, they can absorb some of the primary beam

19
Q

What are some examples of digital artifacts? (5)

A
  1. Look up table/image processing errors
  2. Exposure artifacts
  3. CR & DR artifacts
  4. Interference artifacts
  5. Display artifacts
20
Q

Artifacts (digital or not) (5)

A
  1. Mis-positioning
  2. Motion
  3. Incorrect patient ID
  4. Double exposures
  5. Grid cut off
21
Q

Common grid errors

A
22
Q

CR Artifacts (7)

A
  1. Fading
  2. Light leak
  3. Physical damage
    - cracks, scuffs, scratches
    - contamination
    - dust/dirt
  4. Dirt in reader
  5. Highly sensitive to scatter radiation
  6. Upside down in bucky
  7. Overtime if image not read then electrons fall back to ground energy state
    - Several days of fading req for significant fading to occur
23
Q

Uberschwinger Artifact

A

“Overshoot”
- Image may have black halo in certain objects (nail in a foot)
- Can be mistaken as infection when this happens
- Or loosening of orthopedic device

24
Q

Exposure artifact (5)

A
  1. VERY high exposures
  2. Maximum detector response reached
  3. No response to increased dose
  4. Uniformly dark
  5. Cannot be windowed/leveled
25
Q

Film vs Digital

A

Film:
- Latitude is narrower
- Minor under/over exposure will fail to provide diagnostic image
- Bone and soft tissue cannot be detailed in the same view

Digital:
- Wider latitude
- kVp no effect on image quality
- Detail of both bone and soft tissue in one image

Radiology (13 decks)

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