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MED 107- MEDICAL PHYSICS II > 50. NUCLEAR IMAGING: ANGER CAMERA HEAD > Flashcards

50. NUCLEAR IMAGING: ANGER CAMERA HEAD Flashcards

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1
Q
  1. What components does the Camera Head contain?
A
  • the crystal
  • Photo Multiplier Tubes (PMTs)
  • associated electronics
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2
Q
  1. What is the Head Housing?
A
  • this is the outside structure
  • this envelopes and shields these internal components
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3
Q
  1. What does the Head Housing consist of?
A
  • it has a thin layer of lead
  • this removes any leakage radiation
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4
Q
  1. What does role does the Gantry play?
A
  • it supports the Heavy Camera Head
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5
Q
  1. What happens to the Visible Photons in this image?
A
  • they reach the Scintillator
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6
Q
  1. What are many of the Gamma Rays absorbed by?
A
  • the lead in the Head Housing
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7
Q
  1. What happens with the organ that is imaged?
A
  • the organ has a Radiopharmaceutical inserted into it
  • this is what emits the Gamma rays ]
  • the more penetrative Gamma Rays will reach the
    detector
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8
Q
  1. What is the intensity of the X-Ray beam affected by?
A
  • the sensitivity of the detectors
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9
Q
  1. What is the crystal for the imaging camera?
A
  • a large slab of Thallium
  • this Thallium is a doped Nal crystal
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10
Q
  1. What does the thickness of the crystal affect?
A
  • it affects the resolution of the image
  • it affects the sensitivity of the crystal
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11
Q
  1. What do Thicker Crystals have?
A
  1. THEY HAVE HIGHER SENSITIVITIES
    • they can absorb more photons
  2. THEY HAVE LOWER RESOLUTIONS
    - they can absorb more scattered photons
    - they can blur the image
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12
Q
  1. Why does the thickness of the crystal have an affect on the sensitivity and the resolution?
A
  • the Gamma Rays are scattered and absorbed
  • this may be further from the point at which they
    entered the crystal
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13
Q
  1. Where do the Photomultiplier Tubes (PMTs) attach?
A
  • they are attached to the back surface of the crystal
  • there are about 60 or more PMTs that are attached
  • they are attached using light-conductive jelly

NB:
- each of these functions like a single PMT

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14
Q
  1. What determines the amount of light that enters a Photomultiplier tube?
A
  • it is related to the proximity of the tube to the site of
    the interaction
  • this interaction happens between the gamma rays in
    the crystal
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15
Q
  1. What can be said about the Photo Multiplier tube closest to the site of the interaction?
A
  • it receives the greatest number of photons
  • it generates the greatest output pulse
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16
Q
  1. What can be said about the Photomultiplier tube furthest from the Nuclide source?
A
  • it receives the fewest light photons
  • it generates the smallest pulse
17
Q
  1. How can an X-Ray image be formed using the Anger Camera?
A
  • an image can be formed purely from specific points
  • these points correspond to the Photo Multiplier Tubes
    with the highest output
  • this output is released at each photon interaction
18
Q
  1. What controls the number of Resolvable points?
A

THE NUMBER OF RESOLVABLE POINTS ARE LMITED:
- to the total number of Photo Multiplier Tubes
- this is roughly around 128 per camera

19
Q
  1. What is the function of a Positioning Algorithm?
A
  • it improves the resolution of the image
  • it does this by combining the signals from adjacent
    tubes
20
Q
  1. What is the Analog-to-Digital Converter responsible for?
A
  • it digitises each signal
21
Q
  1. What does the circled part of this image show?
A
  • it shows the strongest Photo Multiplier tube that emits
    the strongest pulse
  • this is the PMT that is closest to the interaction of
    Photons
22
Q
  1. What does each Photo Multiplier Tube generate?
A
  • it generates an electrical pulse
  • this pulse is digitised by the Analog-to-Digital Converter
    (ADC)
23
Q
  1. What happens to the digital values?
A
  • they are transmitted to the Positioning Algorithm
24
Q
  1. What is the Positioning Algorithm?
A
  • it is a part of the Computer-processing equipment
  • this is found in the Camera Head
25
Q
  1. What information is the Positioning Algorithm responsible for?
A
  • it knows the location of each Photo Multiplier tube
  • the PMTs are found on the surface of the Crystal
26
Q
  1. What does the Positioning Algorithm calculate?
A
  • it estimates the site of the Gamma Ray interactions
    that happen in the crystal
27
Q
  1. How does the Positioning Algorithm estimate the site of the Gamma Ray interactions?
A
  • it weighs in the digital value of the amount of light that
    each Photo Multiplier Tube receives

MED 107- MEDICAL PHYSICS II (108 decks)

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