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MED 107- MEDICAL PHYSICS II > 31. CT: TYPES OF BEAMS > Flashcards

31. CT: TYPES OF BEAMS Flashcards

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1
Q
  1. How can we increase the Spatial Resolution?
A
  • we can use multiple detectors
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2
Q
  1. What kind of beam is shown in this image?
A
  • a Fan Beam
  • it is positioned in order to obtain slices

THIS KIND OF CT IS VERY USEFUL:
- when we have to obtain images of the whole body

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3
Q
  1. What kind of beam does this image show?
A
  • the Cone Beam
  • the beam is in the shape of a Cone

THIS KIND OF CT IS VERY USEFUL:
- in dentistry
- it is used for localised abnormalities

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4
Q
  1. What kind of beam does this image represent?
A
  • Multiple Pencil Beams
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5
Q
  1. What did the stop-and-shoot principle result in?
A
  • all the CT scanners sequentially acquired axial slices
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6
Q
  1. What happens during Sequential scanning?
A
  • the slice is acquired
  • the table remains stationary through this process
  • it does this until the Gantry completes a full rotation
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7
Q
  1. What happens after the slice has been acquired in Sequential Scanning?
A
  • the table moves to a new position inside the Gantry
  • the next scan is then performed

NB:
- this is known as the Stop and Shoot Principle

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8
Q
  1. What is the disadvantage of the Sequential Scanning Method?
A
  • it takes a relatively long time
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9
Q
  1. What is the Gantry in a CT scan?
A
  • this is the scanning unit of the CT
  • it rotates
  • it looks like a big circle
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10
Q
  1. What does the Gantry contain?
A
  • the X-ray tube
  • shielding elements
  • photon detectors
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11
Q
  1. What do Spiral CT scanners allow for?
A
  • they allow for continuous Tube-Detector rotations
  • the data is acquired faster

IT INVOLVES:
- taking a series of cross sectional images
- these correspond to one continuous spiral

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12
Q
  1. What technology gave way to Spiral CT scanners?
A
  • Slip Ring Technology
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13
Q
  1. What can be said about the table in Spiral CT Scanner situations?
A
  • the table is not stationary
  • it is moved inside the Gantry
  • the Gantry then obtains images for different areas of
    the patient
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14
Q
  1. What do Sequential CT Scanners rely on?
A
  • they rely on a physical connection
  • this is in the form of cables
  • these are found between the rotating elements
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15
Q
  1. What are the rotating elements of the Sequential CT scanner?
A
  • the X-Ray tube
  • the detectors
  • the stationary base
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16
Q
  1. What happens after each part of data is acquired in a Sequential CT scan?
A
  • the wires unwind
17
Q
  1. What do Spiral CTs transmit?
A
  • they transmit energy and data
  • they do this using electrically conductive brushes
  • the rotating rings also help the transmission
18
Q
  1. What can be said about the rotation of the Spiral CT scanners?
A
  • they rotate continuously
  • the table will also move at a constant speed through
    the gantry
19
Q
  1. Does this diagram make sense?
A
  • yes
20
Q
  1. What kind of CT is a multi-splice spiral CT?
A
  • it is a Mechanical CT
21
Q
  1. What happens in a Mechanical CT?
A
  • the X-Ray tube and the detector array will physically
    rotate around the table
22
Q
  1. What creates the forces in a Mechanical CT?
A
  • the rotation
23
Q
  1. What are the forces in the Mechanical CT responsible for?
A
  • they restrict the rotation speed
  • they restrict the temporal resolution
24
Q
  1. Why was the Electron Beam CT developed?
A
  • to image the heart
25
Q
  1. What does the Electron Beam CT do instead of physically rotating the Tube-Detector unit?
A
  • the Electron Beam (EBCT) generates and directs
    electrons
  • it does this along a stationary Tungsten target ring
  • this then emits X-Rays
  • there is no Gantry
  • there is no X-Ray tube or detector
26
Q
  1. What happens to the X-Rays after they are emitted from the Tungsten ring?
A
  • they are collimated
  • this means that they are made to be accurately parallel
  • they then pass through the patient
27
Q
  1. What happens to the X-Rays after they pass through the patient?
A
  • they are collected by the Stationary Detectors
  • these are found on the opposite side
28
Q
  1. In the absence of rotating parts, what is the Temporal Resolution of the Electron Beam CT?
A
  • 100 ms
29
Q
  1. What do we use the Electron Beam CT for?
A
  • non-invasive coronary angiography

IT IS MOST OFTEN USED FOR:
- the qualification of Coronary Calcium

MED 107- MEDICAL PHYSICS II (108 decks)

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