Radiology: Magnification Imaging
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Radiology: Magnification Imaging

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Questions and Answers

What is required to achieve magnification in imaging?

  • Decreasing the FID
  • Increasing the OID (correct)
  • Decreasing the OID
  • Decreasing the image receptor size

    • How does the actual magnification achieved vary with depth in the patient?

  • It varies with depth in a non-linear manner (correct)
  • It varies inversely with depth
  • It varies directly with depth
  • It remains constant throughout the patient

    • What is a consequence of using magnification in imaging?

  • Increased signal-to-noise ratio
  • Consequences for dose, spatial resolution, and SNR (correct)
  • Improved dose efficiency
  • Increased spatial resolution

    • What happens to the scatter fraction at the image receptor when the OID is increased?

    <p>It decreases substantially</p> Signup and view all the answers

    Why is an increase in mAs required when the OID is increased?

    <p>To maintain the dose to the image receptor</p> Signup and view all the answers

    What is the effect of increasing the OID on image sharpness?

    <p>It reduces the image sharpness due to geometric blur</p> Signup and view all the answers

    Why is a significant reduction in focal spot size required when using magnification techniques?

    <p>To compensate for the geometric blur</p> Signup and view all the answers

    How does magnification improve spatial resolution?

    <p>By increasing the size of the image compared to the unsharpness of the image receptor</p> Signup and view all the answers

    What is the basis for choosing the kV setting in screen-film systems?

    <p>Required contrast</p> Signup and view all the answers

    What is the purpose of choosing the mAs in screen-film systems?

    <p>To produce a suitable optical density for the region of clinical interest</p> Signup and view all the answers

    What is the primary reason for using a larger image receptor in magnification imaging?

    <p>To accommodate larger body regions</p> Signup and view all the answers

    How does the patient thickness affect the magnification achieved?

    <p>It varies the magnification between the exit and entrance sides</p> Signup and view all the answers

    What is the effect of increased OID on geometric blur?

    <p>It increases the geometric blur</p> Signup and view all the answers

    What is the purpose of reducing the focal spot size in magnification techniques?

    <p>To improve the image sharpness</p> Signup and view all the answers

    How does magnification affect the overall sharpness of the complete system?

    <p>It improves the overall sharpness</p> Signup and view all the answers

    What is the primary factor in choosing the kV setting in screen-film systems?

    <p>Required contrast</p> Signup and view all the answers

    What is the purpose of choosing the mAs in screen-film systems?

    <p>To produce a suitable optical density</p> Signup and view all the answers

    How does increasing the OID affect the scatter fraction at the image receptor?

    <p>It decreases the scatter fraction</p> Signup and view all the answers

    Why is an increase in mAs required when the OID is increased?

    <p>To maintain the dose to the image receptor</p> Signup and view all the answers

    What is the effect of magnification on the spatial resolution compared to a simple zoom of a digital image?

    <p>It improves the spatial resolution</p> Signup and view all the answers

    What is the main advantage of using a larger image receptor in magnification imaging?

    <p>To accommodate larger body regions</p> Signup and view all the answers

    What happens to the dose to the image receptor when the OID is increased?

    <p>It increases significantly</p> Signup and view all the answers

    What affects the spatial resolution in digital systems?

    <p>Pixel size</p> Signup and view all the answers

    Why is the scatter fraction reduced at the image receptor when the OID is increased?

    <p>Because the scattered rays are directed away from the receptor</p> Signup and view all the answers

    What is the effect of increasing the OID on geometric blur?

    <p>It increases the geometric blur</p> Signup and view all the answers

    What is the primary factor in choosing the mAs in screen-film systems?

    <p>Suitable optical density</p> Signup and view all the answers

    What is the result of magnification on the overall sharpness of the complete system?

    <p>It improves the overall sharpness</p> Signup and view all the answers

    What is the basis for choosing the kV setting in screen-film systems?

    <p>Required contrast</p> Signup and view all the answers

    What is the effect of magnification on the spatial resolution compared to a simple zoom of a digital image?

    <p>It improves the spatial resolution</p> Signup and view all the answers

    What is the consequence of increasing the OID on the focal spot size?

    <p>It requires a significant reduction in focal spot size</p> Signup and view all the answers

    Study Notes

    Magnification Imaging

    • Magnification is achieved by increasing the OID, which generally requires an increase in the FID as well.
    • The actual magnification achieved varies with depth in the patient.
    • Example: Patient thickness is 20cm, FID 140cm, and FSD 80cm, the magnification varies between 1.4 at the Exit side to 1.75 at the Entrance side.

    Magnification Requirements

    • Magnification requires the use of a larger image receptor.
    • For large body regions, this may not be possible.

    Consequences of Magnification

    • The use of magnification has consequences for:
      • Dose
      • Spatial Resolution
      • SNR

    Dose

    • Increasing the OID leads to a substantial reduction in the Scatter Fraction at the image receptor.
    • To maintain the dose to the image receptor, an increase in mAs and hence the patient dose would be required.

    Unsharpness

    • An increase in the OID leads to a reduction in image sharpness due to the geometric blur of the focal spot.
    • Use of magnification techniques requires a significant reduction in focal spot size compared to contact methods.
    • Improvement in the overall sharpness of the complete system is generally due to the increase in size of the image compared to the Unsharpness of the image receptor.
    • From effects such as Light Spread for screen-film systems and Pixel Size for digital systems, magnification can improve Spatial Resolution.

    Technique Selection

    • With Screen-Film systems, technique selection is relatively straightforward:
      • The choice of kV setting is based largely on the required contrast.
      • The mAs is chosen to produce a suitable optical density for the region of clinical interest.

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    Related Documents

    Magnification Imaging PDF

    Description

    Quiz about magnification imaging in radiology, including how it's achieved and how it varies with depth in the patient.

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