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What is required to achieve magnification in imaging?
What is required to achieve magnification in imaging?
How does the actual magnification achieved vary with depth in the patient?
How does the actual magnification achieved vary with depth in the patient?
What is a consequence of using magnification in imaging?
What is a consequence of using magnification in imaging?
What happens to the scatter fraction at the image receptor when the OID is increased?
What happens to the scatter fraction at the image receptor when the OID is increased?
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Why is an increase in mAs required when the OID is increased?
Why is an increase in mAs required when the OID is increased?
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What is the effect of increasing the OID on image sharpness?
What is the effect of increasing the OID on image sharpness?
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Why is a significant reduction in focal spot size required when using magnification techniques?
Why is a significant reduction in focal spot size required when using magnification techniques?
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How does magnification improve spatial resolution?
How does magnification improve spatial resolution?
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What is the basis for choosing the kV setting in screen-film systems?
What is the basis for choosing the kV setting in screen-film systems?
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What is the purpose of choosing the mAs in screen-film systems?
What is the purpose of choosing the mAs in screen-film systems?
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What is the primary reason for using a larger image receptor in magnification imaging?
What is the primary reason for using a larger image receptor in magnification imaging?
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How does the patient thickness affect the magnification achieved?
How does the patient thickness affect the magnification achieved?
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What is the effect of increased OID on geometric blur?
What is the effect of increased OID on geometric blur?
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What is the purpose of reducing the focal spot size in magnification techniques?
What is the purpose of reducing the focal spot size in magnification techniques?
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How does magnification affect the overall sharpness of the complete system?
How does magnification affect the overall sharpness of the complete system?
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What is the primary factor in choosing the kV setting in screen-film systems?
What is the primary factor in choosing the kV setting in screen-film systems?
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What is the purpose of choosing the mAs in screen-film systems?
What is the purpose of choosing the mAs in screen-film systems?
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How does increasing the OID affect the scatter fraction at the image receptor?
How does increasing the OID affect the scatter fraction at the image receptor?
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Why is an increase in mAs required when the OID is increased?
Why is an increase in mAs required when the OID is increased?
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What is the effect of magnification on the spatial resolution compared to a simple zoom of a digital image?
What is the effect of magnification on the spatial resolution compared to a simple zoom of a digital image?
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What is the main advantage of using a larger image receptor in magnification imaging?
What is the main advantage of using a larger image receptor in magnification imaging?
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What happens to the dose to the image receptor when the OID is increased?
What happens to the dose to the image receptor when the OID is increased?
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What affects the spatial resolution in digital systems?
What affects the spatial resolution in digital systems?
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Why is the scatter fraction reduced at the image receptor when the OID is increased?
Why is the scatter fraction reduced at the image receptor when the OID is increased?
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What is the effect of increasing the OID on geometric blur?
What is the effect of increasing the OID on geometric blur?
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What is the primary factor in choosing the mAs in screen-film systems?
What is the primary factor in choosing the mAs in screen-film systems?
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What is the result of magnification on the overall sharpness of the complete system?
What is the result of magnification on the overall sharpness of the complete system?
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What is the basis for choosing the kV setting in screen-film systems?
What is the basis for choosing the kV setting in screen-film systems?
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What is the effect of magnification on the spatial resolution compared to a simple zoom of a digital image?
What is the effect of magnification on the spatial resolution compared to a simple zoom of a digital image?
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What is the consequence of increasing the OID on the focal spot size?
What is the consequence of increasing the OID on the focal spot size?
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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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Description
Quiz about magnification imaging in radiology, including how it's achieved and how it varies with depth in the patient.
