zFFS

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7th Annual International Symposium on MDCT San
Francisco, June 15-18, 2005 64 from 32
Understanding the Magic or The Effects of
z-Flying Focal Spot (zFFS) Technology
Willi Kalender, Ph.D. Institute of Medical
Physics University of Erlangen www.imp.uni-erlange
n.de
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Acknowledgements
The evaluation of zFFS effects was carried out by
Yiannis Kyriakou, Marc Kachelrieß, Michael Knaup,
Jens U. Krause and Willi A. Kalender and has been
submitted to European Radiology as a Scientific
Note
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The magic lies in the sampling concept!
How about doubling the number of slices without
a change in detector hardware?
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Rotating Vacuum Vessel X-ray Tube Technology
with z-flying focal spot
Straton tube PhotoCourtesyof Siemens
Schardt et al. Medical Physics 2004 312699-2706
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A high-powerX-ray tube (Siemens Straton
rotating vacuum vessel tube)
A mobile tube?A hand-held device?
A new approach to electron-beam CTwith perfect
control of focus position!
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Double z-Sampling Technology
z-Flying Focal Spot
Electromagnetic Control of the Electron beam
32 detector rows (64 slices scanned)
Kalender WA. Computed Tomography. 2nd ed. Wiley
Sons, New York 2005
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Summary and Conclusion (I)

• The novel z-Flying Focal Spot (zFFS) technology
  provides
• double sampling as required bythe Nyquist
  theorem
• measurement of two overlapping slices per
  detector row,i.e. 64 slices for 32 rows
• no change in dose / image quality relations

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Spatial Resolution MeasurementsModulation
transfer function
zFFS increases spatial resolution
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Impact of the zFFS on z-Resolution
x
Scan data reconstructed twice, using one and both
focal spot positions, resp.
Kalender WA. Computed Tomography. 2nd ed.
Wiley-VCH, New York 2005
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Simulated Head Phantom
without zFFS
with zFFS
320.6 mm
2?320.6 mm
pitch1.4, (C30 HU, W300 HU)
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Windmill Artifacts
click to start movie
Reconstruction on the VAMP syngo Explorer p
1.2
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Summary and Conclusions (II)

• The novel z-Flying Focal Spot (zFFS) technology
  provides
• measurement of two overlapping slices per
  detector row,i.e. 64 slices for 32 rows
• no change in dose / image quality relations
• improved spatial resolutionin the z-direction
• Nyquist conformity and therebysuppression of
  windmill artifacts

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Thank you for your attention!