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SUMMARY:Theoretically-exact CT-reconstruction from experimental data - *Va
 rslot\, T\, Kingston\, A\, Myers\, G (Australian National University)
DTSTART:20111212T160000Z
DTEND:20111212T163000Z
UID:TALK34918@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:We demonstrate how an optimisation-based autofocus technique m
 ay be used to overcome physical instabilities that have\, until now\, made
  high-resolution theoretically-exact tomographic reconstruction impractica
 l. We show that autofocus-corrected\, theoretically-exact helical CT is a 
 viable option for high-resolution micro-CT imaging at cone-angles approach
 ing +- 50 degrees. The elevated cone-angle enables better utilisation of t
 he available X-ray flux and therefore shorter image acquisition time than 
 conventional micro-CT systems. By using the theoretically-exact Katsevich 
 1PI inversion formula\, we are not restricted to a low-cone-angle regime\;
  we can in theory obtain artefact-free reconstructions from projection dat
 a acquired at arbitrary high cone-angles. However\, this reconstruction me
 thod is sensitive to misalignments in the tomographic data\, which result 
 in geometric distortion and streaking artefacts. We use a parametric model
  to quantify the deviation between the actual acquisition trajectory and a
 n ideal helix\, and use an autofocus method to estimate the relevant param
 eters. We define optimal units for each parameter\, and use these to ensur
 e consistent alignment accuracy across different cone-angles and different
  magnification factors.\n
LOCATION:Seminar Room 1\, Newton Institute
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