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This page summarizes the existing and the future solutions in RTK for improving image quality of cone-beam (CB) CT images. It is based on discussions at the [RTK/Meetings/OnImageQualityInStaticCBCT|RTK meeting on image quality].
This page summarizes the existing and the future solutions in RTK for improving image quality of cone-beam (CB) CT images. It is based on discussions at the [[RTK/Meetings/OnImageQualityInStaticCBCT|RTK meeting on image quality]].


= X-ray source imperfections =
= X-ray source imperfections =

Revision as of 02:34, 6 August 2015

This page summarizes the existing and the future solutions in RTK for improving image quality of cone-beam (CB) CT images. It is based on discussions at the RTK meeting on image quality.

X-ray source imperfections

  • Geometric blurring can be corrected by the scatter glare correction detailed in the detector imperfections section.
  • Exposure fluctuations from projection to projection are common. They can be corrected by rtk::I0EstimationProjectionFilter which automatically estimates a weighting constant per projection using an histogram analysis. This filter only works if there are pixels in each projections that measure x-rays that traversed air only (except maybe a few projections using a revursive least-square . The filter does not have any parameter except the bitshift template value for the reduction of the histogram size. It is implemented for integer pixel types only.
  • Focal spot motion cannot be corrected currently. It would require geometric calibration for each acquisition.

Detector imperfections

  • Lag: the [ rtk::] filter implements correction implements

, see [Poludniowski et al, PMB, 2011] implemetend in [rtk::]

Beam hardening

Statistical noise

  • RTK has a fast 2D median filter for projection images for a few kernel dimensiosn, see rtk::MedianImageFilter. A GPU version of the median filter will be developed in Salzburg (Austria).
  • Median filters do not preserve edges (see [Arias-Castro and Donoho, Annals of Statistics, 2009]. A multi-pass median filter is required which might be investigated in Louvain-La-Neuve (Belgium) in the future.
  • The Savitzky–Golay filter is a promising solution that will be investigated in Louvain-La-Neuve (Belgium) in the future. This solution also provides derivatives of the image.

Truncated projection images