RTK/ImageQuality: Difference between revisions

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= Beam hardening =
= Beam hardening =


* The acquired data may be linearized for a given material using [http://www.openrtk.org/Doxygen/classrtk_1_1LookupTableImageFilter.html rtk::LookupTableImageFilter]. There are several solutions to compute the lookup table:
* The acquired data may be linearized for a given material using [http://www.openrtk.org/Doxygen/classrtk_1_1LookupTableImageFilter.html rtk::LookupTableImageFilter] as explained, e.g., in Fig. 1 of [http://iopscience.iop.org/0031-9155/21/3/004 <nowiki>[Brooks and Di Chiro, PMB, 1976]</nowiki>]. There are several solutions to compute the lookup table:
** Compute it from the knowledge of the spectrum of the x-ray source and the detector response,
** Compute it from the knowledge of the spectrum of the x-ray source and the detector response,
** Measure the attenuation for several thicknesses of the material of interest,
** Measure the attenuation for several thicknesses of the material of interest,

Revision as of 09:53, 5 August 2015

This page summarizes the existing and the future solutions in RTK for improving image quality of cone-beam (CB) CT images.

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

Truncated projection images