RTK/ImageQuality: Difference between revisions

From Openrtk
Jump to navigation Jump to search
Line 24: Line 24:
= Truncated projection images =
= Truncated projection images =


* The [http://www.openrtk.org/Doxygen/classrtk_1_1FFTRampImageFilter.html rtk::FFTRampImageFilter] implements the heuristic solution of [http://dx.doi.org/10.1118/1.598855 <nowiki>[Ohnesorge et al, Med Phys, 2000]</nowiki>]. The parameter TruncationCorrection must be set.
* The [http://www.openrtk.org/Doxygen/classrtk_1_1FFTRampImageFilter.html rtk::FFTRampImageFilter] implements the heuristic solution of [http://dx.doi.org/10.1118/1.598855 <nowiki>[Ohnesorge et al, Med Phys, 2000]</nowiki>]. The parameter TruncationCorrection must be adjusted.
* Exact reconstruction based differentiated backprojection and inverse Hilbert filtering (see, e.g., [http://dx.doi.org/10.1088/0031-9155/49/17/006 <nowiki>[Noo et al, PMB, 2004]</nowiki>] is investigated in Lyon.
* Exact reconstruction based differentiated backprojection and inverse Hilbert filtering (see, e.g., [http://dx.doi.org/10.1088/0031-9155/49/17/006 <nowiki>[Noo et al, PMB, 2004]</nowiki>]) is investigated in Lyon.

Revision as of 08:57, 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