High-contrast object localization and removal in cone-beam CT

D. J. Moseley, J. H. Siewerdsen, D. A. Jaffray

Research output: Contribution to journalConference articlepeer-review

13 Scopus citations


In image-guided procedures high-contrast objects often appear in the imaging field-of-view for the purpose of guiding treatment (e.g., markers intended to localize the target) or delivering treatment (e.g., surgical tools, or in the case of brachytherapy, radioactive seeds). In cone-beam CT reconstructions, these high-contrast objects cause severe streak artifacts, CT number inaccuracy and loss of soft-tissue visibility. We have developed an iterative approach by which high-contrast objects are localized in the 2-D projection set by re-projecting conspicuities from the first-pass 3-D reconstruction. The projection operator, which finds the unique mapping from the world coordinate system to the detector coordinate system for each view angle, is computed from a geometric calibration of the system. In each projection, a two-dimensional 2nd order Taylor series is used to interpolate over the high-contrast objects. The interpolated surface is further modified using a local noise estimate to completely mask the objects. The algorithm has been applied to remove artifacts resulting from a small number of gold fiducial markers in patients being imaged daily with cone-beam CT for guidance of prostate radiotherapy. The algorithm has also been applied to post-operative images of a prostate brachytherapy patient in which the number of seeds can exceed ∼100. In each case, the method provides excellent attenuation of image artifact and restoration of soft-tissue visibility. Using a local voxel based metric it was shown that the 2nd order Taylor series with added noise performed best at removing the high-contrast objects from the reconstruction volume.

Original languageEnglish (US)
Article number06
Pages (from-to)40-50
Number of pages11
JournalProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Issue numberI
StatePublished - 2005
Externally publishedYes
EventMedical Imaging 2005 - Physics of Medical Imaging - San Diego, CA, United States
Duration: Feb 13 2005Feb 15 2005


  • Computed tomography
  • Cone-beam CT
  • Image-guided procedures
  • Metal artifacts

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging
  • Biomaterials


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