Abstract
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 language | English (US) |
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Article number | 06 |
Pages (from-to) | 40-50 |
Number of pages | 11 |
Journal | Progress in Biomedical Optics and Imaging - Proceedings of SPIE |
Volume | 5745 |
Issue number | I |
DOIs | |
State | Published - 2005 |
Externally published | Yes |
Event | Medical Imaging 2005 - Physics of Medical Imaging - San Diego, CA, United States Duration: Feb 13 2005 → Feb 15 2005 |
Keywords
- 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