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Metal artifact correction in photon-counting detector computed tomography: metal trace replacement using high-energy
Devon Richtsmeier1, Jericho O'Connell1, Pierre-Antoine Rodesch1
1Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, Canada.
Medical Physics
|October 13, 2022
Summary
A new trace replacement MAR (TRMAR) algorithm effectively reduces metal artifacts in photon-counting detector CT (PCD-CT) images. This method uses high-energy data to correct artifacts, offering improved image quality and faster computation than existing techniques.
Area of Science:
- Medical Imaging
- Computed Tomography
- Photon-Counting Detectors
Background:
- Metal artifacts are a persistent challenge in computed tomography (CT), degrading image quality.
- Photon-counting detectors (PCDs) offer energy-discriminating capabilities, showing promise for metal artifact reduction (MAR).
- High-energy data from PCDs can mitigate beam hardening artifacts but may reduce contrast and increase noise.
Purpose of the Study:
- To introduce and evaluate a novel MAR algorithm, trace replacement MAR (TRMAR).
- TRMAR utilizes high-energy PCD data to correct artifacts in full-spectrum projections, aiming for improved image quality.
- To compare TRMAR's performance against existing MAR methods and high-energy reconstructions.
Main Methods:
- Developed and tested the TRMAR algorithm using a bench-top PCD-CT system and simulations.
- Employed XCAT and biological phantoms, including a beef short rib, with and without metal implants.
- Segmented metal implants to identify corrupted data in sinogram space for TRMAR correction.
- Compared TRMAR reconstructions with uncorrected data and normalized metal artifact reduction (NMAR).
Main Results:
- TRMAR significantly reduced streak artifacts in simulations (-978 HU to -10 HU) and phantom studies (-442 HU to -142 HU).
- Relative image noise was reduced from 176% in high-energy images to 56% with TRMAR.
- TRMAR preserved spatial resolution (1.31 lp/mm) better than NMAR (1.22 lp/mm) and showed improved metal shape delineation in realistic phantoms.
Conclusions:
- TRMAR provides effective metal artifact reduction with improved image quality compared to high-energy reconstructions alone.
- While NMAR showed slightly better artifact reduction and density quantification, TRMAR is less sensitive to segmentation errors.
- TRMAR achieves comparable artifact reduction to NMAR at one-third the computational cost, presenting a promising solution for clinical PCD-CT.
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