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Session: Advances in Photon-Counting Imaging [Return to Session]

Metal Artifact Correction Using High-Energy Data in Photon-Counting CT

D Richtsmeier1*, J O'Connell1, P Rodesch1, K Iniewski2, M Bazalova-Carter1, (1) University of Victoria, Victoria, BC, CA, (2) Redlen Technologies, Saanichton, BC, CA


WE-G-201-5 (Wednesday, 7/13/2022) 2:45 PM - 3:45 PM [Eastern Time (GMT-4)]

Room 201

Purpose: To develop an efficient, robust method of metal artifact reduction in photon-counting computed tomography (PCCT) using high-energy data for metal trace replacement.

Methods: Phantom images were acquired using a bench-top PCCT system with a cadmium zinc telluride photon-counting detector (PCD). The high-density polyethylene phantom held small plastic vials containing water and bone analog solutions. Two steel screws were also inserted along with a spatial resolution piece placed between the two screws. The energy thresholds of the PCD were set to 30/50/70/100/110/120 keV. The metal screws were segmented in original PCCT images via simple thresholding and forward projected to obtain a mask of the metal in the sinogram space. The metal traces in the 30-120 keV sinogram were then corrected by replacing them with the equivalent data from the 100-110 keV bin, which suffers less from beam hardening and photon starvation. PCCT images of the phantom without screws and images corrected with the normalized metal artifact reduction (NMAR) method were used for comparison.

Results: The magnitude of the main metal artifact, calculated as the mean value of a region of interest between the screws, was reduced from -442 HU in uncorrected PCCT reconstructions to -157 HU in PCCT images corrected with trace replacement. Relative image noise decreased by 4.3% in the trace replacement reconstructions compared to the uncorrected images. Contrast was reduced by less than 5.5% in trace replacement images compared to PCCT images of the phantom with no metal. Additionally, small features were better preserved using trace replacement compared to NMAR.

Conclusion: Trace replacement provides a simple, efficient method to reduce metal artifacts in PCCT that gives better, or comparable, results to NMAR. With the recent approval of a clinical PCCT system, more advanced avenues for metal artifact reduction are increasingly relevant in clinical practice.

Funding Support, Disclosures, and Conflict of Interest: The authors would like to thank Alexander J. Hart for his contribution in dose calculation. This work was partly funded by NSERC Alliance and Engage Plus grants, NSERC CGS-D, an NSERC Discovery grant, the Canada Foundation for Innovation, the British Columbia Knowledge Development Fund, and the Canada Research Chair program.


CT, Photon Detectors, Image Artifacts


IM- CT: Dual Energy and Spectral

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