Reducing Metal Artifacts in Clinical Photon Counting Detector Computed Tomography-A Phantom Study of an Exemplary Total Hip Arthroplasty.

Abstract

To examine how different photon-counting detector (PCD) CT scanning and reconstruction methods affect the volume of metal artifacts and image quality for a hip prosthesis phantom. A titanium and cobalt-chromium-molybdenum-alloy total hip prosthesis phantom was scanned using a clinical PCD-CT with a constant tube potential (140kV) and Computed-Tomography-Dose- Index (7mGy). Different scan settings were used: with/without tin-filter (Sn), with/without ultra-high resolution (UHR), both individually and combined, resulting in four modes: Quantumplus (Standard), UHR Quantumplus (HighRes), QuantumSn (Standard-Tin) and UHR QuantumSn (HighRes-Tin). Reconstructions included virtual monoenergetic images (VMI) spanning 40-190keV and polychromatic images, with/without iterative metal artifact reduction (MAR). Artifact volumes rendered in a 3D-printing software were quantified in milliliters (ml), and image quality was evaluated using a Likert score. Polychromatic reconstruction: Tin-filter reduced artifact volumes (298 (Standard-Tin) vs. 347ml (Standard) and 310 (HighRes-Tin) vs. 360ml (HighRes)). The smallest artifact volume was measured in HighRes MAR (150ml). VMI reconstruction: The smallest artifact volume was measured in Standard 130keV (150ml) and HighRes 130keV (164ml) and in Standard-Tin 120keV (169ml) and HighRes-Tin 120keV (172ml). MAR further reduced the artifact volumes to 130ml (Standard 150keV MAR) and 140ml (HighRes 160keV MAR). Image quality was rated best for Standard 65keV MAR, polychromatic HighRes MAR, Standard 100keV MAR, polychromatic Standard-tin MAR, HighRes-tin 100keV and polychromatic HighRes-tin. Combining tin-filter, UHR and MAR in VMI or polychromatic images achieve the strongest artifact reduction.