Computed tomography is the modality of choice for measuring osteolysis but suffers from metal-induced artefacts obscuring
periprosthetic tissues. Previous papers on metal artefact reduction (MAR) show qualitative improvements, but their algorithms
have not found acceptance for clinical applications. We investigated to what extent metal artefacts interfere with the segmentation
of lesions adjacent to a metal femoral implant and whether metal artefact reduction improves the manual segmentation of such
Materials and methods
We manually created 27 periprosthetic lesions in 10 human cadaver femora. We filled the lesions with a fibrotic interface
tissue substitute. Each femur was fitted with a polished tapered cobalt-chrome prosthesis and imaged twice—once with the metal,
and once with a substitute resin prosthesis inserted. Metal-affected CTs were processed using standard back-projection as
well as projection interpolation (PI) MAR. Two experienced users segmented all lesions and compared segmentation accuracy.
We achieved accurate delineation of periprosthetic lesions in the metal-free images. The presence of a metal implant led us
to underestimate lesion volume and introduced geometrical errors in segmentation boundaries. Although PI MAR reduced streak
artefacts, it led to greater underestimation of lesion volume and greater geometrical errors than without its application.
CT metal artefacts impair image segmentation. PI MAR can improve subjective image appearance but causes loss of detail and
lower image contrast adjacent to prostheses. Our experiments showed that PI MAR is counterproductive for manual segmentation
of periprosthetic lesions and should be used with care.
Keywords Computed tomography – Metal artifact reduction – Osteolysis – Segmentation – Beam hardening
This study was funded by the Netherlands Organization for Scientific Research (NWO) and the Stichting STW.
All work was performed at Leiden University Medical Center, Leiden, The Netherlands.