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Keywords:
Musculoskeletal bone, Pelvis, Radiation physics, CT, CT-Quantitative, Experimental investigations, Diagnostic procedure, Dosimetry, Prostheses, Dosimetric comparison
Authors:
R. H. H. Wellenberg1, M. F. Boomsma1, J. van Osch1, A. Vlassenbroek2, J. Milles3, D. Mueller4, M. Maas5; 1Zwolle/NL, 2Best/NL, 3Eindhoven/NL, 4Hamburg/DE, 5Amsterdam/NL
DOI:
10.1594/ecr2015/B-0567
Purpose
In CT-imaging metallic composites can cause severe artefacts,
especially in case of a large Metal-on-Metal (MoM) hip prostheses used for total hip arthroplasties (THA).
Sufficient photon detection is severely distorted due to photon-starvation,
beam hardening and scatter resulting in sub-optimal image quality,
illustrated in Figure 1.
Obtaining a reliable diagnose of pseudo-tumours,
capsular reactions and other weak tissue pathologies is difficult or even impossible.
These days several metal artefact reduction (MAR) techniques have shown to be valuable.
One of these MAR techniques is the orthopaedic metal artefact reduction algorithm O-MAR.
O-MAR is an effective iterative loop-algorithm where the output correction image is subtracted from the original input image.
The resultant image can then become the new input image and the process can be repeated. With O-MAR,
not only are severe streaking artifacts reduced,
substantial portions of obscured anatomy can now be visualized.
This new algorithm not only aims at the reduction of the most severe artifacts but also improves the low-contrast visibility close to the implant [1].
Recently,
a model-based iterative reconstruction (MBIR) technique IMR is introduced.
With this MBIR technique no blending with FBP occurs during image reconstructions as in other (hybrid) iterative reconstruction techniques.
Model-based means an optimization process where within many iterations data statistics,
image statistics and system models are taken into account in order to produce the best-fit image [2].
Several recent studies showed that model-based iterative reconstruction techniques are able to reduce image noise up to 75%-88% and radiation dose up to 75%-92% [3,4,5].