Metal artifacts in patients with large dental implants and bridges: combination of metal artifact reduction algorithms and virtual monoenergetic images provides an approach to handle even strongest artifacts

Abstract

Objectives

This study compares reduction of strong metal artifacts from large dental implants/bridges using spectral detector CT-derived virtual monoenergetic images (VMI), metal artifact reduction algorithms/reconstructions (MAR), and a combination of both methods (VMIMAR) to conventional CT images (CI).

Methods

Forty-one spectral detector CT (SDCT) datasets of patients that obtained additional MAR reconstructions due to strongest artifacts from large oral implants were included. CI, VMI, MAR, and VMIMAR ranging from 70 to 200 keV (10 keV increment) were reconstructed. Objective image analyses were performed ROI-based by measurement of attenuation (HU) and standard deviation in most pronounced hypo-/hyperdense artifacts as well as artifact impaired soft tissue (mouth floor/soft palate). Extent of artifact reduction, diagnostic assessment of soft tissue, and appearance of new artifacts were rated visually by two radiologists.

Results

The hypo-/hyperattenuating artifacts showed an increase and decrease of HU values in MAR and VMIMAR (CI/MAR/VMIMAR-200keV: − 369.8 ± 239.6/− 37.3 ± 109.6/− 46.2 ± 71.0 HU, p < 0.001 and 274.8 ± 170.2/51.3 ± 150.8/36.6 ± 56.0, p < 0.001, respectively). Higher keV values in hyperdense artifacts allowed for additional artifact reduction; however, this trend was not significant. Artifacts in soft tissue were reduced significantly by MAR and VMIMAR. Visually, high-keV VMI, MAR, and VMIMAR reduced artifacts and improved diagnostic assessment of soft tissue. Overcorrection/new artifacts were reported that mostly did not hamper diagnostic assessment. Overall interrater agreement was excellent (ICC = 0.85).

Conclusions

In the presence of strong artifacts due to large oral implants, MAR is a powerful mean for artifact reduction. For hyperdense artifacts, MAR should be supplemented by VMI ranging from 140 to 200 keV. This combination yields optimal artifact reduction and improves the diagnostic image assessment in imaging of the head and neck.

Key Points

• Large oral implants can cause strong artifacts.

• MAR is a powerful tool for artifact reduction considering such strong artifacts.

• Hyperdense artifact reduction is supplemented by VMI of 140–200 keV from SDCT.

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Abbreviations

CI:

Conventional images

MAR:

Metal artifact reduction algorithm

SD:

Standard deviation

SDCT:

Spectral detector CT

VMI:

Virtual monoenergetic images

VMIMAR :

Combination of virtual monoenergetic images and metal artifact reduction algorithms

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Funding

The authors state that this work has not received any funding.

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Corresponding author

Correspondence to Kai Roman Laukamp.

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Guarantor

The scientific guarantor of this publication is Kai Roman Laukamp.

Conflict of interest

The authors of this manuscript declare relationships with the following companies: David Maintz, Jan Borggrefe, and Nils Große Hokamp received speakers’ honoraria from Philips Healthcare.

Statistics and biometry

No complex statistical methods were necessary for this paper.

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Written informed consent was waived by the Institutional Review Board.

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Institutional Review Board approval was obtained.

Methodology

• retrospective

• experimental

• performed at one institution

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Laukamp, K.R., Zopfs, D., Lennartz, S. et al. Metal artifacts in patients with large dental implants and bridges: combination of metal artifact reduction algorithms and virtual monoenergetic images provides an approach to handle even strongest artifacts. Eur Radiol 29, 4228–4238 (2019). https://doi.org/10.1007/s00330-018-5928-7

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Keywords

  • Tomography, X-ray computed
  • Artifacts
  • Head and neck neoplasms
  • Neoplasm metastasis