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. 2022 Dec 23;13(1):50.
doi: 10.3390/diagnostics13010050.

Dual-Energy Computed Tomography Applications to Reduce Metal Artifacts in Hip Prostheses: A Phantom Study

Daniele Conti  1 , Fabio Baruffaldi  1 , Paolo Erani  1 , Anna Festa  1 , Stefano Durante  2 , Miriam Santoro  1
Affiliations

Dual-Energy Computed Tomography Applications to Reduce Metal Artifacts in Hip Prostheses: A Phantom Study

Daniele Conti et al. Diagnostics (Basel). .

Abstract

Metal components of hip prostheses cause severe artifacts in CT images, influencing diagnostic accuracy. Metal artifact reduction (MAR) software and virtual monoenergetic reconstructions on dual-energy CT (DECT) systems are possible solutions that should be considered. In this study, we created a customized adjustable phantom to quantify the severity of artifacts on periprosthetic tissues (cortical and spongious bone, soft tissues) for hip prostheses. The severity of artifacts was classified by different thresholds of deviation from the CT numbers for reference objects not affected by artifacts. The in vitro setup was applied on four unilateral and three bilateral configurations of hip prostheses (made of titanium, cobalt, and stainless steel alloys) with a DECT system, changing the energy of virtual monoenergetic reconstructions, with and without MAR. The impact of these tools on the severity of artifacts was scored, looking for the best scan conditions for the different configurations. For titanium prostheses, the reconstruction at 110 keV, without MAR, always minimized the artifacts. For cobalt and stainless-steel prostheses, MAR should always be applied, while monoenergetic reconstruction alone did not show clear advantages. The available tools for reducing metal artifacts must therefore be applied depending on the examined prosthetic configuration.

Keywords: arthroplasty; diagnostic imaging; dual-energy computed tomography; hip prosthesis; metal artifact reduction; spectral imaging CT.

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Conflict of interest statement

The authors declare no conflict of interest. The co-funder had no role in the design of the study, in the collection, analysis, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Adjustable system to put the triplets in direct contact with the hip prosthesis. Translational and rotational degrees of freedom of the triplets.
Figure 2
Figure 2
(a) Pellets positions around the prosthesis, TI configuration; (b) Coronal reconstruction.
Figure 3
Figure 3
TI unilateral configuration, coronal reconstruction (bone CT visualization window WL:300, WW:1500 (a) virtual monochromatic imaging (VMI) reconstructed at 130 keV; and (b) virtual monochromatic reconstruction imaging (VMI) reconstructed at 130 keV + metal artifact reduction spectral (MARS) algorithm.
Figure 4
Figure 4
SS unilateral configuration, coronal reconstruction (bone CT visualization window WL:300, WW:1500 (a) VMI reconstructed at 90 keV; and (b) VMI reconstructed at 90 keV + MARS.
Figure 5
Figure 5
TI+SS bilateral configuration (bone CT visualization window WL:300, WW:1500). TI right prosthesis coupled with a left SS prosthesis. VMI reconstructed at 130 keV.
Figure 6
Figure 6
Mean CT numbers of VMI without (90, 110, 130) and with the MARS algorithm (90+M, 110+M, 130+M) for all the prosthetic configurations. Values are reported for pellets with low (upper), medium (central), and high (lower) density in positions b1, b2, b3, b4, and b5 indicated in blue, orange, yellow, purple, and green, respectively. The reference values are indicated in white. The statistically significant values of the Wilcoxon (W p < 0.05, to determine the effect of the MARS application) and Kruskal-Wallis (K-W p < 0.05, to determine the effect of changing the reconstruction energies, either with or without MARS) tests are also reported.
Figure 7
Figure 7
Mean CT number, noise, and SNR for low-density pellets of classified artifacts as a function of the reconstructed images, i.e., VMI without (90, 110, 130) and with the MARS algorithm (90+M, 110+M, and 130+M). The values for mild low, mild up, and severe artifact are reported with yellow, green, and red lines, respectively. The reference values are indicated with a blue line.
Figure 8
Figure 8
Mean CT number, noise, and SNR for medium-density pellets of classified artifacts as a function of the reconstructed images, i.e., VMI without (90, 110, 130) and with the MARS algorithm (90+M, 110+M, and 130+M). The values for mild low, mild up, and severe artifact are reported with yellow, green, and red lines, respectively. The reference values are indicated with a blue line.
Figure 9
Figure 9
Mean CT number, noise, and SNR for high-density pellets of classified artifacts as a function of the reconstructed images, i.e., VMI without (90, 110, and 130) and with the MARS algorithm (90+M, 110+M, and 130+M). The values for mild low, mild up, and severe artifact are reported with yellow, green, and red lines, respectively. The reference values are indicated with a blue line.
Figure 10
Figure 10
Counts for mild, severe, and total (sum of mild and severe) artifacts in prostheses from unilateral configurations, varying the reconstruction energies (VMI reconstructed without MARS, indicated as 90, 110, and 130, and VMI reconstructed with MARS, indicated as 90+M, 110+M, and 130+M). The counts of mild, severe, and total artifacts are indicated with yellow, red, and black bars, respectively. Results from TI, CO cem., CO, and SS configuration are displayed in panels (a–d), respectively.
Figure 11
Figure 11
Counts for mild, severe, and total (sum of mild and severe) artifacts in prostheses from bilateral configurations, varying the reconstruction energies (VMI reconstructed without MARS, indicated as 90, 110, and 130, and VMI reconstructed with MARS, indicated as 90+M, 110+M, and 130+M). The counts of mild, severe, and total artifacts are indicated with yellow, red, and black bars, respectively. Results from TI(+SS) and (TI+)SS, CO(+TI), (CO+)TI, CO(+SS), and (CO+)SS configurations are displayed in panels (a–f), respectively.
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