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. 2020 Jan-Apr;15(1):1-6.
doi: 10.5005/jp-journals-10080-1446.

Evaluation of Patient Positioning during Digital Tomosynthesis and Reconstruction Algorithms for Ilizarov Frames: A Phantom Study

Yuki Abe  1 , Makoto Shimada  1 , Yoshihiro Takeda  1 , Taisuke Enoki  2 , Kumiko Omachi  3 , Shuji Abe  4
Affiliations

Evaluation of Patient Positioning during Digital Tomosynthesis and Reconstruction Algorithms for Ilizarov Frames: A Phantom Study

Yuki Abe et al. Strategies Trauma Limb Reconstr. 2020 Jan-Apr.

Abstract

Aim: Metallic components from circular external fixators, including the Ilizarov frame, cause artefacts on X-rays and obstruct clear visualisation of bone detail. We evaluated the ability of tomosynthesis to reduce interference on radiographs caused by metal artefacts and developed an optimal image acquisition method for such cases.

Materials and methods: An Ilizarov frame phantom was constructed using rods placed on the bone for the purpose to evaluate the benefits of tomosynthesis. Distances between the rod and bone and the angle between the rod and X-ray tube orbit were set at three different levels. Filtered backprojection images were reconstructed using two different features of the reconstruction function: THICKNESS-- (CONTRAST4) and THICKNESS++ (METAL4); the first is suitable for improving contrast and the second is suitable for metal artefacts. The peak signal-to-noise ratio (PSNR) was used during image evaluation to determine the influence of the metallic rod on bone structure visibility.

Results: The PSNR increased as the angle between the metal rod and the X-ray tube orbit and the distance between the metallic rod and bone increased. The PSNR was larger when using THICKNESS-- (CONTRAST4) than when using THICKNESS++ (METAL4).

Conclusion: The optimal reconstruction function and image acquisition determined using the metallic rod in this study suggest that quality equal to that without the metallic rod can be obtained.

Clinical significance: We describe an optimised method for image acquisition without unnecessary acquisition repetition and unreasonable posture changes when the bone cannot be adequately visualised.

How to cite this article: Abe Y, Shimada M, Takeda Y, et al. Evaluation of Patient Positioning during Digital Tomosynthesis and Reconstruction Algorithms for Ilizarov Frames: A Phantom Study. Strategies Trauma Limb Reconstr 2020;15(1):1-6.

Keywords: Digital tomosynthesis; Ilizarov; Metal artefacts; Metallic rod; Peak signal-to-noise ratio; X-ray.

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Conflict of interest statement

Source of support: Nil Conflict of interest: None

Figures

Figs 1A to H
Figs 1A to H
Phantom setup and determination of regions of interest. (A to C) Lateral view of the examination table. The distance between the metallic rod and bone was set at 45 mm (A), 65 mm (B), and 85 mm (C). (D to F) Vertical view of the examination table. The angle between the metallic rod and X-ray scanning direction was set at 10° (D), 25° (E), and 40° (F). The measurement point, its enlarged view, and corresponding pixel value in the case of the bone phantom only (G). The bone phantom with a metallic rod and the PSNR value (calculated using G) is 10.48 (H). ROI, region of interest
Figs 2A to F
Figs 2A to F
Examples of digital tomosynthesis images: (A) Images acquired at a 10° angle and 45-mm distance using THICKNESS−− (CONTRAST4). The peak signal-to-noise ratio (PSNR) was 12.55; (B) Image acquired at a 10° angle and 45-mm distance using THICKNESS++ (METAL4). The PSNR was 10.48; (C) Image acquired at a 10° angle and 65-mm distance using THICKNESS−− (CONTRAST4). The PSNR was 17.11; (D) Image acquired at a 10° angle and 85-mm distance using THICKNESS−− (CONTRAST4). The PSNR was 19.82; (E) Image acquired at a 25° angle and 45-mm distance using THICKNESS−− (CONTRAST4). The PSNR was 17.01; (F) Image acquired at a 40° angle and 45-mm distance using THICKNESS−− (CONTRAST4). The PSNR was 20.07
Figs 3A and B
Figs 3A and B
(A) Helical nature of the computed tomography scanning process; (B) Digital tomosynthesis scanning process
See this image and copyright information in PMC

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