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. 2023 May;33(2):168-181.
doi: 10.1016/j.zemedi.2022.05.002. Epub 2022 Jul 2.

Additively manufactured test phantoms for mimicking soft tissue radiation attenuation in CBCT using Polyjet technology

Sepideh Hatamikia  1 , Gunpreet Oberoi  2 , Anna Zacher  3 , Gernot Kronreif  4 , Wolfgang Birkfellner  2 , Joachim Kettenbach  5 , Stefanie Ponti  3 , Andrea Lorenz  4 , Martin Buschmann  6 , Laszlo Jaksa  4 , Nikolaus Irnstorfer  7 , Ewald Unger  2
Affiliations

Additively manufactured test phantoms for mimicking soft tissue radiation attenuation in CBCT using Polyjet technology

Sepideh Hatamikia et al. Z Med Phys. 2023 May.

Abstract

Objectives: To develop and validate a simple approach for building cost-effective imaging phantoms for Cone Beam Computed Tomography (CBCT) using a modified Polyjet additive manufacturing technology where a single material can mimic a range of human soft-tissue radiation attenuation.

Materials and methods: Single material test phantoms using a cubic lattice were designed in 3-Matic 15.0 software . Keeping the individual cubic lattice volume constant, eight different percentage ratio (R) of air: material from 0% to 70% with a 10% increment were assigned to each sample. The phantoms were printed in three materials, namely Vero PureWhite, VeroClear and TangoPlus using Polyjet technology. The CT value analysis, non-contact profile measurement and microCT-based volumetric analysis was performed for all the samples.

Results: The printed test phantoms produced a grey value spectrum equivalent to the radiation attenuation of human soft tissues in the range of -757 to +286 HU on CT. The results from dimensional comparison analysis of the printed phantoms with the digital test phantoms using non-contact profile measurement showed a mean accuracy of 99.07 % and that of micro-CT volumetric analysis showed mean volumetric accuracy of 84.80-94.91%. The material and printing costs of developing 24 test phantoms was 83.00 Euro.

Conclusions: The study shows that additive manufacturing-guided macrostructure manipulation modifies successfully the radiographic visibility of a material in CBCT imaging with 1 mm3 resolution, helping customization of imaging phantoms.

Keywords: Additive manufacturing; CT; Cone Beam CT; Imaging phantoms; Macrostructure; Material modification; Micro-CT; Profilometer; Radiation attenuation.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
Test phantom design. A) The base design of the test phantom macrostructure. B) Stereolithographic (STL) file from the design process in Materialise 3-Matic software, x is the length of each internal cubic and s is the thickness of each pillar.
Figure 2
Figure 2
A) represents assembled STL file models imported from 3D Slicer software, B) represents final phantom with the included lattice structures for the corresponding structures in 3Matic software.
Figure 3
Figure 3
A view of profile comparison using a non-contact measurement profilometer in test phantoms printed in Vero PureWhite. A) Optical profile, B) 3D profile, C) profile graph for test phantom height measurement, D) optical diameter.
Figure 4
Figure 4
A) Figure showing Stereolithographic (STL) design of the test phantom in eight different R values (ratio of air: material ratios), R1 to R8 in Materialise 3-Matic software, B) Additively manufactured cylindrical test phantoms using three different Polyjet materials from R1 to R8.
Figure 5
Figure 5
Figure showing the grey value spectrum of the additively manufactured test phantoms derived from CBCT scans. An axial slice of the CBCT using linac CBCT (up) and C-arm CBCT (down) in the three materials Vero PureWhite, VeroClear and TangoPlus using different ratios (R1-R8). The display window shows linear attenuation coefficient and is set to the gray value range [0–4.7].
Figure 6
Figure 6
Graph showing the resulting HUs from CT analysis of test phantoms from the three different materials including Vero PureWhite, VeroClear and TangoPlus related to R1 to R8. The linear graphs are a linear approximation of the corresponding graphs.
Figure 7
Figure 7
A) Additively manufactured example use case phantom B) An axial slice of the CBCT using linac CBCT. The display window shows linear attenuation coefficient and is set to the gray value range [0–6].
Figure 8
Figure 8
Figure showing the results from dimensional comparisons. A) Graph showing the results from non-contact profilometer measurement A) mean height, and B) mean diameter, for additively manufactured test phantoms in three different materials in ratios R1 to R8, C) Results from micro-CT volumetric comparison for test phantoms printed in three different materials from R1 to R8.
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