S1653
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
Digital Poster 2606
Development and CT Based Evaluation of a 3D Printed Head Phantom Derived from the ICRP 145 Mesh Model Kyung-Hwan Jung 1 , Ki-Yoon Lee 1 , Hyun-Dong Kim 1 , Woo-Sang Ahn 2 , Cheol-Ha Baek 3 1 Department of Medical Health Science, Kangwon National University, Samcheok, Korea, Republic of. 2 Department of Radiation Oncology, Gangneung Asan Hospital, University of Ulsan College of Medicine, Gangneung, Korea, Republic of. 3 Department of Radiological Science, Kangwon National University, Samcheok, Korea, Republic of Purpose/Objective: This study aimed to fabricate an adult mesh-type head phantom based on the ICRP Publication 145 mesh- type reference computational phantom (MRCP) using a dual nozzle Fused Filament Fabrication (FFF) 3D printing technique. The purpose was to quantitatively evaluate the X-ray attenuation and electron density of different filament materials through CT imaging, and to verify their tissue equivalency and structural reproducibility by comparison with a commercial head phantom. Material/Methods: The head phantom model was generated by segmenting the skull and soft tissue structures from MRCP data using Rapidform (INUS Technology Inc., Korea), which were then converted into STL format and printed using an FFF 3D printer (MD-600D, Mingda Technology, China) with Mingda Orca Slicer software. PLA+ filament was used to simulate soft tissue and Bone filament for the skull. Cylindrical specimens were printed with varying infill densities (10–100%, in 10% increments) to evaluate the dependence of attenuation on internal density. For quantitative calibration, the HU–electron density (ρ ₑ ) relationship was established using the CIRS Electron Density Phantom 062M under the AAPM TG-66 recommended CT protocol (120 kVp, 200 mAs, slice thickness 2.5 mm). Three repeated scans were performed for both the CIRS phantom and the 3D printed specimens under identical conditions, and mean HU values were measured to determine electron density correlation. Results: The mean HU of PLA+ specimens increased linearly from −866 HU (10% infill) to +119 HU (100% infill) with a correlation coefficient of R² ≈ 0.99. The corresponding electron density rose from 0.12 g/cm³ to 1.23 g/cm³. The Bone filament showed a mean HU of +732 and an electron density of 1.25 g/cm³, closely matching the cortical bone insert of the CIRS phantom. The MRCP based 3D printed head phantom demonstrated accurate reproduction of both attenuation and structural features, when compared
Figure 2: Shielding comparison results at surface.For measurements at depth (figure 1), the dose reduction produced by the change to the FFF beam (around 30%) was substantially greater than the dose reduction produced by adding lead to shield the flattened beam (around 18%). Adding lead shielding to the FFF beam then reduced the dose at depth by only an additional 10%.Measurements at the phantom’s surface (figure 2) showed an obvious dose enhancement for anterior beams that was well-shielded by both the lead blocks and the bolus sheets, due to effective filtration of the substantial low-energy component in the linac head leakage signal [2,3].While the use of a thin layer of bolus produced minimal shielding at depth, application of this bolus to the anterior abdomen during treatment may may be advisable to reduce surface dose and achieve consistent and reliable in vivo measurements for foetal dose estimates during treatment delivery. Conclusion: A substantial reduction in foetal dose was achieved by changing the 6 MV flattened treatment beam to a 6 MV FFF beam, with only an additional 10% dose reduction achieved with lead shielding. This 10% dose reduction may be inadequate justification for using lead shielding with the FFF beam, given the various physical and toxicological hazards associated with lead use. References: 1. Takahashi W, et al., Clin Transl Radiat Oncol 20:9-12 (2020). doi: 10.1016/j.ctro.2019.10.0022. Kairn T, et al., IFMBE Proc 51: 557-560 (2015). doi:10.1007/978-3-319- 19387-8_1363. Peet S C, et al., Phys Eng Sci Med 45(2): 613-621 (2022). doi:10.1007/s13246-022-01131-54. Wani A L, et al., Interdiscip Toxicol 8(2): 55–64 (2015).
doi: 10.1515/intox-2015-00095. Eid A, Zawia N, Neurotoxicology56: 254–261 (2016). doi:
10.1016/j.neuro.2016.04.0066. Stovall M, et al., Med Phys 22(1): 63-82 (1995). doi: 10.1118/1.5975257. Luis SA, et al., J Med Imaging Radiat Oncol 53: 559–568 (2009) doi: 10.1111/j.1754-9485.2009.02124.x Keywords: radiation protection, shielding, pregnant
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