{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T01:33:12Z","timestamp":1769045592471,"version":"3.49.0"},"reference-count":29,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T00:00:00Z","timestamp":1768953600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>Accurate immobilization is critical in head and neck (H&amp;N) radiotherapy to ensure precise dose delivery while minimizing irradiation of surrounding healthy tissues. However, conventional thermoplastic masks cannot secure 100% replicas of the patient\u2019s surface and are often limited by mechanical weakness, patient discomfort, and workflow inefficiencies. Recently, the best replicas of the patient\u2019s face have been obtained by exploring personal CT or MRI scans of patients that are used for manufacturing of immobilization masks. This study aimed to design and evaluate customizable immobilization masks using acrylonitrile butadiene styrene (ABS)-based composites reinforced with bismuth oxide (Bi2O3) and to compare their mechanical performance against commercial thermoplastic masks. ABS and ABS\/Bi2O3 composite filaments (5, 10, and 20 wt%) were fabricated and characterized by tensile testing. A patient-specific virtual mask was modeled and subjected to finite element analysis (FEA) under clinically relevant loading scenarios, including neck flexion and lateral bending. Results were benchmarked against two commercial thermoplastic masks. ABS and ABS-based composites exhibited significantly higher stiffness (1.7\u20132.5 GPa) and yield strength (20\u201325 MPa) compared to commercial thermoplastics (0.25\u20130.3 GPa, ~7 MPa; p &lt; 0.001). FEA simulations revealed markedly reduced displacement in ABS masks (1\u20135 mm at 2 mm thickness; &lt;1 mm at 4 mm thickness) relative to commercial masks, which exceeded 20 mm under lateral load. Hybrid configurations with reinforced edges further optimized rigidity while limiting material usage. Customized ABS-based immobilization masks outperform conventional thermoplastics in mechanical stability and displacement control, with the potential to reduce planning margins and improve patient comfort. In addition, ABS-based masks can be recycled, and Bi2O3-filled composites can be reused for printing new immobilization masks, thus contributing to a reduced amount of plastic waste. These findings support their promise as next-generation immobilization devices for precision radiotherapy, warranting further clinical validation, workflow integration and sustainable implementation within a circular economy.<\/jats:p>","DOI":"10.3390\/polym18020287","type":"journal-article","created":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T11:11:17Z","timestamp":1768993877000},"page":"287","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Modeling and Evaluation of Customizable Immobilization Masks for Precision Radiotherapy"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8683-8757","authenticated-orcid":false,"given":"Diana","family":"Adlien\u0117","sequence":"first","affiliation":[{"name":"Department of Physics, Kaunas University of Technology, Studentu Str. 50, 51368 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9774-9461","authenticated-orcid":false,"given":"Antonio","family":"Jreije","sequence":"additional","affiliation":[{"name":"Department of Physics, Kaunas University of Technology, Studentu Str. 50, 51368 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1011-4469","authenticated-orcid":false,"given":"Paulius","family":"Gri\u0161kevi\u010dius","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, Kaunas University of Technology, Studentu Str. 56, 51424 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Neringa","family":"Ker\u0161ien\u0117","sequence":"additional","affiliation":[{"name":"Department of Physics, Kaunas University of Technology, Studentu Str. 50, 51368 Kaunas, Lithuania"},{"name":"Department of Mechanical Engineering, Kaunas University of Technology, Studentu Str. 56, 51424 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"R\u016bta","family":"Nedzinskien\u0117","sequence":"additional","affiliation":[{"name":"School of Economics and Business, Kaunas University of Technology, Gedimino Str. 50, 44029 Kaunas, Lithuania"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"6490","DOI":"10.18632\/oncotarget.24032","article-title":"3D-Printed masks as a new approach for immobilization in radiotherapy\u2013a study of positioning accuracy","volume":"9","author":"Haefner","year":"2018","journal-title":"Oncotarget"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"72","DOI":"10.1186\/s13014-017-0807-y","article-title":"Setup errors in patients with head-neck cancer (HNC), treated using the Intensity Modulated Radiation Therapy (IMRT) technique: How it influences the customised immobilisation systems, patient\u2019s pain and anxiety","volume":"12","author":"Contesini","year":"2017","journal-title":"Radiat. Oncol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"92","DOI":"10.1016\/j.ejmp.2020.05.005","article-title":"Repositioning accuracy of a novel thermoplastic mask for head and neck cancer radiotherapy","volume":"74","author":"Fukao","year":"2020","journal-title":"Phys. Med."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1032","DOI":"10.1007\/s00066-022-01963-w","article-title":"Evaluation of novel 3D-printed and conventional thermoplastic stereotactic high-precision patient fixation masks for radiotherapy","volume":"198","author":"Miron","year":"2022","journal-title":"Strahlenther. Und Onkol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1002\/jmrs.308","article-title":"Exploring the prevalence and experience of mask anxiety for the person with head and neck cancer undergoing radiotherapy","volume":"65","author":"Nixon","year":"2018","journal-title":"J. Med. Radiat. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"220","DOI":"10.1002\/jmrs.208","article-title":"Reduced patient anxiety as a result of radiation therapist-led psychosocial support: A systematic review","volume":"64","author":"Elsner","year":"2017","journal-title":"J. Med. Radiat. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"101801","DOI":"10.1016\/j.adro.2025.101801","article-title":"Evaluating the Impact of Invasive Intubation on Treatment Accuracy in Head and Neck Cancer Patients Undergoing Image-Guided Radiation Therapy","volume":"10","author":"Kang","year":"2025","journal-title":"Adv. Radiat. Oncol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e70058","DOI":"10.1002\/acm2.70058","article-title":"Assessing the rigidity of thermoplastic masks for head immobilization effectiveness in stereotactic radiosurgery","volume":"26","author":"Apale","year":"2025","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Yoram, F., Dharsee, N., Mkoka, D.A., Maunda, K., and Kisukari, J.D. (2023). Radiation therapists\u2019 perceptions of thermoplastic mask use for head and neck cancer patients undergoing radiotherapy at Ocean Road Cancer Institute in Tanzania: A qualitative study. PLoS ONE, 18.","DOI":"10.1371\/journal.pone.0282160"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"i69","DOI":"10.1093\/jrr\/rrt038","article-title":"Analysis of inter-and intrafraction accuracy of a commercial thermoplastic mask system used for image-guided particle radiation therapy","volume":"54","author":"Amelio","year":"2013","journal-title":"J. Radiat. Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.tipsro.2016.12.001","article-title":"ESTRO ACROP guidelines for positioning, immobilisation and position verification of head and neck patients for radiation therapists","volume":"1","author":"Leech","year":"2017","journal-title":"Tech. Innov. Patient Support Radiat."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1016\/j.phro.2020.03.003","article-title":"A review of 3D printed patient specific immobilisation devices in radiotherapy","volume":"13","author":"Asfia","year":"2020","journal-title":"Phys. Imaging Radiat. Oncol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1043","DOI":"10.1007\/s11548-021-02393-2","article-title":"Individual 3D-printed fixation masks for radiotherapy: First clinical experiences","volume":"16","author":"Mattke","year":"2021","journal-title":"Int. J. Comput. Assist. Radiol. Surg."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Yin, Y., Zhang, W., Zou, L., Liu, X., Yu, L., and Wang, M. (2025). Segmentation methods and dosimetric evaluation of 3D-printed immobilization devices in head and neck radiotherapy. BMC Cancer, 25.","DOI":"10.1186\/s12885-025-13669-0"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1186\/s13014-025-02648-1","article-title":"The investigation of opening modes of head and neck thermoplastic mask for radiotherapy based on finite element analysis","volume":"20","author":"Pang","year":"2025","journal-title":"Radiat. Oncol."},{"key":"ref_16","first-page":"100663","article-title":"A total inverse planning paradigm: Prospective clinical trial evaluating the performance of a novel MR-based 3D-printed head immobilization device","volume":"42","author":"Jablonska","year":"2023","journal-title":"Clin. Transl. Radiat. Oncol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"e14008","DOI":"10.1002\/acm2.14008","article-title":"Clinical experience in the use of 3D printing as a rapid replacement of traditional radiation therapy immobilization materials","volume":"24","author":"Ehler","year":"2023","journal-title":"J. Appl. Clin. Med. Phys."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"165298","DOI":"10.1016\/j.nimb.2024.165298","article-title":"Properties of irradiated Bi2O3 and TiO2 enriched 3D printing polymers for fabrication of patient specific immobilization devices in radiotherapy","volume":"549","author":"Jreije","year":"2024","journal-title":"Nucl. Instrum. Methods Phys. Res. B"},{"key":"ref_19","unstructured":"(2025). Plastics\u2014Determination of Tensile Properties\u2014Part 2: Test Conditions for Moulding and Extrusion Plastics (Standard No. ISO 527-2:2025)."},{"key":"ref_20","unstructured":"(2019). Plastics\u2014Determination of tensile properties\u2014Part 1: General principles (Standard No. ISO 527-1:2019)."},{"key":"ref_21","unstructured":"MakeHuman Community (2025, October 14). MakeHuman, Version 1.3.0; [Computer software]; 2024. Available online: https:\/\/static.makehumancommunity.org\/makehuman.html."},{"key":"ref_22","unstructured":"Blender Foundation (2025, October 14). Blender, Available online: https:\/\/www.blender.org."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"453","DOI":"10.4085\/1062-6050-45.5.453","article-title":"Retest reliability of force-time variables of neck muscles under isometric conditions","volume":"45","author":"Almosnino","year":"2010","journal-title":"J. Athl. Train."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"122","DOI":"10.46475\/asean-jr.v24i2.808","article-title":"Comparative study of setup errors between new and reused thermoplastic masks in irradiated head and neck cancer patients","volume":"24","author":"Chumsuwan","year":"2023","journal-title":"Asean J. Radiol."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Ceretti, D.V., Edeleva, M., Cardon, L., and D\u2019hooge, D.R. (2023). Molecular pathways for polymer degradation during conventional processing, additive manufacturing, and mechanical recycling. Molecules, 28.","DOI":"10.3390\/molecules28052344"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"848","DOI":"10.1002\/pc.26415","article-title":"Development, characterization, and tribological behavior of polymeric carbon nitride\/acrylonitrile butadiene styrene nanocomposites","volume":"43","author":"George","year":"2022","journal-title":"Polym. Compos."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"24454","DOI":"10.1021\/acsomega.3c02246","article-title":"Enhancement of isotropic heat dissipation of polymer composites by using ternary filler systems consisting of boron nitride nanotubes, h-BN, and Al2O3","volume":"8","author":"Pornea","year":"2023","journal-title":"ACS Omega"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"322","DOI":"10.4236\/ojrad.2014.44042","article-title":"Evaluation of 3-D printed immobilisation shells for head and neck IMRT","volume":"4","author":"Fisher","year":"2014","journal-title":"Open J. Radiol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"424","DOI":"10.1007\/s12094-023-03260-z","article-title":"Surface guided radiation therapy with an innovative open-face mask and mouth bite: Patient motion management in brain stereotactic radiotherapy","volume":"26","author":"Chen","year":"2024","journal-title":"Clin. Transl. Oncol."}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/2\/287\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,1,21]],"date-time":"2026-01-21T11:25:06Z","timestamp":1768994706000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/2\/287"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,1,21]]},"references-count":29,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["polym18020287"],"URL":"https:\/\/doi.org\/10.3390\/polym18020287","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,1,21]]}}}