Dosimetric evaluation of ABS, PLA and NR boluses for electron radiotherapy

Abstract

Purpose. This study aims to compare the dosimetric characteristics of 3D-printed bolus materials acrylonitrile butadiene styrene (ABS), polylactic acid (PLA) with recently introduced natural rubber (NR) bolus. Materials and Methods. We employed Monte Carlo simulation to evaluate ABS, PLA, and NR boluses of thicknesses 0.5, 1.0, and 1.5 cm under 6, 9, and 16 MeV electron beam irradiation. Percentage depth dose (PDD) data was analyzed to evaluate dosimetry parameters. Dosimetric stability under varying air-gap conditions was assessed by analyzing PDD curves under air-gap sizes of (0, 1, 3, 5 mm).Results.NR and ABS showed similar dosimetric profiles, whereas PLA showed enhanced deeper-tissue protection and provided 0.7–10.2% higher surface dose (SD). PLA also exhibited the highest stability, with SD and R90 deviations limited to 1% and 1.2%, respectively, under varying air-gap sizes. At 6 and 9 MeV, a 0.5 cm bolus failed to provide a single dose of 90% of maximum dose for nearly all tested materials Conclusion. NR demonstrated comparable dosimetric performance to ABS, serving as a viable substitute. PLA was optimal for maximizing SD and distal tissue sparing while exhibiting the lowest air-gap sensitivity. For tumors located several centimeters deep from the surface, 16 MeV electron beams were suitable. Furthermore, Dual hotspots were identified a substantial risk of localized normal tissue toxicity.

Keywords

ABS / bolus / electron bolus / electron radiotherapy / Monte Carlo simulation / natural rubber / PLA

References

[1] Miloihikova I, Bulavskaya A, Cherepennikov Y, et al. (2019) Feasibility of clinical electron beam formation using polymer materials produced by fused deposition modelling. Phys Med 64: 188-194. https://doi.org/10.1016/j.ejmp.2019.07.014

[2] Moghaddam SH, Baghani HR, Mahdavi SR (2020) Construction and performance evaluation of a buildup bolus for breast intraoperative electron radiotherapy. Radiat Phys Chem 174: 108952. https://doi.org/10.1016/j.radphyschem.2020.108952

[3] Kong D, Wu J, Kong X, et al. (2024) Effect of bolus materials on dose deposition in deep tissues during electron beam radiotherapy. J Radiat Res 65: 215-222. https://doi.org/10.1093/jrr/rrae001

[4] Salguero FJ, Arráns R, Palma BA, et al. (2010) Intensity-and energy-modulated electron radiotherapy by means of an xMLC for head and neck shallow tumors. Phys Med 55: 1413. https://doi.org/10.1088/0031-9155/55/5/010

[5] Edimo P, Clermont C, Kwato MG, et al. (2009) Evaluation of a commercial VMC++ Monte Carlo based treatment planning system for electron beams using EGSnrc/BEAMnrc simulations and measurements. Phys Med 25: 111-121. https://doi.org/10.1016/j.ejmp.2008.07.001

[6] Cho S, (2005) Estimation of tumor dose enhancement due to gold nanoparticles during typical radiation treatments: a preliminary Monte Carlo study. Phys Med Biol 50: N163-N173. https://doi.org/10.1088/0031-9155/50/15/n01

[7] Zheng XJ, Chow JCL (2017) Radiation dose enhancement in skin therapy with nanoparticle addition: A Monte Carlo study on kilovoltage photon and megavoltage electron beams. World J Radiol 9: 63-67. http://doi.org/10.4329/wjr.v9.i2.63

[8] Wang X, Wang X, Xiang Z, et al. (2021) The clinical application of 3D-printed boluses in superficial tumor radiotherapy. Front Oncol 11: 698773. https://doi.org/10.3389/fonc.2021.698773

[9] Aldawood FK, Chang SX, Desai S (2020) Design and manufacture of a high precision personalized electron bolus device for radiation therapy. Med Devices Sens 3: e10077. https://doi.org/10.1002/mds3.10077

[10] Vyas V, Palmer L, Mudge R, et al. (2013) On bolus for megavoltage photon and electron radiation therapy. Med Dosi 38: 268-273. https://doi.org/10.1016/j.meddos.2013.02.007

[11] Diaz-Merchan JA, Español-Castro C, Martinez-Ovalle SA, et al. (2023) Bolus 3D printing for radiotherapy with conventional PLA, ABS and TPU filaments: theoretical-experimental study. Appl Radiat Isot 199: 110908. https://doi.org/10.1016/j.apradiso.2023.110908

[12] Cho Y-I, Kim J-H, Bae S-I (2023) Evaluation of shielding performance of tungsten containing 3D printing materials for high-energy electron radiation therapy. J Korean Soc Radiol 17: 641-649. https://doi.org/10.1016/j.rpor.2020.06.006

[13] Apipunyasopon L, Chaloeiparp C, Wiriyatharaki T, et al. (2020) Characterization of natural rubber as a bolus material for electron beam radiotherapy. Rep Pract Oncol Radio 25: 725-729. https://doi.org/10.1088/2053-1591/aad5ca

[14] Supratman AS, Sutanto H, Hidayanto E, et al. (2018) Characteristic of natural rubber as bolus material for radiotherapy. Mater Res Express 5: 095302. https://doi.org/10.1088/2053-1591/aad5ca

[15] Aisyah S, Carina CCC, Nazara T, et al. (2020) A comparative study of dosimetric characterization of bolus based on natural rubber (hevea brasiliensis) and clinical bolus for therapy with megavolt electron radiation. J Phys Conf 1505: 012026. 10.1088/1742-6596/1505/1/012026

[16] Arianto F, Hidayanto E, Budi WS, et al. (2024) A benchmark for natural rubber (NR) and silicone rubber (SR) as bolus for radiotherapy using Monte Carlo simulation. 12th International seminar on new paradigm and innovation on natural sciences and its applications, 3165: 020004. https://doi.org/10.1063/5.0215893

[17] Diaz-Merchan JA, Martinez-Ovalle SA, Vega-Carrillo HR (2023) Development of a 3D printing process of bolus using BolusCM material for radiotherapy with electrons. Appl Radiat Iso 1999: 110899. https://doi.org/10.1016/j.apradiso.2023.110899

[18] Diaz-Merchan JA, Martinez-Ovalle SA, Vega-Carrillo HR (2022) Characterization of a novel material to be used as bolus in radiotherapy with electrons. Appl Radiat Isotopes 183: 110154. https://doi.org/10.1016/j.apradiso.2022.110154

[19] Zou W, Fisher T, Zhang M, et al. (2015) Potential of 3D printing technologies for fabrication of electron bolus and proton compensators. J Appl Clin Med Phys 16: 90-98. https://doi.org/10.1120/jacmp.v16i3.4959

[20] Łukowiak M, Jezierska K, Boehlke M, et al. (2017) Utilization of a 3D printer to fabricate boluses used for electron therapy of skin lesions of the eye canthi. J Appl Clin Med Phys 18: 76-81. https://doi.org/10.1002/acm2.12013

[21] National Institute of Standard and Technology. Stopping Power and Range Tables for Electrons, Nist. Gov. Available from: https://physics.nist.gov/PhysRefData/Star/Text/ESTAR.html.

[22] Goldstone KE (1989) Tissue Substitutes in Radiation Dosimetry and Measurement in: ICRU Report 44. International Commission on Radiation Units and Measurements, USA.

[23] Kawrakow I, Rogers DWO, Mainegra-Hing E, et al. (2000) EGSnrc toolkit for Monte Carlo simulation of ionizing radiation transport. National Research Council of Canada.

[24] Rogers DWO, Faddegon BA, Ding GX, et al. (1995) BEAM: a Monte Carlo code to simulate radiotherapy treatment units. Med Phys 22: 503-524. https://doi.org/10.1118/1.597552

[25] Rogers DWO, Walters B, Kawrakow I (2009) BEAMnrc user’s manual, National Research Council Canada. Institute for National Measurement Standards, PIRS-0509 (A) (revL), Ottawa, Canda.

[26] Udal MA (1988) Monte Carlo investigation of surface doses for broad electron beams. Phys Med Biol 33: 939-953. https://doi.org/10.1088/0031-9155/33/8/004

[27] International Atomic Energy Agency, phase-space database for external beam radiotherapy. Available from: https://www-nds.iaea.org/phsp/phsp.htmlx.

[28] International Atomic Energy Agency (2000) Absorbed dose determination in external beam radiotherapy: an International Code of Practice for dosimetry based on standards of absorbed dose to water. TRS 398. IAEA, Vienna.

[29] Walters B, Kawrakow I, and Rogers DWO (2002) DOSXYZnrc user’s manual, National Research Council Report PIRS-794 (revB) Ottawa, Canda.

[30] Ma CM, Rogers DWO (1995) BEAMDP user’s manual, National Research Council Report PIRS-0509 (C) (revA) Ottawa, Canda.

[31] Brualla L, Palanco-Zamora R, Duch MA, et al. (2010) Phase-space files documentation for: Varian Clinac 600 C photon beams and Varian Clinac 2100 C/D electron beams. Institut de Tècniques Energètiques, Universitat Politècnica de Catalunya, Barcelona, Spain.

[32] Attix FH (2017) Introduction to Radiological Physics and Radiation Dosimetry, 1 Ed., New York: John Wiley and Son, 160-195. https://doi.org/10.1002/9783527617135

[33] Khan FM, Gibbons JP (2019) The Physics of Radiation Therapy, 6 Eds., Philadelphia: Lippincott Williams & Wilkins, 256-305.

[34] Berger MJ, Hubbell JH, Seltzer SM, et al. (2010) XCOM: Photon cross section database.

[35] García-Cases F, Perez-Calatayud J, Ballester F, et al. (2018) Peripheral dose around a mobile linac for intraoperative radiotherapy: radiation protection aspects. J Radiol Prot 38: 1393. https://doi.org/10.1088/1361-6498/aae5a0

[36] Singh S, Semwal MK, Bhatt CP (2019) Estimation of backscatter from internal shielding in electron beam radiotherapy using Monte Carlo simulations (EGSnrc) and Gafchromic film measurements. J Med Phys 44: 239-245. https://doi.org/10.4103/jmp.JMP_21_19

[37] Fujimoto T, Monzen H, Nakata M, et al. (2014) Dosimetric shield evaluation with tungsten sheet in 4, 6, and 9MeV electron beams. Phys Med 30: 838-842. https://doi.org/10.1016/j.ejmp.2014.05.009

[38] Chow JCL (2008) Monte Carlo simulation of backscatter from lead for clinical electron beams using EGSnrc. Med Phys 35: 1241-1250. https://doi.org/10.1118/1.2874552

[39] Demir H, Gul OV, Aksu T (2024) Investigation of skin dose of post-mastectomy radiation therapy for the halcyon and tomotherapy treatment machine: comparison of calculation and in vivo measurements. Radiat Meas 1: 107112. https://doi.org/10.1016/j.radmeas.2024.107112

[40] Gul OV, Koplay M, Ozturk M (2025) Gantry tilt as a dose reduction strategy for radiosensitive organs in pediatric brain CT: a prospective TLD study. Radiat Prot Dosim 202: 8-14. https://doi.org/10.1093/rpd/ncaf144