Out-of-field doses for scanning proton radiotherapy of shallowly located paediatric tumours—a comparison of range shifter and 3D printed compensator

Wochnik, Agnieszka; Stolarczyk, Liliana; Ambrožová, Iva; Davídková, Marie; Saint-Hubert, Marijke De; Domański, Szymon; Domingo, C.; Knežević, Željka; Kopeć, Renata; Kuć, Michał; Majer, Marija; Mojżeszek, Natalia; Mares, V.; Martínez-Rovira, I.; Caballero-Pacheco, Miguel Ángel; Pyszka, E.; Swakoń, Jan; Trinkl, Sebastian; Tisi, Marco; Harrison, R. M.; Olko, P.

doi:10.1088/1361-6560/abcb1f

Cited by 15 publications

(14 citation statements)

References 51 publications

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“…The closest comparison of our experimental data to literature could be made to two studies performed within EURADOS WG9 ( 42 , 43 ), measuring out-of-field doses during PT in the same anthropomorphic 5-year-old phantom treated for a brain tumor (6-cm diameter). One study described the response of passive detector systems in PT out-of-field dosimetry ( 42 ), where no RS (no RS) was used, while another study verified the impact of using an RS or 3D-printed beam compensator (BC) on the out-of-field doses ( 43 ). At 12 cm, the neutron dose equivalent data were 120 μSv/Gy (no RS) in the study from ( 42 ) versus 130 μSv/Gy (BC) and 180 μSv/Gy (RS) in the study from ( 43 ).…”

Section: Discussionmentioning

confidence: 93%

“…One study described the response of passive detector systems in PT out-of-field dosimetry ( 42 ), where no RS (no RS) was used, while another study verified the impact of using an RS or 3D-printed beam compensator (BC) on the out-of-field doses ( 43 ). At 12 cm, the neutron dose equivalent data were 120 μSv/Gy (no RS) in the study from ( 42 ) versus 130 μSv/Gy (BC) and 180 μSv/Gy (RS) in the study from ( 43 ). Our data reported a dose of 260 μSv/Gy, which could be due to the larger volume in the current study (195.2 cm 3 ) compared to the previous studies (65 cm 3 ) ( 42 , 43 ).…”

Section: Discussionmentioning

confidence: 99%

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Validation of a Monte Carlo Framework for Out-of-Field Dose Calculations in Proton Therapy

et al. 2022

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Proton therapy enables to deliver highly conformed dose distributions owing to the characteristic Bragg peak and the finite range of protons. However, during proton therapy, secondary neutrons are created, which can travel long distances and deposit dose in out-of-field volumes. This out-of-field absorbed dose needs to be considered for radiation-induced secondary cancers, which are particularly relevant in the case of pediatric treatments. Unfortunately, no method exists in clinics for the computation of the out-of-field dose distributions in proton therapy. To help overcome this limitation, a computational tool has been developed based on the Monte Carlo code TOPAS. The purpose of this work is to evaluate the accuracy of this tool in comparison to experimental data obtained from an anthropomorphic phantom irradiation. An anthropomorphic phantom of a 5-year-old child (ATOM, CIRS) was irradiated for a brain tumor treatment in an IBA Proteus Plus facility using a pencil beam dedicated nozzle. The treatment consisted of three pencil beam scanning fields employing a lucite range shifter. Proton energies ranged from 100 to 165 MeV. A median dose of 50.4 Gy(RBE) with 1.8 Gy(RBE) per fraction was prescribed to the initial planning target volume (PTV), which was located in the cerebellum. Thermoluminescent detectors (TLDs), namely, Li-7-enriched LiF : Mg, Ti (MTS-7) type, were used to detect gamma radiation, which is produced by nuclear reactions, and secondary as well as recoil protons created out-of-field by secondary neutrons. Li-6-enriched LiF : Mg,Cu,P (MCP-6) was combined with Li-7-enriched MCP-7 to measure thermal neutrons. TLDs were calibrated in Co-60 and reported on absorbed dose in water per target dose (μGy/Gy) as well as thermal neutron dose equivalent per target dose (μSv/Gy). Additionally, bubble detectors for personal neutron dosimetry (BD-PND) were used for measuring neutrons (>50 keV), which were calibrated in a Cf-252 neutron beam to report on neutron dose equivalent dose data. The Monte Carlo code TOPAS (version 3.6) was run using a phase-space file containing 1010 histories reaching an average standard statistical uncertainty of less than 0.2% (coverage factor k = 1) on all voxels scoring more than 50% of the maximum dose. The primary beam was modeled following a Fermi–Eyges description of the spot envelope fitted to measurements. For the Monte Carlo simulation, the chemical composition of the tissues represented in ATOM was employed. The dose was tallied as dose-to-water, and data were normalized to the target dose (physical dose) to report on absorbed doses per target dose (mSv/Gy) or neutron dose equivalent per target dose (μSv/Gy), while also an estimate of the total organ dose was provided for a target dose of 50.4 Gy(RBE). Out-of-field doses showed absorbed doses that were 5 to 6 orders of magnitude lower than the target dose. The discrepancy between TLD data and the corresponding scored values in the Monte Carlo calculations involving proton and gamma contributions was on average 18%. The comparison between the neutron equivalent doses between the Monte Carlo simulation and the measured neutron doses was on average 8%. Organ dose calculations revealed the highest dose for the thyroid, which was 120 mSv, while other organ doses ranged from 18 mSv in the lungs to 0.6 mSv in the testes. The proposed computational method for routine calculation of the out-of-the-field dose in proton therapy produces results that are compatible with the experimental data and allow to calculate out-of-field organ doses during proton therapy.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Validation of a Monte Carlo Framework for Out-of-Field Dose Calculations in Proton Therapy

et al. 2022

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“…Experimental studies in scanned-beam facilities have been done by EURADOS Working Group 9 ( 38 , 39 ). In their campaigns, a 5-year-old and a 10-year-old anthropomorphic phantom were irradiated with 2 incidences (LAT and oblique) and several types of dosimeters located inside.…”

Section: Out-of-field Doses In Young Patients’ Treatmentsmentioning

confidence: 99%

“…In Wochnik et al. ( 39 ), the irradiation was repeated maintaining the target volume but shallowly located due to the use of an RS or a 3D printed beam compensator (BC). The introduction of these elements in the proton beam becomes a source of external neutrons and, therefore, a behavior in between PS-PBT and PBS-PBT would be expected.…”

Section: Out-of-field Doses In Young Patients’ Treatmentsmentioning

confidence: 99%

Determining Out-of-Field Doses and Second Cancer Risk From Proton Therapy in Young Patients—An Overview

Romero-Expósito

Toma-Daşu²,

Daşu³

2022

Front. Oncol.

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Proton therapy has the potential to provide survival and tumor control outcomes comparable and frequently superior to photon therapy. This has led to a significant concern in the medical physics community on the risk for the induction of second cancers in all patients and especially in younger patients, as they are considered more radiosensitive than adults and have an even longer expected lifetime after treatment. Thus, our purpose is to present an overview of the research carried out on the evaluation of out-of-field doses linked to second cancer induction and the prediction of this risk. Most investigations consisted of Monte Carlo simulations in passive beam facilities for clinical scenarios. These works established that equivalent doses in organs could be up to 200 mSv or 900 mSv for a brain or a craniospinal treatment, respectively. The major contribution to this dose comes from the secondary neutrons produced in the beam line elements. Few works focused on scanned-beam facilities, but available data show that, for these facilities, equivalent doses could be between 2 and 50 times lower. Patient age is a relevant factor in the dose level, especially for younger patients (by means of the size of the body) and, in addition, in the predicted risk by models (due to the age dependence of the radiosensitivity). For risks, the sex of the patient also plays an important role, as female patients show higher sensitivity to radiation. Thus, predicted risks of craniospinal irradiation can range from 8% for a 15-year-old male patient to 58% for a 2-year-old female patient, using a risk model from a radiological protection field. These values must be taken with caution due to uncertainties in risk models, and then dosimetric evaluation of stray radiation becomes mandatory in order to complement epidemiological studies and be able to model appropriate dose–response functions for this dose range. In this sense, analytical models represent a useful tool and some models have been implemented to be used for young patients. Research carried out so far confirmed that proton beam therapy reduces the out-of-field doses and second cancer risk. However, further investigations may be required in scanned-beam delivery systems.

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“…The growing interest in high-energy neutron radiobiology is mainly driven by the increase in proton therapy (PT) facilities around the world and our desire to explore space beyond lower Earth orbit with manned mission to the Moon and Mars. Despite the dose sparing properties of PT, secondary neutrons are inevitably produced outside the primary eld [43][44][45][46][47] . While it is anticipated that the absorbed dose resulting from these secondary neutrons is small, especially for more recent pencil-beam scanning PT facilities, the uncertainty around the high neutron RBE remains a topic of concern, particularly for paediatric patients 48 .…”

Section: Introductionmentioning

confidence: 99%

DNA Damage Response of Haematopoietic Stem and Progenitor Cells to High-LET Neutron Irradiation

Engelbrecht

Ndimba

Kock

et al. 2021

Preprint

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The radiosensitivity of haematopoietic stem and progenitor cells (HSPCs) to neutron radiation remains largely underexplored, notwithstanding their potential role as target cells for radiation-induced leukemogenesis. New insights are required for radiation protection purposes, particularly for aviation, space missions, nuclear accidents and even particle therapy. In this study, HSPCs (CD34+ cells) were isolated from umbilical cord blood and irradiated with 60Co γ-rays (photons) and high energy p(66)/Be(40) neutrons. At 2 hours post-irradiation, a significantly higher number of 1.28 ± 0.12 γ-H2AX foci/cell was observed after 0.5 Gy neutrons compared to 0.84 ± 0.14 foci/cell for photons, but this decreased to similar levels for both radiation qualities after 18 hours. However, a signficant difference in late apoptosis was observed between photon and neutron irradiation at 18 hours, 43.17 ± 6.10 % versus 55.55 ± 4.87 %, respectively. A significant increase in cytogenetic damage was observed after both 0.5 and 1 Gy neutron irradiation compared to photons, while there was no difference in the nuclear division index between both radiation qualities. The results point towards a higher induction of DNA damage after neutron irradiation in HSPCs followed by error-prone DNA repair, which contributes to genomic instability and a higher risk of leukemogenesis.

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Out-of-field doses for scanning proton radiotherapy of shallowly located paediatric tumours—a comparison of range shifter and 3D printed compensator

Abstract: Out-of-field doses for scanning proton radiotherapy of shallowly located paediatric tumours-a comparison of range shifter and 3D printed compensator To cite this article: A Wochnik et al 2021 Phys. Med. Biol. 66 035012 View the article online for updates and enhancements.

Cited by 15 publications

References 51 publications

Validation of a Monte Carlo Framework for Out-of-Field Dose Calculations in Proton Therapy

Validation of a Monte Carlo Framework for Out-of-Field Dose Calculations in Proton Therapy

Determining Out-of-Field Doses and Second Cancer Risk From Proton Therapy in Young Patients—An Overview

DNA Damage Response of Haematopoietic Stem and Progenitor Cells to High-LET Neutron Irradiation

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