Fetus dose calculation during proton therapy of pregnant phantoms using MCNPX and MCNP6.2 codes

Saint-Hubert, Marijke De; Tymińska, K; Stolarczyk, Liliana; Brkić, Hrvoje

doi:10.1016/j.radmeas.2021.106665

Cited by 14 publications

(10 citation statements)

References 19 publications

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“…Previous works mainly evaluated out-of-field doses in PT through experimental measurements in water phantoms ( 1 ) or anthropomorphic phantoms ( 42 – 44 ). Only few studies have modeled the PT beam in detail to allow MC calculations of out-of-field doses in PT ( 45 – 47 ). Studies connecting MC and experimental data in PT are mostly limited to measurements with ambient monitors or Bonner sphere systems in the room ( 33 , 34 , 48 ).…”

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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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: 99%

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

et al. 2022

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“…This phantom is based on the previously published computational phantom, developed by our group 25 . Though MC simulations are valuable research methods, their setup and computational time can take a significant amount of time 26,27 . In addition, MC simulations are subject to uncertainties such as underestimation of the absorbed dose outside the primary radiation field 28–32 .…”

Section: Introductionmentioning

confidence: 99%

Development and validation of the low‐cost pregnant female physical phantom for fetal dosimetry in MV photon radiotherapy

Kopačin,

Brkić,

Ivković

et al. 2023

J Applied Clin Med Phys

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BackgroundMonte Carlo (MC) simulations or measurements in anthropomorphic phantoms are recommended for estimating fetal dose in pregnant patients in radiotherapy. Among the many existing phantoms, there is no commercially available physical phantom representing the entire pregnant woman.PurposeIn this study, the development of a low‐cost, physical pregnant female phantom was demonstrated using commercially available materials. This phantom is based on the previously published computational phantom.MethodsThree tissue substitution materials (soft tissue, lung and bone tissue substitution) were developed. To verify Tena's substitution tissue materials, their radiation properties were assessed and compared to ICRP and ICRU materials using MC simulations in MV radiotherapy beams. Validation of the physical phantom was performed by comparing fetal doses obtained by measurements in the phantom with fetal doses obtained by MC simulations in computational phantom, during an MV photon breast radiotherapy treatment.ResultsMaterials used for building Tena phantom are matched to ICRU materials using physical density, radiation absorption properties and effective atomic number. MC simulations showed that percentage depth doses of Tena and ICRU material comply within 5% for soft and lung tissue, up to 25 cm depth. In the bone tissue, the discrepancy is higher, but again within 5% up to the depth of 5 cm. When the phantom was used for fetal dose measurements in MV photon breast radiotherapy, measured fetal doses complied with fetal doses calculated using MC simulation within 15%.ConclusionsPhysical anthropomorphic phantom of pregnant patient can be manufactured using commercial materials and with low expenses. The files needed for 3D printing are now freely available. This enables further studies and comparison of numerical and physical experiments in diagnostic radiology or radiotherapy.

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“…Several Monte Carlobased codes are used in physics research [36][37][38][39][40][41]. The MCNPX code was developed to study particle physics and nuclear reactions, so they simulate an extensive set of particles in a broad energy spectrum [42][43][44][45] and many medical physics applications [46][47][48][49][50]. On the other hand, codes such as PENELOPE focus on the transport of charged particles and photons to medical applications and simulation of accelerator linear in the context of radiation protection and dosimetry [51][52][53][54][55].…”

Section: Introductionmentioning

confidence: 99%

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

2022

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The present work compared the relative absorbed dose of some dosimetric materials, for energies of 250 kV and 6 MV, using PENELOPE and MNCPX codes. The composition of each material GD-301, TLD-100, MAGIC, and MAGAT were simulated and disposed of in a phantom filled with water following reference conditions recommended by the TRS-398 protocol. Percentage depth dose was used as a parameter of comparison. Since the obtained results with both codes were found a maximum difference of up to 2 % when compared the water material with experimental data before 6cm were found to a maximum difference of up to 2.2% for 6 MV and 5.5 % for 250 kV. Ratios between simulated PPD and experimental PDD values showed a maximum difference in the build-up region, for 6 MV, due to highsensitivityive from the incident fluency in the simulated and experimental conditions. The ratios for 250 kV showed significant differences from the simulated solid-state rather than gel dosimeters, due to its low energy, depth angular dependence from the solid-state dosimeter, as corroborating by literature. Even the differences showed for both codes, especially for lower energy, due to cross-the section database that implied the interaction probability for each Monte Carlo code, this method has been widely used to model radiation transport in several applications in medical physics, especially in dosimetry.

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Fetus dose calculation during proton therapy of pregnant phantoms using MCNPX and MCNP6.2 codes

Cited by 14 publications

References 19 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

Development and validation of the low‐cost pregnant female physical phantom for fetal dosimetry in MV photon radiotherapy

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

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