Essential considerations for accurate evaluation of photoneutron contamination in Radiotherapy

Karimi, Amir Hossein; Brkić, Hrvoje; Shahbazi‐Gahrouei, Daryoush; Haghighi, Somayeh Biparva; Jabbari, Iraj

doi:10.1016/j.apradiso.2018.12.007

Cited by 20 publications

(20 citation statements)

References 26 publications

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“…Here, it should be noted that the Monte Carlo calculation is simply performed because the aim of the calculation is to obtain a typical distribution of neutron dose to a patient. Although precise calculation of the neutron dose also requires the geometry of the treatment room, such as floor, wall, and ceiling, as reported, that is not the aim of the present study. Thus, the present study made use of the relativeness of the neutron dose from the calculation and the use of its absoluteness from the empirical measured values in the literature, as follows.…”

Section: Methodsmentioning

confidence: 96%

Prediction of radiation‐induced malfunction for cardiac implantable electronic devices (CIEDs)

Matsubara¹,

Ezura²,

Hashimoto³

et al. 2020

Medical Physics

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Purpose Cardiac implantable electronic devices (CIEDs) were believed to possess a tolerance dose to malfunction during radiotherapy. Although recent studies have qualitatively suggested neutrons as a cause of malfunction, numerical understanding has not been reached. The purpose of this work is to quantitatively clarify the contribution of secondary neutrons from out‐of‐field irradiation to the malfunction of CIEDs as well as to deduce the frequency of malfunctions until completion of prostate cancer treatment as a typical case. Materials and Methods Measured data were gathered from the literature and were re‐analyzed. Firstly, linear relationship for a number of malfunctions to the neutron dose was suggested by theoretical consideration. Secondly, the accumulated number of malfunctions of CIEDs gathered from the literature was compared with the prescribed dose, scattered photon dose, and secondary neutron dose for analysis of their correlation. Thirdly, the number of malfunctions during a course of prostate treatment with high‐energy X‐ray, passive proton, and passive carbon‐ion beams was calculated while assuming the same response to malfunctions, where X‐rays consisted of 6‐MV, 10‐MV, 15‐MV, and 18‐MV beams. Monte Carlo simulation assuming simple geometry was performed for the distribution of neutron dose from X‐ray beams, where normalization factors were applied to the distribution so as to reproduce the empirical values. Results Linearity between risk and neutron dose was clearly found from the measured data, as suggested by theoretical consideration. The predicted number of malfunctions until treatment completion was 0, 0.02 ± 0.01, 0.30 ± 0.08, 0.65 ± 0.17, 0.88 ± 0.50, and 0.14 ± 0.04 when 6‐MV, 10‐MV, 15‐MV, 18‐MV, passive proton, and passive carbon‐ion beams, respectively, were employed, where the single model response to a malfunction of 8.6 ± 2.1 Sv−1 was applied. Conclusions Numerical understanding of the malfunction of CIEDs has been attained for the first time. It has been clarified that neutron dose is a good scale for the risk of CIEDs in radiotherapy. Prediction of the frequency of malfunction as well as discussion of the risk to CIEDs in radiotherapy among the multiple modalities have become possible. Because the present study quantitatively clarifies the neutron contribution to malfunction, revision of clinical guidelines is suggested.

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Section: Methodsmentioning

confidence: 96%

Prediction of radiation‐induced malfunction for cardiac implantable electronic devices (CIEDs)

Matsubara¹,

Ezura²,

Hashimoto³

et al. 2020

Medical Physics

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“…There is a constant concern about the photo-neutron contamination due to high-z material in the head of LINAC when using photon energy above 10 MeV. 38,39 This concern is more pronounced in the GRID therapy, which uses a highattenuation GRID block (a potential additional source of neutron contamination) and larger monitor units. Undesired photo-neutrons produced in the GRID block can cause an increase in the patient dose.…”

Section: Grid Activation and Photo-neutron Contaminationmentioning

confidence: 99%

The role of the spatially fractionated radiation therapy in the management of advanced bulky tumors

Mahmoudi

Shahbazi‐Gahrouei

Chegeni

2021

Polish Journal of Medical Physics and Engineering

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Spatially fractionated radiation therapy (SFRT) refers to the delivery of a single large dose of radiation within the target volume in a heterogeneous pattern using either a custom GRID block, multileaf collimators, and virtual methods such as helical tomotherapy or synchrotron-based microbeams. The potential impact of this technique on the regression of bulky deep-seated tumors that do not respond well to conventional radiotherapy has been remarkable. To date, a large number of patients have been treated using the SFRT techniques. However, there are yet many technical and medical challenges that have limited their routine use to a handful of clinics, most commonly for palliative intent. There is also a poor understanding of the biological mechanisms underlying the clinical efficacy of this approach. In this article, the methods of SFRT delivery together with its potential biological mechanisms are presented. Furthermore, technical challenges and clinical achievements along with the radiobiological models used to evaluate the efficacy and safety of SFRT are highlighted.

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“…Unfortunately, most of the neutron detectors used in dosimetry for the mixed fields (Photon + Neutron) are inevitably saturated by photons [28] which are challenging for the in-vivo dosimetry of neutron contamination in radiotherapy. Although neutron rem-meter detectors can separate neutrons from photons, they cannot be applied for in-vivo dosimetry due to their large size.…”

Section: Introductionmentioning

confidence: 99%

Semi-experimental assessment of neutron equivalent dose and secondary cancer risk for off-field organs in glioma patients undergoing 18-MV radiotherapy

et al. 2022

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Neutron contamination as a source of out-of-field dose in radiotherapy is still of concern. High-energy treatment photons have the potential to overcome the binding energy of neutrons inside the nuclei. Fast neutrons emitting from the accelerator head can directly reach the patient’s bed. Considering that modern radiotherapy techniques can increase patient survival, concerns about unwanted doses and the lifetime risk of fatal cancer remain strong or even more prominent, especially in young adult patients. The current study addressed these concerns by quantifying the dose and risk of fatal cancer due to photo-neutrons for glioma patients undergoing 18-MV radiotherapy. In this study, an NRD model rem-meter detector was used to measure neutron ambient dose equivalent, H*(10), at the patient table. Then, the neutron equivalent dose received by each organ was estimated concerning the depth of each organ and by applying depth dose corrections to the measured H*(10). Finally, the effective dose and risk of secondary cancer were determined using NCRP 116 coefficients. Evidence revealed that among all organs, the breast (0.62 mSv/Gy) and gonads (0.58 mSv/Gy) are at risk of photoneutrons more than the other organs in such treatments. The neutron effective dose in the 18-MV conventional radiotherapy of the brain was 13.36 mSv. Among all organs, gonads (6.96 mSv), thyroid (1.86 mSv), and breasts (1.86 mSv) had more contribution to the effective dose, respectively. The total secondary cancer risk was estimated as 281.4 cases (per 1 million persons). The highest risk was related to the breast and gonads with 74.4 and, 34.8 cases per 1 million persons, respectively. Therefore, it is recommended that to prevent late complications (secondary cancer and genetic effects), these organs should be shielded from photoneutrons. This procedure not only improves the quality of the patient’s personal life but also the healthy childbearing in the community.

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Essential considerations for accurate evaluation of photoneutron contamination in Radiotherapy

Cited by 20 publications

References 26 publications

Prediction of radiation‐induced malfunction for cardiac implantable electronic devices (CIEDs)

Prediction of radiation‐induced malfunction for cardiac implantable electronic devices (CIEDs)

The role of the spatially fractionated radiation therapy in the management of advanced bulky tumors

Semi-experimental assessment of neutron equivalent dose and secondary cancer risk for off-field organs in glioma patients undergoing 18-MV radiotherapy

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