Experimental evaluation of neutron dose in radiotherapy patients: Which dose?

Romero-Expósito, Maite; Domingo, C.; Sánchez‐Doblado, F.; Ortega-Gelabert, O; Gallego, Soledad

doi:10.1118/1.4938578

Cited by 19 publications

(23 citation statements)

References 20 publications

(21 reference statements)

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“…while neutron dose equivalent was used in this study) and (2) different phantoms (lower values are expected when adult phantom is used instead of a pediatric one). Related to (1), Romero‐Exposito et al 54 . showed that in RT environments Q and w T are approximately equal, and thus neutron doses evaluated using both factors are compatible, with differences below 12%.…”

Section: Discussionmentioning

confidence: 98%

Out‐of‐field doses in pediatric craniospinal irradiations with 3D‐CRT, VMAT, and scanning proton radiotherapy: A phantom study

et al. 2022

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Craniospinal irradiation (CSI) has greatly increased survival rates for patients with a diagnosis of medulloblastoma and other primitive neuroectodermal tumors. However, as it includes exposure of a large volume of healthy tissue to unwanted doses, there is a strong concern about the complications of the treatment, especially for the children. To estimate the risk of second cancers and other unwanted effects,out-of -field dose assessment is necessary.The purpose of this study is to evaluate and compare out-of -field doses in pediatric CSI treatment using conventional and advanced photon radiotherapy (RT) and advanced proton therapy. To our knowledge, it is the first such comparison based on in-phantom measurements. Additionally, for out-of -field doses during photon RT in this and other studies, comparisons were made using analytical modeling. Methods: In order to describe the out-of -field doses absorbed in a pediatric patient during actual clinical treatment, an anthropomorphic phantom, which mimics the 10-year-old child, was used. Photon 3D-conformal RT (3D-CRT) and two advanced, highly conformal techniques: photon volumetric-modulated arc therapy (VMAT) and active pencil beam scanning (PBS) proton RT were used for CSI treatment. Radiophotoluminescent and poly-allyl-diglycol-carbonate nuclear track detectors were used for photon and neutron dosimetry in the phantom, respectively. Out-of -field doses from neutrons were expressed in terms of dose equivalent. A two-Gaussian model was implemented for out-of -field doses during photon RT. Results: The mean VMAT photon doses per target dose to all organs in this study were under 50% of the target dose (i.e., <500 mGy/Gy), while the mean 3D-CRT photon dose to oesophagus, gall bladder, and thyroid, exceeded that value. However, for 3D-CRT, better sparing was achieved for eyes and lungs. The mean PBS photon doses for all organs were up to three orders of magnitude lower compared to VMAT and 3D-CRT and exceeded 10 mGy/Gy only for the oesophagus, intestine, and lungs. The mean neutron dose equivalent during PBS for eight organs of interest (thyroid, breasts, lungs, liver, stomach, gall bladder, bladder, prostate) ranged from 1.2 mSv/Gy for bladder to 23.1 mSv/Gy for breasts. Comparison of out-of -field doses in this and other phantom studies found in the literature showed that a simple and fast two-Gaussian model for out-of -field doses as a function of distance from the field edge can be applied in a CSI using photon RT techniques.

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Section: Discussionmentioning

confidence: 98%

Out‐of‐field doses in pediatric craniospinal irradiations with 3D‐CRT, VMAT, and scanning proton radiotherapy: A phantom study

et al. 2022

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“…It should also be kept in mind that the assumptions of Eq. (20) are not always fulfilled. This concerns, for example, fast neutrons with energies below a few MeV.…”

Section: Discussion and Summarymentioning

confidence: 99%

“…The mass (V) of the gas can be derived from the experimentally measured sensitivity, using relationship (19): (19) By combining Eqs. (14) and (19), the absorbed dose in phantom material t can be expressed as: (20) It is worth underlining that two fi nal factors in Eq. 20, i.e.…”

Section: Calibration Of the Chambers And Correlations Between Chambermentioning

confidence: 99%

“…Recently, the interest in such measurements has increased, mainly because of the attention paid to neutron doses (and equivalent doses) in terms of X-ray radiotherapy [11][12][13][14][15][16][17][18][19][20]. It is also associated with the broader use of proton therapy [21][22][23][24][25] and renewed interest in boron neutron capture therapy (BNCT) [26][27][28][29], thus, in the treatment modalities where the recombination chambers can be used for the characterization and monitoring of the beam for quality assurance purposes.…”

Section: Introductionmentioning

confidence: 99%

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On the role of LET-dependent parameters in the determination of the absorbed dose by in-phantom recombination chambers

Golnik

Maciak

2018

Nukleonika

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The paper discusses the theoretical background in terms of the use of in-phantom recombination chambers in mixed radiation fields, with special attention paid to the question of how the experimentally determined, linear-energy-transfer-dependent (LET) parameters can be applied with regard to the more accurate determination of the chamber response and absorbed dose in mixed radiation fields. Methods of taking the recombination index of radiation quality (RIQ) measurements and theoretical consideration concerning the determination of the absorbed dose are described. Classical Bragg-Gray and Spencer-Attix cavity theories were analysed and their relationship to in-phantom recombination chambers was specifi ed. Methods concerning the estimation of correction factors with regard to RIQ measurements and their importance are highlighted.

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“…The neutron dose equivalent can be derived using the following equation, as discussed in Romero-Expósito et al. ( 28 ):…”

Section: Methodsmentioning

confidence: 99%

Peripheral Organ Equivalent Dose Estimation Procedure in Proton Therapy

et al. 2022

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The aim of this work is to present a reproducible methodology for the evaluation of total equivalent doses in organs during proton therapy facilities. The methodology is based on measuring the dose equivalent in representative locations inside an anthropomorphic phantom where photon and neutron dosimeters were inserted. The Monte Carlo simulation was needed for obtaining neutron energy distribution inside the phantom. The methodology was implemented for a head irradiation case in the passive proton beam of iThemba Labs (South Africa). Thermoluminescent dosimeter (TLD)-600 and TLD-700 pairs were used as dosimeters inside the phantom and GEANT code for simulations. In addition, Bonner sphere spectrometry was performed inside the treatment room to obtain the neutron spectra, some relevant neutron dosimetric quantities per treatment Gy, and a percentual distribution of neutron fluence and ambient dose equivalent in four energy groups, at two locations. The neutron spectrum at one of those locations was also simulated so that a reasonable agreement between simulation and measurement allowed a validation of the simulation. Results showed that the total out-of-field dose equivalent inside the phantom ranged from 1.4 to 0.28 mSv/Gy, mainly due to the neutron contribution and with a small contribution from photons, 10% on average. The order of magnitude of the equivalent dose in organs was similar, displaying a slow reduction in values as the organ is farther from the target volume. These values were in agreement with those found by other authors in other passive beam facilities under similar irradiation and measurement conditions.

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Experimental evaluation of neutron dose in radiotherapy patients: Which dose?

Abstract: Quality factor can be replaced by the radiation weighting factor in the evaluation of dose equivalent in radiotherapy environments simplifying the practical procedure.

Cited by 19 publications

References 20 publications

Out‐of‐field doses in pediatric craniospinal irradiations with 3D‐CRT, VMAT, and scanning proton radiotherapy: A phantom study

Out‐of‐field doses in pediatric craniospinal irradiations with 3D‐CRT, VMAT, and scanning proton radiotherapy: A phantom study

On the role of LET-dependent parameters in the determination of the absorbed dose by in-phantom recombination chambers

Peripheral Organ Equivalent Dose Estimation Procedure in Proton Therapy

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