Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and <sup>60</sup>Co γ‐rays

Vadrucci, Monia; Esposito, Giuseppe; Ronsivalle, C.; Cherubini, R.; Marracino, F; Montereali, R. M.; Picardi, L.; Piccinini, M.; Pimpinella, M.; Vincenti, Maria Aurora; Angelis, C. De

doi:10.1118/1.4926558

Cited by 44 publications

(38 citation statements)

References 29 publications

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“…Film was not used in the proton irradiations owing to its LET-dependent response [30]. Instead, the Markus chamber was chosen, where the sensitive volume is 0.02 cm 3 and measurements are accurate to within 1% of the primary ionization chamber used for clinical dosimetry [31].…”

Section: Methodsmentioning

confidence: 99%

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells

Howard

Beltran

Anderson

et al. 2017

International Journal of Particle Therapy

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Purpose: Relative biological effectiveness (RBE) accounts for the differences in biological effect from different radiation types. The RBE for proton therapy remains uncertain, as it has been shown to vary from the clinically used value of 1.1. In this work we investigated the RBE of protons and correlated the biological differences with the underlying physical quantities. Materials and Methods: Three cell lines were irradiated (CHO, Chinese hamster ovary; A549, human lung adenocarcinoma; and T98, human glioma) and assessed for cell survival by using clonogenic assay. Cells were irradiated with 71- and 160-MeV protons at depths along the Bragg curve and 6-MV photons to various doses. The dose-averaged lineal energy (truey‒normalD) was measured under similar conditions as the cells by using a microdosimeter. Dose-averaged linear energy transfer (LETd) was also calculated by using Monte Carlo (MC) simulations. Survival data were fit by using the linear quadratic model. The RBE values were calculated by comparing the physical dose (D6MV/Dp) that results in 50% (RBE0.5) and 10% (RBE0.1) cell survival, and survival after 2 Gy (RBE2Gy). Results: Proton RBE values ranged from 0.89 to 2.40. The RBE for all 3 cell lines increased with decreasing proton energy and was higher at 50% survival than at 10% survival. Additionally, both A549 and T98 cells generally had higher RBE values relative to the CHO cells, indicating a greater biological response to protons. An increase in RBE corresponded with an increase in truey‒normalD and LETd. Conclusion: Proton RBE was found to depend on mean proton energy, survival end point, and cell type. Changes in both truey‒normalD and LETd were also found to impact proton RBE values, but consideration of the energy spectrum may provide additional information. The RBE values in this study vary greatly, indicating the clinical value of 1.1 may not be suitable in all cases.

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Section: Methodsmentioning

confidence: 99%

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells

Howard

Beltran

Anderson

et al. 2017

International Journal of Particle Therapy

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“…The GAFCHROMIC (Ashland Inc., Cincinnati, OH, USA) EBT, EBT2 and EBT3 radiochromic film models, are widely used for particle beams commissioning and QA procedures . On the other hand it is non‐negligible the decrease in response due to the high specific ionization of ions at Bragg peak …”

Section: Detectors For Absorbed Dose In Nonreference Conditionsmentioning

confidence: 99%

Dose detectors, sensors, and their applications

Giordanengo

2018

Medical Physics

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This article is intended to present the different types of particle and radiation detectors available for applications in particle therapy. Several types of detectors and sensors exist for measurements of absorbed dose in reference and nonreference conditions and the ones in use for beam monitoring. Therefore, this manuscript focuses on the following applications: (a) primary methods for dosimetry in ion beams, (b) measurements of absorbed dose in realistic patient‐specific scenarios with different dose delivery configurations, and (c) beam monitoring. Water and graphite calorimeters, Faraday cups, ionization based gas detectors are described first, followed by the description of the protocols for proton and ion dosimetry. Then films, scintillator and solid‐state detectors are reviewed. Finally, several types of ionization chambers (large, pinpoint, arrays of chambers arranged in regular 1D or 2D pattern, parallel‐plate configuration with large integral electrodes or with anode segmented in strips or pixels, multi‐wire, and the multi‐gap prototype) have been considered. New beam monitors to deal with a wide range of intensity and pulsed beams expected from new accelerators, different dose fractionation and advanced delivery techniques are presented. The existing detectors available for particle therapy have been described taking into account the different requirements for devices used in reference and nonreference conditions and the ones designed for beam monitoring.

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“…Vadrucci et al. observed the EBT3 film under‐responses by as much as 33% relative to

^{60}

Co for 5Mev protons . Reinhardt et al.…”

Section: Introductionmentioning

confidence: 99%

LET response variability of Gafchromic EBT3 film from a Co calibration in clinical proton beam qualities

et al. 2019

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Purpose To establish a method of accurate dosimetry required to quantify the expected linear energy transfer (LET) quenching effect of EBT3 film used to benchmark the dose distribution for a given treatment field and specified measurement depth. In order to facilitate this technique, a full analysis of film calibration which considers LET variability at the plane of measurement and as a function of proton beam quality is demonstrated. Additionally, the corresponding uncertainty from the process was quantified for several measurement scenarios. Materials and methods The net change in optical density (OD) from a single version of GafchromicTM EBT3 film was measured using an Epson flatbed scanner and NIST‐traceable OD filters. Film OD response was characterized with respect to the known dose to water at the point of measurement for both a NIST‐traceable 60Co beam at the UWADCL and several clinical single‐energy and spread‐out Bragg peak (SOBP) proton beam qualities at the Northwestern Medicine Chicago Proton Center. Increasing proton LET environments were acquired by placing film at increasing depths of Gammex HE Solid Water® whose water‐equivalent thickness was characterized prior to measurement. Results A strong LET dependence was observed near the Bragg peak (BP) consistent with previous studies performed with earlier versions of EBT3 film. The influence of range straggling on the film's LET response appears to have a uniform effect toward the BP regardless of the nominal beam energy. Proximal to this depth, the film's response decreased with decreasing energy at the same dose‐average LET. The opposite trend was observed for depths past the BP. Changes in the SOBP energy modulation showed a linear relationship between the film's relative response and dose‐averaged LET. Relative effectiveness factors (RE) were observed to range between 2%–7% depending on the width of the SOBP and depth of the film. Using the field‐specific calibration technique, a total k = 1 uncertainty in the absorbed dose to water was estimated to range from 4.68%–5.21%. Conclusion While EBT3 film's strong LET dependence is a common problem in proton beam dosimetry, this work has shown that the LET dependence can be taken into account by carefully considering the depth and energy modulation across the film using field‐specific corrections. RE factors were determined with a combined k = 1 uncertainty of 3.57% for SOBP environments and between 3.17%–4.69% for uniform, monoenergetic fields proximal to the distal 80% of the BP.

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Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and ⁶⁰Co γ‐rays

Cited by 44 publications

References 29 publications

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells

Dose detectors, sensors, and their applications

LET response variability of Gafchromic EBT3 film from a Co calibration in clinical proton beam qualities

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Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and 60Co γ‐rays

Cited by 44 publications

References 29 publications

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells

Investigating Dependencies of Relative Biological Effectiveness for Proton Therapy in Cancer Cells

Dose detectors, sensors, and their applications

LET response variability of Gafchromic EBT3 film from a Co calibration in clinical proton beam qualities

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Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and ⁶⁰Co γ‐rays