Development of a protocol for small beam bi-dimensional dose distribution measurements with radiochromic films

Moignier, Cyril; Huet, C.; Barraux, V.; Fontaine, J.; Loiseau, C.; Sebe-Mercier, K.; Batalla, A.; Makovicka, Libor

doi:10.1016/j.radmeas.2016.03.010

Cited by 5 publications

(7 citation statements)

References 29 publications

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“…Moreover, they allow 2D dose measurements and they can easily be housed in anthropomorphic phantoms. Measurements were performed according to a rigorous protocol (cutting, calibration, readout) developed in our laboratory 11 . In particular, it is based on a pixel‐to‐pixel background subtraction method with the use of the red channel only in order to overcome the limits of the multichannel correction method at low doses 15 .…”

Section: Methodsmentioning

confidence: 99%

“…In particular, it is based on a pixel‐to‐pixel background subtraction method with the use of the red channel only in order to overcome the limits of the multichannel correction method at low doses 15 . Measurements uncertainty was assessed as described in 11 . This protocol leads to dose measurements with a standard deviation of 2.9% (1 sigma) in the 0.5–4.0 Gy dose range (reaching 4.5% (1 sigma) for doses below 0.5 Gy).…”

Section: Methodsmentioning

confidence: 99%

“…15 Measurements uncertainty was assessed as described in. 11 This protocol leads to dose measurements with a standard deviation of 2.9% (1 sigma) in the 0.5-4.0 Gy dose range (reaching 4.5% (1 sigma) for doses below 0.5 Gy).…”

Section: B | Radiochromic Film Dosimetry and Phantom Irradiationmentioning

confidence: 99%

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Out‐of‐field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

Colnot

Zefkili

Gschwind

et al. 2021

J Applied Clin Med Phys

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Purpose: First, this experimental study aims at comparing out-of-field doses delivered by three radiotherapy techniques (3DCRT, VMAT (two different accelerators), and tomotherapy) for a pediatric renal treatment. Secondly, the accuracy of treatment planning systems (TPS) for out-of-field calculation is evaluated. Methods: EBT3 films were positioned in pediatric phantoms (5 and 10 yr old). They were irradiated according to four plans: 3DCRT (Clinac 2100CS, Varian), VMAT (Clinac 2100CS and Halcyon, Varian), and tomotherapy for a same target volume. 3D dose determination was performed with an in-house Matlab tool using linear interpolation of film measurements. 1D and 3D comparisons were made between techniques. Finally, measurements were compared to the Eclipse (Varian) and Tomotherapy (Accuray) TPS calculations. Results: Advanced radiotherapy techniques (VMATs and tomotherapy) deliver higher out-of-field doses compared to 3DCRT due to increased beam-on time triggered by intensity modulation. Differences increase with distance to target and reach a factor of 3 between VMAT and 3DCRT. Besides, tomotherapy delivers lower doses than VMAT: although tomotherapy beam-on time is higher than in VMAT, the additional shielding of the Hi-Art system reduces out-of-field doses. The latest generation Halcyon system proves to deliver lower peripheral doses than conventional accelerators. Regarding TPS calculation, tomotherapy proves to be suitable for out-of-field dose determination up to 30 cm from field edge whereas Eclipse (AAA and AXB) largely underestimates those doses. Conclusion: This study shows that the high dose conformation allowed by advanced radiotherapy is done at the cost of higher peripheral doses. In the context of treatment-related risk estimation, the consequence of this increase might be significative. Modern systems require adapted head shielding and a particular attention has to be taken regarding on-board imaging dose. Finally, TPS advanced dose calculation algorithms do not certify dose accuracy beyond field edges, and thus, those doses are not suitable for risk assessment.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Out‐of‐field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

Colnot

Zefkili

Gschwind

et al. 2021

J Applied Clin Med Phys

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“…The PENELOPE program (version 2014 and the main program penEasy version 2017) (Salvat 2015) was used to precisely model a 1000 MU min −1 Cyberknife VSI equipped with fixed cylindrical collimators. In this study, the detailed quadric geometry of the Cyberknife head modeled in a previous work (Moignier et al 2014a(Moignier et al , 2016 was completed. This geometry, based on manufacturer drawings and materials, includes the head components shaping the beam line and was previously validated in comparison with films and various detectors measurements for in-field dose evaluation (up to approximatively 6 cm from beam axis).…”

Section: Monte Carlo Simulation Of the Cyberknife For Out-of-field Do...mentioning

confidence: 99%

“…Radiochromic films have been chosen for out-of-field measurements as their response shows little dependence with energy (Massillon-JL et al 2012, Borca et al 2013). A rigorous protocol (Moignier et al 2016), developed in our laboratory, was used for the films' calibration and reading. This protocol enables EBT3 film dose measurements with a standard deviation of 2.9% (1 sigma) in the range from 0.5 to 4.0 Gy (reaching 4.5% (1 sigma) for 0.5 Gy).…”

Section: Radiochromic Films and Detectors Measurementsmentioning

confidence: 99%

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

Colnot¹,

Barraux²,

Loiseau³

et al. 2019

Phys. Med. Biol.

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In a previous work, a PENELOPE Monte Carlo model of a Cyberknife system equipped with fixed collimator was developed and validated for in-field dose evaluation. The aim of this work is to extend it to evaluate peripheral doses and to determine the precision of the treatment planning system (TPS) Multiplan in evaluating the off-axis doses. The Cyberknife® head model was completed with surrounding components based on manufacturer drawings. The contribution of the different head parts on the out-of-field dose was studied. To model the attenuation and the modification of particle energy caused by components not modelled, the photon transport was modified in one of the added components. The model was iteratively adjusted to fit dose profiles measured with EBT3 films and an ionization chamber for several collimator sizes. Finally, dose profiles were calculated using the two Multiplan TPS algorithms and were compared to our simulations. The contributions to out-of-field dose were identified as scattered radiation from the phantom and head leakage and scatter originating at the secondary collimator level. Particle transport in the additional pieces was modified to model this radiation. The maximum differences between simulated and measured doses are of 20.4%. Regarding the detector responses away from axis, EBT3 films and the Farmer chamber give similar response (less than 20% difference). The TPS Monte Carlo algorithm underestimates the doses away from axis more importantly for the smaller field sizes (up to 98%). Besides, RayTracing simplifies peripheral dose to a constant value with no inclusion of particle transport. A Monte Carlo model of a Cyberknife system for the determination of out-of-field doses up to 14 cm off-axis was successfully developed and validated for different depths and field sizes in comparison with measurements. This study also confirms that TPS algorithms do not model peripheral dose properly.

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9 Development of an experimental tool to evaluate normal tissue 3D doses in external-beam radiotherapy

et al. 2018

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Development of a protocol for small beam bi-dimensional dose distribution measurements with radiochromic films

Cited by 5 publications

References 29 publications

Out‐of‐field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

Out‐of‐field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses

9 Development of an experimental tool to evaluate normal tissue 3D doses in external-beam radiotherapy

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Development of a protocol for small beam bi-dimensional dose distribution measurements with radiochromic films

Cited by 5 publications

References 29 publications

Out‐of‐field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

Out‐of‐field doses from radiotherapy using photon beams: A comparative study for a pediatric renal treatment

A new Monte Carlo model of a Cyberknife® system for the precise determination of out-of-field doses

9 Development of an experimental tool to evaluate normal tissue 3D doses in external-beam radiotherapy

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Product

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A new Monte Carlo model of a Cyberknife^® system for the precise determination of out-of-field doses