Development and validation of radiochromic film dosimetry and Monte Carlo simulation tools for acquisition of absolute, high-spatial resolution longitudinal dose distributions in ocular proton therapy

Carnicer, A.; Angellier, G.; Gérard, A.; Garnier, Nicolas; Dubois, C.; Amblard, R.; Hérault, J.

doi:10.1016/j.radmeas.2013.06.011

Cited by 14 publications

(14 citation statements)

References 17 publications

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“…30 Radiochromic film has proven to be useful in measuring dose distributions in proton beams. 31,32 The flatness and symmetry of the beam was measured with radiochromic film (Gafchromic EBT3) for both the raw beam line and eye treatment beam line. Beam divergence was measured with radiochromic films placed 300 mm apart in the raw beam line.…”

Section: B Measurementsmentioning

confidence: 99%

Experimental depth dose curves of a 67.5 MeV proton beam for benchmarking and validation of Monte Carlo simulation

et al. 2015

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The proton Bragg curve measured for the 0.1016 mm thick Ta foil provided the most accurate benchmark, having a low contribution of proton scatter from upstream of the water tank. The accuracy was 0.15% in measured beam energy and 0.3% in measured depth penetration at the Bragg peak. The depth of the distal edge of the Bragg peak in the simulation fell short of measurement, suggesting that the mean ionization potential of water is 2-5 eV higher than the 78 eV used in the stopping power calculation for the simulation. The eye treatment beam line depth dose curves provide validation of Monte Carlo simulation of a Bragg curve and SOBP with 4%/2 mm accuracy.

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Section: B Measurementsmentioning

confidence: 99%

Experimental depth dose curves of a 67.5 MeV proton beam for benchmarking and validation of Monte Carlo simulation

et al. 2015

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“…The relative effectiveness (RE) was introduced to quantify the LET quenching effect . In literature RE is mostly defined either as the ratio of the absorbed dose to water,

D_{w}

, and the film dose,

D_{film}

, required to yield the same effect

R E = {(|, \frac{D_{film}}{D_{w, Q}})}_{iso - effect} = \frac{D (o_{Q_{0}} | p_{Q})}{D (o_{Q_{0}} | p_{Q_{0}})},

or as the ratio of

D_{w}

and the apparent film dose,

D_{w, normalapparent}

, applying the parameters obtained at

Q_{0}

R E = {(|, \frac{D_{w, normalapparent}}{D_{w, Q}})}_{iso - dose} = \frac{D (o_{Q} | p_{Q_{0}})}{D (o_{Q_{0}} | p_{Q_{0}})} .

Those two definitions are fundamentally different and cannot be mutually exchanged due to the nonlinear dependency of dose and net optical density [Eq. ].…”

Section: Introductionmentioning

confidence: 99%

Dose‐ rather than fluence‐averaged LET should be used as a single‐parameter descriptor of proton beam quality for radiochromic film dosimetry

et al. 2020

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Purpose: The dose response of Gafchromic EBT3 films exposed to proton beams depends on the dose, and additionally on the beam quality, which is often quantified with the linear energy transfer (LET) and, hence, also referred to as LET quenching. Fundamentally different methods to determine correction factors for this LET quenching effect have been reported in literature and a new method using the local proton fluence distribution differential in LET is presented. This method was exploited to investigate whether a more practical correction based on the dose-or fluence-averaged LET is feasible in a variety of clinically possible beam arrangements. Methods: The relative effectiveness (RE) was characterized within a high LET spread-out Bragg peak (SOBP) in water made up by the six lowest available energies (62.4-67.5 MeV, configuration "b 1 ") resulting in one of the highest clinically feasible dose-averaged LET distributions. Additionally, two beams were measured where a low LET proton beam (252.7 MeV) was superimposed on "b 1 ", which contributed either 50% of the initial particle fluence or 50% of the dose in the SOBP, referred to as configuration "b 2 " and "b 3 ," respectively. The proton LET spectrum was simulated with GATE/ Geant4 at all measurement positions. The net optical density change differential in LET was integrated over the local proton spectrum to calculate the net optical density and therefrom the beam quality correction factor. The LET dependence of the film response was accounted for by an LET dependence of one of the three parameters in the calibration function and was determined from inverse optimization using measurement "b 1 ." This method was then validated on the measurements of "b 2 " and "b 3 " and subsequently used to calculate the RE at 900 positions in nine clinically relevant beams. The extrapolated RE set was used to derive a simple linear correction function based on dose-averaged LET (L d ) and verify the validity in all points of the comprehensive RE set. Results: The uncorrected film dose deviated up to 26% from the reference dose, whereas the corrected film dose agreed within 3% in all three beams in water ("b 1 ", "b 2 " and "b 3 "). The LET dependence of the calibration function started to strongly increase around 5 keV/lm and flatten out around 30 keV/lm. All REs calculated from the proton fluence in the nine simulated beams could be approximated with a linear function of dose-averaged LET (RE = 1.0258À0.0211 lm/keV L d ). However, no functional relationship of RE-and fluence-averaged LET could be found encompassing all beam energies and modulations. Conclusions: The film quenching was found to be nonlinear as a function of proton LET as well as of the dose-averaged LET. However, the linear relation of RE on dose-averaged LET was a good approximation in all cases. In contrast to dose-averaged LET, fluence-averaged LET could not describe the RE when multiple beams were applied.

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“…The problem lies in the fact that the correction procedure is not simple. Various methods have been suggested and investigated to make a proper correction of the dose profiles measured with EBT2 and EBT3 Gafchromic films (Park et al, 2011;Carnicer et al, 2013;Fiorini et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Measurements of 2D distributions of absorbed dose in protontherapy with Gafchromic EBT3 films

Gambarini

Regazzoni

Artuso

et al. 2015

Applied Radiation and Isotopes

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Development and validation of radiochromic film dosimetry and Monte Carlo simulation tools for acquisition of absolute, high-spatial resolution longitudinal dose distributions in ocular proton therapy

Cited by 14 publications

References 17 publications

Experimental depth dose curves of a 67.5 MeV proton beam for benchmarking and validation of Monte Carlo simulation

Experimental depth dose curves of a 67.5 MeV proton beam for benchmarking and validation of Monte Carlo simulation

Dose‐ rather than fluence‐averaged LET should be used as a single‐parameter descriptor of proton beam quality for radiochromic film dosimetry

Measurements of 2D distributions of absorbed dose in protontherapy with Gafchromic EBT3 films

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