Investigation of EBT2 and EBT3 films for proton dosimetry in the 4–20 MeV energy range

Reinhardt, S.; Würl, Matthias; Greubel, C.; Humble, Nicole; Wilkens, Jan J.; Hillbrand, Martin; Mairani, A.; Assmann, W.; Parodi, Katia

doi:10.1007/s00411-014-0581-2

Cited by 45 publications

(46 citation statements)

References 34 publications

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“…Indeed, flatbed scanners show a reduced response at lateral positions perpendicular to the scanning direction depending on the optical density of the scanned film. When using these films in ion beams, the energy‐dependent dose response in the vicinity of the Bragg peak has to be considered . Since films have been considered with a primary goal of relative dosimetry, mainly to cross‐check transverse dose distributions against 2D‐arrays and scintillating screens, our commissioning work was mainly focused on the plateau part of the depth‐dose distribution.…”

Section: Methodsmentioning

confidence: 99%

“…When using these films in ion beams, the energy-dependent dose response in the vicinity of the Bragg peak has to be considered. 39,40 Since films have been considered with a primary goal of relative dosimetry, mainly to cross-check transverse dose distributions against 2D-arrays and scintillating screens, our commissioning work was mainly focused on the plateau part of the depth-dose distribution. Films were calibrated in terms of dose to water using a 179.2 MeV proton beam by irradiating films with different dose levels between 0 and 5 Gy at 2 cm depth.…”

Section: B3 Equipment Dedicated To Lateral Dose Distributionsmentioning

confidence: 99%

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Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

et al. 2017

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Purpose: To describe the implementation of dosimetry equipment and phantoms into clinical practice of light ion beam therapy facilities. This work covers not only standard dosimetry equipment such as computerized water scanners, films, 2D-array, thimble, and plane parallel ionization chambers, but also dosimetry equipment specifically devoted to the pencil beam scanning delivery technique such as water columns, scintillating screens or multilayer ionization chambers. Method: Advanced acceptance testing procedures developed at MedAustron and complementary to the standard acceptance procedures proposed by the manufacturer are presented. Detailed commissioning plans have been implemented for each piece of dosimetry equipment and include an estimate of the overall uncertainty budget for the range of clinical use of each device. Some standard dosimetry equipment used in many facilities was evaluated in detail: for instance, the recombination of a 2D-array or the potential use of a microdiamond detector to measure reference transverse dose profiles in water in the core of the primary pencil beams and in the low-dose nuclear halo (over four orders of magnitude in dose). Results: The implementation of dosimetry equipment as described in this work allowed determining absolute spot sizes and spot positions with an uncertainty better than 0.3 mm. Absolute ranges are determined with an uncertainty comprised of 0.2-0.6 mm, depending on the measured range and were reproduced with a maximum difference of 0.3 mm over a period of 12 months using three different devices. Conclusion: The detailed evaluation procedures of dosimetry equipment and phantoms proposed in this work could serve as a guidance for other medical physicists in ion beam therapy facilities and also in conventional radiation therapy.

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Section: Methodsmentioning

confidence: 99%

Section: B3 Equipment Dedicated To Lateral Dose Distributionsmentioning

confidence: 99%

Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

et al. 2017

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“…Reinhardt et al. noted that as much as a 24% correction to the film response may be needed for proton energies lower than 11Mev while higher energies result in little change to the film response . The low‐energy proton response of EBT film from Kirby et al.…”

Section: Introductionmentioning

confidence: 99%

“…25 Reinhardt et al noted that as much as a 24% correction to the film response may be needed for proton energies lower than 11Mev while higher energies result in little change to the film response. 23 The low-energy proton response of EBT film from Kirby et al showed the change in efficiency is less than 10% for proton energies greater than 3.2 Mev. 20 The results from these previous studies suggest that careful consideration must be taken when calibrating film response in high linear energy transfer (LET) environments.…”

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 films were irradiated at 18, 20, and 23 cm while the chamber array was irradiated at nearly identical depths of 18, 20 and 24 cm. The LET dependence of radiochromic films has been thoroughly investigated [6,18,22,26–33] and it has been established that the effect is highest for lower (< 11 MeV) proton energies [28]. However, for spot scanning beams, there may be a larger distribution of energies used to irradiate the PTV which could make accounting for LET corrections quite variable.…”

Section: Methodsmentioning

confidence: 99%

Patient-Specific QA of Spot-Scanning Proton Beams Using Radiochromic Film

Chan¹,

Chen²,

Shi³

et al. 2017

IJMPCERO

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Radiochromic film for spot-scanning QA provides high spatial resolution and efficiency gains from one-shot irradiation for multiple depths. However, calibration can be a tedious procedure which may limit widespread use. Moreover, since there may be an energy dependence, which manifests as a depth dependence, this may require additional measurements for each patient. We present a one-scan protocol to simplify the procedure. A calibration using an EBT3 film, exposed by a 6-level step-wedge plan on a Proteus®PLUS proton system (IBA, Belgium), was performed at depths of 18, 20, 24cm using Plastic Water® (CIRS, Norfolk, VA). The calibration doses ranged from 65–250 cGy(RBE) (relative biological effectiveness) for proton energies of 170–200 MeV. A clinical prostate+nodes plan was used for validation. The planar doses at selected depths were measured with EBT3 films and analyzed using One-scan protocol (one-scan digitization of QA film and at least one film exposed to a known dose). The gamma passing rates, dose-difference maps, and profiles of 2D planar doses measured with EBT3 film and IBA MatriXX-PT, versus the RayStation TPS calculations were analyzed and compared. The EBT3 film measurement results matched well with the TPS calculation data with an average passing rate of ~95% for 2%/2mm and slightly lower passing rates were obtained from an ion chamber array detector. We were able to demonstrate that the use of a proton step-wedge provided clinically acceptable results and minimized variations between film-scanner orientation, inter-scan, and scanning conditions. Furthermore, for relative dosimetry (calibration is not done at the time of experiment) it could be derived from no more than two films exposed to known doses (one could be zero) for rescaling the master calibration curve at each depth. The sensitivity of the calibration to depth variations has been explored. One-scan protocol results appear to be comparable to that of the ion chamber array detector. The use of a proton step-wedge for calibration of EBT3 film potentially increases efficiency in patient-specific QA of proton beams.

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Investigation of EBT2 and EBT3 films for proton dosimetry in the 4–20 MeV energy range

Cited by 45 publications

References 34 publications

Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

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

Patient-Specific QA of Spot-Scanning Proton Beams Using Radiochromic Film

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