A protocol for accurate radiochromic film dosimetry using Radiochromic.com

Méndez, Ignasi; Rovira-Escutia, Juan J.; Casar, Božidar

doi:10.2478/raon-2021-0034

Cited by 9 publications

(4 citation statements)

References 41 publications

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“…Gafchromic EBT3 films (ISP, Wayne, NJ) were calibrated in Solid Water ® against a Farmer‐type ion chamber following each center's film dosimetry protocol. Centers used the commercial software Radiochromic.com 32 (centers A and B) and home‐made software (centers C and D) using triple‐channel dosimetry protocols. 33 , 34 , 35 RGB mode with 16 bits per channel with a resolution of 72 and 150 dpi was used.…”

Section: Methodsmentioning

confidence: 99%

Challenges in modeling the Agility multileaf collimator in treatment planning systems and current needs for improvement

et al. 2022

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Background The Agility multileaf collimator (MLC) mounted in Elekta linear accelerators features some unique design characteristics, such as large leaf thickness, eccentric curvature at the leaf tip, and defocused leaf sides (‘tilting'). These characteristics offer several advantages but modeling them in treatment planning systems (TPSs) is challenging. Purpose The goals of this study were to investigate the challenges faced when modeling the Agility in two commercial TPSs (Monaco and RayStation) and to explore how the implemented MLC models could be improved in the future. Methods Four linear accelerators equipped with the Agility, located at different centers, were used for the study. Three centers use the RayStation TPS and the other one uses Monaco. For comparison purposes, data from four Varian linear accelerators with the Millennium 120 MLC were also included. Average doses measured with asynchronous sweeping gap tests were used to characterize and compare the characteristics of the Millennium and the Agility MLCs and to assess the MLC model in the TPSs. The FOURL test included in the ExpressQA package, provided by Elekta, was also used to evaluate the tongue‐and‐groove with radiochromic films. Finally, raytracing was used to investigate the impact of the MLC geometry and to understand the results obtained for each MLC. Results The geometry of the Agility produces dosimetric effects associated with the rounded leaf end up to a distance 20 mm away from the leaf tip end measured at the isocenter plane. This affects the tongue‐and‐groove shadowing, which progressively increases along the distance to the tip end. The RayStation and Monaco TPSs did not account for this effect, which made trade‐offs in the MLC parameters necessary and greatly varied the final MLC parameters used by different centers. Raytracing showed that these challenging leaf tip effects were directly related to the MLC geometry and that the characteristics mainly responsible for the large leaf tip effects of the Agility were its tilting design and its small source‐to‐collimator distance. Conclusions The MLC models implemented in RayStation and Monaco could not accurately reproduce the leaf tip effects for the Agility. Therefore, trade‐offs are needed and the optimal MLC parameters are dependent on the specific characteristics of treatment plans. Refining the MLC models for the Agility to better approximate the measured leaf tip and tongue‐and‐groove effects would extend the validity of the MLC model, reduce the variability in the MLC parameters used by the community, and facilitate the standardization of the MLC configuration process.

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Section: Methodsmentioning

confidence: 99%

Challenges in modeling the Agility multileaf collimator in treatment planning systems and current needs for improvement

et al. 2022

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“…GAFChromic EBT3 (Ashland Inc., Bridgewater, NJ, USA) film fragments were used. The fragments were handled, scanned and calibrated following the protocol detailed by [14]. The flatbed scanner used was an Epson Expression 12000XL (Seiko Epson Corporation, Nagano, Japan).…”

Section: Setup For Measuring the Detector Performance Under Radiationmentioning

confidence: 99%

Embedded bleeding detector into a PMMA applicator for electron intraoperative radiotherapy

et al. 2022

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The aim of this work is to present a ready to industrialize low-cost and easy-to-install bleeding detector for use in intraoperative electron radiation therapy (IOERT). The detector works in stand-alone mode and is embedded into a translucent polymethylmethacrylate (PMMA) applicator avoiding any contact with the patient, which represent a novelty compared to previous designs. The use of this detector will prevent dose misadministration during irradiation in the event of accumulation of fluids in the applicator. Methods: The detector is based on capacitive sensor and wireless power-supply electronics. Both sensor and electronics have been embedded in the applicator, so that any contact with the patient would be avoided. Since access to the tumor can be done through different trajectories, the detector has been calibrated for different tilting angles. Results: The result of the calibration provides us with a fit curve that allows the interpolation of the results at any angle. Comparison of estimated fluid height vs real height gives an error of 1 mm for tilting angles less than 10 • and 2 mm for tilting angles greater than 15 • . This accuracy is better than the one required by clinic. Conclusions: The performance of the bleeding detector was evaluated in situ. No interference was observed between the detector and the beam. In addition, a user-friendly mobile application has been developed to help the surgical team making decisions before and during irradiation. The measurement provided by the mobile application was stable during the irradiation process.

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“…In this method, LET is measured using only one type of detector. However, because radiochromic films do not provide real‐time measurements, several hours are required to obtain results and post‐processing is required 10,11 . Although other detectors, such as optically stimulated luminescence dosimeters, plastic nuclear track detectors, and tissue‐equivalent proportional counters (TEPCs), can be used for measuring LET, they do not provide real‐time measurements and some of these measurements depend on beam condition (TEPCs are suitable only for very l dose rate) 12–15 …”

Section: Introductionmentioning

confidence: 99%

“…However, because radiochromic films do not provide real-time measurements, several hours are required to obtain results and post-processing is required. 10,11 Although other detectors, such as optically stimulated luminescence dosimeters, plastic nuclear track detectors, and tissue-equivalent proportional counters (TEPCs), can be used for measuring LET, they do not provide realtime measurements and some of these measurements depend on beam condition (TEPCs are suitable only for very l dose rate). [12][13][14][15] The amount of luminescent light generated by the interaction between the scintillator and proton beam is reduced with increased proton LET despite receiving the same proton dose.…”

Section: Introductionmentioning

confidence: 99%

Determination of the proton LET using thin film solar cells coated with scintillating powder

Jeong

Kim

et al. 2022

Medical Physics

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Purpose:The amount of luminescent light detected in a scintillator is reduced with increased proton linear energy transfer (LET) despite receiving the same proton dose, through a phenomenon called quenching. This study evaluated the ability of a solar cell coated with scintillating powder (SC-SP) to measure therapeutic proton LET by measuring the quenching effect of the scintillating powder using a solar cell while simultaneously measuring the dose of the proton beam. Methods: SC-SP was composed of a flexible thin film solar cell and scintillating powder. The LET and dose of the pristine Bragg peak in the 14 cm range were calculated using a validated Monte Carlo model of a double scattering proton beam nozzle. The SC-SP was evaluated by measuring the proton beam under the same conditions at specific depths using SC-SP and Markus chamber. Finally, the 10 and 20 cm range pristine Bragg peaks and 5 cm spread-out Bragg peak (SOBP) in the 14 cm range were measured using the SC-SP and the Markus chamber. LETs measured using the SC-SP were compared with those calculated using Monte Carlo simulations. Results:The quenching factors of the SC-SP and solar cell alone, which were slopes of linear fit obtained from quenching correction factors according to LET, were 0.027 and 0.070 µm/keV (R 2 : 0.974 and 0.975). For pristine Bragg peaks in the 10 and 20 cm ranges, the maximum differences between LETs measured using the SC-SP and calculated using Monte Carlo simulations were 0.5 keV/µm (15.7%) and 1.2 keV/µm (12.0%), respectively. For a 5 cm SOBP proton beam, the LET measured using the SC-SP and calculated using Monte Carlo simulations differed by up to 1.9 keV/µm (18.7%). Conclusions: Comparisons of LETs for pristine Bragg peaks and SOBP between measured using the SC-SP and calculated using Monte Carlo simulations indicated that the solar cell-based system could simultaneously measure both LET and dose in real-time and is cost-effective.

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A protocol for accurate radiochromic film dosimetry using Radiochromic.com

Cited by 9 publications

References 41 publications

Challenges in modeling the Agility multileaf collimator in treatment planning systems and current needs for improvement

Challenges in modeling the Agility multileaf collimator in treatment planning systems and current needs for improvement

Embedded bleeding detector into a PMMA applicator for electron intraoperative radiotherapy

Determination of the proton LET using thin film solar cells coated with scintillating powder

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