Absorbed dose distributions from ophthalmic <sup>106</sup>Ru/<sup>106</sup>Rh plaques measured in water with radiochromic film

Hermida-López, M.; Brualla, L.

doi:10.1002/mp.12777

Cited by 8 publications

(4 citation statements)

References 38 publications

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“…The radiochromic film has replaced its predecessor, the radiographic film, as the film of choice for clinical radiology/radiotherapy applications since it eliminates the need for post‐processing and exhibits a wider dynamic range (up to hundreds of Gy). Therapeutic applications of radiochromic films include the patient‐specific Quality Assurance (QA), 1–4 linac commissioning, 5 brachytherapy QA, 6–10 treatment planning system (TPS) dose validation, 11 and so forth. The major advantage of radiochromic film over other dosimeters in brachytherapy applications is its high spatial resolution, customizability into any shape, and 2D measurement capability.…”

Section: Introductionmentioning

confidence: 99%

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Huang

Gaballa

Chang

2022

J Applied Clin Med Phys

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To evaluate the dosimetric accuracy of EBT3 film calibrated with a 6 MV beam for high dose rate brachytherapy and propose a novel method for direct film calibration with an Ir-192 source. Methods: The 6 MV calibration was performed in water on a linear accelerator (linac). The Ir-192 calibration was accomplished by irradiating the film wrapped around a cylinder applicator with an Ir-192 source. All films were scanned 1-day post-irradiation to acquire calibration curves for all three (red, blue, and green) channels. The Ir-192 calibration films were also used for single-dose comparison. Moreover, an independent test film under a H.A.M. applicator was irradiated and the 2D dose distribution was obtained separately for each calibration using the red channel data. Gamma analysis and point-by-point profile comparison were performed to evaluate the performance of both calibrations. The uncertainty budget for each calibration system was analyzed. Results: The red channel had the best performance for both calibration systems in the single-dose comparison. We found a significant 4.89% difference from the reference for doses <250 cGy using the 6 MV calibration, while the difference was only 0.87% for doses >600 cGy. Gamma analysis of the 2D dose distribution showed the Ir-192 calibration had a higher passing rate of 91.9% for the 1 mm/2% criterion, compared to 83.5% for the 6 MV calibration. Most failing points were in the low-dose region (<200 cGy). The point-by-point profile comparison reported a discrepancy of 2%-3.6% between the Ir-192 and 6 MV calibrations in this low-dose region. The linac-and Ir-192-based dosimetry systems had an uncertainty of 4.1% (k = 2) and 5.66% (k = 2), respectively. Conclusions: Direct calibration of EBT3 films with an Ir-192 source is feasible and reliable, while the dosimetric accuracy of 6 MV calibration depends on the dose range. The Ir-192 calibration should be used when the measurement dose range is below 250 cGy.

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Section: Introductionmentioning

confidence: 99%

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Huang

Gaballa

Chang

2022

J Applied Clin Med Phys

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“…We adopted the practical method described by Hermida-López et al [ 27 ] distributions in water produced by Ru ophthalmic applicators using EBT3 radiochromic films. A mold was made for each type of asymmetric plaque using dummy plaques and polymer clay.…”

Section: Methodsmentioning

confidence: 99%

Modified Geometry of 106Ru Asymmetric Eye Plaques to Improve Dosimetric Calculations in Ophthalmic Brachytherapy

Miras

Terrón

Bertolet

et al. 2022

JPM

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Ru/Rh asymmetric plaques for ophthalmic brachytherapy have special geometric designs with a cutout intended to prevent irradiation of critical ocular structures proximal to the tumor. In this work, we present new geometric models for PENELOPE + PenEasy Monte Carlo simulations of these applicators, differing from the vendor-reported geometry, that better match their real geometry to assess their dosimetric impact. Simulation results were benchmarked to experimental dosimetric data from radiochromic film measurements, data provided by the manufacturer in the calibration certificates, and other experimental results published in the literature, obtaining, in all cases, better agreement with the modified geometries. The clinical impact of the new geometric models was evaluated by simulating real clinical cases using patient-specific eye models. The cases calculated using the modified geometries presented higher doses to the critical structures proximal to the cutout region. The modified geometric models presented in this work provide a more accurate representation of the asymmetric plaques, greatly improving the agreement between Monte Carlo calculations and experimental measurements. Lack of consideration of accurate geometric models has been shown to be translated into notable increases in dose to organs at risk in clinical cases.

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“…27 Additional dosimetry studies have included the use of scintillation detectors, thermoluminescent dosimeters, semiconductor detectors, radiochromic films, diamond detectors, diode detectors, alanine pellets, alanine-polymer film, and ionization chambers. [28][29][30][31][32][33][34][35][36][37][38] For 106 Ru/ 106 Rh plaques, all current measurement techniques rely on the use of a calibrated device to perform relative dosimetry, as opposed to an extrapolation chamber where dose is determined directly as a primary measurement device.…”

Section: Introductionmentioning

confidence: 99%

A convex windowless extrapolation chamber to measure surface dose rate from ¹⁰⁶Ru/¹⁰⁶Rh episcleral plaques

2019

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Purpose A convex windowless extrapolation chamber was developed as a primary measurement device to determine surface dose rate from curved 106Ru/106Rh episcleral plaques. Methods A convex extrapolation chamber without an entrance window was constructed for this work, and surface dose rate measurements were performed with two curved CCB‐type 106Ru/106Rh plaques (S/N 2545 and 2596) manufactured by Eckert & Ziegler BEBIG. FARO® Gage measurements were performed to verify the radius of curvature for the convex electrode and the concave plaque surface. Furthermore, the collecting electrode area was verified through capacitance measurements. Chamber correction factors for divergence and backscatter were generated using the EGSnrc cavity user code. For each source, surface dose rate was measured with the convex extrapolation chamber and compared with on‐contact measurements made with curved un‐laminated EBT3 film strips. A Monte Carlo correction was generated for radiochromic film measurements to account for volume averaging within the active layer and effects of phantom scatter. Additionally, extrapolation chamber results for each plaque were compared with scintillation detector measurements performed by the manufacturer. For the second source (S/N 2596), a comparison was also made with the Monte Carlo‐corrected surface dose rate measured at the National Physical Laboratory (NPL) using cylindrical alanine pellets. Finally, source measurements were performed using conventional ionization chambers (Exradin A26, A1SL, and A20) within a custom fixture to investigate the transfer of extrapolation chamber surface dose rate to clinics. Results For the first 106Ru/106Rh plaque (S/N 2545), average surface dose rate from the convex windowless extrapolation chamber was found to be 1.5% higher than the corresponding value from curved un‐laminated EBT3 film measurements and 5.6% lower than the manufacturer value. For the second source (S/N 2596), the extrapolation chamber surface dose rate was 2.5% higher than the un‐laminated EBT3 film result, 4.5% lower than the manufacturer value, and 3.9% higher compared to corrected alanine measurements made at NPL. Total uncertainty in the extrapolation chamber measurement was estimated to be approximately ± 7.0% (k = 2). For the plaque measurements made using conventional ionization chambers with a custom fixture, surface dose rate from the transfer technique was found to agree within 3.8% with the expected convex extrapolation chamber result for S/N 2596. Conclusions A convex windowless extrapolation chamber was developed as a primary measurement device for 106Ru/106Rh plaques. Through comparison with the extrapolation chamber, the accuracy of surface dose rate measurements from current dosimetry techniques was assessed and agreement was seen within 5.6%. Finally, it was found that conventional ionization chambers could be calibrated with a reference 106Ru/106Rh plaque in order to transfer the extrapolation chamber result for surface dose rate to clinics.

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Absorbed dose distributions from ophthalmic ¹⁰⁶Ru/¹⁰⁶Rh plaques measured in water with radiochromic film

Abstract: The proposed method may be useful to the users to perform quality assurance preclinical tests of Ru/ Rh plaques.

Cited by 8 publications

References 38 publications

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Modified Geometry of 106Ru Asymmetric Eye Plaques to Improve Dosimetric Calculations in Ophthalmic Brachytherapy

A convex windowless extrapolation chamber to measure surface dose rate from ¹⁰⁶Ru/¹⁰⁶Rh episcleral plaques

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Absorbed dose distributions from ophthalmic 106Ru/106Rh plaques measured in water with radiochromic film

Abstract: The proposed method may be useful to the users to perform quality assurance preclinical tests of Ru/ Rh plaques.

Cited by 8 publications

References 38 publications

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Evaluating dosimetric accuracy of the 6 MV calibration on EBT3 film in the use of Ir‐192 high dose rate brachytherapy

Modified Geometry of 106Ru Asymmetric Eye Plaques to Improve Dosimetric Calculations in Ophthalmic Brachytherapy

A convex windowless extrapolation chamber to measure surface dose rate from 106Ru/106Rh episcleral plaques

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Product

Resources

About

Absorbed dose distributions from ophthalmic ¹⁰⁶Ru/¹⁰⁶Rh plaques measured in water with radiochromic film

A convex windowless extrapolation chamber to measure surface dose rate from ¹⁰⁶Ru/¹⁰⁶Rh episcleral plaques