Dependency of EBT2 film calibration curve on postirradiation time

Chang, Liyun; Ho, Sheng-Yow; Ding, Hueisch‐Jy; Lee, Tsair-Fwu; Chen, Pang-Yu

doi:10.1118/1.4862511

Cited by 13 publications

(10 citation statements)

References 58 publications

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“…The PV at a given depth in the central beam axis was taken as the average of the PVs of all pixels within a 0.8 × 0.8-cm 2 square centered at the point of interest (POI), and the average was taken from the four films with the same given MU. The vertical midline of the film was irradiated along with the central beam axis and scanned near the midline of the scan bed and parallel to the scan direction; therefore, it was not necessary to correct for scanner nonuniformities when extracting the PVs [33][34][35] there. The corresponding depth dose, D d , was obtained from the dose measured using the 0.6-cm 3 farmer chamber and a verified PDD table that was constructed from the measurements through a PTW MP3-M water phantom.…”

Section: Methodsmentioning

confidence: 99%

Calibration of EBT2 film using a red‐channel PDD method in combination with a modified three‐channel technique

Chang

Lee

et al. 2015

Medical Physics

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Section: Methodsmentioning

confidence: 99%

Calibration of EBT2 film using a red‐channel PDD method in combination with a modified three‐channel technique

Chang

Lee

et al. 2015

Medical Physics

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“…The regular arrangement of the monomer molecules in a diacetylene crystal allows a linear polymerization to propagate, but owing to the slightly reduced atomic spacing in the polymer, the rate of polymerization decreases as the polymer grows. This behavior results in post‐irradiation OD growth which is characteristic of RCFs; namely the OD increases with time whereas the rate of OD change of an irradiated film decreases with time 1–3,5,7,28,29,35,41,75–78 . It previously took up to two weeks for the color in the early RCF models (HD‐810, MD‐55, HS, MD‐V2‐55) to stabilize 1,76 …”

Section: Introductionmentioning

confidence: 99%

Report of AAPM Task Group 235 Radiochromic Film Dosimetry: An Update to TG‐55

et al. 2020

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The use of radiochromic film (RCF) dosimetry in radiation therapy is extensive due to its high level of achievable accuracy for a wide range of dose values and its suitability under a variety of measurement conditions. However, since the publication of the 1998 AAPM Task Group 55, Report No. 63 on RCF dosimetry, the chemistry, composition, and readout systems for RCFs have evolved steadily. There are several challenges in using the new RCFs, readout systems and validation of the results depending on their applications. Accurate RCF dosimetry requires understanding of RCF selection, handling and calibration methods, calibration curves, dose conversion methods, correction methodologies as well as selection, operation and quality assurance (QA) programs of the readout systems. Acquiring this level of knowledge is not straight forward, even for some experienced users. This Task Group report addresses these issues and provides a basic understanding of available RCF models, dosimetric characteristics and properties, advantages and limitations, configurations, and overall elemental compositions of the RCFs that have changed over the past 20 yr. In addition, this report provides specific guidelines for data processing and analysis schemes and correction methodologies for clinical applications in radiation therapy.

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“…The dose verifications for the single‐scan protocol were scanned 30 min after film irradiation, and the measurement accuracy was within 3% of the absolute dose. Chang et al (26) proposed a film calibration method that includes the effect of the postirradiation time, ranging from 1 h to two months. The accuracy of the film doses for delivered doses above 60 cGy were mainly within 2% and the total uncertainties were generally less than 5%.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of a single‐scan protocol for radiochromic film dosimetry

Shimohigashi

Araki

Maruyama

et al. 2015

J Applied Clin Med Phys

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The purpose of this study was to evaluate a single‐scan protocol using Gafchromic EBT3 film (EBT3) by comparing it with the commonly used 24‐hr measurement protocol for radiochromic film dosimetry. Radiochromic film is generally scanned 24 hr after film exposure (24‐hr protocol). The single‐scan protocol enables measurement results within a short time using only the verification film, one calibration film, and unirradiated film. The single‐scan protocol was scanned 30 min after film irradiation. The EBT3 calibration curves were obtained with the multichannel film dosimetry method. The dose verifications for each protocol were performed with the step pattern, pyramid pattern, and clinical treatment plans for intensity‐modulated radiation therapy (IMRT). The absolute dose distributions for each protocol were compared with those calculated by the treatment planning system (TPS) using gamma evaluation at 3% and 3 mm. The dose distribution for the single‐scan protocol was within 2% of the 24‐hr protocol dose distribution. For the step pattern, the absolute dose discrepancies between the TPS for the single‐scan and 24‐hr protocols were 2.0±1.8 cGy and 1.4±1.2 cGy at the dose plateau, respectively. The pass rates were 96.0% for the single‐scan protocol and 95.9% for the 24‐hr protocol. Similarly, the dose discrepancies for the pyramid pattern were 3.6±3.5 cGy and 2.9±3.3 cGy, respectively, while the pass rates for the pyramid pattern were 95.3% and 96.4%, respectively. The average pass rates for the four IMRT plans were 96.7%±1.8% for the single‐scan protocol and 97.3%±1.4% for the 24‐hr protocol. Thus, the single‐scan protocol measurement is useful for dose verification of IMRT, based on its accuracy and efficiency.PACS number: 87.55.Qr

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Dependency of EBT2 film calibration curve on postirradiation time

Abstract: The EBT2 film dose can be modeled as a function of PIT. For the ease of routine calibration, five PITs were suggested to be used. It is recommended that two PITs be located in the fast developing period (1 ∼ 6 h), one in 1 ∼ 2 days, one around a week, and one around a month.

Cited by 13 publications

References 58 publications

Calibration of EBT2 film using a red‐channel PDD method in combination with a modified three‐channel technique

Calibration of EBT2 film using a red‐channel PDD method in combination with a modified three‐channel technique

Report of AAPM Task Group 235 Radiochromic Film Dosimetry: An Update to TG‐55

Evaluation of a single‐scan protocol for radiochromic film dosimetry

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