Variations in dose distribution and optical properties of Gafchromic TM EBT2 film according to scanning mode

Soah Park, Sei Kwon Kang, Kwang Ho Cheong, Taejin Hwang, Haeyoung Kim, Taejin Han, Me Yeon Lee, Kyoungju Kim, Hoonsik Bae, Hyeong Su Kim, Jung Han Kim, Seung Jae Oh, Jinsuck Suh

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Purpose: The authors aim was to investigate the effects of using transmission and reflection scanning modes, the film orientation during scanning, and ambient room light on a dosimetry system based on the GafchromicTM EBT2 film model. Methods: For calibration, the films were cut to 3 × 3 cm2 and irradiated from 20 to 700 cGy at the depth of maximum dose using 6 and 10 MV photon beams in a 10 × 10 cm 2 field size. Absolute dose calibration of the linear accelerator was done according to the TRS398 protocol. An FG65-G ionization chamber was used to monitor the dose while irradiating the films in solid water. The film pieces were scanned with an EPSON Expression 1680 Pro flatbed scanner in transmission and reflection modes. Authors investigated the effect of orientation on films and examined the optical properties of EBT2 film using an ellipsometer and an ultraviolet (UV)/visible spectrometer to explain the dosimetric dependence of the film on orientation during the scanning process. To investigate the effect of ambient room light, films were preirradiated in 6 and 10 MV photon beams with intensity-modulated radiotherapy (IMRT) quality assurance (QA) plans, and then exposed to room light, either directly for 2 days in a workroom or for 2 months in a film box. Gamma index pass criteria of (3, 3 mm) were used. Results: The dose response curves based on net optical density (NOD) indicated that the reflection scanning mode can provide a better dose sensitivity than the transmission scanning mode, whereas the standard deviation of the dose is greater in reflection mode than in transmission mode. When the film was rotated 90° from the portrait orientation, the average dose of the EBT2 film decreased by 11.5-19.6% in transmission mode and by 1.5-2.3% in reflection mode. Using an ellipsometer, variation of the refractive index of EBT2 film-the birefringence property-was found to be the largest between 45° (1.72 and 1.71) and 135° (1.8 and 1.77) for 300 and 800 cGy. Absorption spectra of EBT2 films measured with spectrometer were the function of film orientation. The readings in reflection scanning mode were more stable against room light than those in transmission scanning mode, although dose readings increased in both modes after the films were exposed to room light. Conclusions: The transmission scanning mode exhibited a strong dependence on film orientation during scanning and a change in optical density resulting from room light exposure, so a constant scanning orientation and minimal exposure to light can reduce uncertainty in the measured dose (23 ± 3%). The angular dependence was analyzed using Jones matrices and optical properties of EBT2 film were obtained using an ellipsometer and an UV/visible spectrometer. The reflection scanning mode has relatively good stability with respect to room light and film orientation on a scanner, although the large standard deviation of dose is a disadvantage in measurements of absolute dose. Reflection scanning mode can offer a potential advantage for film dosimetry in radiotherapy, although transmission scanning mode is still recommended for dosimetry as it provides better uncertainty results.

Original languageEnglish
Pages (from-to)2524-2535
Number of pages12
JournalMedical physics
Volume39
Issue number5
DOIs
Publication statusPublished - 2012 Jan 1

Fingerprint

Light
Photons
Calibration
Uncertainty
Reading
Film Dosimetry
Birefringence
Intensity-Modulated Radiotherapy
Particle Accelerators
Refractometry
Radiotherapy
Water

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

Park, Soah ; Kang, Sei Kwon ; Cheong, Kwang Ho ; Hwang, Taejin ; Kim, Haeyoung ; Han, Taejin ; Lee, Me Yeon ; Kim, Kyoungju ; Bae, Hoonsik ; Su Kim, Hyeong ; Han Kim, Jung ; Jae Oh, Seung ; Suh, Jinsuck. / Variations in dose distribution and optical properties of Gafchromic TM EBT2 film according to scanning mode. In: Medical physics. 2012 ; Vol. 39, No. 5. pp. 2524-2535.
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title = "Variations in dose distribution and optical properties of Gafchromic TM EBT2 film according to scanning mode",
abstract = "Purpose: The authors aim was to investigate the effects of using transmission and reflection scanning modes, the film orientation during scanning, and ambient room light on a dosimetry system based on the GafchromicTM EBT2 film model. Methods: For calibration, the films were cut to 3 × 3 cm2 and irradiated from 20 to 700 cGy at the depth of maximum dose using 6 and 10 MV photon beams in a 10 × 10 cm 2 field size. Absolute dose calibration of the linear accelerator was done according to the TRS398 protocol. An FG65-G ionization chamber was used to monitor the dose while irradiating the films in solid water. The film pieces were scanned with an EPSON Expression 1680 Pro flatbed scanner in transmission and reflection modes. Authors investigated the effect of orientation on films and examined the optical properties of EBT2 film using an ellipsometer and an ultraviolet (UV)/visible spectrometer to explain the dosimetric dependence of the film on orientation during the scanning process. To investigate the effect of ambient room light, films were preirradiated in 6 and 10 MV photon beams with intensity-modulated radiotherapy (IMRT) quality assurance (QA) plans, and then exposed to room light, either directly for 2 days in a workroom or for 2 months in a film box. Gamma index pass criteria of (3, 3 mm) were used. Results: The dose response curves based on net optical density (NOD) indicated that the reflection scanning mode can provide a better dose sensitivity than the transmission scanning mode, whereas the standard deviation of the dose is greater in reflection mode than in transmission mode. When the film was rotated 90° from the portrait orientation, the average dose of the EBT2 film decreased by 11.5-19.6{\%} in transmission mode and by 1.5-2.3{\%} in reflection mode. Using an ellipsometer, variation of the refractive index of EBT2 film-the birefringence property-was found to be the largest between 45° (1.72 and 1.71) and 135° (1.8 and 1.77) for 300 and 800 cGy. Absorption spectra of EBT2 films measured with spectrometer were the function of film orientation. The readings in reflection scanning mode were more stable against room light than those in transmission scanning mode, although dose readings increased in both modes after the films were exposed to room light. Conclusions: The transmission scanning mode exhibited a strong dependence on film orientation during scanning and a change in optical density resulting from room light exposure, so a constant scanning orientation and minimal exposure to light can reduce uncertainty in the measured dose (23 ± 3{\%}). The angular dependence was analyzed using Jones matrices and optical properties of EBT2 film were obtained using an ellipsometer and an UV/visible spectrometer. The reflection scanning mode has relatively good stability with respect to room light and film orientation on a scanner, although the large standard deviation of dose is a disadvantage in measurements of absolute dose. Reflection scanning mode can offer a potential advantage for film dosimetry in radiotherapy, although transmission scanning mode is still recommended for dosimetry as it provides better uncertainty results.",
author = "Soah Park and Kang, {Sei Kwon} and Cheong, {Kwang Ho} and Taejin Hwang and Haeyoung Kim and Taejin Han and Lee, {Me Yeon} and Kyoungju Kim and Hoonsik Bae and {Su Kim}, Hyeong and {Han Kim}, Jung and {Jae Oh}, Seung and Jinsuck Suh",
year = "2012",
month = "1",
day = "1",
doi = "10.1118/1.3700731",
language = "English",
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Park, S, Kang, SK, Cheong, KH, Hwang, T, Kim, H, Han, T, Lee, MY, Kim, K, Bae, H, Su Kim, H, Han Kim, J, Jae Oh, S & Suh, J 2012, 'Variations in dose distribution and optical properties of Gafchromic TM EBT2 film according to scanning mode', Medical physics, vol. 39, no. 5, pp. 2524-2535. https://doi.org/10.1118/1.3700731

Variations in dose distribution and optical properties of Gafchromic TM EBT2 film according to scanning mode. / Park, Soah; Kang, Sei Kwon; Cheong, Kwang Ho; Hwang, Taejin; Kim, Haeyoung; Han, Taejin; Lee, Me Yeon; Kim, Kyoungju; Bae, Hoonsik; Su Kim, Hyeong; Han Kim, Jung; Jae Oh, Seung; Suh, Jinsuck.

In: Medical physics, Vol. 39, No. 5, 01.01.2012, p. 2524-2535.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Variations in dose distribution and optical properties of Gafchromic TM EBT2 film according to scanning mode

AU - Park, Soah

AU - Kang, Sei Kwon

AU - Cheong, Kwang Ho

AU - Hwang, Taejin

AU - Kim, Haeyoung

AU - Han, Taejin

AU - Lee, Me Yeon

AU - Kim, Kyoungju

AU - Bae, Hoonsik

AU - Su Kim, Hyeong

AU - Han Kim, Jung

AU - Jae Oh, Seung

AU - Suh, Jinsuck

PY - 2012/1/1

Y1 - 2012/1/1

N2 - Purpose: The authors aim was to investigate the effects of using transmission and reflection scanning modes, the film orientation during scanning, and ambient room light on a dosimetry system based on the GafchromicTM EBT2 film model. Methods: For calibration, the films were cut to 3 × 3 cm2 and irradiated from 20 to 700 cGy at the depth of maximum dose using 6 and 10 MV photon beams in a 10 × 10 cm 2 field size. Absolute dose calibration of the linear accelerator was done according to the TRS398 protocol. An FG65-G ionization chamber was used to monitor the dose while irradiating the films in solid water. The film pieces were scanned with an EPSON Expression 1680 Pro flatbed scanner in transmission and reflection modes. Authors investigated the effect of orientation on films and examined the optical properties of EBT2 film using an ellipsometer and an ultraviolet (UV)/visible spectrometer to explain the dosimetric dependence of the film on orientation during the scanning process. To investigate the effect of ambient room light, films were preirradiated in 6 and 10 MV photon beams with intensity-modulated radiotherapy (IMRT) quality assurance (QA) plans, and then exposed to room light, either directly for 2 days in a workroom or for 2 months in a film box. Gamma index pass criteria of (3, 3 mm) were used. Results: The dose response curves based on net optical density (NOD) indicated that the reflection scanning mode can provide a better dose sensitivity than the transmission scanning mode, whereas the standard deviation of the dose is greater in reflection mode than in transmission mode. When the film was rotated 90° from the portrait orientation, the average dose of the EBT2 film decreased by 11.5-19.6% in transmission mode and by 1.5-2.3% in reflection mode. Using an ellipsometer, variation of the refractive index of EBT2 film-the birefringence property-was found to be the largest between 45° (1.72 and 1.71) and 135° (1.8 and 1.77) for 300 and 800 cGy. Absorption spectra of EBT2 films measured with spectrometer were the function of film orientation. The readings in reflection scanning mode were more stable against room light than those in transmission scanning mode, although dose readings increased in both modes after the films were exposed to room light. Conclusions: The transmission scanning mode exhibited a strong dependence on film orientation during scanning and a change in optical density resulting from room light exposure, so a constant scanning orientation and minimal exposure to light can reduce uncertainty in the measured dose (23 ± 3%). The angular dependence was analyzed using Jones matrices and optical properties of EBT2 film were obtained using an ellipsometer and an UV/visible spectrometer. The reflection scanning mode has relatively good stability with respect to room light and film orientation on a scanner, although the large standard deviation of dose is a disadvantage in measurements of absolute dose. Reflection scanning mode can offer a potential advantage for film dosimetry in radiotherapy, although transmission scanning mode is still recommended for dosimetry as it provides better uncertainty results.

AB - Purpose: The authors aim was to investigate the effects of using transmission and reflection scanning modes, the film orientation during scanning, and ambient room light on a dosimetry system based on the GafchromicTM EBT2 film model. Methods: For calibration, the films were cut to 3 × 3 cm2 and irradiated from 20 to 700 cGy at the depth of maximum dose using 6 and 10 MV photon beams in a 10 × 10 cm 2 field size. Absolute dose calibration of the linear accelerator was done according to the TRS398 protocol. An FG65-G ionization chamber was used to monitor the dose while irradiating the films in solid water. The film pieces were scanned with an EPSON Expression 1680 Pro flatbed scanner in transmission and reflection modes. Authors investigated the effect of orientation on films and examined the optical properties of EBT2 film using an ellipsometer and an ultraviolet (UV)/visible spectrometer to explain the dosimetric dependence of the film on orientation during the scanning process. To investigate the effect of ambient room light, films were preirradiated in 6 and 10 MV photon beams with intensity-modulated radiotherapy (IMRT) quality assurance (QA) plans, and then exposed to room light, either directly for 2 days in a workroom or for 2 months in a film box. Gamma index pass criteria of (3, 3 mm) were used. Results: The dose response curves based on net optical density (NOD) indicated that the reflection scanning mode can provide a better dose sensitivity than the transmission scanning mode, whereas the standard deviation of the dose is greater in reflection mode than in transmission mode. When the film was rotated 90° from the portrait orientation, the average dose of the EBT2 film decreased by 11.5-19.6% in transmission mode and by 1.5-2.3% in reflection mode. Using an ellipsometer, variation of the refractive index of EBT2 film-the birefringence property-was found to be the largest between 45° (1.72 and 1.71) and 135° (1.8 and 1.77) for 300 and 800 cGy. Absorption spectra of EBT2 films measured with spectrometer were the function of film orientation. The readings in reflection scanning mode were more stable against room light than those in transmission scanning mode, although dose readings increased in both modes after the films were exposed to room light. Conclusions: The transmission scanning mode exhibited a strong dependence on film orientation during scanning and a change in optical density resulting from room light exposure, so a constant scanning orientation and minimal exposure to light can reduce uncertainty in the measured dose (23 ± 3%). The angular dependence was analyzed using Jones matrices and optical properties of EBT2 film were obtained using an ellipsometer and an UV/visible spectrometer. The reflection scanning mode has relatively good stability with respect to room light and film orientation on a scanner, although the large standard deviation of dose is a disadvantage in measurements of absolute dose. Reflection scanning mode can offer a potential advantage for film dosimetry in radiotherapy, although transmission scanning mode is still recommended for dosimetry as it provides better uncertainty results.

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