Dependence of radiochromic film response kinetics on fractionated doses

Ali, I; Williamson, Jeffrey F.; Costescu, Corina; Dempsey, James F.

doi:10.1016/j.apradiso.2004.07.014

Cited by 12 publications

(10 citation statements)

References 16 publications

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“…TLD and ion chamber data were used to verify the EBT film dose response at position 2. EBT film that is digitized > 10 min after exposure dose not measure a dose rate dependence (Ali et al 2005, Rink et al 2005, Fuss et al 2007, Rink et al 2007), thus, the results of the ion chamber and TLD measured dose responses at position 2 represent a similar response to dose by EBT film at positions 1 and 3. The ion chamber and TLD detectors were placed inside empty (air filled) 50 ml plastic vials and were positioned on top of a Styrofoam block, Fig.…”

Section: Methodsmentioning

confidence: 99%

CHARACTERIZATION OF A 137Cs IRRADIATOR FROM A NEW PERSPECTIVE WITH MODERN DOSIMETRIC TOOLS

Brady

Toncheva²,

Dewhirst³

et al. 2009

Health Physics

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To provide for accurate dosimetry in a 137Cs irradiator, the following were investigated: (1) correct mapping of the irradiator cavity's dose distribution, (2) rotated versus stationary dose rate measurements, (3) exposure-to-dose calibration selection for exposure time calculation, and (4) irradiator-timer error correction. This work introduces techniques to map dose distributions and measure dose rates with new high-sensitivity radiochromic films and a small-volume ion chamber constructed for in-beam, high-intensity gamma irradiation. Measured film distributions were compared to manufacturer-provided data and independent measurements from an ion chamber and TLD-100 chips. Measured film distributions agreed with the manufacturer-provided data in the central-vertical region, but disagreed by as much as 95% in surrounding regions. The independent measurements agreed within 96% with the measured dose distribution. Dose rates varied by: ~11% for a rotational versus stationary setup, by ~10% for the dose-to-medium correction between air and soft tissue, and by ~4–12% for irradiation times from 0.2–0.7 min due to timer error. In conclusion a critical irradiator characterization should be performed, initially, as apart of the acceptance testing of a newly installed irradiator, and periodically as an ongoing quality assurance protocol. We investigated, and recommend as part of a comprehensive irradiator verification protocol, the inclusion of radiochromic film-measured dose distributions, dose rates measured during rotation–when samples are likewise rotated for exposure, timer error corrections for short-time irradiation, and exposure-to-dose corrections that reflect typical sample compositions, e.g., soft tissue or air.

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Section: Methodsmentioning

confidence: 99%

CHARACTERIZATION OF A 137Cs IRRADIATOR FROM A NEW PERSPECTIVE WITH MODERN DOSIMETRIC TOOLS

Brady

Toncheva²,

Dewhirst³

et al. 2009

Health Physics

View full text Add to dashboard Cite

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“…[1][2][3][4][5][6] Such films have been used for in vivo and small field dosimetry as well as in high-dose gradient regions and other challenging scenarios owing to their high spatial resolution, water equivalency, and ease of use. [7][8][9][10][11][12][13][14][15][16] Radiochromic film response to ionizing radiation is manifested as a change in color, due to increase in the concentration of light absorbing polymers, which is characterized by the optical density (OD) or absorbance (A). 17 The absorbance measured using an optical system can then be correlated with the radiation dose.…”

Section: Introductionmentioning

confidence: 99%

Spectral analysis of the EBT3 radiochromic films for clinical photon and electron beams

et al. 2019

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Purpose The purpose of this study was to investigate the spectral response of the EBT3 radiochromic films to different beam qualities for radiation therapy dosimetry. Dose, dose rate, and interbatch dependencies on the spectral response of the films were investigated as well. Methods Pieces of EBT3 films placed between layers of solid water phantoms were irradiated with 6 and 15 MV photon beams, 6 and 10 MV‐flattening filter free (FFF) photon beams, and 6 and 20 MeV electron beams at dose levels between 0.4 and 50 Gy. Net absorbance was measured as a function of wavelength from the spectra acquired in the wavelength range of 400–800 nm using a fiber‐coupled spectrometer and broadband light source. Results No significant change was observed in the absorption spectra of the EBT3 film from the same batch irradiated with the same amount of dose using different beam qualities. Also, no spectral change with dose rate was observed. The measured net absorbance per Gy was independent of beam quality in the 1–50 Gy dose range. Slight differences in the spectral shape and absorption band positions were observed in film samples from different batches. The net absorbance spectra showed two absorption bands centered around 634–636 nm (primary) and 583–585 nm (secondary). However, depending on the film batch, for doses above a certain level the primary absorption band appears to “split” into two bands centered around ~624–628 and ~641–645 nm. Conclusions The spectral shape of the EBT3 radiochromic films irradiated with photons (including FFF) and electron beams is beam quality and dose rate independent; however, it varies with dose level, batch, and spectroscopy system used.

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“…11,12 However, because polymerization proceeds for some time after the radiation pulse, the development of radiochromic media continues even after the source of irradiation is turned off. 11,12,[16][17][18][19] This introduces some dose-rate effects in real-time measurements that need to be taken into consideration. Dose-rate dependent variations introduced during real-time measurements have been quantified for GAFCHROMIC ® EBT film and are small over certain dose and dose rate ranges.…”

Section: Introductionmentioning

confidence: 99%

Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium

et al. 2008

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The effects of temperature on real time changes in optical density ͑⌬OD͒ of GAFCHROMIC ® EBT film were investigated. The spectral peak of maximum change in absorbance ͑ max ͒ was shown to downshift linearly when the temperature of the film was increased from 22 to 38°C. The ⌬OD values were also shown to decrease linearly with temperature, and this decrease could not be attributed to the shift in max . A compensation scheme using max and a temperature-dependent correction factor was investigated, but provided limited improvement. Part of the reason may be the fluctuations in hydration of the active component, which were found to affect both position of absorbance peaks and the sensitivity of the film. To test the effect of hydration, laminated and unlaminated films were desiccated. This shifted both the major and minor absorbance peaks in the opposite direction to the change observed with temperature. The desiccated film also exhibited reduced sensitivity to ionizing radiation. Rehydration of the desiccated films did not reverse the effects, but rather gave rise to another form of the polymer with absorbance maxima upshifted further 20 nm. Hence, the spectral characteristics and sensitivity of the film can be dependent on its history, potentially complicating both real-time and conventional radiation dosimetry.

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Dependence of radiochromic film response kinetics on fractionated doses

Cited by 12 publications

References 16 publications

CHARACTERIZATION OF A 137Cs IRRADIATOR FROM A NEW PERSPECTIVE WITH MODERN DOSIMETRIC TOOLS

CHARACTERIZATION OF A 137Cs IRRADIATOR FROM A NEW PERSPECTIVE WITH MODERN DOSIMETRIC TOOLS

Spectral analysis of the EBT3 radiochromic films for clinical photon and electron beams

Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium

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