Prospects for quantitative two‐dimensional radiochromic film dosimetry for low dose‐rate brachytherapy sources

Le, Yi; Ali, I; Dempsey, James F.; Williamson, Jeffrey F.

doi:10.1118/1.2390546

Cited by 10 publications

(9 citation statements)

References 36 publications

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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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Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…Radiochromic films due to their high spatial resolution, near tissue‐equivalence, and ability to measure two‐dimensional (2D) planar dose are readily used in radiotherapy dosimetry and quality assurance . The latest of EBT‐series radiochromic films, EBT‐XD (Ashland Inc, Bridgewater, NJ, USA) was specifically designed for high‐dose radiotherapy applications, such as stereotactic radiosurgery and stereotactic body radiation therapy.…”

Section: Introductionmentioning

confidence: 99%

Response characterization of EBT‐XD radiochromic films in megavoltage photon and electron beams

et al. 2019

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Purpose The purpose of this study was to investigate the beam quality dependence of the EBT‐XD radiochromic films for megavoltage photon and electron beam irradiations by studying their spectral response. Dose, dose rate, and interbatch dependencies were investigated as well. Methods EBT‐XD and EBT3 radiochromic films were cut into 5 cm2 × 5 cm2 pieces, placed between solid water phantoms, and irradiated with 6 and 15 MV photon beams, 6 and 10 MV flattening filter free photon beams, and 6 and 20 MeV electron beams at dose levels between 0.5 and 50 Gy. In order to measure the spectral response, the films were illuminated by a deuterium and tungsten‐halogen lamp and net absorption was measured in 400–800 nm spectral range using a fiber‐coupled optical spectrometer. Film samples were then analyzed using a flatbed scanner in the red, green, and blue channel to obtain the optical density of the films. Results The net absorption spectra of the EBT‐XD and EBT3 films showed two absorption bands centered at 635 and 585 nm, characteristic of the EBT model. However, for a given dose, the EBT‐XD films showed lower net absorbance compared to the EBT3 films. At a given dose level, the net absorption spectra and dose–response curves for EBT‐XD films showed only slight variations across various beam qualities. When a calibration curve obtained from a given beam quality is used to measure dose from films irradiated with other beam qualities, the maximum uncertainty in the calculated dose, in ranges 5–40 and 8–50 Gy for red and green channels, respectively, were ~3.1% and ~2.4%. Conclusions The response of the EBT‐XD films is dose rate independent but batch dependent. No significant beam quality dependence was observed in EBT‐XD films in the dose range up to 50 Gy.

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“…Since the introduction of radiochromic films to the radiation therapy community, earlier models like GAFCHROMIC ® HD810, MD55, and HS have been used extensively in twodimensional ͑2D͒ dose measurement for conventional and intravascular brachytherapy sources, as well as external beam and radiosurgery treatment. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] However, due to the low sensitivity of these earlier models, accurate dosimetry was limited to near field within 1 cm from brachytherapy sources. [4][5][6][7][8] A new model of radiochromic film, GAFCHROMIC ® EBT, became available in 2004.…”

Section: Introductionmentioning

confidence: 99%

The use of new GAFCHROMIC® EBT film for I125 seed dosimetry in Solid Water® phantom

2008

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Radiochromic film dosimetry has been extensively used for intravascular brachytherapy applications for near field within 1 cm from the sources. With the recent introduction of new model of radiochromic films, GAFCHROMIC EBT, with higher sensitivity than earlier models, it is promising to extend the distances out to 5 cm for low dose rate (LDR) source dosimetry. In this study, the use of new model GAFCHROMIC EBT film for 125I seed dosimetry in Solid Water was evaluated for radial distances from 0.06 cm out to 5 cm. A multiple film technique was employed for four 125I seeds (Implant Sciences model 3500) with NIST traceable air kerma strengths. Each experimental film was positioned in contact with a 125I seed in a Solid Water phantom. The products of the air kerma strength and exposure time ranged from 8 to 3158 U-h, with the initial air kerma strength of 6 U in a series of 25 experiments. A set of 25 calibration films each was sequentially exposed to one 125I seed at about 0.58 cm distance for doses from 0.1 to 33 Gy. A CCD camera based microdensitometer, with interchangeable green (520 nm) and red (665 nm) light boxes, was used to scan all the films with 0.2 mm pixel resolution. The dose to each 125I calibration film center was calculated using the air kerma strength of the seed (incorporating decay), exposure time, distance from seed center to film center, and TG43U1S1 recommended dosimetric parameters. Based on the established calibration curve, dose conversion from net optical density was achieved for each light source. The dose rate constant was determined as 0.991 cGy U(-1)h(-1) (+/-6.9%) and 1.014 cGy U(-1)h(-1) (+/-6.8%) from films scanned using green and red light sources, respectively. The difference between these two values was within the uncertainty of the measurement. Radial dose function and 2D anisotropy function were also determined. The results obtained using the two light sources corroborated each other. We found good agreement with the TG43U1S1 recommended values of radial dose function and 2D anisotropy function, to within the uncertainty of the measurement. We also verified the dosimetric parameters in the near field calculated by Rivard using Monte Carlo method. The radial dose function values in Solid Water were lower than those in water recommended by TG43U1S1, by about 2%, 3%, 7%, and 14% at 2, 3, 4, and 5 cm, respectively, partially due to the difference in the phantom material composition. Radiochromic film dosimetry using GAFCHROMIC EBT model is feasible in determining 2D dose distributions around low dose rate 125I seed. It is a viable alternative to TLD dosimetry for 125I seed dose characterization.

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Prospects for quantitative two‐dimensional radiochromic film dosimetry for low dose‐rate brachytherapy sources

Cited by 10 publications

References 36 publications

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

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

Response characterization of EBT‐XD radiochromic films in megavoltage photon and electron beams

The use of new GAFCHROMIC® EBT film for I125 seed dosimetry in Solid Water® phantom

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