Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Katsuda, Toshizo; Gotanda, Rumi; Gotanda, Tatsuhiro; Akagawa, Takuya; Tanki, Nobuyoshi; Kuwano, Tadao; Yabunaka, Koichi

doi:10.1120/jacmp.v17i3.5862

Cited by 7 publications

(7 citation statements)

References 17 publications

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“…A median filter was used to reduce noise, as described for the EBT3 analysis. 25 Thereafter, we confirmed the measurement at each depth was highly consistent with the measurement obtained in the PinPoint3D Ion Chamber. The maximum differences between the two measurements were within 2%.…”

Section: Resultssupporting

confidence: 83%

Dosimetric properties of a newly developed thermoluminescent sheet‐type dosimeter for clinical proton beams

Katō

Sagara

Komori

et al. 2021

J Applied Clin Med Phys

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This study aimed to evaluate the dosimetric properties of a newly developed thermoluminescent sheet-type dosimeter (TLD-sheet) for clinical proton beams. Materials and Methods: The TLD-sheet is composed mainly of manganese doped lithium triborate, with a physical size and thickness of 150 mm × 150 mm and 0.15 mm respectively. It is flexible and can be cut freely for usage. The TLD-sheet has an effective atomic number of 7.3 and tissue-equivalent properties. We tested the reproducibility, fading effect, dose linearity, homogeneity, energy dependence, and water equivalent thickness (WET) of the TLD-sheet for clinical proton beams. We conducted tests with both unmodulated and modulated proton beams at energies of 150 and 210 MeV. Results: The measurement reproducibility was within 4%, which included the inhomogeneity of the TLD-sheet. The fading rates were approximately 20% and 30% after 2 and 7 days respectively. The TLD-sheet showed notable energy dependence in the Bragg peak and distal end of the spread-out Bragg peak regions. However, the doseresponse characteristics of the TLD-sheet remained linear up to a physical dose of 10 Gy in this study. This linearity was highly superior to those of commonly used radiochromic film. The thin WET of the TLD-sheet had little effect on the range. Conclusion: Although notable energy dependences were observed in Bragg peak region, the response characteristics examined in this study, such as reproducibility, fading effects, dose linearity, dose homogeneity and WET, showed that the TLDsheet can be a useful and effective dosimetry tool. With its flexible and reusable characteristics, it may also be an excellent in vivo skin dosimetry tool for proton therapy. K E Y W O R D S in vivo skin dosimetry, proton therapy, quality assurance, thermoluminescent dosimeter 1 | INTRODUCTION Proton therapy (PT) is growing at a considerable pace, which is visible in increasing in the number of the installation of new facilities worldwide, 1 and the related technology continues to evolve. Its irradiation techniques are also diversifying, and there is much debate about quality assurance (QA) methods for managing them. In order to overcome the difficulty in PT QA, the QA tools dedicated to PT

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Section: Resultssupporting

confidence: 83%

Dosimetric properties of a newly developed thermoluminescent sheet‐type dosimeter for clinical proton beams

Katō

Sagara

Komori

et al. 2021

J Applied Clin Med Phys

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“…Scanning of the Gafchromic EBT3 films was performed as described by Katsuda et al . for EBT2 and EBT3 films[ 6 ] with reflection mode. [ 12 ] The moiré artifacts (Newton's rings) were reduced by designing a 5 μm gap of the matte polyester surface of the Gafchromic EBT3 film.…”

Section: Aterials and M Ethodsmentioning

confidence: 99%

“…[ 5 ] To resolve this problem, ultraviolet (UV)-A rays have been tried to use in diagnostic radiology. [ 6 ] Under UV irradiation, Gafchromic films are chemically polymerized and their color changes from transparent to dark blue. [ 7 ] UV-A rays emitted from a fluorescent lamp (peak wavelength 365 nm) react more effectively with Gafchromic EBT2 and EBT3 than do UV-B and UV-C (peak wavelength 320 nm and 245 nm[ 8 ]) rays.…”

Section: Introductionmentioning

confidence: 99%

Intensities of incident and transmitted ultraviolet-a rays through gafchromic films

Katsuda

Gotanda

et al. 2017

J Med Phys

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Gafchromic films have been applied to X-ray dosimetry in diagnostic radiology. To correct nonuniformity errors in Gafchromic films, X-rays in the double-exposure technique can be replaced with ultraviolet (UV)-A rays. Intensities of the incident and transmitted UV-A rays were measured. However, it is unclear whether the chemical color change of Gafchromic films affects the UV-A transmission intensity. Gafchromic EBT3 films were suitable to be used in this study because non-UV protection layers are present on both sides of the film. The film is placed between UV-A ray light-emitting diodes and a probe of a UV meter. Gafchromic EBT3 films were irradiated by UV-A rays for up to 60 min. Data for analysis were obtained in the subsequent 60 min. Images from before and after UV-A irradiation were subtracted. When using 375 nm UV-A, the mean ± standard deviation (SD) of the pixel values in the subtracted image was remarkably high (11,194.15 ± 586.63). However, the UV-A transmissivity remained constant throughout the 60 min irradiation period. The mean ± SD UV-A transmission intensity was 184.48 ± 0.50 μm/cm2. Our findings demonstrate that color density changes in Gafchromic EBT3 films do not affect their UV-A transmission. Therefore, Gafchromic films were irradiated by UV-A rays as a preexposure.

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“…The UV-A bandwidth ranged from 315 to 400 nm [8] and a 10-W fluorescent UV lamp was used as a UV-A source. In addition, UV-A pre-irradiation corrected the non-uniformity of Gafchromic EBT2 films [9].…”

Section: Introductionmentioning

confidence: 99%

Determining optimum wavelength of ultraviolet rays to pre-exposure of non-uniformity error correction in Gafchromic EBT2 films

Katsuda

Gotanda

et al. 2018

Polish Journal of Medical Physics and Engineering

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Gafchromic films have been used to measure X-ray doses in diagnostic radiology such as computed tomography. The double-exposure technique is used to correct non-uniformity error of Gafchromic EBT2 films. Because of the heel effect of diagnostic x-rays, ultraviolet A (UV-A) is intended to be used as a substitute for x-rays. When using a UV-A light-emitting diode (LED), it is necessary to determine the effective optimal UV wavelength for the active layer of Gafchromic EBT2 films. This study evaluated the relation between the increase in color density of Gafchromic EBT2 films and the UV wavelengths. First, to correct non-uniformity, a Gafchromic EBT2 film was pre-irradiated using uniform UV-A radiation for 60 min from a 72-cm distance. Second, the film was irradiated using a UV-LED with a wavelength of 353-410 nm for 60 min from a 5.3-cm distance. The maximum, minimum, and mean ± standard deviation (SD) of pixel values of the subtraction images were evaluated using 0.5 inches of a circular region of interest (ROI). The highest mean ± SD (8915.25 ± 608.86) of the pixel value was obtained at a wavelength of 375 nm. The results indicated that 375 nm is the most effective and sensitive wavelength of UV-A for Gafchromic EBT2 films and that UV-A can be used as a substitute for x-rays in the double-exposure technique.

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Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Cited by 7 publications

References 17 publications

Dosimetric properties of a newly developed thermoluminescent sheet‐type dosimeter for clinical proton beams

Dosimetric properties of a newly developed thermoluminescent sheet‐type dosimeter for clinical proton beams

Intensities of incident and transmitted ultraviolet-a rays through gafchromic films

Determining optimum wavelength of ultraviolet rays to pre-exposure of non-uniformity error correction in Gafchromic EBT2 films

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