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

Abstract

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

TLD calibration and absorbed dose measurement in a radiation-induced liver injury model under a linear accelerator

“…TLD dosimetry possesses properties such as dispersion, precision, detection threshold, measurement range, dose-response rate, spatial resolution, dose-rate response independence, energy independence, and tissue equivalence. Their material versatility and different physical forms allow them to measure different radiation qualities over a wide range of absorbed doses, and they are also advantageous in dose distribution measurements caused by techniques such as 3D conformal, intensity-modulated radiotherapy, and computed tomography (CT) [13]. The accuracy of dosimetry in preclinical radiobiology experiments has been a topic of concern, and the mouse liver model involves small-radiation-field dosimetry, for which dosimetry is significantly challenging.…”