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Auteur : Grafiati

Publié le 7 juillet 2024

Mis à jour le 7 juillet 2024

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1

Rousseau, A., C. Stien, S. Dufreneix, G. Boissonnat, JM Bordy et V. Blideanu. « End-to-end quality assurance for Volumetric Modulated Arc Therapy with Fricke-Xylenol orange-Gelatin gel dosimeters and dual-wavelength cone-beam optical CT scanner ». Journal of Physics : Conference Series 2630, n^o 1 (1 novembre 2023) : 012018. http://dx.doi.org/10.1088/1742-6596/2630/1/012018.

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Abstract The whole treatment process undergone by patients in clinics with Volumetric Modulated Arc Therapy (VMAT) can be tested by implementing 3D end-to-end (E2E) quality assurance with gel dosimetry. In this work, a 3D E2E test was performed in a head phantom for the verification of a VMAT treatment, using FXG (Fricke-Xylenol orange-Gelatin) gel dosimetry and a newly developed dual-wavelength reading method on a cone-beam optical CT scanner. This dosimetric method intends to enable accurate measurements in the out-of-field zone and in the tumor volume, with an effective dose range up to 10 Gy. CT images of the phantom with a gel flask were used to create a treatment plan with a brain tumor of complex shape. A very good agreement between 90 %, 80 %, 60 % and 40 % isodose curves and high 3D γ passing rates (2%/2mm) of 98.6 % and 96.7 % between measured and computed dose maps showed that E2E tests can be successfully implemented with this novel dosimetric method.

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Kunkyab, Tenzin, Michelle Hilts, Andrew Jirasek et Derek Hyde. « Spatial and Dosimetric accuracy of 3D polymer gel with CBCT readout - Varian HyperArc® SRS implementation ». Journal of Physics : Conference Series 2630, n^o 1 (1 novembre 2023) : 012015. http://dx.doi.org/10.1088/1742-6596/2630/1/012015.

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Abstract 3D polymer gel dosimetry is a promising means to verify complex radiation treatments such as stereotactic radiosurgery (SRS), as it provides both 3D dosimetric and spatial information. The purpose of the study is to use a polymer gel read-out with cone-beam computed tomography (CBCT) to commission Varian’s HyperArc®-treatment planning and delivery. Three targets (3 cm, 2 cm, 1 cm diameter respectively) were defined on a treatment plan with a maximum dose of 25 Gy, resembling a single isocentre, multiple-lesion SRS plan. Pre- and post-irradiation CBCT images of the gel were obtained for dosimetry analysis. One slice containing two large targets was used to self-calibrate the entire gel volume for dose comparison. We were able to achieve sub-millimeter spatial accuracy and all evaluated gamma criterion (5% 1mm, 3% 1mm, 2% 1 mm were > 95%). In summary, in this study we have demonstrated that CBCT polymer gel dosimetry can be a highly valuable tool for commissioning complex radiation treatment techniques such as SRS.

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Ceberg, S., A. Mannerberg, E. Konradsson, M. Blomstedt, M. Kügele, M. Kadhim, A. Edvardsson et al. « FLASH radiotherapy and the associated dosimetric challenges ». Journal of Physics : Conference Series 2630, n^o 1 (1 novembre 2023) : 012010. http://dx.doi.org/10.1088/1742-6596/2630/1/012010.

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Abstract At Lund University and Skåne University Hospital in Lund, Sweden, we have, as the first clinic, modified a clinical Elekta Precise linear accelerator for convertible delivery of ultra-high dose rate (FLASH) irradiation. Whereas recently published reviews highlighted the need for standardised protocols for ultra-high dose rate beam dosimetry to be able to determine the true potential of FLASH irradiation, several dosimetry studies as well as in-vitro and in-vivo experiments have been carried out at our unit. Dosimetric procedures for verification of accurate dose delivery of FLASH irradiation to cell cultures, zebrafish embryos and small animals have been established using radiochromic films and thermo-luminescent dosimeters. Also, recently the first experience of electron FLASH radiotherapy (FLASH-RT) in canine patients in our clinical setting was published. Our research facilities also include a laboratory for 3D polymer gel manufacturing. Recently, we started investigating the feasibility of a NIPAM polymer gel dosimeter for ultra-high dose rate dosimetry. Furthermore, in the bunker of the modified Elekta linear accelerator, a Surface Guided Radiotherapy (SGRT) system is accessible. The Catalyst™ system (C-Rad Positioning, Uppsala, Sweden) provides optical surface imaging for patient setup, real-time motion monitoring and breathing adapted treatment. Aiming at treating patients using ultra-high dose rates, a real-time validation of the alignment between the beam and the target is crucial as the dose is delivered in a fraction of a second. Our research group has during the last decade investigated and developed SGRT workflows which improved patient setup and breathing adapted treatment for several cancer patient groups. Recently, we also started investigating the feasibility of a real-time motion monitoring system for surface guided FLASH-RT. Both FLASH related studies; 3D polymer gel dosimetry and surface guided FLASH-RT are to our knowledge the first of their kind. Following an introduction to the field of FLASH and the associated dosimetric challenges, we here aim to present the two ongoing studies including some preliminary results.

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Razak, Nik, Azhar Rahman, Sivamany Kandaiya, Iskandar Mustafa, Nor Yahaya, Amer Mahmoud et Ramzun Maizan. « Accuracy and Precision of Magat Gel As a Dosimeter ». Material Science Research India 12, n^o 1 (26 février 2015) : 01–07. http://dx.doi.org/10.13005/msri/120101.

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Polymer gel dosimeter is a radiation sensitive chemical dosimeter that can measure 3 D dose distribution with high resolution. Due to the increasing complexity of radiotherapy treatment planning and delivery, accurate experimental radiation dosimetry plays an important role in the implementation and quality assurance of new treatment techniques. A polymer gel dosimeter must possess several important characteristics of a dosimeter to be able to measure absorbed dose precisely. two important dosimetric properties of a dosimeter were determined in this study; accuracy and precision. The MAGAT gels were made of 5% gelatin, 6% methacrylic acid and 10 mM tetrakis-hydroxy-methyl-phosphonium chloride (THPC). The irradiation of MAGAT gel was performed by 6-MV photon beam at a dose range 1 to 10 Gy and was imaged by 1.5 T Magnetic Resonance Imaging (MRI). The dose response of MAGAT gel dosimeter was obtained from spin-spin relaxation rate (R2) of MRI signal. The accuracy of MAGAT gel dosimeter has a range within 4% for doses greater than and equal to 3 Gy. The reproducibility of the MAGAT gel dosimeter at one irradiation was less than 1% whilst the long term reproducibility was within 3% over the five month period. For temporal stability, the dose sensitivity of MAGAT gel dosimeter irradiate at 1 to 11 days post-manufacturing decreased over time. While the dose sensitivity imaged at 1 to 9 days post-irradiation increased up to 4 days post-irradiation and subsequently starts decreasing after 4 days till 9 days. From the study of two dosimetric properties, MAGAT gel dosimeter shows a great dose response with a superior dose response. Thus the MAGAT gel dosimeter can be apply as a 3 D radiotherapy dosimeter.

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Collins, S., A. Ogilvy, D. Huang, W. Hare, M. Hilts et A. Jirasek. « Iterative Image Reconstruction Methodology in Optical CT Radiochromic Gel Dosimetry ». Journal of Physics : Conference Series 2630, n^o 1 (1 novembre 2023) : 012033. http://dx.doi.org/10.1088/1742-6596/2630/1/012033.

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Abstract Modern advancements in radiation therapy require paralleled advancements in the dosimetric tools used to verify dose distributions. Optical computed tomography (CT) imaged radiochromic gel dosimeters provide comprehensive, tissue equivalent, 3D dosimetric information with high spatial resolution and low imaging times. Traditional CT image reconstruction methods (filtered backprojection) do not account for light refraction within the optical CT system reducing the image quality. Iterative reconstruction methods make use of a system matrix that describes this light refraction thus, improving the reconstructed image quality. However, use of iterative reconstruction methods is not widespread, largely due to the impractical storage size of the required system matrix. Furthermore, current iterative reconstruction methods do not address the issue of image degradation due to a single detector element collecting light from multiple raypaths. For optical CT radiochromic gel dosimetry to be used effectively as a radiation therapy treatment plan verification tool, the system must be both practical and accurate. Thus, this work has two main objectives: (i) reduce the size of system matrices by means of polar coordinate discretization in lieu of the traditional Cartesian coordinate discretization, and (ii) reduce image degradation due to multiple raypaths by a novel approach to populating the system matrix that accounts for multiple raypaths.

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Gibon, David, Philippe Bourel, Bernard Castelain, Xavier Marchandise et Jean Rousseau. « Dosimétrie par gels radiosensibles en radiothérapie. Intérêt et méthodes ». Canadian Journal of Physiology and Pharmacology 79, n^o 2 (1 février 2001) : 130–39. http://dx.doi.org/10.1139/y00-076.

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The goal of conformal radiotherapy is to concentrate the dose in a well-defined volume by avoiding the neighbouring healthy structures. This technique requires powerful treatment planning software and a rigorous control of estimated dosimetry. The usual dosimetric tools are not adapted to visualize and validate complex 3D treatment. Dosimetry by radiosensitive gel permits visualization and measurement of the three-dimensional dose distribution. The objective of this work is to report on current work in this field and, based on our results and our experience, to draw prospects for an optimal use of this technique. Further developments will relate to the realization of new radiosensitive gels satisfying, as well as possible, cost requirements, easy realization and use, magnetic resonance imagery (MRI) sensitivity, tissue equivalence, and stability. Other developments focus on scanning methods, especially in MRI to measure T1 and T2.Key words: gel dosimetry, radiation therapy, quality control.

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Michaś, Edyta, Katarzyna Tyminska, Michal A. Gryzinski, Janusz Kocik et Ryszard J. Barczynski. « Numerical model of human head phantom to ensure dosimetry of dose components for boron neutron capture therapy ». Radiation Protection Dosimetry 199, n^o 15-16 (octobre 2023) : 1922–25. http://dx.doi.org/10.1093/rpd/ncad158.

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Abstract Extremely important aspects of the boron neutron capture therapy are, first of all, administering to the patient a boron compound that selectively reaches the neoplastic cells, and in the second step, the verification of the irradiation process. This paper focuses on the latter aspect, which is the detailed dosimetry of the processes occurring after the reaction of thermal neutrons with the boron-10 isotope. The results of computer simulations with the use of a new type of human head phantom filled with a polymer dosimetric gel will be presented in this article.

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Kipouros, Panagiotis, Georgios Anagnostopoulos, Angelos Angelopoulos, Dimos Baltas, Panagiotis Baras, Anargiros Drolapas, Pantelis Karaiskos et al. « Dosimetric calculations and VIPAR polymer gel dosimetry close to the microSelectron HDR ». Zeitschrift für Medizinische Physik 12, n^o 4 (2002) : 252–59. http://dx.doi.org/10.1016/s0939-3889(15)70481-2.

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Grande, S., A. Palma, A. M. Luciani, P. Sordi, C. Ranghiasci, L. Guidoni et V. Viti. « Dosimetric performances of optically detected Fricke gel ». Journal of Physics : Conference Series 56 (1 décembre 2006) : 307–9. http://dx.doi.org/10.1088/1742-6596/56/1/057.

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Lee, Minsik, Seonyeong Noh, Jun-Bong Shin, Jungwon Kwak et Chiyoung Jeong. « Evaluation of Fused Deposition Modeling Materials for 3D-Printed Container of Dosimetric Polymer Gel ». Gels 10, n^o 2 (14 février 2024) : 146. http://dx.doi.org/10.3390/gels10020146.

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Accurate dosimetric verification is becoming increasingly important in radiotherapy. Although polymer gel dosimetry may be useful for verifying complex 3D dose distributions, it has limitations for clinical application due to its strong reactivity with oxygen and other contaminants. Therefore, it is important that the material of the gel storage container blocks reaction with external contaminants. In this study, we tested the effect of air and the chemical permeability of various polymer-based 3D printing materials that can be used as gel containers. A methacrylic acid, gelatin, and tetrakis (hydroxymethyl) phosphonium chloride gel was used. Five types of printing materials that can be applied to the fused deposition modeling (FDM)-type 3D printer were compared: acrylonitrile butadiene styrene (ABS), co-polyester (CPE), polycarbonate (PC), polylactic acid (PLA), and polypropylene (PP) (reference: glass vial). The map of R2 (1/T2) relaxation rates for each material, obtained from magnetic resonance imaging scans, was analyzed. Additionally, response histograms and dose calibration curves from the R2 map were evaluated. The R2 distribution showed that CPE had sharper boundaries than the other materials, and the profile gradient of CPE was also closest to the reference vial. Histograms and dose calibration showed that CPE provided the most homogeneous and the highest relative response of 83.5%, with 8.6% root mean square error, compared with the reference vial. These results indicate that CPE is a reasonable material for the FDM-type 3D printing gel container.

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Papanikolaou, P., L. Watts, E. Pappas, G. Kalaitzakis, T. Maris, N. Kirby, K. Rasmussen, A. Gutierrez, S. Stathakis et E. Pappas. « SU-F-T-513 : Dosimetric Validation of Spatially Fractionated Radiotherapy Using Gel Dosimetry ». Medical Physics 43, n^o 6Part21 (juin 2016) : 3581. http://dx.doi.org/10.1118/1.4956698.

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Carlier, Bram, Sophie V. Heymans, Sjoerd Nooijens, Gonzalo Collado-Lara, Yosra Toumia, Laurence Delombaerde, Gaio Paradossi et al. « A Preliminary Investigation of Radiation-Sensitive Ultrasound Contrast Agents for Photon Dosimetry ». Pharmaceuticals 17, n^o 5 (14 mai 2024) : 629. http://dx.doi.org/10.3390/ph17050629.

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Radiotherapy treatment plans have become highly conformal, posing additional constraints on the accuracy of treatment delivery. Here, we explore the use of radiation-sensitive ultrasound contrast agents (superheated phase-change nanodroplets) as dosimetric radiation sensors. In a series of experiments, we irradiated perfluorobutane nanodroplets dispersed in gel phantoms at various temperatures and assessed the radiation-induced nanodroplet vaporization events using offline or online ultrasound imaging. At 25 °C and 37 °C, the nanodroplet response was only present at higher photon energies (≥10 MV) and limited to <2 vaporization events per cm2 per Gy. A strong response (~2000 vaporizations per cm2 per Gy) was observed at 65 °C, suggesting radiation-induced nucleation of the droplet core at a sufficiently high degree of superheat. These results emphasize the need for alternative nanodroplet formulations, with a more volatile perfluorocarbon core, to enable in vivo photon dosimetry. The current nanodroplet formulation carries potential as an innovative gel dosimeter if an appropriate gel matrix can be found to ensure reproducibility. Eventually, the proposed technology might unlock unprecedented temporal and spatial resolution in image-based dosimetry, thanks to the combination of high-frame-rate ultrasound imaging and the detection of individual vaporization events, thereby addressing some of the burning challenges of new radiotherapy innovations.

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Elter, A., S. Dorsch, M. Marot, C. Gillmann, W. Johnen, A. Runz, C. K. Spindeldreier, S. Klüter, C. P. Karger et P. Mann. « RSC : Gel dosimetry as a tool for clinical implementation of image-guided radiotherapy ». Journal of Physics : Conference Series 2167, n^o 1 (1 janvier 2022) : 012020. http://dx.doi.org/10.1088/1742-6596/2167/1/012020.

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Abstract The implementation of new image-guided radiotherapy (IGRT) treatment techniques requires the development of new quality assurance (QA) methods including geometric and dosimetric validation of the applied dose in 3D. Polymer gels (PG) provide a promising tool to perform such tests. However, to be used in a large variety of clinical applications, the PG must be flexibly applicable. In this work, we present a variety of phantoms used in clinical routine to perform both hardware and workflow tests in IGRT. This includes the validation of isocenter accuracy in magnetic resonance (MR)-guided RT (MRgRT) and end-to-end tests of online adaptive treatment techniques for inter- and intra-fraction motion management in IGRT. The phantoms are equipped with one or more PG containers of different materials including 3D printed containers to allow for 3D dosimetry in arbitrarily shaped structures. The proposed measurement techniques and phantoms provide a flexible application and show a clear benefit of PG for 3D dosimetry in combination with end-to-end tests in many clinical QA applications.

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Luciani, A. M., A. Palma, N. Adorante, P. Barone, S. Grande, C. Ranghiasci, A. Rosi, L. Guidoni et V. Viti. « Optical images of dose distributions in Gel-Fricke : dosimetric performances of the gel ». Radiation Protection Dosimetry 122, n^o 1-4 (1 décembre 2006) : 455–56. http://dx.doi.org/10.1093/rpd/ncl486.

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Abdelgawad, Mahmoud H., Yasser S. Soliman, Mohammed I. ElGohry, Ahmed A. Eldib, Chang-Ming Charlie Ma et Omar S. Desouky. « Measurements of radiotherapy dosimetric parameters using Fricke gel dosimeter ». Biomedical Physics & ; Engineering Express 3, n^o 2 (20 avril 2017) : 025021. http://dx.doi.org/10.1088/2057-1976/aa6a20.

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Månsson, Sofie, Anna Karlsson, Helen Gustavsson, Johan Christensson et Sven Å. J. Bäck. « Dosimetric verification of breathing adapted radiotherapy using polymer gel ». Journal of Physics : Conference Series 56 (1 décembre 2006) : 300–303. http://dx.doi.org/10.1088/1742-6596/56/1/055.

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Ascención, Yudy, Jennifer Dietrich, Kibret Mequanint et Kalin I. Penev. « Tetrazolium salt monomers for gel dosimetry II : Dosimetric characterization of the ClearView™ 3D dosimeter ». Journal of Physics : Conference Series 847 (mai 2017) : 012049. http://dx.doi.org/10.1088/1742-6596/847/1/012049.

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Rosen, B., K. Lam et J. Moran. « SU-F-T-565 : Assessment of Dosimetric Accuracy for a 3D Gel-Based Dosimetry Service ». Medical Physics 43, n^o 6Part22 (juin 2016) : 3593. http://dx.doi.org/10.1118/1.4956750.

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Papagiannis, P., E. Pantelis, E. Georgiou, P. Karaiskos, A. Angelopoulos, L. Sakelliou, S. Stiliaris, D. Baltas et I. Seimenis. « Polymer gel dosimetry for the TG-43 dosimetric characterization of a new125I interstitial brachytherapy seed ». Physics in Medicine and Biology 51, n^o 8 (3 avril 2006) : 2101–11. http://dx.doi.org/10.1088/0031-9155/51/8/010.

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Soliman, Yasser S., Soad M. Tadros, Wafaa B. Beshir, Gamal R. Saad, Salvatore Gallo, Laila I. Ali et Magdi M. Naoum. « Study of Ag Nanoparticles in a Polyacrylamide Hydrogel Dosimeters by Optical Technique ». Gels 8, n^o 4 (5 avril 2022) : 222. http://dx.doi.org/10.3390/gels8040222.

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The dosimetric characteristics of hydrogel dosimeters based on polyacrylamide (PAC) as a capping agent incorporating silver nitrate as a radiation-sensitive material are investigated using UV-Vis spectrophotometry within the dose range 0–100 Gy. Glycerol was used in the hydrogel matrix to promote the dosimetric response and increase the radiation sensitivity. Upon exposing the PAC hydrogel to γ-ray, it exhibits a Surface Plasmon Resonance (SPR) band at 453 nm, and its intensity increases linearly with absorbed doses up to 100 Gy. The results are compared with the silver nitrate gel dosimeter. Glycerol of 15% in the hydrogel matrix enhances the radiation sensitivity by about 30%. PAC hydrogel dosimeter can be considered a near water equivalent material in the 400 keV–20 MeV photon energy range. At doses less than 15 Gy, the PAC hydrogel dosimeter retains higher radiation sensitivity than the gel dosimeter. The total uncertainty (2σ) of the dose estimated using this hydrogel is about 4%. These results may support the validity of using this hydrogel as a dosimeter to verify radiotherapy techniques and dose monitoring during blood irradiation.

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Luciani, A. M., A. Palma, S. Grande, P. Sordi, L. Guidoni, V. Viti, E. Di Castro, C. De Felice et A. Lo Bosco. « Dosimetric performances of optically detected Fricke-agarose-Xylenol Orange gel ». Journal of Physics : Conference Series 164 (1 mai 2009) : 012015. http://dx.doi.org/10.1088/1742-6596/164/1/012015.

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MacDougall, N. D., M. E. Miquel, D. J. Wilson, S. F. Keevil et M. A. Smith. « Evaluation of the dosimetric performance of BANG3® polymer gel ». Physics in Medicine and Biology 50, n^o 8 (31 mars 2005) : 1717–26. http://dx.doi.org/10.1088/0031-9155/50/8/007.

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Sun, P., Y. C. Fu, J. Hu, N. Hao, W. Huang et B. Jiang. « Development and dosimetric evaluation of radiochromic PCDA vesicle gel dosimeters ». Radiation Measurements 85 (février 2016) : 116–25. http://dx.doi.org/10.1016/j.radmeas.2015.12.037.

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Gómez-Ros, J. M., V. Correcher, L. Sánchez-Muñoz, J. García-Guinea et A. Delgado. « Thermoluminescence dosimetric properties of LiAlSiO4and LiAlSi10O22synthesized by sol-gel method ». physica status solidi (a) 204, n^o 3 (mars 2007) : 861–66. http://dx.doi.org/10.1002/pssa.200622334.

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Colnot, J., S. Chiavassa, G. Delpon et C. Huet. « Study of the use of gel dosimetry in combination with 3D printing phantom for personalized pretreatment QA in radiotherapy ». Journal of Physics : Conference Series 2167, n^o 1 (1 janvier 2022) : 012017. http://dx.doi.org/10.1088/1742-6596/2167/1/012017.

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Abstract In modern radiotherapy, pretreatment patient-specific quality assurance (PSQA) generally consists in delivering the treatment plan to a phantom equipped with a detector and in comparing the measured dose and the dose calculated by the treatment planning system (TPS) in order to detect any gap between both dose distributions. Dosimetric gels have interesting properties for QA. In this work, the use of gel dosimetry together with a patient-based 3D printed phantom for personalized PSQA is investigated. CT images of a patient with a right mesencephalic brain tumor were used to generate a 3D printed phantom. Then it was filled with water and a radiochromic gel jar and irradiated according to the patient intracranial stereotactic plan using a Novalis TrueBeam STX accelerator. Measured dose distributions agree well with the calculated ones. Regarding 3D gamma-index (1 mm – 2%) estimated within the central 85% of the jar volume, 96.3% of points pass the test. In addition, 86.5% of the points pass the local 2D 3 mm-3% gamma-index. Results are promising but further work is needed to improve the protocol and investigate the possibility to extend it to end-to-end tests.

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Locarno, Silvia, Paolo Arosio, Francesca Curtoni, Marco Piazzoni, Emanuele Pignoli et Salvatore Gallo. « Microscopic and Macroscopic Characterization of Hydrogels Based on Poly(vinyl-alcohol)–Glutaraldehyde Mixtures for Fricke Gel Dosimetry ». Gels 10, n^o 3 (28 février 2024) : 172. http://dx.doi.org/10.3390/gels10030172.

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In recent decades, hydrogels have emerged as innovative soft materials with widespread applications in the medical and biomedical fields, including drug delivery, tissue engineering, and gel dosimetry. In this work, a comprehensive study of the macroscopic and microscopic properties of hydrogel matrices based on Poly(vinyl-alcohol) (PVA) chemically crosslinked with Glutaraldehyde (GTA) was reported. Five different kinds of PVAs differing in molecular weight and degree of hydrolysis were considered. The local microscopic organization of the hydrogels was studied through the use of the 1H nuclear magnetic resonance relaxometry technique. Various macroscopic properties (gel fraction, water loss, contact angle, swelling degree, viscosity, and Young’s Modulus) were investigated with the aim of finding a correlation between them and the features of the hydrogel matrix. Additionally, an optical characterization was performed on all the hydrogels loaded with Fricke solution to assess their dosimetric behavior. The results obtained indicate that the degree of PVA hydrolysis is a crucial parameter influencing the structure of the hydrogel matrix. This factor should be considered for ensuring stability over time, a vital property in the context of potential biomedical applications where hydrogels act as radiological tissue-equivalent materials.

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Babaei, Vahidreza, Reza Pourimani, Sedighe Kashian, Peiman Rezaeian et Azam Akhavan. « Feasibility of utilizing radiochromic nickel complex gel for radiation processing ». Journal of Instrumentation 17, n^o 09 (1 septembre 2022) : P09017. http://dx.doi.org/10.1088/1748-0221/17/09/p09017.

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Abstract A radiation-sensitive nickel nitrate complex gel was prepared in three concentrations, and dosimetric characteristics were investigated for routine use in gamma radiation processing. Nickel nitrate hexahydrate/Gelatin/1,5-diphenylcarbazone (Ni/G/DPCO) gel demonstrated a maximum wavelength of 535 nm and linear dose-response of 10–1300 Gy. By increasing the absorbed dose, the Ni/G/DPCO gel has a visual color change from purple to colorless. The dose rate dependence on the gel sensitivity at 1.17 and 0.062 Gy/s dose rates was less than 10% difference at a linear dose range of 10–1300 Gy. Color stability before and after irradiation was up to 35 days, and the overall coefficient of variation, CV%, was found to be 3.87%. Hence, the observations proved that the gel has favorable characteristics for food irradiation, insect population control, and irradiation of agricultural products.

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Brzozowski, Pawel, Kalin I. Penev et Kibret Mequanint. « Gellan gum gel tissue phantoms and gel dosimeters with tunable electrical, mechanical and dosimetric properties ». International Journal of Biological Macromolecules 180 (juin 2021) : 332–38. http://dx.doi.org/10.1016/j.ijbiomac.2021.03.047.

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Gallo, Salvatore, Giorgio Collura, Giuseppina Iacoviello, Anna Longo, Luigi Tranchina, Antonio Bartolotta, Francesco d'Errico et Maurizio Marrale. « Preliminary magnetic resonance relaxometric analysis of Fricke gel dosimeters produced with polyvinyl alcohol and glutaraldehyde ». Nuclear Technology and Radiation Protection 32, n^o 3 (2017) : 242–49. http://dx.doi.org/10.2298/ntrp1703242g.

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This work describes the preliminary analysis of Fricke gels dosimeters characterized by a new formulation making use of a matrix of polyvinyl alcohol cross-linked by adding glutaraldehyde and analyzed by means of nuclear magnetic resonance relaxometry. In previous optical studies, these gels have shown promising dosimetric features in terms of photon sensitivity and low diffusion of ferric ions produced after irradiation. In this work, we used a portable nuclear magnetic resonance relaxometer to measure the relaxation times (which are important for dosimetric applications) of these gel materials. For this purpose, we performed a study for optimizing the acquisition parameters with a nuclear magnetic resonance relaxometer. Gel samples were exposed to clinical 6 MV photons in the dose range between 0 and 20 Gy. Nuclear magnetic resonance relaxometry measurements were per- formed and the sensitivity to photon beams was measured for various values of the Fe2+ ion concentration. The analyses pointed out that the MR signal increases as the Fe2+ content in- creases and the increase is about 75 % when the concentration of Fe2+ ions is increased from 0.5 mM to 2.5 mM. Furthermore, the sensitivity improvement achieved with increasing the Fe2+ concentration is about 60 %. This paper shows that the portable nuclear magnetic resonance relaxometer used for analysis of porous materials can be used for characterization of these dosimetric gels and this study can be considered as the first step for the characterization of these dosimeters which in future could be used for 3-D dose mapping in clinical applications.

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Yewondwossen, M., J. Robar et L. Gates. « 416 A Comparative Study of Polymer Gel and Film Dosimetry in Intensity Modulated Radiosurgery Dosimetric Verification ». Radiotherapy and Oncology 76 (septembre 2005) : S182—S183. http://dx.doi.org/10.1016/s0167-8140(05)81392-1.

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Foroni, R., G. Gambraini, U. Danesi, M. Mauri, E. Pompilio, L. Pirola, A. Nicolato, P. Ferraresi et M. Gerosa. « New dosimetric approach for multidimensional dose evaluation in gamma knife radiosurgery ». Journal of Neurosurgery 93, supplement_3 (décembre 2000) : 239–42. http://dx.doi.org/10.3171/jns.2000.93.supplement_3.0239.

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✓ During the past two decades, the progress in computerized treatment planning systems has led to more accurate imaging and therapy by using the gamma knife, especially with the smallest collimators (4 mm). However, the ionization chambers that have been used to calibrate the gamma knife are not useful with the smallest collimators because the chambers are too big compared with the irradiated volume. Therefore, it is important to develop more suitable dosimeters. This study proposes a new dosimeter method. The FriXyGel method proposed here is based on a phantom dosimeter, an acquisition chain, and dedicated software. This dosimeter uses an agarose gel into which a ferrous sulphate solution (Fricke solution) and a metal ion indicator (xylenol orange) are incorporated. The absorbed dose is detected through measurements of visible light transmission, imaged by means of a charge-coupled device camera provided with a suitable optical filter. Gel layers are imaged before and after irradiation, and the differences in light absorption are related to the absorbed dose. By choosing convenient thickness of gel layers and by building up a phantom with different gel slices, it is possible to obtain a three-dimensional (3D) representation of the absorbed dose. The final 3D representation is reached after several mathematical processes have been applied to the images. The first step identifies and reduces all factors that could alter the original data, such as nonuniformity in illumination. Then, after calibration procedures, it is possible to obtain absorbed dose values and to discover their 3D representation. This goal has been reached by developing appropriate software that performs all the calculations necessary for spatial representation routines and prompt comparison with theoretical calculations.

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Kashihara, Tairo, Naoya Murakami, Nikolaos Tselis, Kazuma Kobayashi, Keisuke Tsuchida, Satoshi Shima, Koji Masui et al. « Hyaluronate gel injection for rectum dose reduction in gynecologic high-dose-rate brachytherapy : initial Japanese experience ». Journal of Radiation Research 60, n^o 4 (29 avril 2019) : 501–8. http://dx.doi.org/10.1093/jrr/rrz016.

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Abstract Perirectal hyaluronate gel injection (HGI) appears to be a promising technique for healthy tissue dose sparing in pelvic radiotherapy. In this analysis, we report our initial experience of HGI in gynecologic brachytherapy, focusing on its safety and effectiveness for dose reduction to the rectum. Between July 2013 and May 2014, 36 patients received HGI for primary/salvage gynecologic brachytherapy. Dosimetric effect analysis was based on pre- and post-HGI computed tomography dataset registration with corresponding dose–volume histogram evaluation. The maximum dose to the most exposed 0.1 cm3 (D0.1cm3) and 2.0 cm3 (D2.0cm3) were used as index values for rectum and bladder dose evaluation. The dose indexes for target volume (TV) coverage were TV D90/V100. In all cases, HGI was well tolerated, with no acute or late adverse events documented at a median follow-up of 220 days (range, 18–1046 days). Rectum D2.0cm3 and D0.1cm3 were significantly decreased by HGI (P < 0.001 and P = 0.003, respectively), with no significant impact on dosimetric parameters of bladder and TV coverage. Factors correlating negatively with the dosimetric effect of HGI were an increasing number of interstitial catheters (P = 0.003) as well as Lcranial100% (P = 0.014) and Lcranial80% (P = 0.001) [i.e. the length from the anal verge to the most cranial point at which the 100% and 80% isodose lines, respectively, crossed the rectum]. The concept of HGI for gynecologic brachytherapy is plausible, and our initial experience indicates it to be an effective technique for rectal dose reduction in radiotherapy of intrapelvic tumours.

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Novotný, Josef, Josef Novotný, Václav Spĕvác˘ek, Pavel Dvor˘ák, Tomás˘ Cechák, Roman Lis˘c˘ák, Gustav Broz˘ek, Jaroslav Tintĕra et Josef Vymazal. « Application of polymer gel dosimetry in gamma knife radiosurgery ». Journal of Neurosurgery 97 (décembre 2002) : 556–62. http://dx.doi.org/10.3171/jns.2002.97.supplement_5.0556.

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Object. The purpose of this study was to investigate the use of a polymer gel—based dosimeter for the evaluation of geometric and dosimetric inaccuracies during gamma knife radiosurgery and during the irradiation of an experimental animal. Methods. A polymer gel dosimeter, based on acrylic monomers, was used for experiments conducted in this study. The accuracy of the dosimeter was evaluated on a Siemens EXPERT 1-tesla scanner in the transmitter/receiver head coil with the use of a multiecho sequence with 16 echoes, TE 22.5 to 360 msec, TR 2000 msec, slice thickness 2 mm, field of view 255 mm, and a pixel size of 0.5 × 0.5 mm2. Two experiments were conducted. First, the head phantom containing the polymer gel dosimeter was irradiated using 4-, 8-, 14-, and 18-mm isocenters. Second, a specially designed rat phantom was irradiated by four 4-mm isocenters. The dose profiles in the x, y, and z axes were calculated in the treatment planning system and measured with the polymer gel dosimeter and the results were compared. There was good agreement between the measured and calculated dose profiles. The maximum deviation in the spatial position of the center of measured and calculated dose profiles was 0.5 mm in the head phantom and 1 mm in the rat phantom. The maximum deviation in the width of the selected reference isodose of measured profiles was 1.2 mm in the head phantom and 1.1 mm in the rat phantom. Conclusions. The use of the polymer gel—based dosimeter for the verification of stereotactic procedures has advantages compared with other dosimetric systems. The dosimeter itself is tissue equivalent. Three-dimensional dose distributions can be measured and the dosimeter allows simulation of the therapeutic procedures.

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Yao, Chun-Hsu, Ting-Yu Tsai, Bor-Tsung Hsieh, Yuk-Wah Tsang, Chung-Yu Chiu, His-Ya Chao et Yuan-Jen Chang. « Dosimetric characteristics of intensity-modulated radiation therapy and RapidArc® therapy using a 3D N-isopropylacrylamide gel dosimeter ». International Journal of Modern Physics : Conference Series 44 (janvier 2016) : 1660221. http://dx.doi.org/10.1142/s2010194516602210.

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This study aimed to investigate the dosimetric characteristics of intensity-modulated radiation therapy (IMRT) and RapidArc therapy by using 3D N-isopropylacrylamide (NIPAM) polymer gel. Optical computed tomography, specifically OCTOPUSTM-10X fast optical computed tomography scanner, was used as a readout tool. Two cylindrical acrylic phantoms (10 cm in diameter, 10 cm in height, and 3 mm in thickness) were filled with NIPAM gel and used for IMRT and RapidArc irradiation by using the Clinac iX treatment machine. The irradiation energies for IMRT and RapidArc® were set as 6 MV photons, but their irradiation angles and dose rates differed during irradiation. The irradiation angles of IMRT were 120°, 155°, 180°, 215°, and 245°, and the dose rate was fixed at 400 cGy/min. RapidArc® rotated continuously during irradiation, and the dose rate varied from 330 cGy/min to 400 cGy/min. The pass rates were 98.02% and 97.48% for IMRT and RapidArc®, respectively, and the rejected area appeared at the edge of the irradiated region. The isodose lines of IMRT and RapidArc® were consistent with those of TPS in most regions. Scattering and edge enhancement effects are main factors that cause dose inaccuracy in the edge region and reduced pass rates. Considering dose rate dependence, we used variable dose rates during irradiation with RapidArc®. Results showed that the dose distribution of NIPAM gel was consistent with that of TPS. The pass rates were also the same for IMRT and RapidArc® irradiation. This study proposes a preliminary profile of dosimetric characteristics of IMRT and RapidArc® by using a NIPAM gel dosimeter.

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Johnston, H., M. Hilts, J. Carrick et A. Jirasek. « Characterization of the essential dosimetric properties of cosolvent-free polymer gel dosimeters : Recent progress in x-ray CT based normoxic polymer gel dosimetry ». Journal of Physics : Conference Series 444 (26 juin 2013) : 012092. http://dx.doi.org/10.1088/1742-6596/444/1/012092.

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Skyt, P. S., E. M. Høye, E. S. Yates, M. L. Schmidt, J. B. B. Petersen, P. Balling et L. P. Muren. « PO-0815 : Dosimetric precision of 3D gel dosimetry compared with radiochromic films in volumetric modulated arc therapy ». Radiotherapy and Oncology 115 (avril 2015) : S409—S410. http://dx.doi.org/10.1016/s0167-8140(15)40807-2.

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Tadros, Soad M., Yasser S. Soliman, W. B. Beshir, Gamal R. Saad et LailaI Ali. « Dosimetric investigations on radiation-induced Ag nanoparticles in a gel dosimeter ». Journal of Radioanalytical and Nuclear Chemistry 329, n^o 1 (2 juin 2021) : 463–73. http://dx.doi.org/10.1007/s10967-021-07776-y.

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Zeidan, O. A., S. I. Sriprisan, O. Lopatiuk-Tirpak, P. A. Kupelian, S. L. Meeks, W. C. Hsi, Z. Li, J. R. Palta et M. J. Maryanski. « Dosimetric evaluation of a novel polymer gel dosimeter for proton therapy ». Medical Physics 37, n^o 5 (26 avril 2010) : 2145–52. http://dx.doi.org/10.1118/1.3388869.

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Uusi-Simola, Jouni, Sami Heikkinen, Petri Kotiluoto, Tom Serén, Tiina Seppälä, Iiro Auterinen et Sauli Savolainen. « MAGIC polymer gel for dosimetric verification in boron neutron capture therapy ». Journal of Applied Clinical Medical Physics 8, n^o 2 (mars 2007) : 114–23. http://dx.doi.org/10.1120/jacmp.v8i2.2409.

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Bero, M. A. « Dosimetric properties of a radiochromic gel detector for diagnostic X-rays ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 580, n^o 1 (septembre 2007) : 186–89. http://dx.doi.org/10.1016/j.nima.2007.05.080.

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Marques, T., M. Schwarcke, C. E. Garrido, O. Baffa et P. Nicolucci. « Dosimetric properties of MAGIC-fpolymer gel assessed to Radiotherapy clinical beams ». Journal of Physics : Conference Series 250 (1 novembre 2010) : 012012. http://dx.doi.org/10.1088/1742-6596/250/1/012012.

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Sedaghat, Mahbod, Rachel Bujold et Martin Lepage. « Effect of the exothermal polymerization reaction on polymer gel dosimetric measurements ». Journal of Physics : Conference Series 250 (1 novembre 2010) : 012018. http://dx.doi.org/10.1088/1742-6596/250/1/012018.

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Venning, A., M. Mundayadan Chandroth, C. Morgan et M. Roberts. « Further investigation of lung tumour peripheral doses using normoxic polymer gel dosimetry techniques ». Journal of Physics : Conference Series 2167, n^o 1 (1 janvier 2022) : 012025. http://dx.doi.org/10.1088/1742-6596/2167/1/012025.

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Abstract This work builds upon previous investigations of lung tumour peripheral doses for 6 MV, 6 MV FFF, and 10 MV FFF conformal arc therapy beams calculated in the Monaco® TPS and delivered using an Elekta® Agility™ linac. An improved patient lung phantom is developed with measurements using the normoxic PAG gel dosimeter and compared against dose planes from the TPS. The gel dosimeter measurements indicate that the TPS is overestimating the secondary build-up in the lung tumour peripheral region. It has been determined that in lung tumours, 6 MV FFF is the optimal beam energy for peripheral dose coverage and that there is a dosimetric compromise using 10 MV FFF.

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Raza, Rameez, Atanu Panja, Manjira Mukherjee, Pabitra Chattopadhyay et Kumaresh Ghosh. « Dosimetric Chromogenic Probe for Selective Detection of Sulfide via Sol–Gel Methodology ». ACS Omega 3, n^o 12 (13 décembre 2018) : 17319–25. http://dx.doi.org/10.1021/acsomega.8b02795.

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Bong, Ji hye, Kum bae Kim, Tae Keun Yang, In ok Ko, Ji ae Park, Kyeong Min Kim, Hai jo Jung, Young hoon Ji et Soo Il Kwon. « Dosimetric Characteristics of a Polymer Gel for a 45 MeV Proton Beam ». New Physics : Sae Mulli 62, n^o 1 (31 janvier 2012) : 84. http://dx.doi.org/10.3938/npsm.62.84.

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Gafar, Sameh Mohamed, et Nehad Magdy Abdel-Kader. « Radiation induced degradation of murexide dye in two media for possible use in dosimetric applications ». Pigment & ; Resin Technology 48, n^o 6 (4 novembre 2019) : 540–46. http://dx.doi.org/10.1108/prt-02-2019-0014.

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Purpose The purpose of this paper is to study the effect of gamma-rays on murexide (Mx) dye and its possible use as radiation dosimeters in two different dosimetry systems. The first system depends on the Mx dye as a liquid dosimeter. The second dosimetry system depends also on the same dye but as in a gel form, which is more sensitive to gamma-rays. Design/methodology/approach The prepared Mx (solutions/gels) have a considerable two peaks at 324 and 521 nm that upon irradiation, the intensity of these peaks decreases with the increasing radiation dose. Findings The gamma-ray absorbed dose for these dosimeters was found to be up to 2 kGy for the solution samples and 40 Gy for the gels. Radiation chemical yield, dose response function, radiation sensitivity and before and after-irradiation stability under various conditions were discussed and studied. Practical implications It is expected that the radiolysis of the Mx dye can be used as radiation dosimeters in two different dosimetry systems; liquid and gel dosimeters. This can be applied in a wide range of gamma radiation practical industrial applications in water treatment, food irradiation dosimeters, radiotherapy and fresh food irradiation and seed production. Originality/value Both of the prepared Mx dyes, either as solutions or gel samples, can be facilely prepared from commercially, cheap, safe, available chemicals and suitable for useful applied Mx solutions and gels radiation dosimeters.

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Ramm, Daniel. « A fast dual wavelength laser beam fluid-less optical CT scanner for radiotherapy 3D gel dosimetry II : dosimetric performance ». Physics in Medicine & ; Biology 63, n^o 4 (16 février 2018) : 045020. http://dx.doi.org/10.1088/1361-6560/aaaa46.

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Bahrami, Farbod, Seyed Mohammad Mahdi Abtahi, Dariush Sardari et Mohsen Bakhshandeh. « Investigation of a modified radiochromic genipin-gel dosimeter : Dosimetric characteristics and radiological properties ». Journal of Radioanalytical and Nuclear Chemistry 328, n^o 1 (10 mars 2021) : 19–31. http://dx.doi.org/10.1007/s10967-021-07635-w.

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Roberto, W. S., Marivalda Pereira et T. P. R. Campos. « Dosimetric Analysis and Characterisation of Radioactive Seeds Produced by the Sol-Gel Method ». Key Engineering Materials 240-242 (mai 2003) : 579–82. http://dx.doi.org/10.4028/www.scientific.net/kem.240-242.579.

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Trombetta, L., G. Magugliani, M. Marranconi, M. Caprioli, A. Gambirasio, F. Locatelli, E. Macerata et al. « Polymer gel dosimeters for absolute high resolution pre-treatment dosimetric QA in RT ». Physica Medica 92 (décembre 2021) : S84. http://dx.doi.org/10.1016/s1120-1797(22)00178-8.

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