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Gel Dosimetry

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A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Analysis and Characterization".

Deadline for manuscript submissions: closed (15 September 2022) | Viewed by 36139

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Dr. Salvatore Gallo

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Department of Physics “Aldo Pontremoli”, University of Milan, 20133 Milan, Italy
Interests: applied physics; medical physics; dosimetry; material sciences
Special Issues, Collections and Topics in MDPI journals

Dr. Silvia Locarno

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Department of Physics, University of Milan, 20133 Milan, Italy
Interests: hydrogels; biomaterials; material sciences; material characterization; polymer science; applied physics; dosimetry; drug delivery systems
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

“gel dosimetry” is a high promising dosimetry technique because this system is the only true 3D dosimeters suitable for relative dose measurements, and it is particularly useful for dose verification in complex clinical situations. These dosimeters are an anthropomorphic phantom that allows to measure absorbed dose distribution in a full 3D geometry. Moreover, gels are nearly tissue-equivalent and can be molded to any desired shape or form.

Gel dosimeters mainly consist of radiation sensitive chemicals and a mobility reducing agent, e.g., gelatin, agarose or poly(vinyl-alcohol) and water. The radiation sensitive chemicals, upon irradiation with ionizing radiation, undergo a fundamental change in their properties as a function of the absorbed radiation dose, while the purpose of the gel matrix is to hold the polymer structures in place, preserving spatial information. Gel dosimeters generally consist of two types: “Fricke gels” and “Polymer gels”.

This Special Issue is a thorough collection of articles dealing with the synthesis and characterization of new hydrogel, of which the author shows the mechanisms of action and possible applications for dosimetry. For this purpose, content includes basic, translational, and clinical research addressing application in dosimetry of ionizing radiations. Furthermore, the overview presented in this Special Issue would not be complete without mentioning the use of binders and stabilizers to be incorporated in the hydrogelic matrices in order to improve the dosimetric characteristics of both "Fricke gels" and "Polymer gels". Publication of original research articles, rapid communications or reviews in this Special Issue will make an important contribution to developing gel dosimetry.

Note: If you would like to contribute a related paper, please consider our 2nd Edition: Gel Dosimetry (2nd Edition)

Dr. Salvatore Gallo
Dr. Silvia Locarno
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Dosimetry
Polymer Gels
Fricke Gels
Hydrogels
Radiation therapy
Synthesis and characterization
Health sciences
Quality assurance

Published Papers (12 papers)

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Editorial

Jump to: Research, Review

4 pages, 211 KiB

Open AccessEditorial

Gel Dosimetry

by Salvatore Gallo and Silvia Locarno

Gels 2023, 9(4), 311; https://doi.org/10.3390/gels9040311 - 7 Apr 2023

Viewed by 1301

Abstract

The purpose of radiation therapy (RT) is to cover tumor tissue homogeneously with a planned dose while minimizing the dose to the surrounding healthy tissue [...] Full article

(This article belongs to the Special Issue Gel Dosimetry)

Research

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12 pages, 3308 KiB

Open AccessArticle

Three-Dimensional Dosimetry by Optical-CT and Radiochromic Gel Dosimeter of a Multiple Isocenter Craniospinal Radiation Therapy Procedure

by Matheus Antonio da Silveira, Juliana Fernandes Pavoni, Alexandre Colello Bruno, Gustavo Viani Arruda and Oswaldo Baffa

Gels 2022, 8(9), 582; https://doi.org/10.3390/gels8090582 - 13 Sep 2022

Cited by 5 | Viewed by 1905

Abstract

Craniospinal irradiation (CSI) is a complex radiation technique employed to treat patients with primitive neuroectodermal tumors such as medulloblastoma or germinative brain tumors with the risk of leptomeningeal spread. In adults, this technique poses a technically challenging planning process because of the complex shape and length of the target volume. Thus, it requires multiple fields and different isocenters to guarantee the primary-tumor dose delivery. Recently, some authors have proposed the use IMRT technique for this planning with the possibility of overlapping adjacent fields. The high-dose delivery complexity demands three-dimensional dosimetry (3DD) to verify this irradiation procedure and motivated this study. We used an optical CT and a radiochromic Fricke-xylenol-orange gel with the addition of formaldehyde (FXO-f) to evaluate the doses delivered at the field junction region of this treatment. We found 96.91% as the mean passing rate using the gamma analysis with 3%/2 mm criteria at the junction region. However, the concentration of fail points in a determined region called attention to this evaluation, indicating the advantages of employing a 3DD technique in complex dose-distribution verifications. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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13 pages, 1954 KiB

Open AccessArticle

HyperArc^TM Dosimetric Validation for Multiple Targets Using Ionization Chamber and RT-100 Polymer Gel

by Lucia Zirone, Elisa Bonanno, Giuseppina Rita Borzì, Nina Cavalli, Alessia D’Anna, Rosaria Galvagno, Andrea Girlando, Anna Maria Gueli, Martina Pace, Giuseppe Stella and Carmelo Marino

Gels 2022, 8(8), 481; https://doi.org/10.3390/gels8080481 - 31 Jul 2022

Cited by 4 | Viewed by 2304

Abstract

Multiple brain metastases single-isocenter stereotactic radiosurgery (SRS) treatment is increasingly employed in radiotherapy department. Before its use in clinical routine, it is recommended to perform end-to-end tests. In this work, we report the results of five HyperArc^TM treatment plans obtained by both ionization chamber (IC) and polymer gel. The end-to-end tests were performed using a water equivalent Mobius Verification Phantom^TM (MVP) and a 3D-printed anthropomorphic head phantom PseudoPatient^® (PP) (RTsafe P.C., Athens, Greece); 2D and 3D dose distributions were evaluated on the PP phantom using polymer gel (RTsafe). Gels were read by 1.5T magnetic resonance imaging (MRI). Comparison between calculated and measured distributions was performed using gamma index passing rate evaluation by different criteria (5% 2 mm, 3% 2 mm, 5% 1 mm). Mean point dose differences of 1.01% [min −0.77%–max 2.89%] and 0.23% [min 0.01%–max 2.81%] were found in MVP and PP phantoms, respectively. For each target volume, the obtained results in terms of gamma index passing rate show an agreement >95% with 5% 2 mm and 3% 2 mm criteria for both 2D and 3D distributions. The obtained results confirmed that the use of a single isocenter for multiple lesions reduces the treatment time without compromising accuracy, even in the case of target volumes that are quite distant from the isocenter. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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11 pages, 20091 KiB

Open AccessArticle

Pilot Study of Polymerization Dynamics in nMAG Dose Gel

by Mantvydas Merkis, Benas Gabrielis Urbonavicius, Diana Adliene, Jurgita Laurikaitiene and Judita Puiso

Gels 2022, 8(5), 288; https://doi.org/10.3390/gels8050288 - 6 May 2022

Cited by 5 | Viewed by 1950

Abstract

The essential component of modern radiation therapy is the application of steep dose gradients during patient treatment in order to maximize the radiation dose to the target volume and protect neighboring heathy tissues. However, volumetric dose distribution in an irradiated target is still a bottleneck of dose verification in modern radiotherapy. Dose gels are almost the only known dosimetry tool which allows for the evaluation of dose distribution in the irradiated volume due to gel’s polymerization upon irradiation. The accuracy of dose gel dosimetry has its own obstacle, which is related to the continuation of the gel’s polymerization after the radiation treatment procedure is finished. In this article, a method to monitor the polymerization dynamics of dose gels in real-time is proposed using a modified optical spectrometry system. Using the proposed method, the changes of the optical characteristics of irradiated nMAG dose gels in situ were assessed. The investigation revealed that the detectable polymerization in dose gel proceeds up to 6 h after irradiation. This time is significantly shorter compared with a commonly recommended 24 h waiting time allocated for polymer gel to settle. It was also found that dose rate significantly influences the temporal response of the nMAG dosimeter. By increasing the irradiation dose rate by a factor of 2, the time needed for the polymerization process to settle was increased by 22%. Identification of the gel’s post-irradiation polymerization time interval and its dependence on irradiation parameters will contribute to more accurate dose verification using dose gel dosimetry. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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15 pages, 6089 KiB

Open AccessArticle

Study of Ag Nanoparticles in a Polyacrylamide Hydrogel Dosimeters by Optical Technique

by Yasser S. Soliman, Soad M. Tadros, Wafaa B. Beshir, Gamal R. Saad, Salvatore Gallo, Laila I. Ali and Magdi M. Naoum

Gels 2022, 8(4), 222; https://doi.org/10.3390/gels8040222 - 5 Apr 2022

Cited by 10 | Viewed by 2291

Abstract

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. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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17 pages, 4791 KiB

Open AccessEditor’s ChoiceArticle

How Xylenol Orange and Ferrous Ammonium Sulphate Influence the Dosimetric Properties of PVA–GTA Fricke Gel Dosimeters: A Spectrophotometric Study

by Martina Scotti, Paolo Arosio, Elisa Brambilla, Salvatore Gallo, Cristina Lenardi, Silvia Locarno, Francesco Orsini, Emanuele Pignoli, Luca Pedicone and Ivan Veronese

Gels 2022, 8(4), 204; https://doi.org/10.3390/gels8040204 - 23 Mar 2022

Cited by 14 | Viewed by 3799

Abstract

The development of Fricke gel (FG) dosimeters based on poly(vinyl alcohol) (PVA) as the gelling agent and glutaraldehyde (GTA) as the cross-linker has enabled significant improvements in the dose response and the stability over time of spatial radiation dose distributions. However, a standard procedure for preparing FG in terms of reagent concentrations is still missing in the literature. This study aims to investigate, by means of spectrophotometric analyses, how the sensitivity to the radiation dose and the range of linearity of the dose–response curve of PVA-GTA-FG dosimeters loaded with xylenol orange sodium salt (XO) are influenced by ferrous ammonium sulphate (FAS) and XO concentrations. Moreover, the effect of different concentrations of such compounds on self-oxidation phenomena in the dosimeters was evaluated. PVA-GTA-FG dosimeters were prepared using XO concentrations in the range 0.04–0.80 mM and FAS in the range 0.05–5.00 mM. The optical absorbance properties and the dose response of FG were investigated in the interval 0.0–42.0 Gy. The results demonstrate that the amount of FAS and XO determines both the sensitivity to the absorbed dose and the interval of linearity of the dose–response curve. The study suggests that the best performances of FG dosimeters for spectrophotometric analyses can be obtained using 1.00–0.40 mM and 0.200–0.166 mM concentrations of FAS and XO, respectively. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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20 pages, 5616 KiB

Open AccessArticle

Induced Radionuclides and Their Activity Concentration in Gel Dosimeters Irradiated by Carbon Ion Beam

by Masumitsu Toyohara, Shinichi Minohara, Yohsuke Kusano, Hiroaki Gotoh, Yoichiro Tanaka, Masaru Yuhara, Yu Yamashita and Yoshiaki Shimono

Gels 2022, 8(4), 203; https://doi.org/10.3390/gels8040203 - 23 Mar 2022

Cited by 2 | Viewed by 1959

Abstract

Radioactivity was measured in a micellar gel dosimeter, a polymer gel dosimeter, and water was irradiated by carbon ion beams at various beam energy conditions. Monte Carlo simulation was also performed to estimate the radioactivity. Short-lived positron-emitting nuclides were observed immediately after irradiation, but they decayed rapidly into the background. At 24 h post-irradiation, the dominant measured radioactivity was of ⁷Be. The simulation also showed minor activity of ²⁴Na and ³H; however, they were not experimentally observed. The measured radioactivity was independent of the type of gel dosimeter under all irradiation conditions, suggesting that the radioactivity was induced by the interaction of carbon ions with water (the main component of the gel dosimeters). The ratio between the simulated and measured radioactivity was within 0.9–1.5. The activity concentration of ⁷Be was found to be less than 1/10 of the value derived using the exemption concept proposed by the International Atomic Energy Agency. This result should be applicable to irradiated gel dosimeters containing mainly water and 0–4 wt.% C and 0–1.7 wt.% N. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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9 pages, 1833 KiB

Open AccessArticle

Improved Dose Response of N-(hydroxymethyl)acrylamide Gel Dosimeter with Calcium Chloride for Radiotherapy

by Khalid A. Rabaeh, Rawan E. Al-Tarawneh, Molham M. Eyadeh, Issra’ M. E. Hammoudeh and Moneeb T. M. Shatnawi

Gels 2022, 8(2), 78; https://doi.org/10.3390/gels8020078 - 26 Jan 2022

Cited by 12 | Viewed by 2454

Abstract

The impact of calcium chloride (CaCl₂) on the performance of N-(hydroxymethyl)acrylamide (NHMA) polymer gel dosimeter is studied in this article. The dosimeter was exposed to doses of up to 10 Gy with radiation beam-energy of 10 MV and dose-rates of 300 cGy/min. The relaxation rate (R₂) parameter was utilized to explore the performance of irradiated NHMAGAT gels. The dose response in terms of R₂ increased from 0.29 to 0.63 Gy⁻¹·s⁻¹ with increasing calcium chloride concentration from 0 to 1000 mM. The results show no substantial impact of dose-rates as well as radiation energies on NHMAGAT samples. For the steadiness of irradiated NHMAGAT dosimeters, it was found that there is no apparent variation in R₂ (less than ±3%; standard deviation) up to 3 days. The overall uncertainty of the gel dosimeter with calcium chloride is 4.96% (double standard deviation, 95% confidence level). Full article

(This article belongs to the Special Issue Gel Dosimetry)

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12 pages, 2419 KiB

Open AccessEditor’s ChoiceArticle

Whole Three-Dimensional Dosimetry of Carbon Ion Beams with an MRI-Based Nanocomposite Fricke Gel Dosimeter Using Rapid T₁ Mapping Method

by Shinya Mizukami, Yusuke Watanabe, Takahiro Mizoguchi, Tsutomu Gomi, Hidetake Hara, Hideyuki Takei, Nobuhisa Fukunishi, Kenichi L. Ishikawa, Shigekazu Fukuda and Takuya Maeyama

Gels 2021, 7(4), 233; https://doi.org/10.3390/gels7040233 - 25 Nov 2021

Cited by 14 | Viewed by 2958

Abstract

MRI-based gel dosimeters are attractive systems for the evaluation of complex dose distributions in radiotherapy. In particular, the nanocomposite Fricke gel dosimeter is one among a few dosimeters capable of accurately evaluating the dose distribution of heavy ion beams. In contrast, reduction of the scanning time is a challenging issue for the acquisition of three-dimensional volume data. In this study, we investigated a three-dimensional dose distribution measurement method for heavy ion beams using variable flip angle (VFA), which is expected to significantly reduce the MRI scanning time. Our findings clarified that the whole three-dimensional dose distribution could be evaluated within the conventional imaging time (20 min) and quality of one cross-section. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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Review

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27 pages, 6450 KiB

Open AccessReview

Chemical Overview of Gel Dosimetry Systems: A Comprehensive Review

by Micaela A. Macchione, Sofía Lechón Páez, Miriam C. Strumia, Mauro Valente and Facundo Mattea

Gels 2022, 8(10), 663; https://doi.org/10.3390/gels8100663 - 17 Oct 2022

Cited by 26 | Viewed by 2904

Abstract

Advances in radiotherapy technology during the last 25 years have significantly improved both dose conformation to tumors and the preservation of healthy tissues, achieving almost real-time feedback by means of high-precision treatments and theranostics. Owing to this, developing high-performance systems capable of coping with the challenging requirements of modern ionizing radiation is a key issue to overcome the limitations of traditional dosimeters. In this regard, a deep understanding of the physicochemical basis of gel dosimetry, as one of the most promising tools for the evaluation of 3D high-spatial-resolution dose distributions, represents the starting point for developing new and innovative systems. This review aims to contribute thorough descriptions of the chemical processes and interactions that condition gel dosimetry outputs, often phenomenologically addressed, and particularly formulations reported since 2017. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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Graphical abstract

54 pages, 26509 KiB

Open AccessFeature PaperReview

Radiation Dosimetry by Use of Radiosensitive Hydrogels and Polymers: Mechanisms, State-of-the-Art and Perspective from 3D to 4D

by Yves De Deene

Gels 2022, 8(9), 599; https://doi.org/10.3390/gels8090599 - 19 Sep 2022

Cited by 34 | Viewed by 4239

Abstract

Gel dosimetry was developed in the 1990s in response to a growing need for methods to validate the radiation dose distribution delivered to cancer patients receiving high-precision radiotherapy. Three different classes of gel dosimeters were developed and extensively studied. The first class of gel dosimeters is the Fricke gel dosimeters, which consist of a hydrogel with dissolved ferrous ions that oxidize upon exposure to ionizing radiation. The oxidation results in a change in the nuclear magnetic resonance (NMR) relaxation, which makes it possible to read out Fricke gel dosimeters by use of quantitative magnetic resonance imaging (MRI). The radiation-induced oxidation in Fricke gel dosimeters can also be visualized by adding an indicator such as xylenol orange. The second class of gel dosimeters is the radiochromic gel dosimeters, which also exhibit a color change upon irradiation but do not use a metal ion. These radiochromic gel dosimeters do not demonstrate a significant radiation-induced change in NMR properties. The third class is the polymer gel dosimeters, which contain vinyl monomers that polymerize upon irradiation. Polymer gel dosimeters are predominantly read out by quantitative MRI or X-ray CT. The accuracy of the dosimeters depends on both the physico-chemical properties of the gel dosimeters and on the readout technique. Many different gel formulations have been proposed and discussed in the scientific literature in the last three decades, and scanning methods have been optimized to achieve an acceptable accuracy for clinical dosimetry. More recently, with the introduction of the MR-Linac, which combines an MRI-scanner and a clinical linear accelerator in one, it was shown possible to acquire dose maps during radiation, but new challenges arise. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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14 pages, 2794 KiB

Open AccessReview

Recent Advances in Hydrogel-Based Sensors Responding to Ionizing Radiation

by Ping Zhang, Li Jiang, Hong Chen and Liang Hu

Gels 2022, 8(4), 238; https://doi.org/10.3390/gels8040238 - 12 Apr 2022

Cited by 23 | Viewed by 3114

Abstract

Ionizing radiation and its applications are widely spread throughout life. Similar to many other things, both the positive and negative aspects of ionizing radiation should always be kept in mind. For example, a proper radiation dose can be delivered to tumor tissue to kill malignant cells in radiotherapy. On the other hand, exceeding this dose can damage the normal tissues of a human organism. Therefore, the application of sensors for measuring ionizing radiation doses is of utmost importance in many fields, especially in cancer therapy. Traditional dosimeters, such as ionization chambers, silicon diodes and thermoluminescence dosimeters, are widely used. However, they have limitations in certain aspects. Hydrogel-based sensors (or dosimeters) for measuring ionizing radiation doses attract extensive attention for decades due to their equivalence to living tissue and biocompatibility. In this review, we catalog hydrogel-based dosimeters such as polymer, Fricke, radio-chromic, radio-fluorescence and NPs-embedded dosimeters. Most of them demonstrate desirable linear response and sensitivity regardless of energy and dose rate of ionizing radiation. We aim to review these dosimeters and their potential applications in radiotherapy as well as to stimulate a joint work of the experts from different fields such as materials science, chemistry, cancer therapy, radiobiology and nuclear science. Full article

(This article belongs to the Special Issue Gel Dosimetry)

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