Examination of fundamental characteristics of a polymer gel detector in a proton beam irradiation

Yoshioka, Munenori; Tominaga, Takahiro; Usui, Shuji; Hayashi, Shin-ichiro; Haneda, Kiyofumi; Tsunei, Y.; Katahira, K; Suga, Daisaku; Hishikawa, Yoshio; Teshima, T.

doi:10.1016/j.radmeas.2010.08.007

Cited by 13 publications

(2 citation statements)

References 12 publications

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“…A 3D chemical dosimeter using a gel matrix has been proposed by Gore, in which the amount of radiation-induced chemical reaction products stored in the gel matrix provides information on the spatial dose distribution. The 3D dose distribution can be extracted from measurements of irradiated gel samples using a 3D imaging technique such as magnetic resonance imaging (MRI). , On the other hand, the practical application of a gel dosimeter to heavy ion beam dosimetry is complicated by the degradation in sensitivity as a function of linear energy transfer (LET). − This LET dependence of the radiation sensitivity is well-known as LET effects that are caused by radical–radical recombinations of radical products (i.e., OH, e aq – , and H) that contribute to radiation-induced chemical reactions . A Fricke gel dosimeter prepared using an aqueous Fricke solution and a gel matrix such as gelatin or agarose also shows LET dependence .…”

Section: Introductionmentioning

confidence: 99%

Organic-Gelatin-Free Nanocomposite Fricke Gel Dosimeter

et al. 2017

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We report a nanocomposite Fricke gel (NC-FG) dosimeter prepared using only Fe and nanoclay in water, without any organic gelling agents. This dosimeter gels due to its thixotropic properties and exhibits linear energy transfer (LET)-independent radiological properties under carbon ion beam irradiation. The radiation sensitivity of this dosimeter was 1.8 [s kGy], which is three times higher than that reported previously (0.6 [s kGy]) for a similar dosimeter containing gelatin. The Fe yield was determined to be 0.19 μmol/J by evaluating the difference in spin-lattice relaxivity between Fe and Fe. A further increase in the radiation sensitivity was observed upon addition of the hydrated electron scavenger NO, suggesting the reduction of Fe by a hydrated electron. LET-dependent variations of the contributions of OH radicals and hydrated electrons compensate each other in the oxidation yield of NC-FG. This is the main mechanism of the suppression of LET effects in the Bragg peak compared to conventional Fricke dosimeters. The radiation-induced oxidation yield G(Fe) can be described by the stoichiometric equation {G(Fe) = G(OH) - G(e) + 2G(HO) + G(H)} with the reported LET dependence of the primary yield of water decomposition radicals. The calculated results are in approximate agreement with the absolute value of the experimental oxidation yield of NC-FG. The effects of the addition of small amounts of radical scavengers (nitrate, selenate, or cadmium) are also evaluated. The sensitivity was divided into two types, and influences of intermediate radicals after scavenging reaction are indicated.

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Section: Introductionmentioning

confidence: 99%

Organic-Gelatin-Free Nanocomposite Fricke Gel Dosimeter

et al. 2017

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“…It should be noted that the LET dependence of radiation sensitivity is common to virtually all types of 3D dosimeters and is also not unique to gel dosimeters, e.g. film, scintillation and semiconductor dosimeters are LET-dependent as well [ 21 – 30 ].…”

Section: Introductionmentioning

confidence: 99%

Radiological properties of nanocomposite Fricke gel dosimeters for heavy ion beams

Maeyama¹,

Fukunishi²,

Ishikawa³

et al. 2016

Journal of Radiation Research

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The radiological properties of nanocomposite Fricke gel (NC-FG) dosimeters prepared with different concentrations of nano-clay, perchloric acid and ferrous ions in deaerated conditions were investigated under carbon and argon ion beam irradiation covering a linear-energy-transfer (LET) range of 10 to 3000 eV/nm. We found that NC-FG exhibits radiological properties distinct from those of conventional Fricke gel. The radiation sensitivity of NC-FG is independent of the LET and is nearly constant even at very high LET (3000 eV/nm) values in the Bragg peak region of the argon ion beam. In addition, whereas conventional Fricke gel dosimeters only operate under acidic conditions, NC-FG dosimeters function under both acidic and neutral conditions. The radiation sensitivity decreases with decreasing nano-clay concentration in NC-FG, which indicates that the nano-clay plays a vital role in the radiation-induced oxidation of Fe2+.

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Three‐dimensional radiation dosimetry of carbon ion beams using surfactant hydrogels: Fundamental investigation

Toyohara,

Kusano,

Kobayashi

et al. 2024

Medical Physics

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BackgroundIn carbon ion radiotherapy, accurate measurement of the three‐dimensional (3D) absorbed dose distribution is critical for effectively targeting tumors. Although micellar gel dosimeters exhibit considerable potential for measuring 3D absorbed dose distributions, few studies have focused on radiotherapy using carbon ion beams.PurposeThis study investigated the applicability of the surfactant hydrogel dosimeter (SHD), a micellar gel dosimeter, to measuring a 3D dose absorbed through carbon ion beam irradiation.MethodsA cubic target region of 34 mm per side was established at a depth of 46 mm below the upper surface of an SHD specimen. Scanning irradiation was performed using a pencil beam of carbon ions at the Ion‐beam Radiation Oncology Center in Kanagawa (“i‐ROCK”), Japan, under irradiation conditions set by the treatment planning system (“Monaco for Carbon”, Ver. 5.20, Elekta AB, Sweden) to create a spread‐out Bragg peak within the target. The physical dose was set to 10 Gy at the isocenter, situated at the center of the target. The SHD responsiveness was measured twice using optical computed tomography (CT) (“Vista 15”, Modus Medical Devices, Canada) for three irradiated specimens, and six types of measured optical attenuation coefficient (OAC) were obtained. To assess whether the OAC represented the absorbed dose expected in the treatment plan, we compared the relative distribution of the OAC and that of the absorbed dose. Relative fraction (RF) was used to measure the difference between the relative value of the OAC and that of the absorbed dose. Moreover, the distribution of OH radical (•OH) concentration obtained by Monte Carlo simulation (“PHITS” ver. 3.24 JAEA, Japan) and that of the OAC were compared.ResultsIn the direction of beam travel, the relative distribution of the OAC was lower than that of the absorbed dose. This discrepancy could be attributed to a decrease in the concentration of •OH produced by irradiation owing to the recombination reaction, which does not accurately reflect the absorbed dose. By contrast, the distributions in the plane perpendicular to the beam travel were consistent. The RF increased from ± 3% to ± 13% along the beam travel direction. The small RF in the plane perpendicular to the beam travel could be attributed to the constant distribution of linear energy transfer, regardless of the irradiation position, and the generation of radicals proportionally to the absorbed dose. The increase in RF along the beam travel direction was ascribed to ring artifacts in the irradiated region.ConclusionThe measurement of the absorbed dose distribution in the beam travel direction should be improved. The observed discrepancy is attributed to the reduced reactivity of the SHD due to a high liner energy transfer near the Bragg peak. However, the absorbed dose distribution can be effectively evaluated in the plane perpendicular to the direction of beam travel.

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Examination of fundamental characteristics of a polymer gel detector in a proton beam irradiation

Cited by 13 publications

References 12 publications

Organic-Gelatin-Free Nanocomposite Fricke Gel Dosimeter

Organic-Gelatin-Free Nanocomposite Fricke Gel Dosimeter

Radiological properties of nanocomposite Fricke gel dosimeters for heavy ion beams

Three‐dimensional radiation dosimetry of carbon ion beams using surfactant hydrogels: Fundamental investigation

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