X-Ray and γ-Ray Shielding Efficiency of Polymer Composites: Choice of Fillers, Effect of Loading and Filler Size, Photon Energy and Multifunctionality

Prabhu, Srilakshmi; Bubbly, S. G.; Gudennavar, S. B.

doi:10.1080/15583724.2022.2067867

Cited by 55 publications

(21 citation statements)

References 232 publications

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“…More work has been conducted for loading higher-Z elements, such as Bi, into flexible polymers for radiation protection applications. 24 Nonetheless, the prior literature suggests that integrating Gd into reflectors could be technically feasible.Another potential approach could be to replace plastic reflectors with a metal alloy that contains Gd. Sawant et al demonstrated tungsten reflectors in megavoltage detectors, and showed that they could outperform other materials by functioning as a buildup layer to improve signal detection in adjacent scintillator pixels.…”

Section: Discussionmentioning

confidence: 99%

Possible improvements in effective fill factor using X‐ray fluorescent interpixel reflectors

Hsieh

2024

Medical Physics

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BackgroundThe spatial resolution of energy‐integrating diagnostic CT scanners is limited by interpixel reflectors on the detector, which optically isolate pixels but create dead space. Because the width of the reflector cannot easily be decreased, fill factor diminishes as resolution increases.PurposeWe propose loading (or mixing) a high‐Z element into the reflectors, causing the reflectors to be X‐ray fluorescent. Re‐emitted characteristic X‐rays could be detected in adjacent pixels, increasing the effective fill factor and compensating for fill factor loss with higher‐resolution detectors. The purpose of this work is to understand the physical principles of this approach and to analyze its effectiveness using Monte Carlo simulations.MethodsDetector pixels were modeled using the GEANT4 Monte Carlo package. The width of the reflector was kept constant at 0.1 mm throughout, and we considered pixel pitches between 0.5 and 1 mm. The pixelated scintillator material was gadolinium oxysulfide, 3 mm thick. The baseline reflector material was chosen to be acrylic, and varying concentrations of a high‐Z element were loaded into the material. We assumed that the optical characteristics of pixels were ideal (no absorption within pixels, perfect reflection at boundaries). The detector was irradiated uniformly with 10,000 X‐ray photons to estimate its spectral response. The figure of merit was the variance of the detector signal at zero frequency normalized to that of an ideal single‐bin photon‐counting detector with 100% fill factor. Sensitivity analyses were conducted to understand the effect of varying the high‐Z element concentration and the spectrum.ResultsInitial simulations suggested that a k‐edge near 50 keV would be ideal. Gd was therefore selected as the high‐Z material. The relative variances for a conventional energy integrating detector without Gd at 1 mm pixel pitch (81% fill factor) and 0.5 mm pixel pitch (64% fill factor) were 1.38 and 1.74, compared to 1.00 for an ideal photon counting detector, implying a 26% variance penalty for 0.5 mm pitch. When 1 g/cm3 Gd was loaded into the interpixel reflector, the relative variance improved to 1.27 and 1.43, respectively, implying that the variance penalty for including Gd together with 0.5 mm pitch is only 4%. Performance was nearly maximized at 1.0 g/cm3 of Gd, but a concentration of 0.5 g/cm3 of Gd showed most of the benefit. Improvements depend weakly on kV, with lower kV associated with higher improvements. An external anti‐scatter grid was not modeled in our simulations and would reduce the expected benefit, depending greatly on the pitch and dimensionality of the anti‐scatter grid.ConclusionsThe losses in fill factor associated with smaller pixel pitch can be reduced if Gd or a similar element could be loaded into the interpixel reflector. These improvements in noise efficiency are yet to be verified experimentally.

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Section: Discussionmentioning

confidence: 99%

Possible improvements in effective fill factor using X‐ray fluorescent interpixel reflectors

Hsieh

2024

Medical Physics

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“… That is, neutron shielding materials require substances with large neutron absorption cross sections such as boron and heavy metals to attenuate secondary γ-rays . Therefore, developing wearable articles bearing heavy metals and boron-containing substances is of vital importance to the radiation protection safety of human being in complex radiations. , …”

Section: Introductionmentioning

confidence: 99%

Large-Scale Fabrication of Highly Filled Polymer Fibers for Radiation Protection Safety and Wear Comfort of Multilayer Fabrics in Complex Radiations

Meng,

Zhang,

Mai

et al. 2024

ACS Appl. Polym. Mater.

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Developing wearable articles with radiation protection safety and wear comfort in complex radiations is one of the urgent issues because flourishing nuclear technologies lead to increasing radiation threats. However, current wearable articles either shield neutrons or γ-rays or display poor permeability of air and water vapor and so on, which leads to difficulty in satisfying the requirements of complex radiations. Herein, surface modification techniques are applied to construct sufficient hydrogen bonds between functional particles (B 4 C and PbWO 4 ) and PVA matrixes for intensifying the interface interaction, which facilitate the smooth wet spinning of as high as 50 wt % B 4 C/ PVA and 70 wt % PbWO 4 /PVA fibers under an exclusive pilot line for large-scale preparation. Then, both of the highly filled PVA fibers are woven into two kinds of fabrics that are overlapped for multilayer fabrics. They jointly shield neutrons and γ-rays while giving good permeability of air and water vapor. The overlapping two-layer B 4 C/PVA and two-layer PbWO 4 /PVA fabrics are provided with 72.90% thermal neutron adsorption (0.025 eV) and 38.62% γ-ray attenuation (105 keV). In addition, they also display 155.88 mm/s and 2536.37 g/m 2 •24 h air and water vapor permeabilities, respectively. Besides, good flexibility of the fabrics is not sacrificed in spite of the extremely high loading of functional particles in PVA fibers. This work provides a feasible approach to deal with the challenge of radiation protection safety and wear comfort of wearable articles in complex radiations.

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“…Regarding rigid protective materials, the x‐ray shielding effectiveness is influenced by factors such as the chemical nature, loading amount, size, and shape of the filler 16 . Barium, tungsten, and bismuth compounds have been extensively studied as functional fillers in rigid systems.…”

Section: Introductionmentioning

confidence: 99%

“…Regarding rigid protective materials, the x-ray shielding effectiveness is influenced by factors such as the chemical nature, loading amount, size, and shape of the filler. 16 Barium, tungsten, and bismuth compounds have been extensively studied as functional fillers in rigid systems. For all the investigated materials, the maximum filler loading was always limited due to difficulties in processing composites at very high filler content.…”

Section: Introductionmentioning

confidence: 99%

High filler content acrylonitrile‐butadiene‐styrene composites containing tungsten and bismuth oxides for effective lead‐free x‐ray radiation shielding

Olivieri,

Avolio,

Gentile

et al. 2023

Polymer Composites

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Acrylonitrile‐butadiene‐styrene (ABS) based composites with a high content of tungsten and bismuth oxide were developed using an innovative process to obtain lead‐free x‐ray shielding materials. ABS was chosen for its good mechanical properties and its widespread availability as a recycled material. The composites underwent flexural tests, Shore D hardness tests, thermogravimetric and morphological analysis, and their x‐ray attenuation properties were determined through numerical simulations and experimental measurements. Despite their high filler content (up to 75 wt%), the composites showed good filler dispersion within the polymeric matrix and maintained their mechanical properties. Across the investigated energy range (50–150 kV), the lead equivalence for x‐ray shielding was achieved with composite plates containing 75 wt% of tungsten and bismuth oxide, at thickness values corresponding to a weight increase of only 29% and 36%, respectively, in comparison to lead. These findings pave the way for a new generation of lead‐free x‐ray shielding materials. Moreover, their mechanical properties, including flexibility for potential application in wearable personal protective equipment, can be tailored by adjusting the filler content.Highlights High filler content lead‐free ABS composites with WO3 and Bi2O3 were developed. They show good polymer/filler interfacial adhesion and flexural properties. Numerical simulations of their x‐ray shielding properties were performed. Experimental tests with polychromatic sources confirmed good x‐ray attenuation. Results pave the way for the development of new lead‐free x‐ray shielding systems.

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X-Ray and γ-Ray Shielding Efficiency of Polymer Composites: Choice of Fillers, Effect of Loading and Filler Size, Photon Energy and Multifunctionality

Cited by 55 publications

References 232 publications

Possible improvements in effective fill factor using X‐ray fluorescent interpixel reflectors

Possible improvements in effective fill factor using X‐ray fluorescent interpixel reflectors

Large-Scale Fabrication of Highly Filled Polymer Fibers for Radiation Protection Safety and Wear Comfort of Multilayer Fabrics in Complex Radiations

High filler content acrylonitrile‐butadiene‐styrene composites containing tungsten and bismuth oxides for effective lead‐free x‐ray radiation shielding

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