Phy-X/ZeXTRa: a software for robust calculation of effective atomic numbers for photon, electron, proton, alpha particle, and carbon ion interactions

Radiation attenuation parameters and intrinsic efficiency of a few semiconductor crystals for radiation detection applications

This study investigates the effectiveness of nine inorganic semiconductor crystals - LiGaSe2, LiInSe2, CsHgInS3, SnS, GaTe, BiI3, Sb2Te3, Tl4CdI6, and TlBr - for radiation detection applications based on photon and charged particle (electrons, protons, and heavy ions) interaction parameters. Mass attenuation coefficient (μ/ρ), half value layer (HVL), relaxation length (λ), effective atomic number (Zeff), electron density (Neff), equivalent atomic number (Zeq), and exposure buildup factor (EBF) were computed using PAGEX software. These results, along with their intrinsic efficiencies calculated, were compared with that of standard materials (NaI(Tl), CdZnTe, and CdTe). The μ/ρ values of the studied semiconducting materials are ranked in the decreasing order as: TlBr, Tl4CdI6, BiI3, CsHgInS3, Sb2Te3, GaTe, SnS, LiInSe2, and LiGaSe2. TlBr, Tl4CdI6, BiI3, and Sb2Te3 show superior photon detection capabilities compared to the reference materials. TlBr and Tl4CdI6 have the highest intrinsic efficiency across nearly all energy regions, while LiGaSe2 has the lowest. Interaction parameters like range and Zeff for charged particles were also computed using standard databases, with SnS and Sb2Te3 showing the least range for all the charged particles studied throughout the entire energy region. The study indicates that TlBr and Tl4CdI6 have strong potential for developing next-generation radiation detectors with enhanced sensitivity, addressing needs in healthcare and national security.

TEMPy: a toolkit for the modeling of weighted tissue equivalent material in diagnostic imaging

Objective.Accurate simulation of human tissues is imperative for advancements in diagnostic imaging, particularly in the fields of dosimetry and image quality evaluation. Developing Tissue Equivalent Materials (TEMs) with radiological characteristics akin to those of human tissues is essential for ensuring the reliability and relevance of imaging studies. This study presents the development of a mathematical model and a new toolkit (TEMPy) for obtaining the best composition of materials that mimic the radiological characteristics of human tissues. The model and the toolkit are described, along with an example showcasing its application to obtain desired TEMs.Approach.The methodology consisted of fitting volume fractions of the components of TEM in order to determine its linear attenuation coefficient as close as possible to the linear attenuation coefficient of the reference material. The fitting procedure adopted a modified Least Square Method including a weight function. This function reflects the contribution of the x-ray spectra in the suitable energy range of interest. TEMPy can also be used to estimate the effective atomic number and electron density of the resulting TEM.Main results.TEMPy was used to obtain the chemical composition of materials equivalent to water and soft tissue, in the energy range used in x-ray imaging (10 -150 keV) and for breast tissue using the energy range (5-40 keV). The maximum relative difference between the linear attenuation coefficients of the developed and reference materials was ±5% in the considered energy ranges.Significance.TEMPy facilitates the formulation of TEMs with radiological properties closely mimicking those of real tissues, aiding in the preparation of physical anthropomorphic or geometric phantoms for various applications. The toolkit is freely available to interested readers.

Performance of Iron Phosphate Glass Containing Various Heavy Metal Oxides for Particulate Nuclear Radiation Shielding

BACKGROUND

Employees may be exposed to different kinds of ionizing radiation at work. When ionizing radiation interacts with human cells, it can cause damage to the cells and genetic material. Therefore, one of the scientists' primary objectives has always been to create the best radiation-shielding materials. Glass could offer promising shielding material resulting from the high flexibility of composition, simplicity of production, and good thermal stability.

MATERIALS AND METHODS

The melt-quenching technique was used to create a glass having the following formula: 50% P2O5+20% Na2O+20% Fe2O3+10% X, where X = As2O3, SrO, BaO, CdO, and Sb2O3 mol %. The impact of the different heavy metal additions on the structure of the glass networks was studied using FTIR spectroscopy. Glass's ability to attenuate neutrons and/or charged particles has been theoretically investigated. The performance of the developed glass as a shield was examined by a comparison against commercial glass (RS 253 G18), ordinary concrete (OC), and water (H2O).

RESULTS

For charged particle radiations (Electrons, Protons, and Alpha), the shielding parameters like the mass stopping power, the projected range, and the effective atomic number were evaluated, where S5/Sb glass achieves the best performance. In the case of Neutrons, the results values reveal that S3/Ba glass ( ΣR = 0.105) is the best-modified glass for neutron shielding.

CONCLUSION

Among all the investigated glasses, S5/Sb glass composition has a smaller range and provides superior protection against charged particles. In contrast, the S3/Ba glass composition is a superior choice for shielding against neutron radiation.

Investigation of the nuclear radiation interaction parameters of selected polymers for radiation therapy and dosimetry

The mass attenuation coefficient (MAC), effective atomic number (Z_eff), equivalent atomic number (Z_eq), fast neutron removal cross-section (FNRCS), energy absorption buildup factor (EABF), mass-energy absorption coefficient (MenAC), relative kerma, and computed tomography (CT) numbers were calculated for the alginates, bisphenol A-glycidyl methacrylate (Bis-GMA), chitin, hyaluronic acid, polycaprolactone (PCL), polyether ether ketone (PEEK), polyethylene glycol (PEG), polyglycolide (PGA), polylactic acid (PLA), poly lacto-co-glycolic acid (PLGA), poly methyl methacrylate (PMMA), poly vinyl alcohol (PVA), polyvinylpyrrolidone (PVP), triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) polymers using the Phy-X/PSD and Py-MLBUF software. The total stopping power (TSP) of electrons, protons, and alpha particles was calculated for the selected polymers using the ESTAR, PSTAR, and ASTAR programs. The effective atomic number for absorption and charged particle (electron, proton, alpha, and carbon ion) interactions were estimated for the selected polymers using Phy-X/ZeXTRa software. The FNRCS values of Bis-GMA, PCL, PEG, PMMA, and PVP were similar to those of the human tissues. For the selected polymers, the Z_eff values for electron, proton, alpha, and carbon ion interactions of PCL, PEG, PLGA, and PVA were similar to those of human tissues, except for the cortical bone, across the entire energy range. These results are expected to assist in selecting suitable polymers as tissue-equivalent materials in the desired energy range for photon, neutron, and charged-particle interactions. This study is expected to be useful for radiation therapy and dosimetry.

Insights into the Effect of Aggregate Sizes on the Soil Radiation Interaction Properties Based on X-ray Fluorescence

Soils subjected to disaggregation can break into aggregates of different sizes composed of sand, clay, and silt particles. Each aggregate contains different oxides, which can vary according to the aggregate size and influence its properties, such as the radiation interaction parameters. These parameters are relevant in the evaluation of radiation shielding and soil physical properties. Thirteen tropical/subtropical soils of contrasting textures (clayey and loamy/sandy) with two aggregate sizes (2-1 mm and <45 μm) were studied. The radiation parameters analyzed were the atomic (σ_A), electronic (σ_E), and molecular (σ_M) cross-sections; the effective atomic number (Z_eff); and the electron density (N_el). We verified that the aggregate sizes affected the major oxides (SiO₂, Al₂O₃, Fe₂O₃). In general, the attenuation coefficient and Z_eff were sensitive to the clayey soils' aggregate sizes (low photon energies). However, the loamy/sandy soils did not exhibit differences among the parameters. As the photon energy increased, only Z_eff presented differences for most soils. We also verified that σ_M, Z_eff, and N_el were the most sensitive parameters to the soil composition. Although the soil chemical composition was influenced by the studied aggregate sizes, the radiation parameters exhibited differences for only some of these parameters. This means that the aggregate size is practically irrelevant when radiation parameters are determined based on X-ray fluorescence.

Effective atomic number and photon buildup factor of bismuth doped tissue for photon and particles beam interaction

Introduction: The doping of high Z nanoparticles into the tumor tissue increases the therapeutic efficiency of radiotherapy called nanoparticle enhanced radiotherapy (NERT). In the present study, we are identifying the effective types of radiation and effective doping concentration of bismuth radiosensitizer for NERT application by analyzing effective atomic number (Zeff) and photon buildup factor (PBF) of bismuth (Bi) doped soft tissue for the photon, electron, proton, alpha particle, and carbon ion interactions.

Material and methods: The direct method was used for the calculation of Zeff for photon and electron beams (10 keV-30 MeV). The phy-X/ZeXTRa software was utilized for the particle beams such as proton, alpha particle, and carbon ions (1-15 MeV). Bismuth doping concentrations of 5, 10, 15, 20, 25 and 30 mg/g were considered. The PBF was calculated over 15 keV-15 MeV energies using phy-X/PSD software.

Results: The low energy photon (<100 keV) interaction with a higher concentration of Bi dopped tissue gives the higher values of Zeff. The Zeff increased with the doping concentration of bismuth for all types of radiation. The Zeff was dependent on the type of radiation, the energy of radiation, and the concentration of Bi doping. The particle beams such as electron, proton, alpha particle, and carbon ion interaction gives the less values of Zeff has compared to photon beam interaction. On the other hand, the photon buildup factor values were decreased while increasing the Bi doping concentration.

Conclusions: According to Zeff and PBF, the low energy photon and higher concentration of radiosensitizer are the most effective for nanoparticle enhanced radiotherapy application. Based on the calculated values of Zeff, the particle beams such as electron, proton, alpha particle, and carbon ions were less effective for NERT application. The presented values of Zeff and PBF are useful for the radiation dosimetry in NERT.

A Monte Carlo investigation of some important radiation parameters and tissue equivalency for photons below 1 keV in human tissues

The attenuation coefficients are important input values in estimating not only the dose and exposure in radiotherapy and medical imaging, but also in the proper design of photon shields. While studies are widely available above 1 keV, the attenuation coefficients of human tissues for photon energies less than 1 keV have not been studied yet. In this study, the attenuation coefficients of water and some human tissues were estimated for low energy photons using the MCNP6.1 code in the energy region 0.1 keV-1 keV. Mass attenuation coefficients were estimated at photon energies of 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 and 1000 eV for water and ten human tissues (Soft, Breast, Lung, Bone, Brain, Eye lens, Ovary, Skin, Thyroid and Prostate). Results were compared with those available in literature and a fairly good agreement has been obtained. These data were then used to calculate the mean free path, half value layer, tenth value layer, effective atomic number and specific gamma-ray constant (useful for calculation of dose rate) as well. Moreover, for comparison the effective atomic number of the water has been obtained using the results of this work and using the data available in NIST database from 0.1 to 1 keV. In addition, the human tissues were compared with some tissue equivalent materials in terms of effective atomic number and specific gamma-ray constant to study the tissue equivalency from the results, the muscle-equivalent liquid with sucrose has been found to be the best tissue equivalent material for soft tissue, eye lens and brain with relative difference below 4.1%.

A simple software for swift computation of photon and charged particle interaction parameters: PAGEX

PAGEX is a compact and user-friendly cross-platform software developed for swift computation of photon (X-ray and γ-ray) and charged particle interaction parameters for various applications. It is designed based on well-established theoretical formulations and computational techniques integrating various Python packages to effectively calculate parameters such as partial/total photon interaction cross-sections and mass attenuation coefficients, charged particle mass stopping powers and cross-sections, effective atomic number and electron density, mass-energy absorption coefficient, KERMA and build-up factors over a wide energy range. This tool is capable of generating both tabular and graphical outputs which can be saved in any user desired format. PAGEX has been verified against other widely employed software and databases, demonstrating good agreement. This software which facilitates robust computation is freely available from the authors.

Nuclear Radiation Shielding Characteristics of Some Natural Rocks by Using EPICS2017 Library

Radiation leakage is a serious problem in various technological applications. In this paper, radiation shielding characteristics of some natural rocks are elucidated. Mass attenuation coefficients (µ/ρ) of these rocks are obtained at different photon energies with the help of the EPICS2017 library. The obtained µ/ρ values are confirmed via the theoretical XCOM program by determining the correlation factor and relative deviation between both of these methods. Then, effective atomic number (Zeff), absorption length (MFP), and half value layer (HVL) are evaluated by applying the µ/ρ values. The maximum μ/ρ values of the natural rocks were observed at 0.37 MeV. At this energy, the Zeff values of the natural rocks were 16.23, 16.97, 17.28, 10.43, and 16.65 for olivine basalt, jet black granite, limestone, sandstone, and dolerite, respectively. It is noted that the radiation shielding features of the selected natural rocks are higher than that of conventional concrete and comparable with those of commercial glasses. Therefore, the present rocks can be used in various radiation shielding applications, and they have many advantages for being clean and low-cost products. In addition, we found that the EPICS2017 library is useful in determining the radiation shielding parameters for the rocks and may be used for further calculations for other rocks and construction building materials.

Accuracy and reproducibility of effective atomic number and electron density measurements from sequential dual energy CT

PURPOSE

This study assesses the accuracy of effective atomic number (Z_eff ) and electron density measurements acquired from dual energy CT and characterizes the response to clinically relevant variables representative of challenges in patient imaging, including: phantom size, material position within the phantom, variation over time, off-center positioning, and large cone beam angle.

METHODS

The Gammex Multi-Energy CT head and body phantoms were used to measure Z_eff and electron density from 35 rod inserts that mimic tissues and varying concentrations of iodine and calcium. Scans were performed on a Canon Aquilion ONE Genesis CT scanner over a period of 6 months using default dual energy protocols appropriate for each phantom size. Theoretical Z_eff and electron density values were calculated using data provided by the phantom manufacturer and compared to the measurements. Sources of variance were separated and quantified to identify the influences of random photon statistics, ROI placement, and variation over time. A subset of measurements were repeated with the phantom shifted in the vertical and horizontal directions, and over all slices in the volumetric scan.

RESULTS

All measurements showed strong correlation (r > 0.98) with their corresponding theoretical values; however, the system did demonstrate a bias of -0.58 atomic units in the body phantom and 0.28 atomic units in the head phantom for Z_eff measurements. The mean absolute percent error (MAPE) was 6.3% for the body phantom and 3.2% for the head phantom. Electron density measurements of the body and head phantoms gave MAPE values of 4.6% and 1.0%, respectively. Z_eff and electron density measurements significantly varied within the solid water background, showing a positional dependence within the phantom that dominated the total standard deviation in measurements. Z_eff values dropped by 0.2 atomic units when the phantom was off-center; electron density measurements were less affected by phantom position. Along the z-axis, the accuracy drops off markedly at more than 50-60 mm from the central slice.

CONCLUSION

The Canon dual energy system offers an accurate way of measuring the Z_eff and electron density of clinically relevant materials. Accuracy could be improved further by calibration to remove bias, careful attention to centering within the FOV, and avoiding measurements at the edges of the cone beam.

Structural, Mechanical, and Dielectric Properties of Polydimethylsiloxane and Silicone Elastomer for the Fabrication of Clinical-Grade Kidney Phantom

This study aimed to introduce an alternative, inexpensive, and straightforward polymer with specific mechanical and dielectric properties suitable for the fabrication of a clinical-grade kidney phantom. Two polymer-based phantom materials, polydimethylsiloxane (PDMS) and silicone elastomer (SE), were investigated for their capability to meet the requirements. The concentration ratios of base to curing agent (B/C) were 9.5/1.5, 19/3, 10/1, 20/2, 10.5/0.5, and 21/1 for PDMS and 4.5/5.5, 10/12, 5/5, 11/11, 5.5/4.5, and 12/10 for SE. All samples were mixed, degassed, and poured into Petri dishes and small beakers. The polymer was cured under room temperature for 2 h and then demolded from the hard mold. The air bubbles produced were removed using a vacuum desiccator for 30 min. All samples underwent mechanical testing (tensile strength and elastic modulus), and their dielectric properties were measured using a dielectric probe kit equipped with 85071E materials measurement software. The radiation attenuation properties were also measured using PhyX-Zetra for PDMS phantoms with the chemical formula C2H6OSi. Small changes in base and cross-linker play an essential role in modifying the elastic modulus and tensile strength. The effective atomic number of PDMS showed a similar pattern with human kidney tissue at the intermediate energy level of 1.50 × 10−1 to 1 MeV. Therefore, PDMS can potentially be used to mimic the human kidney in terms of tensile strength, flexibility, the acceptable real part of the complex dielectric constant ε′r, and conductivity, which allows it to be used as a stable kidney phantom for medical imaging purposes.