Application of the medical linear accelerator ELEKTA AXESSE in the study of sorption properties of impurities and absorption coefficients of medium and heavy chemical elements

In this article, the authors propose a new technique for measuring linear attenuation coefficients on the medical linear accelerator Elekta Axesse. Linear attenuation coefficients were obtained for four samples at different concentrations of substances at a gamma-ray energy of 6 MeV. A unified ionization chamber was used as a detector to register the transmitted gamma-ray beam through the samples under study. Linear absorption coefficients were obtained for elements B, C, O, S, Fe, Ba taking into account their concentration, as well as taking into account the different mass inclusion of paraffin in the samples under study, which is acyclic hydrocarbons CnH2n+2. The measurement results showed that taking into account certain components in impurities leads to relatively small, but quite noticeable differences in the determination of the total absorption coefficients. This is especially important to take into account for determining the concentration of light elements in samples. To determine the content of medium and heavy chemical elements, taking into account the content of light elements can be neglected. The use of a 6 MeV gamma-ray beam made it possible to reduce the errors in determining the absorption coefficients, since their dependence on energy in the region of applicable gamma-ray energies is not so great in comparison with the low-energy region, in which the shell effects for heavy elements will introduce significant contribution.

Structural, Optical, Magnetic and Photon Attenuation of Novel Potassium Lead Borate Glasses Doped with MnO

Potassium lead borate glasses doped with MnO (40B2O3+40PbO+(20-x)K2O+xMnO: x= 0-5 mol%) have been prepared via standard melting quenching process. The impact of MnO on the structure, optical, magnetic and gamma-ray protection properties of pottisium lead borate glasses have been examined. The density was increased from 4.83±0.01 to 5.23±0.01 g/cm3 as MnO content increased. The obtained direct optical gap (Eg) values were 2.84, 2.59, 2.41, 2.19, 1.95, and 1.84 eV for the Mn-x (x=0, 1, 2, 3, 4, and 5) glass samples, respectively. FTIR spectra demonstrated that as the MnO concentration increases in the glass network the intensity and width of the IR bands were increased. The magnetic measurement revealed that the magnetic situation (Ms) was decreased while the magnetic coercivity (Hc) was increased with increasing MnO substitution ratio. The linear attenuation coefficient of the follows the order: µMn-0 < µMn-1 < µMn-2 < µMn-3 < µMn-4 < µMn-5. Half value layer (HVL) rises as µ decreases and vice versa. The range of the HVL is 0.002 – 3.378, 0.002 – 3.334, 0.002 – 3.291, 0.002 – 3.248, 0.002 – 3.176, and 0.002 – 3.106 cm for Mn-x (x=0, 1, 2, 3, 4, and5). The trend of Zeff variation is related to that of both linear and mass attenuation coefficients (µ and µm). The produced Mn-glasses can be employed in a variety of optical, magnetic and radiation protective applications.

Gamma-Ray Attenuation Characteristics of Some Essential Amino Acids for 57Co, 192Ir, 18F, and 116mIn Sources

Purpose: In different tissues of the body, proteins are important parts that are made up of building blocks called amino acids. Considering the wide applications of radioactive sources in industry and medicine, the need to study the attenuation characteristics of amino acids is determined. Materials and Methods: To study the attenuation characteristics of five types of amino acids, MCNPX Monte Carlo code and XMuDat program were used. Linear and mass attenuation coefficients, half and tenth value layers, mean free path, effective atomic and electronic cross-sections, effective atomic numbers and effective electron densities were calculated. 57Co, 192Ir, 18F, and 116mIn gamma sources were considered for this study. To validate the theoretical results, the obtained values were compared with the available experimental data. Results: The difference between the theoretical and experimental results was less than 11%. The results showed that with increasing photon energy, the linear and mass attenuation coefficients and effective atomic and electronic cross-sections decreased, while the half and tenth value layers and mean free path quantities increased. Furthermore, the linear attenuation coefficients, the effective atomic and electronic cross-sections, as well as the effective atomic number values increased with increasing amino acid density, while the effective electron density behaves independently of the amino acid density. Conclusion: The presented theoretical methods produced data similar to experimental results with fair accuracy, so by using these methods, attenuation properties of other amino acids can be obtained over a wide range of energies.

TEMPERATURE DEPENDENCE OF OPTICAL TRANSMISSION OF GERMANIUM SINGLE CRYSTALS

Проведены исследования оптического пропускания в диапазоне длин волн 2 - 14 мкм монокристаллов германия, легированных донорными и акцепторными примесями (удельное сопротивление германия 1 - 3 Ом⋅см), в интервале температур от 86 К до 523 К. Рассчитаны значения коэффициентов ослабления α для исследуемых кристаллов; минимальные значения коэффициентов ослабления (0,0015 - 0,0231 см) в интервале температур от 86 К до 323 К характерны для монокристаллов германия, легированных сурьмой, в диапазоне 2 - 11 мкм. Исследования показали, что низкие значения α и коэффициента пропускания на длине волны 3,39 мкм для кристаллов Ge: Sb и Ge: Bi позволяют применять эти низкоомные кристаллы германия для газовых гелий-неоновых лазеров при температурах от 86 К до 323 К. Исследованы температурные изменения геометрии поверхности кристалла на наноразмерном уровне. Показано, что нагрев кристаллического германия приводит к увеличению диффузного отражения излучения от поверхности. Сделан вывод о возможности использования низкоомных кристаллов германия, легированных сурьмой, в качестве элементов инфракрасной оптики в интервале температур 86 - 373 К. In this work, we investigated optical transmission in the wavelength range of 2-14 μm of low-resistance germanium crystals (1 - 3 Ω⋅cm) doped with donor and acceptor impurities in the temperature range from 86 K to 523 K. The values of the attenuation coefficients for investigated crystals are obtained. Minimum attenuation coefficients α of 0,0015 - 00231 cm in the temperature range from 86 K to 323 K are characteristic for germanium single crystals doped with antimony in the range 2,1-11 μm. Studies have shown that the low values of α and the transmittance at a wavelength of 3,39 pm for Ge: Bi and Ge: Sb crystals make it possible to use these low-resistance germanium crystals for gas helium-neon lasers at temperatures from 86 K to 323 K. The temperature changes in the geometry of the crystal surface are investigated at the nanoscale level. It is shown that heating crystalline germanium leads to an increase in the diffuse reflection of radiation from the surface. The possibility of using the low-resistance germanium crystals doped with antimony as elements of infrared optics in the temperature range 86 - 373 K has been demonstrated.

Material-separating regularizer for multi-energy X-ray tomography

Dual-energy X-ray tomography is considered in a context where the target under imaging consists of two distinct materials. The materials are assumed to be possibly intertwined in space, but at any given location there is only one material present. Further, two X-ray energies are chosen so that there is a clear difference in the spectral dependence of the attenuation coefficients of the two materials. A novel regularizer is presented for the inverse problem of reconstructing separate tomographic images for the two materials. A combination of two things, (a) non-negativity constraint, and (b) penalty term containing the inner product between the two material images, promotes the presence of at most one material in a given pixel. A preconditioned interior point method is derived for the minimization of the regularization functional. Numerical tests with digital phantoms suggest that the new algorithm outperforms the baseline method, Joint Total Variation regularization, in terms of correctly material-characterized pixels. While the method is tested only in a two-dimensional setting with two materials and two energies, the approach readily generalizes to three dimensions and more materials. The number of materials just needs to match the number of energies used in imaging.

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%.

Calculate Effective Atomic Number, Mass and Cross-Section Attenuation Coefficients for Nonanoic Acid by Using Gamma-Ray Sources

The effective atomic number (Z effective), total atomic cross-section (б Total) electron density (N effective) have been Measured depending on the mass attenuation coefficient (μ/ρ). By using Gamma-ray radiation (γ), emitted from sources (57𝐶𝑜, 133𝐵𝑎, 22𝑁𝑎, 137𝐶𝑠, 54𝑀𝑛, 𝑎𝑛𝑑 60𝐶𝑜) with energies from (0.122, 0.356, 0.511, 0.662, 0.84, 1.17, 1.275 𝑎𝑛𝑑 1.33𝑀𝑒𝑉) respectively. using the Sodium Iodide Scintillation Detectors NaI (Tl) at 662 keV and resolution about 8.2% have been measured the mass attenuation coefficients for the sample “Nonanoic acid its common name Pelargonic acid” it’s chemical formula C9H18O2. The data from the mass attenuation coefficient were then employed to study Zeffective, Neffective, and бtotal of the sample. In the presence of gamma-ray energy, it was discovered that the effective atomic number and effective electron densities first drop and they tend to remain nearly constant. The experimental values obtained by Zeffective and Neffective were in excellent agreement with the theoretical values. The theoretical data that is accessible is obtained from XCom, which is available online. The study's findings aid in understanding how (μ/ρ) values change when Zeff and Neff values vary in the case of H, C, and O based biological molecules such as fatty acids.

Low- and High-Attenuation Lung Volume in Quantitative Chest CT in Children without Lung Disease

In contrast to studies of adults with emphysema, application of fixed thresholds to determine low- and high-attenuation areas (air-trapping and parenchymal lung disease) in pediatric quantitative chest CT is problematic. We aimed to assess age effects on: (i) mean lung attenuation (full inspiration); and (ii) low and high attenuation thresholds (LAT and HAT) defined as mean attenuation and 1 SD below and above mean, respectively. Chest CTs from children aged 6–17 years without abnormalities were retrieved, and histograms of attenuation coefficients were analyzed. Eighty examinations were included. Inverse functions described relationships between age and mean lung attenuation, LAT or HAT (p < 0.0001). Predicted value for LAT decreased from −846 HU in 6-year-old to −950 HU in 13- to 17-year-old subjects (cut-off value for assessing emphysema in adults). %TLCCT with low attenuation correlated with age (rs = −0.31; p = 0.005) and was <5% for 9–17-year-old subjects. Inverse associations were demonstrated between: (i) %TLCCT with high attenuation and age (r2 = 0.49; p < 0.0001); (ii) %TLCCT with low attenuation and TLCCT (r2 = 0.47; p < 0.0001); (iii) %TLCCT with high attenuation and TLCCT (r2 = 0.76; p < 0.0001). In conclusion, quantitative analysis of chest CTs from children without lung disease can be used to define age-specific LAT and HAT for evaluation of pediatric lung disease severity.