Photon Attenuation Research Articles

Radiation shielding ability and optical features of La2O3+TiO2+Nb2O5+WO3+X2O3 (X=B, Ga, and In) glass system containing high-entropy oxides

Three high entropy materials (La2O3+TiO2+Nb2O5+WO3+X2O3 coded as LTNWM1, LTNWM2, and LTNWM3 for X = B, Ga, and In) produced by aerodynamic containerless processing were evaluated for optical attributes, and their gamma-radiation absorption abilities were investigated in this report. Optical related parameters such as the molar refractivity (Rm), optical transmission (T), molar polarizability (αm), metallization criterion (M), reflection loss (RL), static (εstatic), and optical (εoptical) dielectric constants were estimated through standard expressions, while photon attenuation parameters were estimated from data from photon transmission simulations in FLUKA code and XCOM software. The attenuation parameters were calculated for a wide energy photon spectrum (15 keV–15 MeV). LTNWM1, LTNWM2, and LTNWM3 had Rm values of 18.94 cm3/mol, 21.45 cm3/mol, and 26.09 cm3/mol respectively. The αm has a value of 7.52 × 10−24 cm3 for LTNWM1, 8.51 × 10−24 cm3 for LTNWM2, and 10.35 × 10−24 cm3 for LTNWM3. The photon shielding parameters evaluated by FLUKA and XCOM are compatible. The mass attenuation coefficient for the glasses was between 0.0338 and 52.8261 cm2/g, 0.0336–58.0237 cm2/g, and 0.0344–52.1560 cm2/g for LTNWM1, LTNWM2 and LTNWM3, respectively. The effective atomic number at 1.5 MeV was 18.718, 20.857, and 22.440 for LTNWM1, LTNWM2, and LTNWM3, respectively. The shielding parameters of the HMOs compared to traditional gamma radiation absorbers are exceptional and highlight the potential of using them as optically transparent gamma-shields.

Comprehensive assessment of radiation shielding properties of novel multi-component lead boro-tellurite glasses

The present work is intended to establish the addition of the different modifier cations (Na, Li, Mg) along with different anionic combination (oxygen and fluorine) in the novel Lead boro-tellurite glass network in the point of view of radiation shielding material. The present novel lead boro-tellurite glasses have been synthesized following the melt quenching technique with three modifier elements (Na, Li, Mg) in the form of oxides as well as fluoride in the glass network. The variation in density and molar volume confirms the atomic rearrangements and FTIR spectral analysis reveals the presence of non-bridging oxygens in the prepared glasses. The optical absorption spectra confirm the changes in the bandgap due to the incorporation of modifiers into the glass network. The radiation shielding ability of the glasses were investigated by determining the transmission factor (TF) and other related parameters. The gamma photon attenuation abilities of the prepared Lead boro-tellurite glasses shows improved linear attenuation coefficient (μ), effective atomic number (Zeff) and half value layer (HVL) when the cations are incorporated in the form of fluorides. Authors found that the TF for NaO:Pr glass at a thickness of 0.6 cm increases from 0.69 at 0.3 MeV to 0.89 at 1 MeV, and 0.94 at 5 MeV. The TF results demonstrated that adding MgO instead of Na2O to the glasses reduces the number of photons that can penetrate the glass, enhancing the radiation-shielding properties of the glass system. Authors evaluated the effective atomic number (Zeff) and found that the Zeff values vary between 56.55 and 57.14 at 0.015 MeV. Also, the Zeff results confirmed that adding MgO into the glasses leads to a great increase in Zeff values. Among the prepared glasses, Mg2+ cations incorporated glass exhibits higher shielding efficacy and it may be suggested as a promising radiation shielding material.

Optical and radiation absorption properties of bismuth-borate glasses doped with Ce4 +, Nd3 +, and Sm3 +

Three bismuth-borate glasses with the chemical configuration 15Bi2O3-75 H3BO2-10CeO2, 15Bi2O3-75 H3BO2-10Nd2O3, and 15Bi2O3-75 H3BO2-10Sm2O3 and coded as BHB-Ce, BHB-Nd, and BHB-Nd were investigated for their optical and gamma-radiation absorption behaviour. Optical parameters of the glasses such as the molar refractivity, Rm, molar polarizability, αm, reflection loss RL, optical transmission T, metallization criterion M, static dielectric constant εstatic, and optical dielectric constant εoptical were calculated using standard theoretical models. The mass attenuation coefficient μ/ρof the glass samples was estimated by FLUKA simulations and XCOM for discrete photon beams with energies of 0.282, 0.662, 1.33, and 2.51 MeV. The value of Vm was 21.35, 22.61, and 19.60 cm3/mol for BHB-Ce, BHB-Nd, and BHB-Sm, respectively. Also, the highest Rm (16.52 cm3/mol) and αm (6.56 ×10−24 cm3) were obtained for BHB-Ce, while the lowest value was recorded for BHB-Nd (12.035 cm3/mol and 4.78 ×10−24 cm3). Other optical parameters varied with the dopant ion. The photon attenuation coefficient obtained from XCOM calculation and simulations agreed within a 2.90% margin. The μ/ρ varied within the interval 0.0422–0.3086 cm2/g for BHB-Ce, 0.0420–0.3005 cm2/g for BHB-Nd and 0.0420–0.3029 cm2/g for BHB-Sm. The half-value layers (HVLs) vary from 0.3948 cm to 2.8854 cm for BHB-Ce, from 0.3782 cm to 2.7063 cm for BHB-Nd and from 0.3223 cm to 2.3252 cm for BHB-Sm. Based on the values of the photon shielding parameters, the investigated glasses showed better ability to absorb photons compared to conventional shields such as barite concrete, ordinary concrete, and some commercial glass shields. The analysis of the optical and radiation absorption parameters shows that the BHB-glasses are useful in optical and gamma-radiation absorption technologies.

Dosimetric Characterization of DSF/NaOH/IA-PAE/R. spp. Phantom Material for Radiation Therapy

Background: Different compositions of DSF/NaOH/IA-PAE/R. spp. composite particleboard phantoms were constructed. Methods: Photon attenuation characteristics were ascertained using gamma rays from 137Cs and 60Co. Absorbed doses at the location of an ionization chamber and Gafchromic EBT3 radiochromic films were calculated for high-energy photons (6 and 10 MV) and electrons (6, 9, 12, and 15 MeV). Results: The calculated TPR20,10 values indicate that the percentage discrepancy for 6 and 10 MV was in the range of 0.29-0.72% and 0.26-0.65%. It was also found that the relative difference in the dmax to water and solid water phantoms was between 1.08-1.28% and 5.42-6.70%. The discrepancies in the determination of PDD curves with 6, 9, 12, and 15 MeV, and those of water and solid water phantoms, ranged from 2.40-4.84%. Comparable results were found using the EBT3 films with variations of 2.0-7.0% for 6 and 10 MV photons. Likewise, the discrepancies for 6, 9, 12, and 15 MeV electrons were within an acceptable range of 2.0-4.5%. Conclusions: On the basis of these findings, the DSF/NaOH/IA-PAE/R. spp. particleboard phantoms with 15 wt% IA-PAE addition level can be effectively used as alternative tissue-equivalent phantom material for radiation therapy applications.

γ-Photon attenuation study on CaF2

γ- Photon Attenuation Study has been conducted on CaF2 to determine mass attenuation coefficient (μm), linear attenuation coefficient (μl), density (ρ), and the coefficient of linear thermal expansion (α). The variations in density, linear attenuation coefficient and thermal expansion with temperature in the temperature range 300 K-1000 K have been represented by second and third degree polynomials respectively Photon interaction parameters of the compound at different γ-energies are reported. We understand that (μm) is useful and sensitive physical quantity to determine the (Zeff) and (Neff) of a compound. (μm) values of CaF2 decreases with the increase in photon energy. Variation of (σt and σe) with the energy is same as the mass attenuation coefficient.

Behaviour of tungsten oxide on phosphor-tellurite glasses for photon proton and alpha particles shielding

This research, photons shielding properties such as mass attenuation coefficients (mm), effective atomic number (Zeff), effective electron density (Nel) and kinetic energy per unit mass (kerma) relative to air for WO3 based on TeO2–P2O5–WO3 glass system have been simulated by WinXCom software program at energies of 10–3–105 MeV. Also, buildup factors (BFs) have been estimated at widely energy ranging 15 keV – 15 MeV for penetration depths (PD) until 40 mean free path (mfp). The results of glass system in formula (70–x) TeO2–30P2O5–xWO3 at x = 10, 20, 30, 40, and 50 mol% exhibited that the partial replacement of TeO2 by WO3 was adjusted photons attenuation behaviors for get better. In addition, mass sopping power (MSP) and projected range (PR) were evaluated using SRIM software program for proton (H+1) and alpha particles (He+2) at kinetic energy ranging 10 keV – 10 MeV. The results may be inferred that glass sample with high WO3 content was superb for photons, proton and alpha particles attenuation. The results of this research may be useful in enhancing optimization and potential to use as a transparent material to against photon, proton and alpha particles.

A personal acquisition time regimen of 68Ga-DOTATATE total-body PET/CT in patients with neuroendocrine tumor (NET): a feasibility study

BackgroundThe injection activity of tracer, acquisition time, patient-specific photon attenuation, and large body mass, can influence on image quality. Fixed acquisition time and body mass related injection activity in clinical practice results in a large difference in image quality. Thus, this study proposes a patient-specific acquisition time regimen of 68 Ga-DOTATATE total-body positron emission tomography-computed tomography (PET/CT) to counteract the influence of body mass (BM, kg) on image quality, and acquire an acceptable and constant image of patients with neuroendocrine tumors (NETs).MethodsThe development cohort consisting of 19 consecutive patients with full activity (88.7–204.9 MBq, 2.0 ± 0.1 MBq/kg) was to establish the acquisition time regimen. The liver SNR (signal-to-noise ratio, SNRL) was normalized (SNRnorm) by the product of injected activity (MBq) and acquisition time (min). Fitting of SNRnorm against body mass (BM, kg) in linear correlation was performed. Subjective assessment of image quality was performed using a 5-point Likert scale to determine the acceptable threshold of SNRL, and an optimized acquisition regimen based on BM was proposed, and validated its feasibility through the validation cohort of 57 consecutive NET patients with half activity (66.9 ± 11.3 MBq, 1.0 ± 0.1 MBq/kg) and a fixed acquisition time regimen.ResultsThe linear correlation (R2 = 0.63) between SNRnorm and BM (kg) was SNRnorm = -0.01*BM + 1.50. The threshold SNRL of acceptable image quality was 11.2. The patient-specific variable acquisition time regimen was determined as: t (min) = 125.4/(injective activity)*(-0.01*BM + 1.50)2. Based on that proposed regimen, the average acquisition time for acceptable image quality in the validation cohort was 2.99 ± 0.91 min, ranging from 2.18 to 6.35 min, which was reduced by 36.50% ~ 78.20% compared with the fixed acquisition time of 10 min. Subjective evaluation showed that acceptable image quality could be obtained at 3.00 min in the validation group, with an average subjective score of 3.44 ± 0.53 (kappa = 0.97, 95% CI: 0.96 ~ 0.98). Bland–Altman analysis revealed good agreement between the proposed regimen and the fixed acquisition time cohort.ConclusionA patient-specific acquisition time regimen was proposed in NET patients in development cohort and validated its feasibility in patients with NETs in validation cohort by 68 Ga-DOTATATE total-body PET/CT imaging. Based on the proposed regimen, the homogenous image quality with optimal acquisition time was available independent of body mass.

Sensitivity analysis of gamma-ray shielding characteristics to the TiO2 concentration in the Bi2O3–ZnO–Pb3O4–Al2O3 glass sample based on the Monte Carlo method

In this paper, the MCNP Monte Carlo (MC) code, was adopted for evaluation the properties of protection against gamma-rays of the glass system with the composition of (55-x)Bi2O3–15Pb3O4–20Al2O3–10ZnO- xTiO2 with specific concentrations of (x = 0, 5, 10, 15, 20, 25, 30 and 35 mol percent). For this purpose, several parameters related to photon attenuation such as the, Half-Value Layer (HVL), Tenth-Value Layer (TVL), mean free range (MFP), mass attenuation coefficient (μm), effective atomic number (Zeff) and buildup factor (BF) was investigated at the different energy levels between 0.1 and 1.5 MeV. To verify the results of the simulation, the data obtained from the simulation were compared with the experimental data available in the XCOM database. The NIST-XCOM database and the results of the simulation in the present study were in good agreement. The percentage deviation (PD) between the XCOM database and the MCNP program for calculating the μm was less than 0.59% in most cases. The results show that compared to conventional protective materials such as concrete and lead, the new combination shows more effective attenuation parameters. The glass with the highest concentration of TiO2 has the most favorable state in terms of density compared to the investigated protective materials. The close agreement of μm measurements with the XCOM database of this research shows that MC modeling in this research is a valuable and valid method.

Neutral Atmospheric Density Measurement Using Insight-HXMT Data by the Earth Occultation Technique

The Earth occultation technique has broad applications in both astronomy and atmospheric density measurements. We construct the background model during the occultation of the Crab Nebula observed by the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) at energies between 6 and 100 keV. We propose a Bayesian atmospheric density retrieval method based on the Earth occultation technique, combining Poisson and Gaussian statistics. By modeling the atmospheric attenuation of X-ray photons during the occultation, we simultaneously retrieved the neutral densities of the atmosphere at different altitude ranges. Our method considers the correlation of densities between neighboring atmospheric layers and reduces the potential systematic bias to which previous work may be subject. Previous analyses based on light-curve fitting or spectral fitting also lost some spectral or temporal information of the data. In contrast to previous work, the occultation data observed by the three telescopes on board Insight-HXMT is fully used in our analysis, further reducing the statistical error in density retrieval. We apply our method to cross-check the (semi)empirical atmospheric models, using 115 sets of occultation data of the Crab Nebula observed by Insight-HXMT. We find that the retrieved neutral density is ∼10%, ∼20%, and ∼25% less than the values of the widely used atmospheric model NRLMSISE-00, in the altitude range of 55–80 km, 80–90 km, and 90–100 km, respectively. We also show that the newly released atmospheric model NRLMSIS 2.0 is generally consistent with our density measurements.

Polylactic acid tungsten trioxide reinforced composites: A study of their thermal, optical, and gamma radiation attenuation performance

In the current investigation, the gamma radiation shielding abilities, structure, and thermal and optical properties of Polylactic acid PLA have been tried to be developed by introducing tungsten trioxide WO3. PLA/WO3 composites were fabricated by a solution mixing method at different weights percent (1%, 3%, 5%, and 7%). SEM indicates the good dispersion of WO3 in the PLA matrix, and the X-ray diffraction (XRD) pattern displays the existence of recognizable peaks for PLA and WO3. The thermal properties were investigated by thermo-gravimetric analysis (TGA), which enhances the thermal stability of the PLA/WO3 composites more than pure PLA. The transmittance decreases with increasing the WO3 content in the PLA matrix while the absorption and extinction coefficients α and k as well as the refractive index, rise with the increase of the WO3 content in the PLA matrix. The radiation shielding parameters have been experimentally reported. The equipment used in the experiment consisted of a NaI detector as well as a variety of radioactive point sources that released photons with energy of 80, 238, 356, 662, 1173, 1333, and 2164 keV, respectively. Examining the linear attenuation coefficient (μ), the half-value layer (T0.5), and the radiation protection effectiveness of the PLA/WO3 composites was done in order to investigate the gamma radiation shielding capabilities of the materials (RPE). Pure PLA (free WO3) was found to have the lowest μ values, and it was discovered that increasing the WO3 content led to an improvement in the photon attenuation competency of the present epoxy. The T0.5 lengths of the PLA/WO3 composites were lowered when WO3 was added. This verified that adding WO3 increases the radiation absorption capabilities of the PLA/WO3 composites. The four different energies were tested. Based on the findings, it is possible to draw the conclusion that non-toxic, naturally occurring composites that are low in cost and have a high WO3 content could play an important part in enhancing the gamma-ray shielding capabilities of PLA/WO3 composites for low-energy radiation applications, which can used as protective cover for solar cell against harm radiation.

Radiation shielding performance of a newly synthesized bismuth borate glass system

The melt-quenching process was used to produce 9Na2O–5BaO–Fe2O3–25Bi2O3-(20–0.5x)SiO2-(40–0.5x)B2O3- x ZrO2 glasses, where 0 ≤ x ≤ 12 mol. %. The lead-free glasses were mechanically investigated in terms of hardness and fracture toughness via the indentation method. The hardness of glasses was meaningfully increased from 4.28 to 5.0 GPa, 17% while the fracture toughness of glasses was slightly reduced from 1.66 to 1.26 MPa m1/2, 24%.. The phase formation of the lead-free glass was studied using the X-ray diffraction peaks in the range of 20⁰-60⁰. The chemical bonds and bonding mechanisms in the prepared glasses were examined through Fourier transform infrared (FT-IR) spectra. The gamma mass attenuation coefficient μ/ρ of the glasses was determined for a 15 keV‒15 MeV energy spectrum by XCOM computation and FLUKA simulation data. The μ/ρ estimated through FLUKA simulations and XCOM agreed well. The photon shielding related parameters showed that the radiation absorption competence of the glasses decreased as Zr content increased for energies below 500 keV. The variation in the chemical structure of the glasses did not significantly affect the photon attenuation competence at energies beyond 500 keV. The absence of Pb makes the present glasses more attractive for shielding applications from health and environmental perspectives.

Flexible stretchable low-energy X-ray (30–80 keV) radiation shielding material: Low-melting-point Ga1In1Sn7Bi1 alloy/thermoplastic polyurethane composite

A highly flexible stretchable thermoplastic polyurethane (TPU) composite loaded with a low-melting-point Ga1In1Sn7Bi1 multiprincipal element alloy (LMPEA) was prepared, and its radiation shielding performance was evaluated. The fluid characteristic of LMPEA and the flexibility of TPU enable good interface compatibility. Ga1In1Sn7Bi1 LMPEA consists of two eutectic structures, and the liquid gallium-rich phases are distributed at the boundary of the InBi intermetallic compound and Sn solid solution. In the low-photon energy range of 30–80 keV, LMPEA has a theoretical specific lead equivalent of 0.803 mmPb/mm and a theoretical weight reduction of 17.27% compared with lead. To evaluate the photon attenuation capability for the LMPEA/TPU composites, the Phy-X procedure and Monte Carlo simulations were used to determine the shielding parameters, such as the mass attenuation coefficient, linear attenuation coefficient, half-value layer, tenth-value layer, mean free path, effective atomic number, and fast neutron removal cross section. The attenuation performance test of X-ray protective materials measured the actual lead equivalent. At the same thickness, the LMPEA/TPU composite (66.667, 50.000 wt% LMPEA loading) has a higher measured lead equivalent than the in-service medical shielding materials, which meets the lead equivalent requirements of X-ray protective clothing. LMPEA/TPU composites are nontoxic, lightweight, and have excellent low-energy X-ray shielding ability, offering great potential for application in medical wearable materials.

Nuclear radiation shielding performance of borosilicate glasses: Numerical simulations and theoretical analyses

The photon shielding performances of five different borosilicate-based glasses were investigated in this study using the FLUKA, GEANT4 and MATLAB codes, as well as the XCOM program, at photon energies ranging from 0.03 to 15 MeV. In this context, dependencies of the photon attenuation features with the variation of the photon energy and the chemical compositions have been carefully evaluated with Monte Carlo simulation and theoretical evaluation tools. The mass attenuation coefficient values and effective atomic numbers obtained for BaO-doped G5 glasses are found to be higher than those derived for G1-G4 samples. In other words, the Zeff results showed that high Z-elements such as Ba in a suitable amount should be inserted into the glass composition in order to improve the photon attenuation capability of the borosilicate glasses. The HVLs, TVLs, and MFPs of the studied borosilicate glasses are determined further, and the gamma shielding characteristics of the analyzed samples are found to be associated to the density of the glass, implying that high-density glass can be used for high-level attenuation performance. The exposure buildup factor (EBF) values have been further estimated via the G-P fitting approach. The results of such investigations, according to the work given, may be valuable in designing and fabricating new borosilicate-based glasses, which can then shield against potential radiation damage to environmental health.

Lead-free inorganic metal perovskites beyond photovoltaics: Photon, charged particles and neutron shielding applications

Over the last few years, lead-free inorganic metal perovskites have gained impressive ground in empowering satellites in space exploration owing to their material stability and performance evolution under extreme space environments. The present work has examined the versatility of eight such perovskites as space radiation shielding materials by computing their photon, charged particles and neutron interaction parameters. Photon interaction parameters were calculated for a wide energy range using PAGEX software. The ranges of heavy charged particles (H, He, C, N, O, Ne, Mg, Si and Fe ions) in these perovskites were estimated using SRIM software in the energy range 1 keV–10 GeV, and that of electrons was computed using ESTAR NIST software in the energy range 0.01 MeV–1 GeV. Further, the macroscopic fast neutron removal cross-sections were also calculated to estimate the neutron shielding efficiencies. The examined shielding parameters of the perovskites varied depending on the radiation type and energy. Among the selected perovskites, Cs2TiI6 and Ba2AgIO6 displayed superior photon attenuation properties. A 3.5 cm thick Ba2AgIO6-based shield could reduce the incident radiation intensity to half its initial value, a thickness even lesser than that of Pb-glass. Besides, CsSnBr3 and La0.8Ca0.2Ni0.5Ti0.5O3 displayed the highest and lowest range values, respectively, for all heavy charged particles. Ba2AgIO6 showed electron stopping power (on par with Kovar) better than that of other examined materials. Interestingly, La0.8Ca0.2Ni0.5Ti0.5O3 demonstrated neutron removal cross-section values greater than that of standard neutron shielding materials - aluminium and polyethylene. On the whole, the present study not only demonstrates the employment prospects of eco-friendly perovskites for shielding space radiations but also suggests future prospects for research in this direction.

Gamma photons attenuation features of PbO-doped borosilicate glasses: a comparative evaluation

Gamma photons attenuation features of PbO-doped borosilicate glasses: a comparative evaluation

PHSOR08 Presentation Time: 1:05 PM: Retrospective Comparison of TG43 vs. AcurosBV Model-Based Dose Calculation Algorithm (MBDCA) in Cervical Cancer Patients Treated with HDR Brachytherapy Boost

<h3>Purpose</h3> To evaluate dosimetric impact of heterogeneity from applicators and patient tissue between plans treated with tandem and ovoid applicators with interstitial needles calculated with the TG43 formalism and Acuros®BV MBDCA (Varian Medical Systems (VMS), Inc). <h3>Materials Methods</h3> For this retrospective analysis, HDR plans prescribing 5.5 Gy to high-risk clinical target volume (CTV) D_90% for locally advanced cervical cancer patients were selected. The implants consisted of tandem and ovoid (T&O) with or without interstitial needles, treated using a GammaMedPlus™ iX afterloader with a ¹⁹²Ir source. Implants were stabilized by Alatus vaginal balloons (Angiodynamics) filled with a 5% IsoVue to 95% saline ratio. Imaging for applicator digitization and planning was done using either Acuity CBCT (VMS, Inc), or AIRO CT (BrainLab AG). For standard TG43 clinical dose calculation, all applicators were manually digitized on the CT or CBCT images. Solid renderings of Fletcher-Suit Delclos applicators included in BrachyVision (VMS, Inc) were matched to those used clinically. The composition of the applicators was assigned from the applicator library. Titanium needles were left unchanged, as there is no solid applicator model available. The dose was recalculated using Varian's Acuros®BV 13.5 and dose-to-medium-in-medium (D_m,m) was reported. Equivalent dose in 2 Gy per fraction (EQD2) values for targets and organs at risk (OARs) were compared between TG43 formalism and the Acuros®BV plans. D_90% and D_98% values were reported for the high and intermediate-risk CTVs, and D_2cm3 values were reported for OARs including bladder, rectum, sigmoid, bowel, and vagina. In a separate analysis, we compared dosimetric endpoint differences between TG43 and Acuros®BV plans imaged with CT versus CBCT, and also between plans with T&O applicators with and without needles. Linear regression and Bland Altman Analysis (BAA) were performed between the two plans to show the correlation and dosimetric differences between both methods. <h3>Results</h3> Thirty-two patients with a total of 156 fractions were included in this study, 70 planned on CBCT, and 86 planned on AIRO CT. Consistently, Acuros®BV plans showed lower dosimetric values for all plans compared to TG43. The average ± standard deviation of dosimetric reduction in D_90% was 4.33 ± 0.09% (0.41 ± 0.13 Gy) for CTV_HR and 4.12 ± 0.09% (0.21 ± 0.07Gy) for CTV_IR . Fig.1 shows an example BAA plot for differences between TG43 and Acuros®BV D_90% for the targets. The reduction to OARs D_2cm3 was: 4.99 ± 0.15% (0.34 ± 0.17 Gy) for bladder, 7.87 ± 0.16% (0.20 ± 0.09 Gy) for rectum, 5.79 ± 0.17% (0.21 ± 0.09 Gy) for sigmoid, 6.91 ± 0.14% (0.25 ± 0.13 Gy) for bowel, and 4.55 ± 0.14% (0.46 ± 0.27 Gy) for vagina. There was no statistically significant difference between TG43 and Acuros®BV plans calculated on CBCT versus CT images (p value = 0.24). A set of 5 patients with a total of 24 fractions planed with T&O applicators without needles was used for comparison with plans with interstitial needles, and no statistically significant difference between TG43 and Acuros®BV plans was observed (p value = 0.35). <h3>Conclusion</h3> This large patient cohort study confirms that plans calculated using Acuros®BV MBDCA show a reduction in dose to all structures when compared to the standard TG43 formalism. This is expected mainly due to more photon attenuation by high-density material of the applicators, as well as tissue heterogeneities. Clinical implementation of Acuros®BV can be challenging due to increased calculation time, alteration of the clinical flow, and increased planning complexity. These factors must be evaluated, and further investigation should be conducted in order to understand the effects of its utilization as a primary dose calculation method.

Radiation shielding studies of low melting point MCP alloys in the photon energy range of 10 keV–10 MeV

Photon attenuation properties of low melting-point MCP alloys of 5 N Plus Company are evaluated for 10 keV–10 MeV using MCNPX code, XCOM and XMuDat programs, Auto-Zeff software and linear interpolation method. The simulated and calculated results were in good agreement with differences of < ± 2 %. MCP-124 had the highest shielding efficiency compared to other alloys. It was found that, the µm and σa values of studied alloys decreased with photon energy. MCP-200 had the highest values of 2.7 HVL at the 6 MeV photon energy. The σa values of MCP alloys increased as follow at the photon energies above 0.1 MeV: MCP-69 < MCP-200 < MCP-137 < MCP-96 < MCP-124. In addition, the Zeff values averaged on studied photon energy range were 30.86, 47.74, 68.14, 76.63 and 82.55 respectively for MCP-69, MCP-200, MCP-137, MCP-96 and MCP-124 alloys. The Neff values of alloys varied in the range of 1.63 × 1023 – 3.03 × 1023 electron/g.

A dedicated breast-PET/CT scanner: Numerical observer study of lesion detection.

Dedicated, breast-specific positron emission tomography (BPET)-cone-beam computed tomography (BPET/CT) systems have been developed to improve detection and diagnosis of cancer in women with indeterminate mammograms caused by radiodense breasts. The absorption of X-rays that often vexes mammography in this subset of women does not affect the detection of the high energy annihilation photons used in PET. PET imaging of the breast, however, is subject to limitations caused by their comparatively low spatial resolution (∼2mm) and often moderate radiotracer uptake in lesions. The purpose of this investigation is to explore the PET-based lesion detection capabilities of a BPET/CT scanner developed by the Department of Radiology Instrumentation group at West Virginia University. The PET component of the system consists of a rotating pair of 96×72 arrays of 2×2×15mm3 LYSO scintillator elements. The cone-beam-CT component utilized a pulsed X-ray source and flat panel detector operated in portrait orientation. The density maps created by the CT scanner were used to correct the BPET data for photon attenuation and Compton scattering. The nonuniform uptake of 18 F-fluorodeoxyglucose (FDG) in normal breast tissue was emulated in a specially designed phantom consisting of an acrylic cylinder filled with a mixture of acrylic beads and liquid containing FDG. FDG-avid lesions were simulated with agar spheres (3, 4, 6, 8, and 10mm diameters) containing vary amounts of FDG to produce target-to-background ratios (TBR) of 6:1, 8:1, and 10:1. The spheres also contained X-ray contrast agent to make even the smallest ones readily visible in CT images. Positions of all the lesions were identified in the CT images. These positions were used to extract signal present and signal absent sub-images from the PET images. The sub-images were then input to software that calculated areas-under-the-curve for two numerical model observers (Laguerre-Gauss channelized Hotelling observer and non-prewhitening matched filter). The results showed that the smallest detectable lesion with this system is no smaller than ∼3mm in diameter with a TBR of 6:1. Simulated lesions with diameters of 4mm and greater were calculated to have good to excellent likelihood of detection for all TBRs tested. The results from this investigation identified the detectability capabilities and limitations for a dedicated breast-PET/CT scanner. Its ability to detect relatively small simulated FDG-avid breast lesions for a range of TBRs indicates its potential for clinical application. Finally, the study used methodologies that could be applied to a detectability assessment of other PET/CT scanners.

A comprehensive study on structural properties, photon and particle attenuation competence of CoNiFeCr-Ti/Al high entropy alloys (HEAs)

It is well known that high entropy alloys (HEAs) have a wide range of potential applications as radiation shielding due to their superior properties. The CoNiFeCr-Ti/Al compositions were chosen for their low cost as HEA in this study. The HEAs were successfully produced using the mechanical alloying (MA) method with equimolar CoNiFeCr, CoNiFeCrAl, and CoNiFeCrTi compositions. The production and structural properties of the alloys were investigated in detail. Besides, the photon and particle radiation shielding properties of the HEAs were calculated with the help of Phy-X/PSD, SRIM (10 keV-20 MeV), and ESTAR (10 keV-20 MeV) programs. The photon-matter interaction parameters were calculated in both specific photon energies emitted from 241Am, 133Ba, 109Cd, 60Co, 137Cs, 131I, and 22Na nuclides and a continuous energy range of 15 keV-15 MeV. The characterization of the alloys was investigated by using X-ray diffraction (XRD) and scanning electron microscopes (SEM) attached to an energy dispersive spectroscopy (EDX). It was found that the HEAs have a highly amorphous structure due to the selected production method. The crystal size of the alloys was calculated as 70, 35, and 20 nm for CoNiFeCr, CoNiFeCrAl, and CoNiFeCrTi, respectively. In terms of shielding properties, it has been determined that the produced HEAs have better shielding characteristics for photon and particle radiations than standard shielding concretes. In addition, the results demonstrated that CoNiFeCr alloy, which has the best shielding ability among the HEA alloys, can be used as a shielding material application requiring photon, electron, proton, alpha, and neutron radiations.

PET Oncological Radiopharmaceuticals: Current Status and Perspectives.

Molecular imaging is the visual representation of biological processes that take place at the cellular or molecular level in living organisms. To date, molecular imaging plays an important role in the transition from conventional medical practice to precision medicine. Among all imaging modalities, positron emission tomography (PET) has great advantages in sensitivity and the ability to obtain absolute imaging quantification after corrections for photon attenuation and scattering. Due to the ability to label a host of unique molecules of biological interest, including endogenous, naturally occurring substrates and drug-like compounds, the role of PET has been well established in the field of molecular imaging. In this article, we provide an overview of the recent advances in the development of PET radiopharmaceuticals and their clinical applications in oncology.