Giant bipolar unidirectional photomagnetoresistance.

Positive magnetoresistance (PMR) and negative magnetoresistance (NMR) describe two opposite responses of resistance induced by a magnetic field. Materials with giant PMR are usually distinct from those with giant NMR due to different physical natures. Here, we report the unusual photomagnetoresistance in the van der Waals heterojunctions of WSe2/quasi-two-dimensional electron gas, showing the coexistence of giant PMR and giant NMR. The PMR and NMR reach 1,007.5% at -9 T and -93.5% at 2.2 T in a single device, respectively. The magnetoresistance spans over two orders of magnitude on inversion of field direction, implying a giant unidirectional magnetoresistance (UMR). By adjusting the thickness of the WSe2 layer, we achieve the maxima of PMR and NMR, which are 4,900,000% and -99.8%, respectively. The unique magnetooptical transport shows the unity of giant UMR, PMR, and NMR, referred to as giant bipolar unidirectional photomagnetoresistance. These features originate from strong out-of-plane spin splitting, magnetic field-enhanced recombination of photocarriers, and the Zeeman effect through our experimental and theoretical investigations. This work offers directions for high-performance light-tunable spintronic devices.NMR).

Optimizing the Quality of Machine Learning for Identifying the Share of Biogenic and Fossil Carbon in Solid Waste.

Insights into carbon sources (biogenic and fossil carbon) and contents in solid waste are vital for estimating the carbon emissions from incineration plants. However, the traditional methods are time-, labor-, and cost-intensive. Herein, high-quality data sets were established after analyzing the carbon contents and infrared spectra of substantial samples using elemental analysis and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), respectively. Then, five classification and eight regression machine learning (ML) models were evaluated to recognize the proportion of biogenic and fossil carbon in solid waste. Using the optimized data preprocessing approach, the random forest (RF) classifier with hyperparameter tuning ranked first in classifying the carbon group with a test accuracy of 0.969, and the carbon contents were successfully predicted by the RF regressor with R2 = 0.926 considering performance-interpretability-computation time competition. The above proposed algorithms were further validated with real environmental samples, which exhibited robust performance with an accuracy of 0.898 for carbon group classification and an R2 value of 0.851 for carbon content prediction. The reliable results indicate that ATR-FTIR coupled with ML algorithms is feasible for rapidly identifying both carbon groups and content, facilitating the calculation and assessment of carbon emissions from solid waste incineration.

Observation of Electric Hysteresis, Polarization Oscillation, and Pyroelectricity in Nonferroelectric p-n Heterojunctions.

The switchable electric polarization is usually achieved in ferroelectric materials with noncentrosymmetric structures, which opens exciting opportunities for information storage and neuromorphic computing. In another polar system of p-n junction, there exists the electric polarization at the interface due to the Fermi level misalignment. However, the resultant built-in electric field is unavailable to manipulate, thus attracting less attention for memory devices. Here, we report the interfacial polarization hysteresis (IPH) in the vertical sidewall van der Waals heterojunctions of black phosphorus and quasi-two-dimensional electron gas on SrTiO_{3}. A nonvolatile switching of electric polarization can be achieved by reconstructing the space charge region (SCR) with long-lifetime nonequilibrium carriers. The resulting electric-field controllable IPH is experimentally verified by electric hysteresis, polarization oscillation, and pyroelectric effect. Further studies confirm the transition temperature of 340 K, beyond which the IPH vanishes. The second transition is revealed with the temperature dropping below 230 K, corresponding to the sharp improvement of IPH and the freezing of SCR reconstruction. This work offers new possibilities for exploring the memory phenomena in nonferroelectric p-n heterojunctions.

Metal-Free Semiconductor-Based Bio-Nano Hybrids for Sustainable CO2 -to-CH4 Conversion with High Quantum Yield.

Bio-nano hybrids with methanogens and nano-semiconductors provide an innovative strategy for solar-driven CO2 -to-CH4 conversion; however, the efficiency mismatch between electron production and utilisation results in low quantum yield and CH4 selectivity. Herein, we report the integration of metal-free polymeric carbon nitrides (CNx ) decorated with cyanamide (NCN) groups and Methanosarcina barkeri (M. b). The self-assembled M. b-NCN CNx exhibited a quantum yield of 50.3 % with 92.3 % CH4 selectivity under illumination, which outperforms other reported bio-nano hybrid systems and photocatalytic systems for CO2 reduction. This excellent performance was attributed to the distinct capacitance and conductive effects of NCN CNx , which promoted electron storage and redistribution at the biotic-abiotic interface to alleviate recombination losses and side reaction. This study provides new design guidelines for bio-nano hybrids for the sustainable photocatalytic reduction of CO2 into fuels.

Coexistence of Photoelectric Conversion and Storage in van der Waals Heterojunctions.

Van der Waals (vdW) heterojunctions, based on two-dimensional (2D) materials, have great potential for the development of ecofriendly and high-efficiency nanodevices, which shows valuable applications as photovoltaic cells, photodetectors, etc. However, the coexistence of photoelectric conversion and storage in a single device has not been achieved until now. Here, we demonstrate a simple strategy to construct a vdW p-n junction between a WSe_{2} layer and quasi-2D electron gas. After an optical illumination, the device stores the light-generated carriers for up to seven days, and then releases a very large photocurrent of 2.9 mA with bias voltage applied in darkness; this is referred to as chargeable photoconductivity (CPC), which completely differs from any previously observed photoelectric phenomenon. In normal photoconductivity, the recombination of electron-hole pairs occurs at the end of their lifetime; in contrast, infinite-lifetime photocarriers can be generated and stored in CPC devices without recombination. The photoelectric conversion and storage are completely self-excited during the charging process. The ratio between currents in full- and empty-photocarrier states below the critical temperature reaches as high as 10^{9}, with an external quantum efficiency of 93.8% during optical charging. A theoretical model developed to explain the mechanism of this effect is in good agreement with the experimental data. This work paves a path toward the high-efficiency devices for photoelectric conversion and storage.

Contribution of microglial reaction to increased nociceptive responses in high-fat-diet (HFD)-induced obesity in male mice.

The progressive increase in the prevalence of obesity in the population can result in increased healthcare costs and demands. Recent studies have revealed a positive correlation between pain and obesity, although the underlying mechanisms still remain unknown. Here, we aimed to clarify the role of microglia in altered pain behaviors induced by high-fat diet (HFD) in male mice. We found that C57BL/6CR mice on HFD exhibited enhanced spinal microglial reaction (increased cell number and up-regulated expression of p-p38 and CD16/32), increased tumor necrosis factor-α (TNF-α) mRNA and brain-derived neurotrophic factor (BDNF) protein expression as well as a polarization of spinal microglial toward a pro-inflammatory phenotype. Moreover, we found that using PLX3397 (a selective colony-stimulating factor-1 receptor (CSF1R) kinase inhibitor) to eliminate microglia in HFD-induced obesity mice, inflammation in the spinal cord was rescued, as was abnormal pain hypersensitivity. Intrathecal injection of Mac-1-saporin (a saporin-conjugated anti-mac1 antibody) resulted in a decreased number of microglia and attenuated both mechanical allodynia and thermal hyperalgesia in HFD-fed mice. These results indicate that the pro-inflammatory functions of spinal microglia have a special relevance to abnormal pain hypersensitivity in HFD-induced obesity mice. In conclusion, our data suggest that HFD induces a classical reaction of microglia, characterized by an enhanced phosphorylation of p-38 and increased CD16/32 expression, which may in part contribute to increased nociceptive responses in HFD-induced obesity mice.

A denoising method based on deep learning for proton radiograph using energy resolved dose function.

Objective.Proton radiograph has been broadly applied in proton radiotherapy which is affected by scattered protons which result in the lower spatial resolution of proton radiographs than that of x-ray images. Traditional image denoising method may lead to the change of water equivalent path length (WEPL) resulting in the lower WEPL measurement accuracy. In this study, we proposed a new denoising method of proton radiographs based on energy resolved dose function curves.Approach.Firstly, the corresponding relationship between the distortion of WEPL characteristic curve, and energy and proportion of scattered protons was established. Then, to improve the accuracy of proton radiographs, deep learning technique was used to remove scattered protons and correct deviated WEPL values. Experiments on a calibration phantom to prove the effectiveness and feasibility of this method were performed. In addition, an anthropomorphic head phantom was selected to demonstrate the clinical relevance of this technology and the denoising effect was analyzed.Main results.The curves of WEPL profiles of proton radiographs became smoother and deviated WEPL values were corrected. For the calibration phantom proton radiograph, the average absolute error of WEPL values decreased from 2.23 to 1.72, the mean percentage difference of all materials of relative stopping power decreased from 1.24 to 0.39, and the average relative WEPL corrected due to the denoising process was 1.06%. In addition, WEPL values correcting were also observed on the proton radiograph for anthropomorphic head phantom due to this denoising process.Significance.The experiments showed that this new method was effective for proton radiograph denoising and had greater advantages than end-to-end image denoising methods, laying the foundation for the implementation of precise proton radiotherapy.

The correlation between tic disorders and allergic conditions in children: A systematic review and meta-analysis of observational studies.

Aim: To evaluate the correlation between tic disorders and allergies and to inform strategies for the treatment and prevention of tic disorders. Methods: We conducted online searches of the MEDLINE, Embase, Cochrane, CNKI, CBM, WanFang, and VIP Information databases. Case-control studies and cohort studies related to tic disorders and allergic conditions were searched. Two researchers screened the literature, extracted data, and evaluated quality in strict accordance with the predetermined retrieval strategy and inclusion criteria. Finally, RevMan 5.4 software was used to conduct a meta-analysis. We used the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) approach to rating the certainty of evidence about each allergy outcome as high, moderate, low, or very low. Results: We obtained seven eligible studies involving eight allergic conditions. The following allergic conditions were significantly associated with the presence of a tic disorder: asthma (OR = 1.90, 95% CI = 1.57-2.30, P < 0.001), allergic rhinitis (OR = 2.61, 95% CI = 1.90-3.57, P < 0.001), allergic conjunctivitis (OR = 3.65, 95% CI = 1.53-8,67, P = 0.003), eczema (OR = 3.87, 95% CI = 2.24-6.67, P < 0.001) and food allergy (OR = 2.79, 95% CI = 1.56-4.99, P < 0.001). There was no significant correlation between atopic dermatitis, urticaria, drug allergy, and tic disorder. Conclusion: The occurrence of tic disorders may be associated with the presence of certain allergic disorders. However, whether allergy is one of the causes of tic disorders remains unclear. Systematic review registration: The registration number for this systematic review is PROSPERO: CRD42021231658.

Recent Progress in Strain Engineering on Van der Waals 2D Materials: Tunable Electrical, Electrochemical, Magnetic, and Optical Properties.

Strain engineering is a promising way to tune the electrical, electrochemical, magnetic, and optical properties of 2D materials, with the potential to achieve high-performance 2D-material-based devices ultimately. This review discusses the experimental and theoretical results from recent advances in the strain engineering of 2D materials. Some novel methods to induce strain are summarized and then the tunable electrical and optical/optoelectronic properties of 2D materials via strain engineering are highlighted, including particularly the previously less-discussed strain tuning of superconducting, magnetic, and electrochemical properties. Also, future perspectives of strain engineering are given for its potential applications in functional devices. The state of the survey presents the ever-increasing advantages and popularity of strain engineering for tuning properties of 2D materials. Suggestions and insights for further research and applications in optical, electronic, and spintronic devices are provided.

Rapid determination of moisture content of multi-source solid waste using ATR-FTIR and multiple machine learning methods.

Rapid determination of moisture content plays an important role in guiding the recycling, treatment and disposal of solid waste, as the moisture content of solid waste directly affects the leachate generation, microbial activities, pollutants leaching and energy consumption during thermal treatment. Traditional moisture content measurement methods are time-consuming, cumbersome and destructive to samples. Therefore, a rapid and nondestructive method for determining the moisture content of solid waste has become a key technology. In this work, an attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and multiple machine learning methods was developed to predict the moisture content of multi-source solid waste (textile, paper, leather and wood waste). A combined model was proposed for moisture content regression prediction, and the applicability of 20 combinations of five spectral preprocessing methods and four regression algorithms were discussed to further improve the modeling accuracy. Furthermore, the prediction result based on the water-band spectra was compared with the prediction result based on the full-band spectra. The result showed that the combination model can efficiently predict the moisture content of multi-source solid waste, and the R2 values of the validation and test datasets and the root mean square error for the moisture prediction reached 0.9604, 0.9660, and 3.80, respectively after the hyperparameter optimization. The excellent performance indicated that the proposed combined models can rapidly and accurately measure the moisture content of solid waste, which is significant for the existing waste characterization scheme, and for the further real-time monitoring and management of solid waste treatment and disposal process.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies.

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, and EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low/moderate levels may favor tumorigenesis, while higher levels would exert antitumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "doubleedged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

Mechanistic Modelling of Slow and Fast NHEJ DNA Repair Pathways Following Radiation for G0/G1 Normal Tissue Cells.

Mechanistic in silico models can provide insight into biological mechanisms and highlight uncertainties for experimental investigation. Radiation-induced double-strand breaks (DSBs) are known to be toxic lesions if not repaired correctly. Non-homologous end joining (NHEJ) is the major DSB-repair pathway available throughout the cell cycle and, recently, has been hypothesised to consist of a fast and slow component in G0/G1. The slow component has been shown to be resection-dependent, requiring the nuclease Artemis to function. However, the pathway is not yet fully understood. This study compares two hypothesised models, simulating the action of individual repair proteins on DSB ends in a step-by-step manner, enabling the modelling of both wild-type and protein-deficient cell systems. Performance is benchmarked against experimental data from 21 cell lines and 18 radiation qualities. A model where resection-dependent and independent pathways are entirely separated can only reproduce experimental repair kinetics with additional restraints on end motion and protein recruitment. However, a model where the pathways are entwined was found to effectively fit without needing additional mechanisms. It has been shown that DaMaRiS is a useful tool when analysing the connections between resection-dependent and independent NHEJ repair pathways and robustly matches with experimental results from several sources.

Natural products attenuate PI3K/Akt/mTOR signaling pathway: A promising strategy in regulating neurodegeneration.

BACKGROUND: As common, progressive, and chronic causes of disability and death, neurodegenerative diseases (NDDs) significantly threaten human health, while no effective treatment is available. Given the engagement of multiple dysregulated pathways in neurodegeneration, there is an imperative need to target the axis and provide effective/multi-target agents to tackle neurodegeneration. Recent studies have revealed the role of phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) in some diseases and natural products with therapeutic potentials. PURPOSE: This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating various neuronal disorders via the PI3K/Akt/mTOR signaling pathway. STUDY DESIGN AND METHODS: A systematic and comprehensive review was done based on the PubMed, Scopus, Web of Science, and Cochrane electronic databases. Two independent investigators followed the PRISMA guidelines and included papers on PI3K/Akt/mTOR and interconnected pathways/mediators targeted by phytochemicals in NDDs. RESULTS: Natural products are multi-target agents with diverse pharmacological and biological activities and rich sources for discovering and developing novel therapeutic agents. Accordingly, recent studies have shown increasing phytochemicals in combating Alzheimer's disease, aging, Parkinson's disease, brain/spinal cord damages, depression, and other neuronal-associated dysfunctions. Amongst the emerging targets in neurodegeneration, PI3K/Akt/mTOR is of great importance. Therefore, attenuation of these mediators would be a great step towards neuroprotection in such NDDs. CONCLUSION: The application of plant-derived secondary metabolites in managing and/or treating various neuronal disorders through the PI3K/Akt/mTOR signaling pathway is a promising strategy towards neuroprotection.

Tribulus terrestris and female reproductive system health: A comprehensive review.

BACKGROUND: Tribulus terrestris L. (T. terrestris) positive performance on the male sexual system has been confirmed, but little is known about its effects on the female reproductive system. PURPOSE: This review discussed in detail the beneficial impact of T. terrestris and its secondary metabolites on the female reproductive system. STUDY DESIGN AND METHODS: In this review, the scientific Databases of Science direct, Pubmed, Web of Science, Google, Google Scholar, Researchgate, EMBASE, Scientific Information (SID), and Elsevier were searched profoundly. Studies about the pharmacological activities of T. terrestris on the female reproductive system in each aspect of investigations: human, in vivo, and in vitro studies, in the period from 1998 to 2020 were admitted. Our study was not limited by the language of publications. RESULTS: 23 articles about the effects of T. terrestris on the female reproductive system were found. These studies approved the T. terrestris efficacy on improvements in histological features of the ovary and uterus of polycystic ovary syndrome patients as well as the well-working of normal ovaries, enhancements in the sexual desire of postmenopausal syndrome, improve ovarian and breast cancers. CONCLUSION: These studies showed that the positive effect of T. terrestris on the female reproductive system was due to the presence of a secondary metabolite called protodioscin; a steroidal saponin compound, as the dominant active component of this plant.

Monte carlo study of organ doses and related risk for cancer in Tanzania from scattered photons in cervical radiation treatment involving Co-60 source.

PURPOSE: The present work aimed to evaluate organ doses and related risk for cancer from external beam radiation treatment (EBRT) and high-dose-rate (HDR) brachytherapy (BT) involving Co-60 source for patients with cervical carcinoma in Tanzania based on Monte Carlo methods and to evaluate the secondary cancer risks in their lifetime. METHODS: EBRT and HDR-BR were modelled by using the MCNPX Monte Carlo (MC) code. The MC simulations were performed by using validated models and isocentric irradiation of an adult female computational phantom. The organ doses and cancer risks estimates were obtained. RESULTS: The highest absorbed doses of 6.98 × 10-2 and 5.74 × 10-2 Sv/Gy were recorded in the bladder for BT and EBRT. The higher risk was found for colon at 1.06 × 10-3 in the HDR-BT and 9.75 × 10-5 in the EBRT per 100,000 population at exposure age of 35 years than in the other organs. The risk magnitude decreased with increasing age at exposure. In general, the secondary cancer risks in all sites considered from EBRT and HDR-BR for cervical cancer patient were lower than the baseline risks. CONCLUSIONS: The chances of developing secondary cancer take years following radiation therapy are extremely low, but the results of present study can support to establish a future database on secondary cancer risks involving radiation therapy in patients with cervical cancer by using HDR-BR and EBRT with Co-60 source in Tanzania and other developing countries.

Cathode ray tubes glass recycling: A review.

With the rapid development in kinescope technologies, Cathode Ray Tubes (CRTs) now are almost completely replaced by thinner and lighter flat panel displays, such as liquid crystal displays (LCD), plasma display panels (PDP) and light emitting diode (LED) displays. Waste CRT glass contains many poisonous and harmful substances, especially lead. If it is not properly disposed of, it would pose a serious threat to the environment and human health. This paper reviews the existing waste CRT glass recycling technologies, analyses the obstacles that hinder their industrial application, pinpoints its future directions. This paper also points out the academic conflict in the risk of lead contained CRT glass and proposes a basic rule for waste treatment and disposal: the lower risk principle. The results of this study could help to understand waste CRT glass recycling and guide its future research and development.

Effect of ionic liquid [MIm]HSO4 on WPCB metal-enriched scraps refined by slurry electrolysis.

Waste printed circuit boards (WPCBs) are usually dismantled, crushed, and sorted to WPCB metal-enriched scraps, still containing an amount of non-metallic materials. This research used slurry electrolysis to refine these WPCB metal-enriched scraps and to examine if a standard ionic liquid, [MIm]HSO4, can replace H2SO4 in the system. The impact of the refinement process on metal migration and transformation is discussed in detail. The results demonstrated that metals in WPCB metal-enriched scraps could be successfully refined using slurry electrolysis, and [MIm]HSO4 can be used to replace H2SO4 in the system. When 80% of H2SO4 was replaced by [MIm]HSO4 (electrolyte of 200 mL, 30 g/L CuSO4·5H2O, 60 g/L NaCl, 130 g/L H2SO4, and 1.624 A for 4 h), the total metal recovery rate is 85%, and the purity, current efficiency, and particle size of cathode metal powder were 89%, 52%, and 3.77 µm, respectively. Moreover, the microstructure of the cathode metal powder was dendritic in the H2SO4-CuSO4-NaCl slurry electrolysis system, whereas at an 80% [MIm]HSO4 substitution rate slurry electrolysis system, the cathode metal powder was irregular and accumulated as small-sized spherical particles. Thus, replacing inorganic leaching solvents with ionic liquids may provide a potential choice for the resources in WPCB metal-enriched scraps.

Effect of electrolyte reuse on metal recovery from waste CPU slots by slurry electrolysis.

As an indispensable part of printed circuit boards (PCBs), central processing unit (CPU) slots contain a significant amount of precious metals which makes economic sense to recycle these materials. Slurry electrolysis is an attractive approach for electronic waste (e-waste) recycling. In this study, the effect of electrolyte reuse on the recovery of metals (Primarily aluminum, nickel, copper, lead, silver, palladium, platinum and gold), from waste CPU slots by slurry electrolysis is discussed in detail. These results show that metal recovery rate, more than 95% for all 13 cycles, was not affected by slurry electrolyte reuse during metal recycling from waste CPU slots, though the reuse of slurry electrolyte greatly impacted the distribution of metals in the anode residues, electrolyte and cathode metal powders. However, slurry electrolysis recovered metals from waste CPU slots and the effect of electrolyte reuse on the recovery of metals from waste CPU slots is discussed for the first time in this study. This could benefit the recycling process since it could improve cathode metal powders recovery rates by approximately 2 times. The acid usage could be significantly reduced by electrolyte reuse when compared to fresh electrolyte. Therefore, electrolyte reuse is demonstrated and slurry electrolysis is a feasible and potentially economically friendly choice for industrial e-waste recycling.

VirtualDose-IR: a cloud-based software for reporting organ doses in interventional radiology.

A cloud-based software, VirtualDose-IR (Virtual Phantoms Inc., Albany, New York, USA), designed to report organ doses and effective doses for a diverse patient population from interventional radiology (IR) procedures has been developed and tested. This software is based on a comprehensive database of Monte Carlo-generated organ dose built with a set of 21 anatomically realistic patient phantoms. The patient types included in this database are both male and female people with different ages reflecting reference adults, obese people with different BMIs and pregnant women at different gestational stages. Selectable parameters such as patient type, tube voltage, filtration thickness, beam direction, field size, and irradiation site are also considered in VirtualDose-IR. The software has been implemented using the 'Software as a Service (SaaS)' delivery concept permitting simultaneous multi-user, multi-platform access without requiring local installation. The patient doses resulting from different target sites and patient populations were reported using the VirtualDose-IR system. The patient doses under different source to surface distances (SSD) and beam angles calculated by VirtualDose-IR and Monte Carlo simulations were compared. For most organs, the dose differences between VirtualDose-IR results and Monte Carlo results were less than 0.3 mGy at 15 000 mGy * cm2 kerma-area product (KAP). The organ dose results were compared with measurement data previously reported in literatures. The doses to organs that were located within the irradiation field match closely with experimental measurement data. The differences in the effective dose values between calculated using VirtualDose-IR and those measured were less than 2.5%. The dose errors of most organs between VirtualDose-IR and literature results were less than 40%. These results validate the accuracy of organ doses reported by VirtualDose-IR. With the inclusion of pre-specified clinical IR examination parameters (such as beam direction, target location, field of view and beam quality) and the latest anatomically realistic patient phantoms in Monte Carlo simulations, VirtualDose-IR provides users with accurate dose information in order to systematically compare, evaluate, and optimize IR plans.

MONTE CARLO SIMULATION OF OUT-OF-FIELD ORGAN DOSES AND CANCER RISK IN TANZANIA FOR RADIATION THERAPY OF UNILATERAL RETINOBLASTOMA USING A 60Co UNIT.

The use of 60Co teletherapy unit for the treatment of unilateral retinoblastoma (Rb) patients is a very common procedure in many developing countries including Tanzania. The aim of this study was to estimate organ-specific absorbed doses from an external beam radiation therapy 60Co unit for unilateral Rb and to assess the risks of the patients developing a secondary primary cancer. The absorbed dose estimations were based on a Monte Carlo method and a set of age-dependent computational male phantoms. The estimated doses were used to calculate the secondary cancer risks in out-of-field organs using the Biological Effects of Ionising Radiation VII risk models. The survival information and baseline cancer risks were based on relevant statistics for the Tanzanian population. The resulting out-of-field organ doses data showed that organs which are close to the target volume, such as the brain, salivary glands and thyroid glands, received the highest absorbed dose from scattered photons during the treatment of Rb. It was also found that the resulting photons dose to specific organs depends on the patient's age. Younger patients are more sensitive to radiation and also received higher dose contributions from the treatment head due to a larger part of the body exposed to the photon radiation. In all sites considered, the overall risks associated with radiation-induced secondary cancer were relatively lower than the baseline risks. Thus, the results in this article can help to provide good estimations of radiation-induced secondary cancer after radiation treatment of unilateral Rb using 60Co teletherapy unit in Tanzania and other developing countries.