[Assessment of biological activities of exopolysaccharides with different relative molecular masses extracted from Rhizopus nigricans].

OBJECTIVE: To evaluate the antioxidant, anti-tumor and immunomodulatory activities of exopolysaccharides with different molecular masses isolated from Rhizopus nigricans. METHODS: Three polysaccharides with different molecular masses, namely RPS-1, RPS-2 and RPS-3, were separated from the fermentation broth of Rhizopus nigricans by fractional ethanol precipitation, and their capacity for scavenging DPPH, ABTS, and hydroxyl radicals was assessed. Cell counting kit-8 was used to analyze the changes in the viability of MFC, A549 and RAW 264.7 cells following treatments with the 3 polysaccharides; The level of nitric oxide in the supernatant of RAW 264.7 cells was detected using a nitric oxide detection kit, and the apoptosis rate of A549 cells was analyzed with flow cytometry. RESULTS: All the 3 polysaccharides had good antioxidant activities, and among them RPS-1 with a medium molecular mass exhibited the strongest scavenging capacity for DPPH and ABTS radicals (P < 0.05) while RPS-3 with the lowest molecular mass had the best scavenging activity for hydroxyl radicals (P < 0.01). All the 3 polysaccharides were capable of inhibiting the proliferation of MFC cells and A549 cells, activating the macrophages RAW 264.7 cells, and inducing apoptosis of A549 cells. RPS-2 with the highest molecular mass showed the strongest inhibitory effects against MFC and A549 cells (P > 0.05), and RPS-2 had the strongest activity for inducing apoptosis in A549 cells (P < 0.05). Compared with the other two polysaccharides, RPS-2 more strongly promoted the proliferation of RAW 264.7 cells and enhanced NO release from the cells (P < 0.05). CONCLUSION: The 3 polysaccharides all have antioxidant, anti-tumor and immunomodulatory activities, and among them RPS-1 and RPS-3 have better antioxidant activities, and RPS-2 has stronger anti-tumor and immunomodulatory activities.

[Factors associated with selection of breast-conserving surgery in early female patients with breast cancer].

Objective: To analyse the factors associated with the selection of breast- conserving surgery in early female patients with breast cancer. Methods: The targeted patients were females diagnosed with early-stage breast cancer and received surgical treatment at Fujian Provincial Hospital from January 1, 2015, to December 31, 2019. The targeted patients' clinical, demographic, and social-economic characteristics were extracted from the hospital health information system. Relevant information of their attending surgeons was collected through a smart-phone based self-respond online survey. We performed multivariate logistic regression to explore the associated factors with breast-conserving surgery (BCS) decision-making. Results: The age of the patient and attending surgeon and the economic development level of the patient's residence area were the associated factors with BCS decision-making of female early-stage breast cancer. By controlling the other factors unchanged, patients from middle-income areas were more likely to accept BCS (OR=1.91, 95%CI: 1.01-3.62, P=0.05) than those from low-income areas. When the attending surgeon was at the average age of 45 years old, increasing of 1 year age of patient led to 4% decrease of the probability of BCS (95%CI: -0.07 - -0.01, P=0.01). When the patient was at the average age of 52 years old, increasing of 1 year age of the attending surgeon reduced 10% of the probability of BCS (95%CI: -0.19 - -0.01, P=0.03). The interaction effects related to the age of attending surgeon and patient for some observations to choose BCS were statistically significant, and the average interaction effect was 0.06% (Z=2.11, sx =0.000 3, P<0.05). Conclusion: To promote breast-conserving surgery in the indicated early female patients with breast cancer, it is necessary to consider factors from both the surgeons and the patients.

[Follow-up and retrospective investigation of patients with pneumoconiosis in Jiangsu Province, China].

Objective: To investigate the features, changing trend, and rules of pneumoconiosis in Jiangsu Province, China, as well as the health status of patients with pneumoconiosis. Methods: From July to October 2019, the patients with pneumoconiosis, reported up to the end of 2018 in Jiangsu Province, were enrolled as respondents, and follow-up and retrospective investigation were performed. A total of 24405 patients with pneumoconiosis were investigated, and related data were collected from the monitoring system of cause of death for residents, pneumoconiosis network reporting system, occupational disease diagnosis institution, management institutions for the reporting of occupational diseases, and related residents' committee or village committee. The patients with pneumoconiosis, who had been reported, were followed up by telephone or on-site visit to obtain the information on their conditions. A descriptive analysis was performed for age of onset, working years, sex, category of industry, type of pneumoconiosis, annual disease onset, geographic distribution, and medical security. Results: Among the 24405 patients, a male/female ratio was 16.81∶1. Of all 24405 patients, 15948 (65.35%) had stage 1 pneumoconiosis, 5289 (21.67%) had stage 2 pneumoconiosis, and 1637 (6.71%) had stage 3 pneumoconiosis. The mean working years for dust exposure was 16.25±9.95 years for all patients, and the mean working years for dust exposure was 15.80±9.95 years for patients with stage 1 pneumoconiosis, 17.82±9.80 years for patients with stage 2 pneumoconiosis, and 16.31±9.90 years for patients with stage 3 pneumoconiosis. The highest number of cases of pneumoconiosis was reported in Wuxi (5744 cases, accounting for 23.54%) , followed by Zhenjiang (4160 cases, accounting for 17.05%) , Xuzhou (3851 cases, accounting for 15.78%) , Yancheng (3340 cases, accounting for 13.69%) , and Suzhou (2948 cases, accounting for 12.08%) . Major types of pneumoconiosis included silicosis (15392 cases, accounting for 63.07%) and coal workers' pneumoconiosis (5253 cases, accounting for 21.52%) . In this survey, 21115 completed follow-up, among whom 15924 survived and 5191 died, 15924 patients with pneumoconiosis survived, among whom 7461 (46.85%) had an age of ≥70 years and 2515 (15.79%) were exposed to dust for 5-9 years. The industries involved were mainly coal mining and washing industry (5687 cases, accounting for 35.71%) and public management, social security, and social organization (3349 cases, accounting for 21.03%) ; in terms of security, 7999 patients (50.23%) were covered by occupational injury insurance, 946 (5.94%) were compensated by employers, 4537 (28.49%) were covered by basic medical insurance for urban and rural residents, 1590 (9.98%) were covered by critical illness insurance, and 5458 (34.28%) were covered by other types of social security, such as medical assistance and poverty relief. Conclusion: Silicosis and coal worker's pneumoconiosis are the key points for the prevention and treatment of pneumoconiosis in Jiangsu Province, and supervision should be strengthened for industries and regions with serious dust hazards.

Cost-effectiveness analysis of capecitabine plus bevacizumab versus capecitabine alone in elderly patients with previously untreated metastatic colorectal cancer from Chinese societal perspective.

PURPOSE: The aim of the study was to evaluate the cost-effectiveness of capecitabine plus bevacizumab compared with capecitabine alone in elderly patients with metastatic colorectal cancer (CRC) from a Chinese societal perspective. METHODS: A decision-analytic Markov model was conducted to simulate the process of metastatic CRC. Three distinct health states: progression-free survival (PFS), progressive disease and death were included. Clinical data were derived from the AVEX trial. Health effectiveness was denoted in quality-adjusted life years (QALYs) and health utilities were derived from previously published studies. Incremental cost-effectiveness ratio (ICER) was regarded as the primary endpoint and willingness-to-pay (WTP) threshold was set at $26,753.37/QALY (3 × per capita GDP of China, 2017). One-way sensitivity analyses and probabilistic sensitivity analysis were also performed to explore the parameters uncertainty in the study. RESULTS: Over a 10-year life horizon, capecitabine plus bevacizumab gained 1.14 QALYs at an average cost of $21,609.48, while the effectiveness and cost of capecitabine group were 0.99 QALYs and $7274.83, respectively. The ICER between the two groups was $95,564.33/QALY. Parameters that mostly influenced the results of the model were utility of PFS state, duration of PFS state for capecitabine plus bevacizumab, total cost of PFS state for capecitabine plus bevacizumab and price of bevacizumab. The probabilities of capecitabine plus bevacizumab and capecitabine as the dominant option were 0% and 100% at the WTP threshold of $26,753.37/QALY. CONCLUSIONS: The results of the study showed that capecitabine plus bevacizumab is unlikely to be a cost-effective treatment option for elderly patients with metastatic CRC.

Monte Carlo study for correcting the broadened line-scan profile in scanning electron microscopy.

Line-scan profile is always broadened due to the probe shape of the primary electron (PE) beam in scanning electron microscopy (SEM), which leads to an inaccurate dimension metrology. Currently, the effective electron beam shape (EEBS) is suggested as the broadening function to overcome this issue for theoretical analysis, rather than the widely used Gaussian profile. However, EEBS is almost impossible to be acquired due to it strongly depends on both the sample topography and the electron beam focusing condition, which makes it is impossible to be applied in practical analysis. Taking the case of gate linewidth measurement, an approach is proposed to find a best-fit traditional Gaussian profile, which can optimally replace the EEBS in the case of the same sample structure and experimental condition for construction of a database of the parameter in traditional Gaussian profile. This approach is based on the use of the ideal and broadened line-scan profiles which are both obtained from Monte Carlo (MC) simulation, but respectively by an ideal and a focusing incident electron beam model. The expected value of parameter can be obtained through deconvoluting (here using a maximum-entropy algorithm) the broadened line-scan profile then fitting it to the ideal profile. Experimenters can benefit from this database to obtain true line-scan profiles for accurate gate linewidth measurement. This work should prove useful for samples of other structures and be an extension of the database in the future.

Monte Carlo Simulation on the CD-SEM Images of SiO2/Si Systems.

Silicon dioxide (SiO2) has been the most important insulator in the highly-developed field of silicon (Si) technology. Accurate pitch and gate linewidth measurements for SiO2/Si systems (systems with a SiO2 insulating layer and Si substrate) have become necessary. Studying one such system obviously presents different results from that of the widely researched Si/Si structure, because the edge profile of the secondary electron (SE) signal contains contributions from two materials. In this work, several scanning electron microscope (SEM) images and SE profiles of SiO2/Si pitch and trapezoidal line structures, using various geometric and experimental parameters, were simulated through the use of Monte Carlo (MC) methods. It was found that, in contrast to Si/Si systems, the height of the insulating layer cannot be ignored during the evaluation of pitch and linewidth. The thickness (i.e., height) factor does play an important role in the contrast of SEM imaging and the shape of the SE profile in these two-material systems. The mechanism of the influence of insulating layer thickness for imaging was studied in detail. In addition, the SiO2/Si pitch structure with a real rough surface was also studied. This work has significant implications for the study of various kinds of two-material systems and could help to optimize the pitch and gate linewidth measurements.

[Three-dimensional visual assessment and virtual reality study of centrally located hepatocellular carcinoma on the axis of blood vessels].

Objective: To explore a novel method for preoperative precision assessment of centrally located hepatocellular carcinoma(HCC) with blood vessel as axis based on three-dimensional(3D) visualization and virtual reality(VR) technology and its application values. Methods: High-quality thin-layer enhanced CT data were collected from 20 patients with centrally located HCC who treated at First Department of Hepatobiliary Surgery, Zhujiang Hospital, Southern Medical University from March 2017 to August 2018 diagnosed by preoperative examination. There were 18 males and 2 females, aged 28 to 69 years, all of Child-Pugh grade A. First of all, 3D reconstruction was performed by a 3D visualization software; then, the reconstructed 3D image was imported into VR development engine for VR research; afterwards, the analysis and evaluation system with blood vessel as axis was established based on 3D visualization classification of centrally located HCC; therefore, the relationship of the tumor to its major peripheral blood vessels was accurately judged and the surgical planning was formulated. Two images were brought into the operating room for navigation in surgery. The assessments results of preoperative data (CT and (or) MRI) and three-dimensional visualization of blood vessels in VR environment were compared; the values of the preoperative and postoperative hemoglobin, serum albumin and bilirubin were recorded and compared. Chi-square test, t-test and non-parametric test were used for the analysis of counting data, continuous measurement data and non-normal distribution measurement data, respectively. Results: 3D visualization modeling was completed in all of the 20 patients with centrally located HCC. According to the results of 3D visualization classification of centrally located HCC, there were 3 cases of type Ⅰ,1 case of type Ⅱ,4 cases of type Ⅲ,7 cases of type Ⅳ and 5 cases of type Ⅴ; according to the assessment and classification based on blood vessel as the axis, there were 6 cases of type Ⅰa,2 cases of type Ⅰb,2 cases of type Ⅱa,9 cases of type Ⅱb and 1 case of type Ⅱc. All patients underwent successful resection of tumor under the guidance of 3D visualization and VR technology. There were 15 cases whose assessment results based on preoperative CT/MRI were consistent with intraoperative findings, with a coincidence rate of 75.0%(15/20); while in VR environment, the assessment results of 3D visualization with blood vessel as axis were all consistent with the intraoperative findings, with coincidence rate of 100%(20/20). There was a statistically significant difference between the groups (χ(2)=5.714, P=0.017). There was no red blood cell transfusion in all patients during the operation. The preoperative hemoglobin was (128.8±14.9)g/L, and it was (119.8±12.5)g/L on postoperative day 1. There was no significant difference between these two sets of data (t=2.07, P=0.054). No death during the perioperative period and no complications such as hepatic failure, hemorrhage and biliary fistula after operation occurred. Conclusion: Preoperative evaluation based on 3D visualization and VR technology with blood vessel as the axis has significant clinical value for preoperative planning and surgical navigation of centrally located HCC.

[Construction and use of big data for health management].

Population-based lifetime health services rely on health management practice. Collection, management and analysis of big data are highly suitable for the huge population base in China. Nowadays, more and more research focus on the methods, security and ethnicity of health management and big data, and a plenty of instructive results have been made, which could be used to guide the future practice and development. Yichang mode has set a precedent for construction and use of big data for health management.

[Applied study of Singapore occupational semi-quantitative risk assessment technique in occupational health risk assessment in a chair furniture manufacturing enterprise].

Objective: To assess the occupational health risk level of a small-scale furniture manufacturer, and to explore the applicability of the Singapore-developed semi-quantitative occupational risk assessment model for chemical exposure (Singapore model) in small-scale furniture manufacturers, and to provide a basis for the continuous occupational health management of manufacturers. Methods: A small-scale furniture manufacturer was selected as the study subject; an on-site occupational hygiene investigation was performed on the above manufacturer during April to June in 2017, and a risk assessment was carried out using the Singapore model. Results: The assessment results of the Singapore model indicated that risk levels of occupational exposure to harmful chemicals for the key positions in the workplace were inconsistent between the actual exposure level method and the exposure index method except for the following: high risk for formaldehyde exposure (risk level: 3.5 and 4.1, respectively) during woodworking process, high risk for dimethyl benzene exposure (risk level: 3.5 and 3.5, respectively) during burnishing process, medium risk for methyl benzene and dimethyl benzene exposure (risk level: 3.0 and 3.4, respectively) as well as for dimethyl benzene exposure (risk level: 3.0 and 3.3, respectively) during primer coating process, medium risk for methyl benzene exposure (risk level: 3.0 and 3.4, respectively) during gel painting process, and medium risk for cyclohexanone exposure (risk level: 2.8 and 2.8, respectively) during oil polishing process. The exposure index method yielded a higher risk level than the actual exposure level method, especially in the risk level of benzene exposure, which was rated as "high" and "very high" by the former but "low" by the latter. Conclusion: The Singapore model is suitable for risk assessment of occupational exposure to harmful chemicals in small-scale furniture manufacturers, which can provide a basis for further prevention and control measures taken by manufacturers.

Cost-effectiveness analysis of sensitive relapsed small-cell lung cancer based on JCOG0605 trial.

PURPOSE: Since combined strategy with cisplatin, etoposide, and irinotecan has shown the superiority to topotecan alone as second-line chemotherapy in patients with sensitive relapsed small-cell lung cancer, this study aimed to compare these two treatments based on JCOG0605 trail from Chinese cost-effectiveness perspective. METHODS: Basic medical information was derived from a multicenter, open-label, randomized phase III trial (JCOG0605). A Markov model including three health states: progression-free state, progressive disease (PD), and death, was developed to simulate the process of sensitive relapsed small-cell lung cancer. Cost was calculated from the perspective of Chinese society. Sensitivity analyses were applied to explore the impact of essential variables. RESULTS: Treatment with combination chemotherapy was estimated to increase costs by $6947.32 compared with topotecan alone, with a gain of 0.26 quality-adjusted life years (QALYs). Thus, the incremental cost-effective ratio was $26720.46/QALY for combination treatment versus monotherapy, which was beyond the threshold of 3 × the per capita GDP of China, $24423.00. The costs of PD state were the most influential factors to the model. CONCLUSION: The combination chemotherapy with cisplatin, etoposide, and irinotecan was not a cost-effectiveness choice for patients with sensitive relapsed SCLC in China from the cost-effectiveness perspective.

Cost of intervention delivery in a lifestyle weight loss trial in type 2 diabetes: results from the Look AHEAD clinical trial.

OBJECTIVE: The Action for Health in Diabetes (Look AHEAD) trial was a randomized controlled clinical trial to compare the effects of 10 years of intensive lifestyle intervention (ILI) with a control condition of diabetes support and education (DSE) on health outcomes in over 5,000 participants with type 2 diabetes. The ILI had significantly greater weight losses than DSE throughout the trial. The goal of this analysis is to describe the cost of delivering the intervention. METHODS: The ILI was designed to promote weight loss and increase physical activity. It involved a combination of group plus individual intervention sessions, with decreasing frequency of contact over the 10 years. The intervention incorporated a variety of strategies, including meal replacement products, to improve weight loss outcomes. The costs of intervention delivery were derived from staff surveys of effort and from records of intervention materials from the 16 US academic clinical trial sites. Costs were calculated from the payer perspective and presented in 2012 dollars. RESULTS: During the first year, when intervention delivery was most intensive, the annual cost of intervention delivery, averaged (standard deviation) across clinical sites, was $2,864.6 ($513.3) per ILI participant compared with $202.4 ($76.6) per DSE participant. As intervention intensity declined, costs decreased, such that from years 5 to 9 of the trial, the annual cost of intervention was $1,119.8 ($227.7) per ILI participant and $102.9 ($33.0) per DSE participant. Staffing accounted for the majority of costs throughout the trial, with meal replacements and materials to promote adherence accounting for smaller shares. CONCLUSIONS: The sustained weight losses produced by the Look AHEAD intervention were supported by intervention costs that were within the range of other weight loss programmes. Future work will include an evaluation of the cost-effectiveness of the ILI and will contain additional follow-up data.

[First aid system for trauma: development and status].

With the great progress of the economy, the level of industrialization has been increasing year by year, which leads to an increase in accidental trauma accidents. Chinese annual death of trauma is already more than 400 000, which makes trauma the fifth most common cause of death, following malignant tumor, heart, brain and respiratory diseases. Trauma is the leading cause of the death of young adults. At the same time, trauma has become a serious social problem in peace time. Trauma throws great treats on human health and life. As an important part in the medical and social security system, the emergency of trauma system occupies a very important position in the emergency medical service system. In European countries as well as the United States and also many other developed countries, trauma service system had a long history, and progressed to an advanced stage. However, Chinese trauma service system started late and is still developing. It has not turned into a complete and standardized system yet. This review summarizes the histories and current situations of the development of traumatic first aid system separately in European countries, the United States and our country. Special attentions are paid to the effects of the pre- and in-hospital emergency care. We also further try to explore the Chinese trauma emergency model that adapts to the situations of China and characteristics of different regions of China. Our review also introduces the trauma service system that suits the situations of China proposed by Professor Jiang Baoguo's team in details, taking Chinese conditions into account, they conducted a thematic study and made an expert consensus on pre-hospital emergency treatment of severe trauma, providing a basic routine and guidance of severe trauma treatment for those pre-hospital emergency physicians. They also advised to establish independent trauma disciplines and trauma specialist training systems, and to build the regional trauma care system as well as the standards for graded treatment, thus establishing a multiple disciplinary team (MDT) of severe trauma. In this way, we can reduce the mortality and disability risks of severe trauma, improve the quality of patients' life, and save more lives.

Efficacy and cost-effectiveness of second-line chemotherapy in elderly patients with advanced gastric cancer.

PURPOSE: Second-line chemotherapy has been shown to benefit patients with advanced gastric cancer (AGC), extending the overall survival (OS) and progression-free survival (PFS). This study aimed to assess the efficacy and cost-effectiveness of second-line treatment for elderly patients with AGC. METHODS: Medical records and follow-up information of elderly patients (≥70 years) with AGC who received second-line chemotherapy were collected. A Markov model comprising three health states PFS, progressive disease and death was developed to simulate the process of AGC. Cost was calculated from the perspective of Chinese society. Sensitivity analyses were applied to explore the impact of essential variables. RESULTS: Forty-three elderly patients with AGC receiving second-line chemotherapy were included in our study. The median OS was 6.0 months (95% confidence interval (CI) 3.90-8.10) and PFS was 3.1 months (95% CI 1.38-4.82). No treatment-related death occurred. The most frequently drug-related grade 3/4 AEs were diarrhea (2.3%), leukopenia (16.3%) and nausea (7.0%). The incremental cost-effective ratio was $18,223.75/QALY for second-line chemotherapy versus BSC, which was below the threshold of 3× the per capita GDP of China, $23,970.00. CONCLUSION: Second-line chemotherapy was an optimal strategy for elderly AGC patients in China from the efficacy and cost-effectiveness perspective.

Simultaneous detection of 45 fusion genes in leukemia by dual-color fluorescence real-time PCR.

INTRODUCTION: Detection of recurrent genetic abnormalities is of great significance for a refined diagnosis and assessment of prognosis in leukemia. Conventional nested reverse transcription PCR is labor intensive and time-consuming. METHODS: We have developed a novel dual-color TaqMan probe-based real-time PCR method for the simultaneous screening of 45 fusion transcripts in 12 parallel reactions. The method was tested and validated with cell lines carrying known fusion transcripts and patient samples. RESULTS: A multiplex real-time PCR method was successfully developed for rapid detection of 45 fusion genes and validated for 15 of the more commonly detected fusion genes. Intra-assay reproducibility assessed for the most frequent rearrangements ranged from 0.41% to 0.74% for the coefficient of variation (CV) of cycle threshold (Ct) and the interassay reproducibility ranged from 1.62% to 2.83% in five separate experiments. The lowest detection limit for the translocations tested ranged between 1 : 16 000 and 1 : 32 000. Validation of the method with 213 patient samples showed 100% specificity and excellent consistence with conventional nested RT-PCR. CONCLUSION: Overall, we believe that this method is easily applicable, cost-effective, and clinically useful for a rapid screening of fusion genes in the initial diagnostic phase of leukemia. Its use can also be extended to the monitoring of minimal residual disease.

Radial free forearm flap versus pectoralis major pedicled flap for reconstruction in patients with tongue cancer: Assessment of quality of life.

BACKGROUND: This study investigated the quality of life of Chinese patients with tongue cancer who had undergone immediate flap reconstruction surgery. In addition, we compared 2 groups of patients: those who had received radial forearm free flap (RFFF) surgery and others who had received pectoralis major myocutaneous flap (PMMF) surgery. MATERIAL AND METHODS: Patients who received RFFF or PMMF reconstruction after primary tongue cancer treated with total and subtotal tongue resection were eligible for the current study. The patients' demographic data, medical history, and quality of life scores (14-item Oral Health Impact Profile (OHIP-14) and the University of Washington Quality of Life (UW-QOL) questionnaires) were collected. RESULTS: A total of 41 of 63 questionnaires were returned (65.08%). There were significant differences between the 2 groups in the gender (p< .05). Patients reconstructed with RFFF performed better in the shoulder domains, in addition to worse appearance domains. CONCLUSIONS: Using either RFFF or PMMF for reconstruction of defects after tongue cancer resection significantly influences a patient's quality of life. Data from this study provide useful information for physicians and patients during their discussion of reconstruction modalities for tongue cancers.

A new pencil beam model for photon dose calculations in heterogeneous media.

The pencil beam method is commonly used for dose calculations in intensity-modulated radiation therapy (IMRT). In this study, we have proposed a novel pencil model for calculating photon dose distributions in heterogeneous media. To avoid any oblique kernel-related bias and reduce computation time, dose distributions were computed in a spherical coordinate system based on the pencil kernels of different distances from source to surface (DSS). We employed two different dose calculation methods: the superposition method and the fast Fourier transform convolution (FFTC) method. In order to render the superposition method more accurate, we scaled the depth-directed component by moving the position of the entry point and altering the DSS value for a given beamlet. The lateral components were thus directly corrected by the density scaling method along the spherical shell without taking the densities from the previous layers into account. Significant computation time could be saved by performing the FFTC calculations on each spherical shell, disregarding density changes in the lateral direction. The proposed methods were tested on several phantoms, including lung- and bone-type heterogeneities. We compared them with Monte Carlo (MC) simulation for several field sizes with 6 MV photon beams. Our results revealed mean absolute deviations <1% for the proposed superposition method. Compared to the AAA algorithm, this method improved dose calculation accuracy by at least 0.3% in heterogeneous phantoms. The FFTC method was approximately 40 times faster than the superposition method. However, compared with MC, mean absolute deviations were <3% for the FFTC method.

Monte Carlo simulation of CD-SEM images for linewidth and critical dimension metrology.

In semiconductor industry, strict critical dimension control by using a critical dimension scanning electron microscope (CD-SEM) is an extremely urgent task in near-term years. A Monte Carlo simulation model for study of CD-SEM image has been established, which is based on using Mott's cross section for electron elastic scattering and the full Penn dielectric function formalism for electron inelastic scattering and the associated secondary electron (SE) production. In this work, a systematic calculation of CD-SEM line-scan profiles and 2D images of trapezoidal Si lines has been performed by taking into account different experimental factors including electron beam condition (primary energy, probe size), line geometry (width, height, foot/corner rounding, sidewall angle, and roughness), material properties, and SE signal detection. The influences of these factors to the critical dimension metrology are investigated, leading to build a future comprehensive model-based library.

Monte Carlo simulation of secondary electron images for real sample structures in scanning electron microscopy.

Monte Carlo simulation methods for the study of electron beam interaction with solids have been mostly concerned with specimens of simple geometry. In this article, we propose a simulation algorithm for treating arbitrary complex structures in a real sample. The method is based on a finite element triangular mesh modeling of sample geometry and a space subdivision for accelerating simulation. Simulation of secondary electron image in scanning electron microscopy has been performed for gold particles on a carbon substrate. Comparison of the simulation result with an experiment image confirms that this method is effective to model complex morphology of a real sample.