The characteristics of high energy cosmic-ray muons make them strongly penetrative in materials. It has great potential to monitor the stability of buildings by reconstructing the tracks of cosmic-ray muons. In this work, a buildings stability monitoring system based on plastic scintillator strips is proposed. The monitoring system consists of a single-plane upper telescope to record the incoming track of a muon, and a three-plane lower telescope to track its outgoing trajectory. Every detector plane is formed by orthogonally placed scintillator strips. The impacts of the scintillator geometry and spatial placement on the stability monitoring precision are carefully studied using Geant4 simulations. A sub-millimeter position resolution is achievable by selecting a proper data taking time. The triangular scintillator strips always outperform rectangular ones of the same size and placement. Two empirical formulas have been derived to quantitatively estimate the position resolution with respect to the abovementioned influential factors. In addition, the comprehensive effects of multiple parameters are also studied. Accordingly, triangular scintillator strips will be utilized in the construction of a real monitoring system with better performance and less detection channels. The simulation study in this work can provide good guidance for the manufacturing of triangular strips and their experimental configurations.

Muon spin rotation/relaxation/resonance (μSR) spectroscopy uses highly polarized muons to study the microscopic magnetic structure and dynamics of condensed matter. In addition to the five existing muon facilities, the first Chinese muon source, the Muon station for sciEnce technoLOgy and inDustrY (MELODY), is planned to be constructed in Phase II of the China Spallation Neutron Source (CSNS). It aims to provide intense and pulsed muon beams to conduct μSR applications in multiple disciplines. The group from the University of Science and Technology of China (USTC) participated in the collaboration with the CSNS accelerator group for the construction of the muon source. The USTC group led the research and development (R&D) of the first-generation photomultiplier tube (PMT)-based μSR spectrometer, and the design of the second-generation silicon photomultiplier (SiPM)-based spectrometer. The PMT-based spectrometer is a 128-channel prototype to demonstrate and develop key detector and electronics technologies for the planned MELODY. After several iterative designs and updates of detectors and electronics, the spectrometer prototype achieved a 7-ns dead time, which can record more than 12 positrons per channel per pulse according to the ISIS running experience. Based on the technologies developed from the first-generation spectrometer, the second-generation spectrometer will use SiPMs to accommodate over 2500 detector units to make better use of muons in MELODY. The two generation developments of Chinese μSR spectrometers will greatly advance the construction of MELODY, and provide high-quality data for users to interpret material properties in the near future.

Cosmic muon imaging (muography) has gained popularity in recent years for density reconstruction in various applications. However, evaluations of image quality in reconstructed images have been lacking. This work addresses this gap by applying muon transmission imaging to a teaching building on a university campus. Multiple impacts on reconstruction image quality, including filtering methods, total counts, building thickness thresholds, and reconstruction formulas, were integrally studied. The area under the curve (AUC) of the receiver operating characteristic analysis and mean squared error (MSE) were calculated to quantitatively evaluate and optimize these parameters. Based on the simulation using the Geant4 toolkit, the recommended parameters for the building model were median filtering, a total count of 5×104 in the building region, a thickness threshold of 3 m, and either the constant energy loss method or cubic polynomial form fitting method. Implementing these parameters in the experimental data analysis, the reconstructed image well revealed the inner structure of the teaching building from the view angle of the detector. The optimization of the two-dimensional (2D) reconstruction method facilitates the detection of hidden cavities or regions with abnormal density in large-scale objects.

A position-sensitive multi-compound inspection methodology using Muonic X-ray Emission Spectroscopic (������-XES) element analysis is proposed due to the ability of the coded aperture imaging technique to maintain the relative intensity of X-rays. This methodology can simultaneously obtain the atomic ratio of different regions of the sample under study. Therefore, the mis-judgements of material compositions caused by averaging results can be reduced. The atomic ratio reconstruction quality is mainly related to X-ray counts (������x), atomic ratios of materials (������T), size and placement of sample blocks. In this work, several different sample blocks made of light elements were designed by GEANT4 Monte Carlo (MC) simulations to study the influences of ������x, ������T, size and placement of sample on atomic ratio reconstruction quality. In the inspection of multiple sample blocks, this methodology successfully distinguished the material compositions from different regions by reconstructing the atomic ratios of C/N and O/N. Moreover, this methodology can clearly image element blocks larger than 2 x 2 mm2.

Cosmic-ray muon imaging (muography) has been applied in various fields in recent years, in which plastic scintillators are one of the frequently selected detectors internationally. Therefore, a triangular scintillator strip based muography detection system has been proposed in the development of the μ Scattering and Transmission imaging faCility ( μ STC). Before the mass production of detector units, this work studied the impacts of multiple factors on the light collection efficiency (LCE) and the position resolution ( σ ) of plastic scintillators. These factors include configurations of wavelength shifting (WLS) fibers, fiber grooves on scintillators, coupling optical glues and silicon photomultiplier (SiPM) readout mode. According to the simulated results, an empirical formula was proposed to quantitatively describe the relation between the LCE and σ , which has seldom been studied before. In this formula, σ reduces as a power-law function of the LCE. The SiPM readout mode (single-end or double-end output) and fiber groove treatments show no significant influence on the σ -LCE relation. LCE variations due to different factors lead to a difference in σ of less than 0.2 mm in the whole range of LCE. Accordingly, these factors are nearly equivalent in the improvement of detector position resolution. In comparison, the muon hit position reconstruction method nearly halves the σ after using angular and gap corrections. Thus, a better reconstruction method shows greater importance than the efforts made to increase LCEs. The simulation study in this work will provide good references for the construction of plastic scintillators of the μ STC platform in the near future.

A highly segmented muon spin rotation/relaxation/resonance (μSR) spectrometer with over 2500 channels has been proposed in the construction of Phase II of the China Spallation Neutron Source (CSNS). Plastic scintillators are chosen as the detector material due to their high sensitivity to charged particles and good flexibility to various geometries. Gamma-ray sources are commonly used to calibrate the light yield of plastic scintillators. Accordingly, a derivative method has been developed to efficiently locate the Compton edge in gamma-ray spectra. In this method, the minimum and width of the derivative data are regarded as the position of the Compton edge and an estimation of energy resolution, respectively. Both experiments and simulations demonstrate the good reliability of this method for Compton edge positioning and energy resolution characterization. The derived Compton edge shows a systematic shift to the right of its real location. The relative shift is proportional to the energy resolution with a factor of ∼0.13. The assumed energy resolution should be corrected by a factor of ∼1.19 which is confirmed by inorganic scintillator measurements. In the measurement of plastic scintillators, the assumed Compton edge and energy resolution can well reproduce the energy response spectra for different types of gamma-ray sources.

Patients with lung cancer have high incidence of venous thromboembolism (VTE), which might aggravate the overall survival. This prospective real-world study aims to investigate the incidence of VTE and determine the VTE-high-risk population of lung cancer.

A new muon source has been proposed to conduct muon spin rotation/relaxation/resonance ($μ$SR) measurements at China Spallation Neutron Source (CSNS). Only 1 Hz of the CSNS proton beams (25 Hz in total) will be allocated for muon production. To make better use of muons in every pulse, an ultrahigh-array $μ$SR spectrometer (UHAM) with thousands of detector channels is under design. Due to such a high granularity of detectors, multiple counting events generated from particle scattering or spiral motions of positrons in a strong longitudinal field should be carefully considered in the design. Six different structures were modeled and simulated based on two types of angular orientations (parallel arrangement and pointing arrangement) and three kinds of spectrometer geometries (cylinder, cone and sphere). A quality factor, $Q$, was proposed to evaluate the performance of these structures by integrating their impacts on the overall asymmetry, the counting rate and the percentage of multiple counts. According to the simulation, the conical structure with detectors pointing to the sample has the highest $Q$ in both zero field and longitudinal field. The results also show that all kinds of structures cannot be operated under strong longitudinal fields with a strength over 2 T. The full simulation of a $μ$SR spectrometer can provide good guidance for the construction of the UHAM in the upcoming upgrade of CSNS.

In applications of transmission muography for large objects, plastic scintillator strips with triangular or rectangular cross-sections are frequently selected to construct imaging detectors. Triangular scintillator strips have a better position resolution over those of rectangular ones by a factor of similar to 3.5 with the same width. The big difference has been carefully studied using Geant4. Simulations show a good agreement with those of existing muography instruments. The position resolution is influenced by the geometry (the size and base angle of triangular strips) and the energy resolution of scintillators, and angles of incoming muons. Two empirical formulas have been proposed to quantitatively estimate the position resolution with respect to the abovementioned influential factors. Perpendicularly and randomly (real angular distribution) incoming muons are considered separately in them. A more widely spread angular distribution of muons can make the position resolution worse. For commonly used triangular scintillator strips with a base angle of 45 degrees, the ratio of the triangle base length to the position resolution is almost fixed to similar to 12 varying the base length or energy resolution if an uncorrected Centre of Gravity (CoG) method is used. Such a ratio has a potential to be increased by a factor of similar to 2 if the CoG method is corrected with the muon incoming angle. The influence of the energy resolution on the position resolution can be ignored.

Objective: To understand the current practice of preoperative bowel preparation in elective colorectal surgery in China. Methods: A cross-sectional questionnaire survey was conducted through wechat. The content of the questionnaire survey included professional title of the participants, the hospital class, dietary preparation and protocol, oral laxatives and specific types, oral antibiotics, gastric intubation, and mechanical enema before elective colorectal surgery. A stratified analysis based on hospital class was conducted to understand their current practice of preoperative bowel preparation in elective colorectal surgery. Result: A total of 600 questionnaires were issued, and 516 (86.00%) questionnaires of participants from different hospitals, engaged in colorectal surgery or general surgeons were recovered, of which 366 were from tertiary hospitals (70.93%) and 150 from secondary hospitals (29.07%). For diet preparation, the proportions of right hemicolic, left hemicolic and rectal surgery were 81.59% (421/516), 84.88% (438/516) and 84.88% (438/516) respectively. The average time of preoperative dietary preparation was 2.03 days. The study showed that 85.85% (443/516) of surgeons chose oral laxatives for bowel preparation in all colorectal surgery, while only 4.26% (22/516) of surgeons did not choose oral laxatives. For mechanical enema, the proportions of right hemicolic, left hemicolic and rectal surgery were 19.19% (99/516), 30.04% (155/516) and 32.75% (169/516) respectively. Preoperative oral antibiotics was used by 34.69% (179/516) of the respondents. 94.38% (487/516) of participants were satisfied with bowel preparation, and 55.43% (286/516) of participants believed that preoperative bowel preparation was well tolerated. In terms of preoperative oral laxatives, there was no statistically significant difference between different levels of hospitals [secondary hospitals vs. tertiary hospitals: 90.00% (135/150) vs. 84.15% (308/366), χ(2)=2.995, P=0.084]. Compared with the tertiary hospitals, the surgeons in the secondary hospitals accounted for higher proportions in diet preparation [87.33% (131/150) vs. 76.78% (281/366), χ(2)=7.369, P=0.007], gastric intubation [54.00% (81/150) vs. 36.33% (133/366), χ(2)=13.672, P<0.001], preoperative oral antibiotics [58.67% (88/150) vs. 24.86% (91/366), χ(2)=12.259, P<0.001] and enema [28.67% (43/150) vs. 15.30% (56/366), χ(2)=53.661, P<0.001]. Conclusion: Although the preoperative bowel preparation practice in elective colorectal surgery for most of surgeons in China is basically the same as the current international protocol, the proportions of mechanical enema and gastric intubation before surgery are still relatively high.

Objective: To investigate the feasibility and safety of the medial approach "four-step method" in the laparoscopic mobilization of splenic flexure. Methods: A retrospective cohort study was performed. Clinical data of 157 colorectal cancer patients undergoing the medial approach "four-step method" in the laparoscopic mobilization of splenic flexure at Gastrointestinal Surgical Department of Guangdong Provincial People's Hospital from July 2015 to June 2018 were retrospectively analyzed. Of 157 cases, 17 were transverse colon cancer, 94 were descending colon cancer, 25 were sigmoid cancer and 21 were rectal cancer; 89 were male and 68 were female; mean age was (61.8±10.3) years and mean body mass index was (23.2±3.7) kg/m(2). The medial approach "four-step method" in the laparoscopic mobilization of splenic flexure was performed as follows: (1) The root vessels were treated with the "provocation" technique to expand the Toldt's gap. This expansion was extended from the lateral side to the peritoneum reflex of left colonic sulcus, from the caudal side to the posterior rectal space, and from the cephalad side to the lower edge of pancreas. (2) The left colonic sulcus was mobilized, converging with the posterior Toldt's gap. Mobilization was carried out from cephalad side to descending colon flexure, freeing and cutting phrenicocolic ligament and splenocolic ligament, and from caudal side to peritoneal reflex. (3) Gastrocolic ligament was moblized. Whether to enter the great curvature of stomach omentum arch when the gastrocolic ligament was cut, that was, whether to clean the fourth group of lymph nodes, should be according to the tumor site and whether serosal layer was invaded. (4) Transverse mesocolon was moblized and transected at the lower edge of the pancreatic surface, merging with the posterior Toldt's gap, and from lateral side to lower edge of the pancreatic body, merging with the lateral left paracolonic sulcus. Safety and short-term clinical efficacy of this surgical procedure was summarized. Results: All the patients completed this procedure. During operation, 3 cases were complicated with organ injury, including 1 case of colon injury, 1 case of spleen injury and 1 case of pancreas injury. No operative death and conversion to open surgery was found. The average operation time was (147.5±35.1) minutes, the average intra-operative blood loss was (40.8±32.7) ml and the average number of harvested lymph node was (16.1±5.8), including (4.0±2.3) of positive lymph nodes. The first exhaust time after surgery was (41.3±20.6) hours, the fluid intake time was (1.5±1.3) days, the postoperative hospital stay was (5.2±2.3) days. Eight (5.1%) cases developed postoperative complications, and all were improved and discharged after conservative treatments. According to the TNM classification system, postoperative pathology revealed that 31 patients were stage I, 51 were stage II, 53 were stage III, 22 were stage IV. Conclusion: The medial approach "four-step method" is safe and feasible, which can effectively decrease the operation difficulty of the laparoscopic mobilization of the splenic flexure.