Objective:To explore high-risk sexual behaviors of HIV/AIDS and related factors in young students in Guangzhou.Methods:A cross-sectional survey was conducted in 5 different types of Guangzhou colleges by convenience sampling with minimum number of classes per grade and 600 samples per school from September to November 2021. The R 4.2.2 software was used to consolidate databases. Simultaneously, a logistic regression model and a decision tree algorithm model, stratifying by whether sexual behaviors had occurred before, were constructed. In each layer, the prediction performance of the two models was evaluated through area under receiver operating characteristic and the confusion matrix, and then the model with high prediction performance was retained.Results:A total of 7 346 students were surveyed. The proportion of the respondents reporting sexual experience were 9.08% (667/7 346), in whom 26.24% (175/667) had risky sexual activity in the past year. The decision tree algorithm model performs well in predicting whether high-risk sexual behaviors have occurred in the past year. When the complexity parameter value is 0.018, and nsplit reaches 4, which means there are 5 leaf nodes in the model, the cross error of the tree will be the smallest. The first best grouping variable in the decision tree was whether to use condoms throughout the first sexual behavior. If condoms were used at their sexual debut, but homosexual practices have occurred in the past year, the probability of risky sexual behavior will increase. If homosexual practices have not occurred in the past year, but the age of sexual debut was below 18 years old while the period of HIV education was after high school, the probability of risk sexual behavior will also increase.Conclusions:AIDS-related risky behaviors of young students still deserved attention. The experience of sexual debut and whether AIDS-related health education has been received before the sexual debut were significant predictors for the occurrence of high-risk sexual behavior. The decision tree algorithm model has particular applicability for predicting and screening potential risk populations.

Objective:To investigate the safety and therapeutic effect of split liver transplantation (SLT) in clinical application.Methods:This is a retrospective case-series study. The clinical data of 203 consecutive SLT, 79 living donor liver transplantation (LDLT) and 1 298 whole liver transplantation (WLT) performed at the Third Affiliated Hospital of Sun Yat-sen University from July 2014 to July 2023 were retrospectively analyzed. Two hundred and three SLT liver grafts were obtained from 109 donors. One hundred and twenty-seven grafts were generated by in vitro splitting and 76 grafts were generated by in vivo splitting. There were 90 adult recipients and 113 pediatric recipients. According to time, SLT patients were divided into two groups: the early SLT group (40 cases, from July 2014 to December 2017) and the mature SLT technology group (163 cases, from January 2018 to July 2023). The survival of each group was analyzed and the main factors affecting the survival rate of SLT were analyzed. The Kaplan-Meier method and Log-rank test were used for survival analysis.Results:The cumulative survival rates at 1-, 3-, and 5-year were 74.58%, 71.47%, and 71.47% in the early SLT group, and 88.03%, 87.23%, and 87.23% in the mature SLT group, respectively. Survival rates in the mature SLT group were significantly higher than those in the early SLT group ( χ2=5.560, P=0.018). The cumulative survival rates at 1-, 3- and 5-year were 93.41%, 93.41%, 89.95% in the LDLT group and 87.38%, 81.98%, 77.04% in the WLT group, respectively. There was no significant difference among the mature SLT group, the LDLT group and the WLT group ( χ2=4.016, P=0.134). Abdominal hemorrhage, infection, primary liver graft nonfunction,and portal vein thrombosis were the main causes of early postoperative death. Conclusion:SLT can achieve results comparable to those of WLT and LDLT in mature technology liver transplant centers, but it needs to go through a certain time learning curve.

Objective:To investigate the safety and therapeutic effect of split liver transplantation (SLT) in clinical application.Methods:This is a retrospective case-series study. The clinical data of 203 consecutive SLT, 79 living donor liver transplantation (LDLT) and 1 298 whole liver transplantation (WLT) performed at the Third Affiliated Hospital of Sun Yat-sen University from July 2014 to July 2023 were retrospectively analyzed. Two hundred and three SLT liver grafts were obtained from 109 donors. One hundred and twenty-seven grafts were generated by in vitro splitting and 76 grafts were generated by in vivo splitting. There were 90 adult recipients and 113 pediatric recipients. According to time, SLT patients were divided into two groups: the early SLT group (40 cases, from July 2014 to December 2017) and the mature SLT technology group (163 cases, from January 2018 to July 2023). The survival of each group was analyzed and the main factors affecting the survival rate of SLT were analyzed. The Kaplan-Meier method and Log-rank test were used for survival analysis.Results:The cumulative survival rates at 1-, 3-, and 5-year were 74.58%, 71.47%, and 71.47% in the early SLT group, and 88.03%, 87.23%, and 87.23% in the mature SLT group, respectively. Survival rates in the mature SLT group were significantly higher than those in the early SLT group ( χ2=5.560, P=0.018). The cumulative survival rates at 1-, 3- and 5-year were 93.41%, 93.41%, 89.95% in the LDLT group and 87.38%, 81.98%, 77.04% in the WLT group, respectively. There was no significant difference among the mature SLT group, the LDLT group and the WLT group ( χ2=4.016, P=0.134). Abdominal hemorrhage, infection, primary liver graft nonfunction,and portal vein thrombosis were the main causes of early postoperative death. Conclusion:SLT can achieve results comparable to those of WLT and LDLT in mature technology liver transplant centers, but it needs to go through a certain time learning curve.

Objective:To analyze the relationship between volumetric-modulated arc therapy (VMAT) plan delivery time and machine parameters, aiming to exploring the methods of shortening plan delivery time by improving machine performance.Methods:A total of 25 treatment plans of patients who completed VMAT in Cancer Hospital of Chinese Academy of Medical Sciences from March 2017 to July 2017 were selected by simple random sampling. The machine parameters were subject to modeling by using software. For conventional fraction and hyperfraction plans, the parameters that have the strongest limitations on delivery time were simulated by observing the relative change of delivery time in increasing the gantry speed, dose rate, multi-leaf collimator (MLC) leaf speed independently. The speed of the parameter which has the strongest limitations was simulated to obtain the dynamic changes of the limitation strength of these three parameters on the treatment time. The measured data were subject to statistical description.Results:For conventional segmentation plans with 2 Gy fractional dose, the gantry speed had the strongest limitations on delivery time and the MLC leaf speed had the strongest limitations on delivery time instead when the gantry speed was increased by 15%. For hyperfraction plans with 5 Gy fractional dose, dose rate had the strongest limitations on delivery time and the gantry speed had the strongest limitations when the gantry speed was increased by 12%.Conclusions:The relationship between VMAT plan delivery time and machine parameters depends on the characteristics of each plan. The relationship between different machine parameters and plan characteristics should be considered when shortening plan delivery time by improving the machine parameters.

Objective:To investigate the risk perception for risky behavior of HIV/AIDS infection among young students and to analyze the related influencing factors.Methods:A cross-sectional survey was conducted in 5 different types of Guangzhou colleges from September to November 2021, in which convenience sampling and a minimum number of classes per grade and 600 samples per school were used according to the national unity program. Disordered multi-classification logistic regression was used to construct a risk perception model and analyze influencing factors in different risk perception levels.Results:A total of 7 346 young students were surveyed, and most rated themselves at low risk of HIV/AIDS infections (90.58%, 6 654/7 346). A total of 89.10% (6 545/7 346) of subjects' perception of their HIV/AIDS infection risk was consistent with their risk behavior, while 10.90% (801/7 346) was inconsistent. Among those inconsistent subjects, 19.10% (153/801) showed underestimating their risk , while 80.90% (648/801) seen overestimating their risk. Disordered multi-classification logistic regression analysis showed that, after controlling for other factors, compared with the non-sexual group, respondents whose first sex age under 18 had a higher rate of underestimating their risk of infection ( OR=129.39, 95% CI: 73.28-228.48), as well as a higher rate of overestimated their risk of infection ( OR=1.76, 95% CI: 1.04-2.99). First sexual intercourse at age 18 or older was a risk factor for underestimating risk ( OR=70.56, 95% CI: 42.72-116.53), but was not statistically associated with overestimating risk. Being female, other school type, non-heterosexual orientation, and self-rated HIV-related knowledge as fair or no knowledge were risk factors for overestimating risk but were not statistically associated with underestimating risk. Conclusions:Overall, young students in universities of Guangzhou have a good risk perception of HIV/AIDS infection. Individual factors, education factors and sexual experience will influence students' risk perception of HIV/AIDS infection. Raising the awareness rate of HIV/AIDS knowledge and delaying the age of first sexual intercourse will improve the risk perception ability of young students.

Objective To analyze the distribution features of the Bragg peak of carbon ion beams in materials using SRIM software, and to explore the use of computed tomography (CT) number to calculate the incident energy of carbon ion beams. Methods SRIM software was used to study the travel of carbon ion beams (100 to 300 MeV/u) in different equivalent materials, and analyze the effects of the incident energy of carbon ion beams and the type and thickness of equivalent materials on the depth of the Bragg peak of carbon ion beams. Origin 2017 was used to analyze the functional relationship between CT number and water-equivalent Bragg peak depth ratio (Di) through data fitting. Results The ratios of the Bragg peak depths in equivalent materials to that in water almost stayed constant with the increase in the incident energy of carbon ion beams. Through the functional relation between CT number and D_i, the Bragg peak depth of a carbon ion beam of a given energy in an equivalent material could be converted to the equivalent Bragg peak depth in water. Conclusion With the water-equivalent Bragg peak depth ratio D_i and CT number of different volume units of human tissues, the equivalent Bragg peak depth in water required for the Bragg peak to fall in the tumor can be accurately calculated, which can be used to reversely infer the needed incident energy of carbon ion beams.

Sudden sensorineural hearing loss (SSNHL) refers to the sudden and unexplained sensorineural hearing loss within 72 h and a decrease in hearing of ≥30 dB affecting at least 3 consecutive frequencies. It is one of the common emergencies in neurology and otolaryngology. Early etiological evaluation and systematic and targeted treatment are very important for delaying the progression of SSNHL and restoring hearing. Recent studies have shown that SSNHL overlaps with vascular risk factors of ischemic stroke, and may predict the risk of ischemic stroke. SSNHL may be one of the clinical manifestation and even the prodromal symptoms of ischemic stroke, especially the infarction of the blood supply area of the anterior inferior cerebellar artery or its branch internal auditory artery. Although these factors can not fully reveal the relationship between SSNHL and ischemic stroke, they are enough to warn clinicians that they should consider the possibility of ischemic stroke when receiving patients with SSNHL. Screening of vascular risk factors for patients with SSNHL as early as possible is helpful to avoid the risk of recurrence of ischemic stroke.

Objective: To analyze the status of follow-up cell testing of HIV/AIDS cases among young students aged 15-24 in Guangdong Province from 2008 to 2019. Methods: Using the historical database downloaded from the AIDS Comprehensive Prevention and Control Information System from January 1, 2018 to December 31, 2019, eligible newly discovered cases were screened by year and were linked with follow-up database. Joinpoint regression model and trend test were used to explore the annual changes in the follow-up and CD4 testing status, and Logistic regression was used to analyze relevant influencing factors. Results: The number of infected students showed a rapid upward trend before 2015(APC=41.7，β=0.3，P<0.01), and the growth rate slowed down(APC=3.6，β=-0.3，P<0.01). The proportion of follow-up and CD4 testing completed within one year increased from 58.3% in 2008 to 93.6% in 2019, and the timely detection rate increased from 33.3% in 2008 to 86.2% in 2019. The Cochran Armitage trend test was statistically significant. Pairwise comparison test showed time trends of the idnex differed in regions and education groups (Z=4.7，8.7，9.8，P<0.01). The Pearl River Delta region, cases from other cities in the province, with precise transmission routes, from voluntary counseling and testing, and cases flowing within the province, the proportion of follow up and testing completed within one year is relatively high (P<0.05). Conclusion The growth rate of HIV/AIDS cases among young students aged 15-24 in Guangdong Province has slowed down in recent years. The route of infection, source and flow of cases affect follow-up and testing compliance. And to do a good job of referrals for off-site mobility, and explore and promote student-friendly VCT service models.

Objective:To design and implement a plan data archiving system (PDAS) for radiotherapy treatment, in order to improve the efficiency of plan archiving and avoid plan data loss.Methods:The original plan file in the treatment planning system (TPS) was read and parsed, and the record and verification (R&V) system database was accessed to obtain the patient′s treatment record. PDAS processed all parameters involved in the plan archiving and saved the structured data into a local database. PDAS included two major modules, the plan archiving module and the plan loss detection module. The former could be divided into four parts, data sorting, data compression, archiving check and plan recovery. For different modules, we designed corresponding logic rules and wrote programs to realize the system. Compared with the plan data of manual archiving, the clinical application effect of PDAS was evaluated.Results:Each module of PDAS was developed and implemented. During 31 months of clinical application, the system was stable, and 17 614 plans were archived. Compared with manual archiving, PDAS improved the archiving efficiency significantly and reduced the plan loss rate from 0.004 or so to 0.Conclusions:PDAS can improve the efficiency of plan archiving and ensure the security and integrity of plan data.

Objective:To establish the basic procedures of the application of optical surface monitoring system (OSMS) in the deep inspiration breath hold (DIBH) radiotherapy for patients with left sided breast cancer and compare the performance of OSMS and cone-beam CT (CBCT) in the determination of the set-up errors of DIBH radiotherapy for patients with left sided breast cancer.Methods:Twenty patients with left sided breast cancer received DIBH radiotherapy. Through the registration of CBCT images with the planning CT images, and the registration of OSMS radiography images with the outer contour of the body surface, translational set-up errors and rotational errors were determined along the lateral-medial ( Rx), superior-inferior ( Ry) and anterior-posterior ( Rz) directions. Pearson correlation analysis was performed to evaluate the correlation of the set-up errors determined by two methods, and Bland- Altman plot analysis was used to assess the coincidence of these two methods. Results:Two methods were positively correlated. The Rz volume was 0.84, 0.74 and 0.84 in the x, y and z directions, and 0.65, 0.41 and 0.54 in the Rx, Ry and Rz directions, respectively (all P<0.01). The 95% CI of agreement were within preset 5 mm tolerance (-0.37-0.42cm, -0.39-0.41cm, -0.29-0.49cm ) in x, y and z directions for two methods. The 95% CI of agreement were within preset 3 ° tolerance -2.9°-1.4°, -2.6°-1.4°, -2.4°-2.5°in Rx, Ry and Rz directions for two methods. The system errors of 20 patients with left sided breast cancer receiving DIBH radiotherapy were <0.18cm and the random errors were <0.24cm. Conclusions:OSMS is equivalent to CBCT in the determination and stimulation of set-up errors for patients with left sided breast cancer receiving DIBH radiotherapy. The combination of CBCT and OSMS is a safe and reliable method.