Transmission X-ray tubes are relatively new devices characterized by portability,suitability for miniaturization,and low requirements for shielding,making them ideal radiation sources for kilovoltage X-ray therapy.However,their application in radiotherapy remains underexplored.An electron target model of a transmission X-ray tube is developed using the Monte Carlo toolkit TOPAS 3.8.1.The study investigates the effect of tungsten target thickness on X-ray output efficiency,finding that a tube voltage of 50 kV and a tungsten thickness of 1.4 μm yields the highest emission efficiency.Based on the energy spectrum at this optimal efficiency,polynomial fitting approach is applied to determine the corresponding aluminum filter thickness for mean energies ranging from 20 keV to 35 keV,achieving a mean fitting error of 0.91%.Next,the study simulates dose deposition in a water phantom for spectra with different mean energies and various source-to-surface distances,and plots percent-depth-dose curves,relative normalized dose-depth curves,and relative normalized dose histograms under each treatment condition.Finally,the simulated results are compared with experimental data from the intraoperative radiotherapy system Intrabeam and the superficial X-ray therapy unit SRT-100,obtaining average relative errors of 3.71%and 4.38%,respectively.These findings provide a theoretical foundation for further optimization of transmission X-ray tubes in kilovoltage radiotherapy.

Transmission X-ray tubes are relatively new devices characterized by portability,suitability for miniaturization,and low requirements for shielding,making them ideal radiation sources for kilovoltage X-ray therapy.However,their application in radiotherapy remains underexplored.An electron target model of a transmission X-ray tube is developed using the Monte Carlo toolkit TOPAS 3.8.1.The study investigates the effect of tungsten target thickness on X-ray output efficiency,finding that a tube voltage of 50 kV and a tungsten thickness of 1.4 μm yields the highest emission efficiency.Based on the energy spectrum at this optimal efficiency,polynomial fitting approach is applied to determine the corresponding aluminum filter thickness for mean energies ranging from 20 keV to 35 keV,achieving a mean fitting error of 0.91%.Next,the study simulates dose deposition in a water phantom for spectra with different mean energies and various source-to-surface distances,and plots percent-depth-dose curves,relative normalized dose-depth curves,and relative normalized dose histograms under each treatment condition.Finally,the simulated results are compared with experimental data from the intraoperative radiotherapy system Intrabeam and the superficial X-ray therapy unit SRT-100,obtaining average relative errors of 3.71%and 4.38%,respectively.These findings provide a theoretical foundation for further optimization of transmission X-ray tubes in kilovoltage radiotherapy.

Objective: To analysis the epidemiological characteristics of overweight and obesity among middle school students in Taizhou from 2013 to 2020, to provide support for prevention and control efforts. Methods: Through stratified sampling, one primary school, one junior middle school and one senior high school were randomly selected from nine counties (cities and districts) in Taizhou, and continuous monitoring was conducted in all participants Height, weight and other variables were assessed and body mass index was calculated. The epidemic characteristics were analyzed according to the detection rate, fixed base ratio, sequential growth ratio and average growth rate. Results: From 2013 to 2020, the overall overweight rate among primary and middle school students in Taizhou was 14.5%(36 592/252 583), and the obesity rate was 11.2%(28 256/252 583). The rates of overweight and obesity increased, with average annual growth rates of 1.9% and 5.5%, respectively; thus, the rate of obesity increased more rapidly. The obesity rate was higher among boys (13.2%) than girls (9.0%)( χ 2=1 119.57, P <0.01), and the average annual growth rate was higher among girls than boys (6.1%, 5.2%, respectively). The rate of overweight among boys (17.6%) was higher than that among girls (10.9%)( χ 2=2 307.35, P <0.01). The average annual growth rate of overweight in girls was 2.3% and 1.7%, respectively. The obesity rate among primary school students (17.5%) was higher than that among middle school (9.7%) and high school (4.9%) students( χ 2=7 291.33, P <0.01). The average annual growth rate in students in middle school was fastest, followed by those in high and primary schools (6.5%, 3.9% and 2.6%, respectively). The rate of overweight in primary school students ( 15.8 %) was higher than that in middle school students (15.3%), and both were higher than that in high school students(12.2%)( χ 2=521.06, P <0.01). The average annual growth rate was also fastest in students in middle school, followed by high and primary schools (2.4%, 2.2% and 0.6%, respectively). Conclusion The detection rate of overweight and obesity among primary and middle school students in Taizhou is high and increasing rapidly, indicating high pressure on prevention and control. Boys and primary school students are the key target groups for prevention and control. Comprehensive prevention and control strategies should be adopted specifically.