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Objective To analyze the failure and processing methods of helical tomotherapy multileaf collimator (MLC) and summarize relevant maintenance experience,aiming to accurately identify the faulty parts,shorten the downtime and enhance the work time.Methods The failure data of the helical tomotherapy MLC system in the past 48 months were analyzed to identify the common faulty parts,causes and processing methods.Results During the previous 48 months,the MLC failure occurred for 20 times,11 times for air compressor failure,4 times for position verification board failure,twice for leaf driver failure,twice for cushion valve failure and once for the slip of leaf position verification rod.The MLC failure was significantly correlated with the humidity of high-pressure gas.The work time of machine exerted significant effect upon the service time of MLC parts.Conclusions The structure of the helical tomotherapy MLC system is complex.The high-intensity work increases the failure rate.The humidity of high-pressure gas affects the normal operation of the MLC equipment.The faulty parts can be identified,the downtime can be reduced and the work time can be enhanced by summarizing the experience of MLC maintenance.
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Objective:To understand the status of two -week prevalence and the influencing factors in rural preschool leftover children of Shandong , so as to provide evidence for putting forward effective health intervention means .Methods:Using the method of stratified -cluster-random sampling and elect 646 cases of preschool lefto-ver children from 2 counties of Shandong .We surveyed with self -made questionnaire .Results:The two-week prevalence of the rural preschool leftover children is high;the influencing factors of the two -week prevalence with the rural preschool leftover children including whether children are only -child, the type of children guardianship , whether children piddle and whether left -behind children can avoid dangerous .Conclusion: The two -week prevalence present situation of rural preschool left -behind children is low , and its problems of health and ethics are clear.Therefore, effective measures should be carried out to improve the health level of rural leftover children .
ABSTRACT
Objective To study the dosimetric peculiarity of 3D intracavitary brachytherapy in the application of endometrial carcinoma comparing with traditional 2D plans. Method 39 3D brachytherapy treatment plans of 11 patients with endometrial carcinoma were retrospectively analyzed with re?planning 2D treatment plan, the dose volume histogram ( DVH) parameters such as the target dose volume parameters V150 and D90 , the 2?cc doses to organs such as bladder, small intestine, rectum and sigmoid and the total reference air kerma TRAK were analyzed. The differences between the two groups are compared by paired samples T test. Results For target with V<60 cm3 ,there is no statistically significant difference between 2D and 3D plans,the D90 is (551?17±90?33) cGy and (574?15±117?18) cGy,respectively (P=0?390). As the increase of target volume,the D90 came to be significantly different ( P=0?001) , high dose region V150 for 3D and 2D plans is (51?05±21?61) cm3 and (53?41±11?71) cm3, respectively (P=0?482). With the target volume larger than 60 cm3 ,compare to 2D plans, the 3D plan can increase the target coverage as well as OAR dose except for small intestine ( P=0?128) . In addition, with different plan mode,the BMI did not affect the crisis organ dose such as rectum, small intestine, bladder and sigmoid, the P value is 0?239, 0?198,0?744 and 0?834,respectively. Conclusions For endometrial carcinoma,compared with traditional two?dimensional plans,the 3D brachytherapy treatment plans can significantly improve the target coverage and avoiding overdose of organs, clinical curative effect and side effect still needs further observation.