Objective To evaluate the penumbra of a new multileaf collimator equipped with Elekta Synergy accelerator. Methods The penumbra were derived from beam profiles measured in air and water using PinPoint ion chamber with PTW MP3 water phantom. Variations of penumbra with X-ray beam energy, depth in water, and leaf position were investigated. Results The penumbra in air for 6 MV X-ray was 2 mm less than that at depth of maximal dose in water. The penumbra of leaf side was 1 mm less than that of the leaf end. The penumbra had close relationship with beam energy, depth in water and leaf position. Penumbra was increased with beam quality and water depth. The leaf position had great influence on the penumbra. Conclusions The penumbra of the multileaf collimator is related to its original design and radiation delivery technique. Special considerations should be taken into during treatment planning.Regular measurement should be performed to guarantee the delivery quality.

BACKGROUND:At present,plant-derived absorbable hemostats are mainly imported,so it is necessary to develop domestic alternatives that are not inferior to similar imported products. OBJECTIVE:To investigate the hemostatic effect of oxidized regenerated cellulose hemostatic material on a model of minipig liver hemorrhage. METHODS:A total of 24 Bama minipigs were selected and randomly divided into three groups.In the sham operation group(n=6),only an open operation was performed,and the damaged side of the liver was removed and put back in situ.In the experimental group(n=12),the liver hemorrhage model was established,and the oxidized regenerated cellulose hemostatic material was applied to the wound.In the control group(n=6),commercially available absorbable hemostatic gauze was used on the wound after establishing liver hemorrhage models.Hemostatic time and blood loss were recorded.The venous blood of the minipig anterior cavity was collected at different time points before and after modeling,and the blood routine and liver and kidney functions were analyzed.Hematoxylin-eosin staining and Masson staining were performed at 2,6,and 14 weeks after modeling.The main organs were observed by histopathology at 14 weeks after modeling.A liver ultrasound examination was performed at different time points after modeling to observe the degradation and absorption of materials. RESULTS AND CONCLUSION:(1)There was no significant difference in intraoperative hemostatic time and blood loss between the experimental group and the control group(P>0.05).(2)The monitoring results of blood biochemical indexes demonstrated that the levels of aspartate transaminase and glutamic pyruvic transaminase in the three groups were higher 24 hours after modeling than before modeling,and the indexes basically recovered to the normal levels 72 hours after modeling.There were no significant differences in blood biochemical indexes such as liver and kidney functions,blood glucose and inflammatory factors among the three groups(P>0.05).(3)Hematoxylin-eosin staining and Masson staining of histopathology revealed that 2 weeks after surgery,granulation tissue formation and a large amount of collagen fiber deposition were observed on the liver wounds of the two groups,and there were obvious fibrous hyperplasia zones and inflammatory cell infiltration,and the wound healed well.14 weeks after modeling,the liver wounds of two groups of minipigs exhibited mild fibrous hyperplasia zone,collagen fiber deposition and a small amount of inflammatory cell infiltration,complete material degradation,and the healed wound.Hematoxylin-eosin staining showed no significant pathological changes in major organs.(4)Ultrasonic examination demonstrated that the materials of both groups were degraded gradually with the extension of implantation time,and most of them were degraded and absorbed by 56 days after molding.(5)The results confirm that the oxidized regenerated cellulose hemostatic material can effectively prevent liver wound hemorrhage in minipigs,and the hemostats are safe and reliable.

Objective:To analyze the 6-year operation faults of PHILIPS Brilliance big bore CT, identify the common problems, make corresponding maintenance plans, reduce the incidence of failures, and carry out simulation prediction of the occurrence rate of failures in the next few years.Methods:The failure data of Brilliance big bore CT from June 2012 to June 2018 were collected, and the curve estimation function in SPASS 19.0 software and the pareto diagram were used to analyze the relationship between the number of failures, time and failure types, and the prediction was made.Results:A total of 28 faults occurred during the 6-year opeation of Brilliance big bore CT. During the first half year, five times of faults occurred with the highest fault rate and then tended to stabilize. The linear function model was obtained using the curve estimation: y=-0.033 x+ 2.099( y for the number of fault, unit for times, x for the unit of time for half a year), the model of R2=0.003. In the next three years, approximately twice faults occurred within half year. The pareto chart showed that 16 faults occurred during data collection, including 3 faults in the treatment bed and 3 faults in the power supply system, respectively. The accumulative ratio of the above three faults was 71.4%, which were the main fault sources. Conclusion:The fault statistical analysis of Brilliance big bore CT is helpful for department maintenance personnel to better understand CT, develop effective maintenance programs, reduce the occurrence of faults, and predict the incidence of faults in the future.

Objective:To evaluate the clinical effect of the position pillows for neuraxial anesthesia.Methods:This was a prospective randomized controlled trial. Four hundred and twelve patients regardless of gender, aged ≥18 yr, of American Society of Anesthesiologists Physical Status classification Ⅰ-Ⅲ, who underwent elective surgery under neuraxial anesthesia at Peking University Third Hospital from February to October 2023, were selected and divided into 2 groups ( n=206 each) using a random number table method: pillow group (P group) and control group (C group). Group C underwent the conventional procedure for neuraxial anesthesia. The patients were placed in a position using the position pillow on the basis of oral education before routine anesthesia in group P. The success rate of puncture at first attempt, puncture time and position placement time were recorded. The adjustment of position, body movement and occurrence of discomfort during the puncture were also recorded. The visual analogue scale score was used to evaluate the level of anxiety before positioning, after positioning and after anesthesia. The visual analogue scale score was used to evaluate the patient′s comfort and the operator′s satisfaction with position after the anesthesia was completed. Results:Compared with group C, the time for positioning was significantly shortened, the anxiety level was decreased after positioning and after anesthesia, the rate of improvement in anxiety was increased, the scores for the patient′s comfort and the operator′s satisfaction with position were increased ( P<0.05), and no significant changes were found in the success rate of puncture at first attempt, puncture time and incidence of body movement during the puncture and incidence of the adjustment of position ( P>0.05). No discomfort was observed in either group during the puncture. Conclusions:This new type of position pillows for the neuraxial anesthesia can not only optimize the effect of position placement, but also improve the patients′ comfort.