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Objective To study the compressive mechanical properties and constitutive models of brain tissue at different strain rates.Methods Quasi-static and medium-velocity compression tests were carried out on the white and gray matter of pig brain tissue using an electronic universal testing machine,and stress-strain curves of pig brain tissue at different strain rates were obtained.The Ogden constitutive model was used to fit the test curve,the parameters of the constitutive model were determined,and the simulation was verified using finite element software.Results The brain tissue stress-strain curves showed nonlinear characteristics,with a strong strain rate correlation and sensitivity.When tissues were compressed to 0.6 strain,the stress of white and gray matter increased by 102%and 129%,respectively,at a strain rate of 5×10-4-5×10-2 s-1,and by 50.7%and 54.6%,respectively,at a strain rate of 1-1.5 s-1.At a strain rate of 1.5 s-1,the stress in the white and gray matter increased by 347%and 413%,respectively,compared with that at 5×10-4 s-1 strain rate.The R2 value of the Ogden model was greater than 0.99,and the error between the simulation and experimental results was within 15%,thereby verifying the validity of the model.Conclusions This study is helpful for the prediction of brain tissue deformation and provides an accurate scientific theoretical basis for the establishment of scientific and reasonable human simulation targets as well as the design and improvement of brain-protective equipment.
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Objective To establish a valid human head-neck model and ballistic helmet model, and analyze biomechanical responses of the cervical spine under bullet impacts on ballistic helmet with different weights. Methods A uniformly distributed weight of 2 kg was applied on the helmet (1.24 kg), and bullet impacts from frontal, lateral and crown directions at the speed of 450 m/s were considered to obtain the mechanical response of human vertebrae. Results The stress of the cervical spine was significantly higher than that of the skull under bullet impacts, and the stress of C3 segment was the largest, indicating that the cervical spine was more vulnerable than the head during bullet impacts under the protection of ballistic helmet. When the weight of helmet attachment was not considered, the maximum stress of the cervical spine under lateral impact was 2.58% higher than that under frontal and crown impacts. The frontal impact led to the greatest damage to the head, with an increase of 59.4% in head stress. When the weight of helmet attachment was considered, a lager helmet weight would cause a more serious spine injure. When the helmet weight was increased from 1.24 kg to 3.24 kg, the crown impact led to the greatest damage to the cervical spine, with an increase of 12.98% in cervical stress compared with impacts from other directions. Conclusions Lightweight should be considered in the design of ballistic helmet, and the research findings provide scientific references for the design of ballistic helmet.
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Objective To establish a valid human head-neck model and ballistic helmet model, and analyze biomechanical responses of the cervical spine under bullet impacts on ballistic helmet with different weights. Methods A uniformly distributed weight of 2 kg was applied on the helmet (1.24 kg), and bullet impacts from frontal, lateral and crown directions at the speed of 450 m/s were considered to obtain the mechanical response of human vertebrae. Results The stress of the cervical spine was significantly higher than that of the skull under bullet impacts, and the stress of C3 segment was the largest, indicating that the cervical spine was more vulnerable than the head during bullet impacts under the protection of ballistic helmet. When the weight of helmet attachment was not considered, the maximum stress of the cervical spine under lateral impact was 2.58% higher than that under frontal and crown impacts. The frontal impact led to the greatest damage to the head, with an increase of 59.4% in head stress. When the weight of helmet attachment was considered, a lager helmet weight would cause a more serious spine injure. When the helmet weight was increased from 1.24 kg to 3.24 kg, the crown impact led to the greatest damage to the cervical spine, with an increase of 12.98% in cervical stress compared with impacts from other directions. Conclusions Lightweight should be considered in the design of ballistic helmet, and the research findings provide scientific references for the design of ballistic helmet.
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Objective@#To evaluate the value of 18F-FDG PET-CT in predicting the malignant potential of Gastrointestinal Stromal Tumors (GIST).@*Methods@#The clinical and pathological features of 31 patients with GIST confirmed by surgery or biopsy were retrospectively analyzed. The malignant potential of GIST before treatment was assessed by 18F-FDG PET-CT. The GIST risk classification was graded according to the Standard revised by the National Institutes of Health (NIH) in 2008. The relationship between the maximal standard uptake value (SUVmax) and GIST risk classification, tumor diameter, Ki-67 index, and mitotic count were analyzed respectively. The cut-off level of SUVmax for the diagnosis of malignant GIST was calculated from the Receiver Operating Characteristic (ROC) curve.@*Results@#Among the 31 cases of GIST patients, 14 cases were gastric primary (stomach group) and 17 cases were nongastric primary (outside stomach group). The SUVmax, tumor diameter, Ki-67 index and mitotic count of the 31 patients were 8.21±4.68, (7.82±5.12)cm, (10.03±11.07)% and (12.29±10.55)/50 HPF, respectively. SUVmax was significantly correlated with GIST risk classification (r=0.727, P<0.01), but not with tumor diameter, Ki-67 index and mitotic count (r=0.348, r=0.284, r=0.290, P=0.055, P=0.121, P=0.114). The SUVmax, tumor diameter, Ki-67 index and mitotic count in the stomach group were 4.36±2.36, (6.08±4.31)cm, (3.43±3.03)% and (5.71±2.20)/50 HPF, respectively. SUVmax was significantly correlated with tumor diameter, GIST risk classification and Ki-67 index (r=0.682, r=0.868, r=0.732, P<0.01) but not with mitotic count (r=0.510, P=0.063). The SUVmax of the GIST in the gastric group and the outside gastric group were 4.36±2.36 and 10.68±5.50, respectively. The difference was statistically significant (P=0.001). The SUVmax in the malignant group of GIST (middle or high risk grade) was 8.90±4.89, which was significantly higher than 2.22±0.86 in the benign group (low or very low risk grade). The difference was statistically significant between the two group (P<0.01). ROC curve analysis showed that a SUVmax cut-off of 3.75 was the most sensitive for predicting malignant GIST. When the area under the curve of 0.969, the sensitivity was 84.6% and the specificity was 100%.@*Conclusions@#The SUVmax was strongly correlated with the GIST risk category and also with the tumor diameter and Ki-67 index in the gastric primary GIST, so it can be used as an effective indicator in predicting malignant potential of GIST before treatment.
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Objective To compare the diagnostic values of 18F-FDG and 18F-FLT PET/CT in patients with suspicious recurrence of glioma after multimodal treatment.Methods A total of 20 patients (13 males,7 females;age range:12-73 years) with glioma who underwent 18F-FDG and 18F-FLT PET/CT due to abnormal enhancement on MRI from January 2012 to June 2015 were enrolled in this retrospective study.According to the pathological or follow-up results,patients were divided into therapy-related benign changes (TRBC) group and recurrent glioma group,the later was subdivided into initial low-grade glioma (LGG) group and initial high-grade glioma(HGG) group.T/NT ratios of 18F-FDG and 18F-FLT between HGG (LGG) group and TRBC group were compared using one-way analysis of variance and the least significant difference t test.ROC curve analysis was conducted to calculate the differential diagnostic efficiency of 18F-FDG and 18F-FLT between TRBC and recurrent glioma.Results A total of 14 patients were proved as recurrent glioma and 6 patients as TRBC.The mean 18F-FDG T/NT ratios of HGG group,LGG group and TRBC group were 2.31±0.86,1.32±0.86 and 1.32±0.64,respectively.The 18F-FDG T/NT ratio of the HGG group was significantly higher than that of the TRBC group(F=3.671,t=-2.471,P＜0.05).The mean 18F-FLT T/NT ratios of HGG group,LGG group and TRBC group were 8.94±3.14,7.18±3.29 and 1.92±1.20,respectively (F=13.301,t values:-5.150 and-2.360,both P＜0.05).The optimal T/NT cutoff values for 18 F-FDG and 18F-FLT PET/CT were 1.62 and 4.58,respectively.The sensitivity,specificity and accuracy of detecting recurrent glioma with optimal T/NT cutoff value were 11/14,5/6 and 16/20 for 18F-FDG PET/CT,and those for 18F-FLT PET/CT were 13/14,6/6 and 19/20,respectively.No significant difference was observed between the diagnostic efficiencies of the two imaging modalities (x2 values:1.167,1.091 and 2.057;all P＞0.05).Conclusion There were no statistical significances between 18F-FDG and 18F-FLT PET/CT on the differential diagnosis of glioma recurrence.
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Creativity is the demand of the time.The cultivation of creativity is what we should put first in the education of graduates.The Fourth Military Medical University attempts to consummate the selection,training and evaluating system of supervisors by strictly checking the qualification of supervisors and examining the enrollment qualification,sending supervisors abroad for further education and making them attending academic conferences for academic communication.The university also modularizes English teaching and giving lectures on political theory courses in order to establish a curriculum system which integrates the education of theory,practicing and the cultivation of comprehensive quality.Moreover,by creating funds for graduates' searching and international academic communication of academy,the university tries to complete stipend and scholarship systems to encourage innovation and exploration.By doing these,the cultivation of graduates' innovation ability has been improved.
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This paper analyzes the characteristics of the follow-up quality survey and evaluation of medical graduate students in China.It raises that the follow-up quality survey of graduate students in medical schools should be institutionalized,standardized and normalized; the survey and evaluation should be conducted through close cooperation with the relevant departments and training units; comparative studies on graduates of different years should be conducted; and the indicator system and survey content should value the characteristics of times,training units and subjects; Finally,specific technical issues such as when and to whom the evaluation and survey should be conducted,survey arrangements,evaluation methods,the diversity of participants and determination of results are discussed and suggestions are put forward.
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Epidemiology,as a major subject in the field of public health science,plays a pivotal role in the construction and development of disease prevention and control system.It is also vital for the public health system to improve the emergency response ability and to cultivate high-quality talents.After analyzing current situation of graduate education of epidemiology,we found some problems.In our research,deepgoing dissection was carried out and possible solution was provided.