Objective To investigate the role of large-diameter magnetic resonance imaging (MRI) simulation in target volume delineation in radiotherapy for nasopharyngeal carcinoma (NPC).Methods Eighteen patients with NPC underwent computed tomography (CT) simulation and MRI simulation scans and localization in the same body position,with SOMATOM Sensation Open 40-row 82-cm large-diameter CT simulator and Siemens 3T MRI MAGNETOM Skyra 70-cm large-diameter simulator,respectively.The gross tumor volume (GTV) and parotid glands were delineated on all images according to the ICRU Report 50/62,and MRI was applied to observe the changes in GTV and parotid volume during radiotherapy.Paired t-test was applied to analyze the differences between GTVCT and GTVMRI and between GTVnx-CT and GTVnx-MRI.Results GTVMRI decreased significantly compared with GTVCT,and the average volume decreased from (213.64±84.59) cm3 to (199.68±84.69) cm3(p=0.006).As for the volume of primary lesions in the nasopharynx,GTVnx-MRI was significantly smaller than GTVnx-CT,and the volume decreased from (95.75± 24.76) cm3 to (88.12±26.25) cm3 (P =0.001);as for the volume of cervical lymph nodes,GTVnd-MRI was significantly smaller than GTVnd-CT,and the volume decreased from (117.89± 72.69) cm3 to (111.56± 70.69) cm3 (P=0.018).The targets delineated by CT and MRI did not overlap completely,with major differences in skull base bone and cervical soft tissue.The volume of both parotid glands delineated on MRI image was higher than that delineated on CT image,with a major difference in the deep lobe.MRI showed that GTV was reduced by 82.64± 16.87％ during radiotherapy,and the volumes of the left and right parotid glands were reduced by (32.7± 23.95) ％ and (34.7± 21.72) ％,respectively.Conclusions The delineation of target volume based on MRI simulation is more accurate than that based on CT simulation and can achieve a smaller volume range,which helps to guide target volume delineation in radiotherapy for NPC accurately.

Objective To reveal the difference between the standards for genu varum and genu valgum in the medical standard directory PLA Air Force( PLAAF) for recruitment of flying cadets and those adopted in the United States Air Force ( USAF) , and suggest a method for the reform of our flying cadets recruitment.Methods The rejection rate and comprehe nsive assessment qualification rate of genu varum and genu valgum during physical examinations for recruitment of flying cadets between 2012 and 2015 were analyzed.The different standards for genu varum and genu valgum in PLAAF and USAF flying cadets recruitment were compared and subjected to an empirical study.Results During the final physical examination for selection of flying cadets between 2012 and 2015, only 18 candidates were eliminated because of genu varum and genu valgum, accounting 9.1% of the total eliminated candidates because of orthopadics diseases.Four candidates with genu varum and genu valgum passed the comprehensive assessment in 2014 and 31 in 2015, which accounted for 15%of the candidates with orthopaedics diseases approved by comprehensive assessment.The standards for genu varum and genu valgum in PLAAF were based on morphology while those in the USAF based on the function of knees.According to the USAF medical standard directory, 9 of the candidates rejected because of genu varum and genu valgum were qualified and 9 disqualified.Among the candidates with genu varum and genu valgum approved by comprehensive assessment, 32 were qualified and 3 disqualified.Conclusion The standards for genu varum and genu valgum in PLAAF medical standard directory are of lower accuracy.The standards of USAF should be referred to and the function of knees should be considered in selection of flying cadets.Femur-tibia angle should be measured to improve the morphological standards.

Objective To analyze the spectrum of anus disease during the medical selection of flying cadets and com-pare the medical standard between US Air Force and Chinese Air Force in order to improve the system of medical selection. Methods The data on flying cadets of Chinese Air Force medical selection from 2012 to 2015 were retrospectively analyzed and these data were re-analyzed by medical standards for US Air Force flying cadets.Results Ninety students were elimi-nated because of anal disease,including 65 hemorrhoids,14 fistula and 11 fissure.The rate of disqualification from 2012 to 2015 was 48.28%, 33.33%, 31.37%, 39.69%and there was no significant statistical difference between each two years (x2 =2.6154,P=0.4548).There was statistically significant difference(P=0<0.05)in hemorrhoids standards between CAF and USAF,and significant difference in fistula and fissure standards.Conclusion Compared with Chinese medical se-lection standards,the US Air Force standards focus on whether the symptoms of disease have effect on air safety and effi-ciency.To improve our medical selection standards,we need to learn from foreign air forces and take our own conditions into account.

This study was directed at analyzing the stress distribution of the implant in three different models whose cusp inclinations are 45, 35, 25 degrees respectively; the aim was to improve the success rate of implant rehabilitation. The method of is 3-dimensional finite element analysis (3D-FEA) was adopted. A volunteer's mandible was scanned using helix computer tomography and then we got the data of the mandible's margin in digital instrument. ANSYS program files were prepared using these data. Three models were created, meshed, analyzed in computer. Stress concentration was located on the cortical bone around the neck of implant and apical area of implant. Among the three designs, 25 degrees inclination of cusp was appropriate and in such a situation Von Mises stress was minimal.
Biomechanical Phenomena ; Bite Force ; Dental Implants ; Dental Prosthesis, Implant-Supported ; Dental Stress Analysis ; Finite Element Analysis ; Humans ; Mandible ; Stress, Mechanical

On the basis of the well-established principles and techniques about flow chamber, we have designed and made a kind of parallel plate system to apply steady fluid shear stress to osteoclast-like cells etc. in vitro. Biocompatible rubber and metal clamping apparatus made of aluminium alloy are used to seal the flow chamber without changing its even height designed beforehand. The influence of hydrostatic pressure on cells is minimized by adjusting the glass slide and the fluid surface in the upper reservoir to the same horizontal plane. This system can be used to investigate the responses of osteoclast-like cells etc. to fluid shear force in terms of morphology, physiology or biochemistry.
Biomechanical Phenomena ; Cell Culture Techniques ; instrumentation ; Humans ; Osteoclasts ; cytology ; Pulsatile Flow ; Stress, Mechanical

Objective To review the failure patterns and clinical outcomes for patients with cervical esophageal carcinoma (CEC) undergoing definitive radiotherapy (RT).Methods Medical records,clinical characteristics and outcomes of patients with CEC treated by definitive RT from August 2008 to May 2017 were retrospectively reviewed and analyzed.Results A total of 97 patients with squamous cell CEC were enrolled in this study with a median age of 59 years old (range 18-78 years old).There were 34 patients with limited cervical esophagus,and 63 patients with diseases beyond cervical region,respectively.There were 69,7,and 6 patients with Bronchi invasion,thyroid lobes involvement and aortic involvement,respectively.There were 11,80 and 6 patients with stage Ⅱ,Ⅲ and Ⅳ (non-regional lymph node metastases),respectively.The median dose to the gross tumor volume (GTV) was 66 Gy,in which 46 patients received above 66 Gy and 51 patients received less than 66 Gy,respectively.The median progression free survival (PFS) and overall survival (OS) were 16.03 and 23.30 months,respectively,with a median follow-up of 14.90 months.The 1,2,3-year PFS and OS were 56.86％,30.35％,26.34％,and 72.54％,47.94％,40.81％,respectively.Sixty-one patients had treatment failure at their last follow-up,in which 40,27,and 18 patients developed local failure,regional failure,and distant metastasis,respectively.Univariate analysis revealed that thyroid lobes involvement resulted in lower PFS (x2 =5.773,P＜0.05) and OS (x2 =13.461,P＜0.05),and bronchi involvement (x2 =4.283,P＜0.05) was associated with lower OS.Multivariate analysis indicated that aortic involvement and thyroid lobes involvement were associated with lower PFS (x2 =6.796,4.548,P＜0.05) and OS (x2 =13.421,10.581,P＜0.05),and GTV dose above 66 Gy was associated with higher OS (x2=5.296,P＜0.05).Conclusions Local-regional recurrence was the main failure pattern for patients with CEC after definitive RT.Aortic,thyroid lobes,and/or bronchi involvement were associated with poor prognosis,and GTV dose ≥66 Gy tended to improve OS.Prospective studies with larger population were needed to further confirm this study.