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Objective:To evaluate the effect of leaf position error of Varian high-definition multi-leaf collimator (HD120) on the dosimetry of stereotactic body radiation therapy (SBRT) for lung tumors.Methods:Nine SBRT plans based on HD120 for lung tumors were selected as the reference plans. The parameters of the plans were modified by the in-house program based on the Varian Eclipse 15.6 scripting application program interface to generate the simulation plans with three types of leaf position errors including the isotropic systematic error, the anisotropic systematic error and the random error, respectively. Then, the dosimetric metric deviation between each simulation plan and the corresponding reference plan was calculated and regression analysis was performed to evaluate the dosimetric effect of three types of leaf position errors of HD120 on SBRT.Results:The planning target volume (PTV) D 99%, D 2cm and V 5Gy of double lungs were decreased quadraticly with the increase of the absolute value of the isotropic systematic error. The first-order sensitivity was -0.06%/mm to -0.26%/mm, and the second-order sensitivity was -0.55%/mm 2 to -1.17%/mm 2 ( R2=0.96-0.99, P<0.01). The maximum change of PTV D 99% was -3.13%. The linear regression analysis of the effects of the anisotropic systematic error and random error showed that the sensitivity of CI was 25.16%/mm ( R2=0.98, P<0.01) and -4.84%/mm( R2=0.99, P<0.01), and the sensitivity of other dosimetric deviations with the anisotropic systematic error was 4.80%/mm to 5.12%/mm ( R2=0.96-0.98, P<0.01), whereas the sensitivity with the random error was -0.47%/mm to -1.01%/mm ( R2=0.96-0.99, P=0-0.02). Conclusions:The dosimetric deviation of SBRT plan based on HD120 for lung cancer is highly sensitive to the anisotropic systematic error of leaf position, but less sensitive to the random error. In addition, the isotropic systematic error of leaf position will lead to the decrease of target coverage to a certain extent. Consequently, it is necessary to strictly control the systematic error of HD120 leaf position in the implementation of SBRT plan in clinical work.
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BACKGROUND: Porous hydroxyapatite scaffolds have good osteogenesis in vivo and in vitro. However, little research has been done on the complex regulation mechanisms of miRNAs involved. OBJECTIVE: To investigate the changes of related miRNA expression in rat bone marrow mesenchymal stem cells during osteogenic mineralization by porous hydroxyapatite scaffolds. METHODS: Rat bone marrow mesenchymal stem cells were isolated, cultured and identified in vitro. Bone marrow mesenchymal stem cells co-cultured with porous hydroxyapatite scaffold were as experimental group, and bone marrow mesenchymal stem cells cultured alone served as blank control group, both of which underwent osteogenic induction for 7 days. During the osteogenic mineralization, miRNA high-throughput sequencing technology was used to analyze the changes of miRNA expression profiles followed by GO analysis. The miRNA molecules with obvious expression differences were screened and verified by qRT-PCR. RESULTS AND CONCLUSION: (1) Compared with the blank control group, in the experimental group, the expression levels of BMP2, ALP and Runx2 mRNA were up-regulated, and the expression level of BMP2 was up-regulated significantly (P < 0.05). (2) Results of miRNA high-throughput sequencing showed that 13 miRNAs such as miR-210-3p and miR-146a-5p were up-regulated, and 17 miRNAs such as let-7c-3p and let-3615 were down-regulated significantly. (3) GO analysis revealed that up-regulated miRNA target genes were mainly involved in biological regulation, cellular gene expression, and gene expression regulation, mainly including nuclear factor-κB, Toll-like receptor 9, intercellular adhesion, interleukin-1 regulation, and signaling pathways such as angiogenesis and Hippo. (4) Real-time fluorescence quantitative qPCR results showed that miRNA-210 was up-regulated 15 times and miR-146a-5p was up-regulated 10 times in the experimental group (P < 0.05). These results indicate that the new microchannel porous hydroxyapatite scaffold can promote the differentiation of bone marrow mesenchymal stem cells by up-regulating miRNA-210-3p and miR-146a.
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Objective The simulation of the human mandible injury was carried out by using the finite element simulation technology ,and the biomechanical analysis of simulation results was developed to explore the mechanism of injuries .Methods The Chinese Visible Human digital data were used to establish the three-dimensional element model of mandible injuries ,and the dynam-ic processes of human mandible injuries in different conditions were simulated ,and the biomechanical analysis were carried out by u-sing the Von Mises stress and effective strain .Results The three-dimensional element model of mandible injuries was established , the dynamic damage and fracture of human mandible were simulated successfully ,the mandibular angle and condylar were the predi-lection parts of high-stress ,high-strain and fractures .Conclusion The Von Mises stress and effective strain can be used to predict and judge the bone tissue injuries ,the finite element method can simulate the impact injuries of mandible effectively ,and the simula-ted results can provide guidance and reference for basic research and clinical treatment of oral and maxillofacial injuries .
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Objective To develop a three-dimensional element model of pig mandible impact injury and test the simulation results in an attempt to determine the feasibility and reliability of finite element numerical simulation method used in the maxillofacial impact injury.Methods CT data was used to develop a three-dimensional finite element model of pig mandible impact injury,and the dynamic process of impact injury was simulated.The simulation results were compared with the animal experiment and had energy check to validate the reliability and feasibility of the modeling and simulation methods.Results The three-dimensional finite element model was established successfully,containing 61,512 hexahedrons,5,450 tetrahedrons,4,030 trihedrons,and 67,159 nodes.The simulation process was realistic,and the simulation results showed no statistical difference with the animal experiment with regard to strain,acceleration,and other biomechanical properties (P ＞ 0.05).The simulated damage shape had a high similarity with animal specimens,and the result of energy check also complied with energy conservation law.Conclusion Finite element method is effective to simulate the dynamic process of mandible impact which ensures a correct and reliable model and simulation,and thus can be used to analyze the mechanism of maxillofacial impact injury.
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Objective To simulate a finite element model for biomechanical analysis of mandible chin blast injury and analyze the mechanism of maxillofacial blast injury.Methods The three-dimensional element model of human mandible blast injury was established to simulate the dynamic process of injury to the mandible chin.Von Mises stress and effective strain were evaluated in biomechanical study of the simulation results.Results The dynamic damage process of human mandible chin blast injury was simulated successfully.In the condition of 1 000 mg and 3 cm,the Von Mises stress and effective were maximum at condylar neck region (9.1 × 106 Pa,0.62 × 10-3ε),were second at mandibular angle region (6.1 × 106 Pa,0.42 × 10-3ε),and minimum at mental foramen region (6.1 × 106 Pa,0.39 × 10-3ε).Blast distance rather than blast equivalent produced more effect on the mechanical parameters and damage degree.Conclusions Von Mises stress and effective strain can be applied to the evaluation of bone tissue damage.The finite element method is effective in simulating mandible blast injury and can provide a new thought and approach to clinical treatment of oral and maxillofacial blast injury.
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Objective Finite element numerical simulation technique was applied to simulate the dynamic projectile injury process of human chin in different injury conditions and the mechanism of injury was discussed by using biomechanical analysis . Methods The 3D finite element model of human mandible projective injury was established to simulate the dynamic projectile inju‐ry process of human chin in different injury conditions (high ,medium and low speeds) ,and the simulation results were used to com‐parative analysis of biomechanics .Results The dynamic damage process of human chin projectile injury was simulated successfully in different injury conditions ,and the more serious injury of mandible was caused by faster speed .Conclusion The finite element method can simulate the projectile injury of mandible effectively ,and can provide a new thought and method for basic research and clinical treatment of oral and maxillofacial war injury .