The objective of this study was to determine the visco-hyperelastic constitutive law of brain tissue under dynamic impacts. A method combined by finite element simulations and optimization algorithm was employed for the determination of material variables. Firstly, finite element simulations of brain tissue dynamic uniaxial tension, with a maximum stretch rate of 1.3 and strain rates of 30 s–1 and 90 s–1, were developed referring to experimental data. Then, fitting errors between the engineering stress-strain curves predicted by simulations and experimental average curves were assigned as objective functions, and the multi-objective genetic algorithm was employed for the optimation solution. The results demonstrate that the brain tissue finite element models assigned with the novel obtained visco-hyperelastic material law could predict the brain tissue’s dynamic mechanical characteristic well at different loading rates. Meanwhile, the novel material law could also be applied in the human head finite element models for the improvement of the biofidelity under dynamic impact loadings.
The nondestructive reconstruction of three-dimensional (3D) temperature field in biological tissue is always an important problem to be resolved in biomedical engineering field. This paper presents a novel method of nondestructive reconstruction of 3D temperature field in biological tissue based on multi-island genetic algorithm (MIGA). By this method, the resolving of inverse problem of bio-heat transfer is transformed to be a solving process of direct problem. An experiment and its corresponding simulation were carried out to verify the feasibility and reliability. In the experiment a high purity polypropylene material, whose thermophysical parameters were similar to the fat tissue being tested, were adopted so that it could avoid the negative results created by the other factors. We set the position P(x, y, z) as the point heat source in the biological tissue and its temperature t as optimization variable, got the experimental temperature values of the points in a module surface, subtracted them from the corresponding simulating temperature values in the same module surface, and then took the sum of absolute value. We took it as the objective function of successive iteration. It was found that the less the target value was, the more optimal the current variables, i.e. the heat source position and the temperature values, were. To improve the optimization efficiency, a novel establishment method of objective function was also provided. The simulating position and experimental position of heat source were very approximate to each other. When the optimum values are determined, the corresponding 3D temperature field is also confirmed, and the temperature distribution of arbitrary section can be acquired. The MIGA can be well applied in the reconstruction of 3D temperature field in biological tissue. Because of the differences between the MIGA and the traditional numerical methods, we do not have to acquire all the data of surface. It is convenient and fast, and shows a prosperous application future.
Transcranial electrical stimulation (TES) is a non-invasive neuromodulation technique with great potential. Electrode optimization methods based on simulation models of individual TES field could provide personalized stimulation parameters according to individual variations in head tissue structure, significantly enhancing the stimulation accuracy of TES. However, the existing electrode optimization methods suffer from prolonged computation times (typically exceeding 1 d) and limitations such as disregarding the restricted number of output channels from the stimulator, further impeding their clinical applicability. Hence, this paper proposes an efficient and practical electrode optimization method. The proposed method simultaneously optimizes both the intensity and focality of TES within the target brain area while constraining the number of electrodes used, and it achieves faster computational speed. Compared to commonly used electrode optimization methods, the proposed method significantly reduces computation time by 85.9% while maintaining optimization effectiveness. Moreover, our method considered the number of available channels for the stimulator to distribute the current across multiple electrodes, further improving the tolerability of TES. The electrode optimization method proposed in this paper has the characteristics of high efficiency and easy operation, potentially providing valuable supporting data and references for the implementation of individualized TES.
In order to improve the wearing comfort and bearing effectiveness of the exoskeleton, based on the prototype and working mechanism analysis of a relaxation wearable system for knee exoskeleton robot, the static optimization synthesis and its method are studied. Firstly, based on the construction of the virtual prototype model of the system, a comprehensive wearable comfort evaluation index considering the factors such as stress, deformation and the proportion of stress nodes was constructed. Secondly, based on the static simulation and evaluation index of system virtual prototype, multi-objective genetic optimization and local optimization synthesis of armor layer topology were carried out. Finally, the model reconstruction simulation data confirmed that the system had good wearing comfort. Our study provides a theoretical basis for the bearing performance and prototype construction of the subsequent wearable system.
ObjectiveTo identify a more popularized preparation protocol of leukocytes-rich platelet-rich plasma (L-PRP) for higher tolerance rate.MethodsThe peripheral blood samples of 76 volunteers (45.0 mL/case) were mixed with 5 mL sodium citrate injection for blood transfusion, and L-PRP was prepared by twice centrifugations. All blood samples were divided into three groups according to the parameters of twice centrifugation: experimental group A (12 cases, 400×g, 10 minutes for the first time and 1 100×g, 10 minutes for the second time), experimental group B (27 cases, 800×g, 10 minutes for the first time and 1 100×g, 10 minutes for the second time), and control group (37 cases, 1 360×g, 10 minutes for the first time and 1 360×g, 10 minutes for the second time). The platelet recovery rate and platelet and leukocyte enrichment coefficient of L-PRP in each group were calculated and compared.ResultsAfter removal of abnormal blood samples (platelet recovery rate was more than 100% or white thrombus), the remaining 55 cases were included in the statistical analysis, including 10 cases in experimental group A, 21 cases in experimental group B, and 24 cases in control group. The platelet enrichment coefficient and platelet recovery rate of experimental group B were significantly higher than those of experimental group A and control group (P<0.05); there was no significant difference between experimental group A and control group (P>0.05). There was no significant difference in leukocyte enrichment coefficient between experimental groups A, B, and control group (P>0.05).ConclusionThe preparation quality of PRP is affected by various factors, including centrifugal force, centrifugal time, temperature, and operation process, etc. Twice centrifugation (800×g, 10 minutes for the first time and 1 100×g, 10 minutes for the second time) is an ideal and feasible centrifugation scheme, which can obtain satisfactory platelet recovery rate and enrichment coefficient with thicker buffy coat, which can reduce the fine operation requirements for operators, improve the fault tolerance rate and generalization.
Thoracic trauma has the characteristics of complexity, specificity, urgency and severity. Therefore, the treatment is particularly important. Thoracic Traumatology Group, Trauma Medicine Branch of Zhejiang Medical Association organized the writing of the thoracic trauma and further optimization consensus of Zhejiang thoracic surgery industry Treatment and diagnosis of rib and sternum trauma: A consensus statement by Zhejiang Association for Thoracic Surgery (version 2021), compiled the popular science book Emergency Treatment and Risk Avoidance Strategy of Thoracic Trauma and Illustration of Real Scene Treatment of Trauma, actively prepared to build the trauma database of Zhejiang Province, and participated in the construction of trauma group in the Yangtze River Delta. Although Zhejiang Province has carried out many related works in the diagnosis and treatment of chest trauma, it is still inconsistent with the development requirements of the times. Standardization of chest trauma treatment, popularization of relevant knowledge, management of trauma big data, grass-roots radiation promotion tour and further optimization of industry consensus are the requirements and objectives of this era.
Objective To explore the application effect of process optimization in perioperative venous access management. Methods A total of 205 general surgery patients in the Operating Room of Cheng Du Shang Jin Nan Fu Hospital, West China Hospital of Sichuan University from April to May 2018 were selected as the control group, and 205 general surgery patients from June to August 2018 were selected as the observation group. The traditional management process was used in the control group, and the process optimization management was performed in the observation group. The establishment of venous access and related complications between the two groups of patients, as well as the satisfaction of patients and staff before and after the process optimization were compared. Results There was no significant difference in gender, age, education level, operation type, anesthesia method, operation duration, or intraoperative intravenous infusion channels between the two groups of patients (P>0.05). There was no statistically significant difference in gender, age, educational background, job title, job nature, or working years of the staff participating in the satisfaction survey before and after the process optimization (P>0.05). The rate of repetitive venous puncture (15.61% vs. 58.05%) and the idelness ratio of the intraoperative indwelling needle approach (10.73% vs. 52.20%) in the observation group were lower than those of the control group, and the differences were statistically significant (P<0.05). There was no statistically significant difference in the incidence of tube blockage, detubation, or phlebitis/exudation between the two groups (P>0.05). After process optimization, patient satisfaction (22.91±3.43 vs. 17.44±4.90) and staff satisfaction (28.17±2.56 vs. 20.65±3.71) were higher than before optimization, and the differences were statistically significant (P<0.05). Conclusions The process optimization of venous access management for perioperative patients can effectively reduce the rate of venous repeated venipuncture and the idelness ratio of the intraoperative indwelling needle approach, reduce invasive operations on patients, reduce the ineffective work of nurses, avoid the waste of medical resources such as manpower and materials, and improve the satisfaction of patients and staff. It is worthy of promotion and application.
The stiffness of an ideal fracture internal fixation implant should have a time-varying performance, so that the fracture can generate reasonable mechanical stimulation at different healing stages, and biodegradable materials meet this performance. A topology optimization design method for composite structures of fracture internal fixation implants with time-varying stiffness is proposed, considering the time-dependent degradation process of materials. Using relative density and degradation residual rate to describe the distribution and degradation state of two materials with different degradation rates and elastic modulus, a coupled mathematical model of degradation simulation mechanical analysis was established. Biomaterial composite structures were designed based on variable density method to exhibit time-varying stiffness characteristics. Taking the bone plate used for the treatment of tibial fractures as an example, a composite structure bone plate with time-varying stiffness characteristics was designed using the proposed method. The optimization results showed that material 1 with high stiffness formed a columnar support structure, while material 2 with low stiffness was distributed at the degradation boundary and inside. Using a bone remodeling simulation model, the optimized bone plates were evaluated. After 11 months of remodeling, the average elastic modulus of callus using degradable time-varying stiffness plates, titanium alloy plates, and stainless steel plates were 8 634 MPa, 8 521 MPa, and 8 412 MPa, respectively, indicating that the use of degradable time-varying stiffness plates would result in better remodeling effects on the callus.
In the present study, packaging system composed of pAAV-CMV-GFP, pAAV-RC and pHelper were transfected into human embryonic kidney 293 cells (HEK293 cells) mediated by polyethyleneimine (PEI) to explore an optimal transfection condition. Different total plasmid DNA dosages (1, 2, 3, 4, 5, 6μg) and different PEI/Plasmid ratios (1:1, 3:1, 5:1, 7:1) were tested with detection of green fluorescence protein (GFP) with ImagePro Plus6.0 Software. Then transfection efficiency of the optimized transfection system was further observed for different time periods(12, 24, 36, 48, 60, 72 h). The results showed that total plasmid dosage of 4μg/well with PEI/plasmid ratio of 3:1~5:1 was an efficient transfection condition. Transfection efficiency-time curve was an S-shaped curve. Transfection efficiency reached a plateau at 60 h after transfection. The optimized conditions for PEI-mediated transfection at the optimal time result in enhanced transfection efficiency of triple plasmid into HEK293 cells.
Triply periodic minimal surface (TPMS) is widely used because it can be used to control the shape of porous scaffolds precisely by formula. In this paper, an I-wrapped package (I-WP) type porous scaffolds were constructed. The finite element method was used to study the relationship between the wall thickness and period, the morphology and mechanical properties of the scaffolds, as well as to study the compression and fluid properties. It was found that the porosity of I-WP type scaffolds with different wall thicknesses (0.1 ~ 0.2 mm) and periods (I-WP 1 ~ I-WP 5) ranged from 68.01% ~ 96.48%, and the equivalent elastic modulus ranged from 0.655 ~ 18.602 GPa; the stress distribution of the scaffolds tended to be uniform with the increase of periods and wall thicknesses; the equivalent elastic modulus of the I-WP type scaffolds was basically unchanged after the topology optimization, and the permeability was improved by 52.3%. In conclusion, for the I-WP type scaffolds, the period parameter can be adjusted first, then the wall thickness parameter can be controlled. Topology optimization can be combined to meet the design requirements. The I-WP scaffolds constructed in this paper have good mechanical properties and meet the requirements of repairing human bone tissue, which may provide a new choice for the design of artificial bone trabecular scaffolds.