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Objective:The microstructure, tensile strength, and bursting strength of different brands of hernia meshes were compared and analyzed through experiments to evaluate the performance of different meshes.Methods:The balance and microscope were used to test the weight and microstructure of 15 common meshes and the tensile testing machine and burst testing machine were used to test the tensile and bursting properties of the mesh, and the mechanical properties of the mesh were analyzed.Results:The woven structures of the mesh are diamond, polygon and circle. The average weight of inguinal meshes is 0.08 mg/mm 2, and the average weight of abdominal wall hernia meshes is 0.18 mg/mm 2. The wire diameters of G3 - G6 meshes are larger, while the mesh opening ratio of G12 is lower. In the tensile performance test, it is known that G15 has the highest tensile strength, G12 and G14 have lower tensile strengths in lightweight meshes, and G1, G2, and G7 have lower tensile strengths in lightweight meshes. In the burst performance test, it is known that G3, G9, and G15 have the highest burst strength, while G12, G13, and G14 have the lowest burst strength in lightweight meshes. G1, G2, and G4 have the lowest burst strength in lightweight meshes. Conclusions:The mesh with a polygonal mesh and a large mesh opening ratio has better mechanical properties. The results of this study provide experimental evidence for optimizing hernia meshes, which is expected to provide better support for related research and applications.
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Objective Aiming at improving biomechanical strength of the anastomotic stoma as well as reducing tissue thermal damage, a novel radiofrequency (RF) tissue welding electrode was developed. Methods A novel electrode with a hollow structure on the surface ( the plum electrode) was designed and the ring electrode was used as control group to conduct the welding of intestinal tissues based on RF energy. Biomechanical properties of anastomotic stoma were studied by shear test and burst pressure test. The tissue thermal damage during welding was investigated by finite element electro-thermal-mechanical multi-field coupling simulation analysis and thermocouple probe, and the tissue microstructures were also studied. Results Under 120 W RF energy, 8 s welding duration and 20 kPa compression pressure, the anastomotic stoma had the optimal biomechanical properties. Compared with the ring electrode group, biomechanical strength of the anastomotic stoma in plum electrode group was higher, with the shear strength and burst pressure increasing from (9. 7±1. 47) N, (84. 0±5. 99) mmHg to (11. 1±1. 71) N, (89. 4±6. 60) mmHg, respectively. There was a significant reduction in tissue thermal damage, and intact and fully fused stomas could be formed in anastomotic area. Conclusions The proposed novel electrode could improve biomechanical strength of the anastomosis as well as reduce tissue hermal damage, thus achieve better fusion. The research result provide references for realizing the seamless connection of human lumen tissues
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Magnetic resonance (MR) imaging is an important tool for prostate cancer diagnosis, and accurate segmentation of MR prostate regions by computer-aided diagnostic techniques is important for the diagnosis of prostate cancer. In this paper, we propose an improved end-to-end three-dimensional image segmentation network using a deep learning approach to the traditional V-Net network (V-Net) network in order to provide more accurate image segmentation results. Firstly, we fused the soft attention mechanism into the traditional V-Net's jump connection, and combined short jump connection and small convolutional kernel to further improve the network segmentation accuracy. Then the prostate region was segmented using the Prostate MR Image Segmentation 2012 (PROMISE 12) challenge dataset, and the model was evaluated using the dice similarity coefficient (DSC) and Hausdorff distance (HD). The DSC and HD values of the segmented model could reach 0.903 and 3.912 mm, respectively. The experimental results show that the algorithm in this paper can provide more accurate three-dimensional segmentation results, which can accurately and efficiently segment prostate MR images and provide a reliable basis for clinical diagnosis and treatment.
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Male , Humans , Prostate/diagnostic imaging , Image Processing, Computer-Assisted/methods , Magnetic Resonance Imaging/methods , Imaging, Three-Dimensional/methods , Prostatic Neoplasms/diagnostic imagingABSTRACT
Objective:To analyze the microstructure of commonly used surgical hemostatic powders and investigate their hemostatic properties.Methods:The microstructures of seven commonly used surgical hemostatic powders were observed by scanning electron microscopy and analyzed by particle size testing, and then the hemostatic properties of the seven commonly used surgical hemostatic powders were evaluated by an in vitro coagulation promotion test and a rabbit liver bleeding model.Results:The average particle size of Aristide hemostatic powder was 45.143 μm, and there were many grooves on the surface of the particles with increased specific surface area. The results of in vitro coagulation promotion tests showed that the absorbance and coagulation index of Aviagen were the lowest, which were 0.039 30±0.006 03 and 3.42, respectively. The rabbit liver bleeding experiment showed that the hemostatic effect of hemostatic powder materials in the experimental group was better than that in the control group (all P<0.001), among which Aviagen and Aristide were more effective. The hemostatic time and the effective bleeding volume of the experimental group and the control group were (44±17) s and (48±9) s, and (63±19) mg and (73±18) mg, respectively, and the differences were statistically significant (all P<0.05). Conclusions:There are many grooves on the surface of Arista granules, which gives them a better performance in homeostasis in surgical applications. Avitene has lower absorbance and coagulation index, and better hemostatic properties.
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Objective:To conduct theoretical analysis and experimental research on peripherally inserted venous catheters, establish theoretical models of interaction between different materials catheters and simulated skin tissues, and test different catheters at the same time to provide theoretical basis and experimental basis for the optimization design.Methods:According to the mechanical properties of the catheter at 25 ℃ and 37 ℃, a finite element model of the catheter and simulate skin tissue was established. The relationship between catheter folds and material and structure during puncture was analyzed, and the stiffness, radiographic properties, etc. were tested experimentally.Results:The performance of the catheter at different temperatures is closely related to its material. The wrinkle situation of the catheter is related to the catheter material and the inclination of the wedge surface. The elastic modulus of the polyurethane (PU) catheter is about 500 MPa and 250 MPa, respectively at room temperature (25 ℃) and body temperature (37 ℃), which meets the clinical needs of high rigidity during puncture and soft material during indwelling. When the catheter structure is the same, the PU catheter is less prone to wrinkles than the fluorinated ethylene propylene copolymer (FEP) catheter. When the catheter material is the same, the smaller the inclination of the wedge surface, the less likely the catheter to wrinkle.Conclusions:Appropriately reducing the inclination of the wedge-shaped surface of the needle of peripherally inserted venous catheters can improve the success rate of puncture. The PU catheters have good mechanical properties, they are not prone to wrinkles during puncture, and their stiffness can be reduced at body temperature, which can not only increase the success rate of puncture, but also reduce the occurrence of complications. Therefore, PU catheters have a better clinical application prospect.
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Objective In order to avoid early restenosis after drug-eluting stent (DES) implantation, the retrievable structure of the NiTi alloy stent and its biomechanical analysis were studied. Methods The geometric models of the retrievable vascular stent and the retrieval system were established. The retrieval part of the stent consisted of four symmetrically distributed tendons, which were designed as circular meshes. The distribution of the maximum strain during stent compression and its uniformity during compression and self-expansion were analyzed, and the simulation experiments of the retrieval process were also performed. Results The maximum strain of the stent was 3.7% and the index of non-uniformity (INU) was 0.62% when the stent was compressed to the minimum size. While the IBU was 1.31% after the self-expansion process completed. The maximum strain was 1.2% when half of the stent was retrieved into the outer sheath. Conclusions The stent could be safely and successfully retrieved into the outer sheath as the strain was within the bearable range of the material and the compression and self-expansion process was relatively uniform. The research findings provide important references for structural design, biomechanical analysis and potential clinical applications of the novel retrievable vascular stent.
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Objective The ileum of porcine intestines with radiofrequency (RF) energy was fused through a novel linkage-type pressure controlled electrode, so as to verify feasibility and security of intestinal reconstruction in the RF energy tissue fusion technology. Methods Fresh porcine intestines were fixed on negative electrode in the order of ‘mucosa-serosa’, and then different compressive pressures （497，796，995，1 194，1 492 kPa）and RF energy were applied to the tissues through positive electrode of pressure cone to complete intestinal anastomosis. Biomechanical properties of the fused area were studied by tensile strength and bursting pressure test, and the thermal diffusion and tissue microstructure also studied. ResultsThe anastomotic tensile strength and bursting pressure could reach （8.73±1.11） N and （8.29±0.41） kPa, respectively, when the energy output power, pressure and welding time were 160 W, 995 kPa and 13 s, respectively, and an intact microstructure with little free collagen in the fused area could be observed. Conclusions The technology of RF energy-based tissue fusion could accomplish fast and stable intestinal tract reconstruction, showing great potential in clinical application. It is of great significance to shorten the operation time, simplify the operation process and improve the operation quality.
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Objective To establish the pushing transmission model of tendon-sheath system (TSS) for endoscopic flexible instrument, and study the key influencing factors of transmission efficiency. Methods The force and displacement transmission models of TSS in pushing configuration were built and simulated. The tendon-sheath transmission testing platform was designed to validate the model. The influencing factors, such as transmission velocity, tendon-sheath diameter ratio, curvature radius, were explored using this setup. Results There were obvious nonlinear phenomenon in force and displacement transmission. The model simulation results accorded quite well with the experiment results. Transmission velocity, tendon-sheath diameter ratio, curvature radius all had great effects on pushing force transmission of endoscopic flexible instrument, while they had a smaller effect on displacement transmission. Conclusions The proposed model can be used for calculating pushing force transmission of tendon-sheath system for endoscopic flexible instrument, so as to provide the doctors with force feedback at the tip of the end effector, and ensure the safe operation and improve the surgical effects. For better design and control of endoscopic flexible instrument, the transmission velocity, tendon-sheath diameter ratio, curvature radius must be comprehensively considered.
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Objective To design a notched flexible articulation applied to electric stapler and study its turning performance. Methods The notched flexible articulation was designed and modeled. The kinematics and statics models of the articulation were established for simulation calculations. The stress, deflection angle, top displacement and driving force of the articulation with 3 different turning structures were studied under equal and variable stiffness of symmetrical notches by using finite element simulation. An experimental platform for performance test of the turning structure was built to verify the simulation results and the model. Results The theoretical model of the turning structure in bending process was basically consistent with the experimental results. With the optimization of symmetrical notch stiffness, the maximum stress of the articulation with variable stiffness was reduced by 20.64% and 39.20%, respectively. The articulation with variable stiffness required the smallest tensile force during bending, which was 33.41% lower than that of the articulation with equal stiffness, and the tip displacement (30.8 mm) along the bending plane was the smallest. The maximum deflection angle for the articulation with 3 different turning structures all could reach 90°. Conclusions The kinematics and statics models of the articulation can be used for the calculation of its tensile force and position changes. The turning performance of the articulation with variable stiffness using symmetrical notch is better than that with equal stiffness. The notched flexible articulation meets the design requirements and the turning needs of electric stapler.
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Objective:To perform 3D modeling based on CT images of human stomach-esophagus structure and provide 3D models of normal and reflux forms of gastroesophagus.Methods:Based on CT images of stomach-esophagus structure, 3D models was established using Mimics 10.01, Geomagic Studio 2012 and SolidWorks 2018 software. In the modeling process, the Mimics software was used to coarsely and finely divide the model to export stomach-esophageal point cloud data. On the basis of the point cloud data, Geomagic Studio software was used to simplify and repair the model, and complete the operations of filling holes and smooth surfaces. SolidWorks software was used to process the structure of the cardia and establish a normal model of stomach-esophagus and a model of cardiac disease. Finally, the model was replicated using soft 3D printing technology.Results:The geometric parameters of the established stomach-esophagus model were within the actual range, which proved that the model has certain practicality.Conclusions:The model can be used as a basic material for gastric surgery simulation training, to help doctors or medical students to be proficient and improve the operation skills and surgical level of gastric surgery.
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Objective To develop a new type of electric stapler, so as to solve the problems of insufficient rotation angle, inconvenient operation and difficulty in controlling the pressing strength of existing products. Methods An electric stapler was designed and manufactured. The motion trajectory curve of the prototype was measured by using the three-coordinate imaging instrument to build functional test platform of the prototype, and the goodness of fit was used to evaluate consistency between the theoretical curve and the measured curve. The small intestine tissues of fresh pig were anastomosed at different bending angles of the front end, and the forming rate of the anastomotic stoma was measured. Results The goodness of fit between the test curve and the theoretical curve for both turning motion and shooting motion was ideal, while the goodness of fit between the test curve and the theoretical curve for pressing motion was not ideal when the turning joint was bent at 0°-30°, and was ideal when it was bent at 45°-60°. In performance test, the deformity rate of the nail was smaller than 1.14%, indicating that the bending angle had no significant impacts on the anastomotic effect. Conclusions The kinematics curves of shooting motion and turning motion are consistent with the theoretical curves. The pressing motion curves fluctuate at different bending angles, which will not affect the anastomotic effect, and the effect of the electric stapler meets the clinical requirements.
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Objective The current manipulator with double parallel quadrilateral mechanism should be connected in series with a flexible degree of freedom (DOF) mechanism, which increases the volume of the manipulator, decreases the motion flexibility and creates the interference between the mechanical arms that hold the mirror and the device. Aimed at solving this problem, a novel mechanical arm was put forward to enhance the motion flexibility and reduce the volume of the manipulator. Methods The mechanical arm was designed by using the mechanism of five-link, slider and slide rail lower pair and wire transmission to realize the telescopic movement of the end effector. The kinematics model of the manipulator was established, and the MATLAB was used as the simulation tool to verify the correctness of the D-H parameters under the specific zero joint angle, and the motion equation of the manipulator was solved. Meanwhile, the three-dimensional workspace of the end effector was obtained by using Monte Carlo algorithm, and the preoperative plan of animal experiment for 3 arms was performed. Finally, cholecystectomy and other operations were acted in pigs, to verify the rationality and maneuverability of the design of double 5-link 2-DOF manipulator. Results The working space of Monte Carlo algorithm under MATLAB environment was -650.4 mm＜x＜649 mm, 163.8 mm＜y＜1 202 mm and -254.6 mm＜z＜829.8 mm. Sixteen cases of pig cholecystectomy were successfully completed, with an average operation time of 51 minutes. Conclusions The novel double 5-link 2-DOF manipulator could successfully complete cholecystectomy and other operations in pigs, which had no other symptoms after the operation. There was no interference between the mechanical arms, which fully verified the feasibility of the design scheme of the robot manipulator for minimally invasive surgery.
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Objective To analyze the influence of different geometric parameters on flexibility of the commonly used Z-shaped stent-grafts for treating thoracic aortic aneurysm, as well as the primary and secondary order of such influence. Methods The three-dimensional models of the stent-grafts with different strut numbers, wire diameters, crest height, bending radius were established by SolidWorks and imported to ANSYS software for finite element analysis．The 60° rotation of X-axis was applied to the stent-grafts, and the flexibility of the stent-grafts was evaluated according to 3 evaluation parameters (Von Mises stress, reaction force and bending torque)． Results After bending of the stent-grafts, the maximum stress was concentrated on the inside of the bend；reducing the wire diameter, crest height and strut number of the stent-grafts, the flexibility of the stent-grafts would increase; increasing the bending radius， the flexibility of the stent grafts would increase; the effect of the wire diameter and strut number on flexibility of the stent-grafts was stronger than that from the bending radius and crest height． Conclusions The strut number, wire diameter, crest height, bending radius had a significant impact on flexibility of the stent-grafts. The research findings can provide theoretical references for the selection and optimal design of the stent-grafts in clinic, and have a positive influence on reducing the incidence rate of complications such as new entry.
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Objective To analyze the influence regularities of different sizes on thermal stress field of bipolar high-frequency electric knife. Methods Based on the ANSYS software, the electric-thermal coupling simulation analysis was performed for thermal stress field of bipolar high-frequency electric knife during working. The effects of 3 different insulation layer thicknesses (0-5, 1-0, 1-5 mm), electrode thicknesses (0-5, 1-0, 1-5 mm) and coating thicknesses (3, 6, 9 μm) on thermal stress field of bipolar high-frequency electric knife were studied. Results If thickness of the insulation layer was larger, deformation of the myocardial tissues would be smaller due to thermal stress, that is, the thickness of the insulation layer was inversely proportional to thermal deformation of the myocardial tissue during working process of the high-frequency electric knife. For the 3 electrode thicknesses, 1-0 mm was a better choice. And for the 3 coating thicknesses, 6 μm was a better choice. Conclusions The component sizes for the high-frequency electric knife have an important influence on thermal stress field, and the result can provide guidance for design of the high-frequency electric knife.
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Objective To develop a novel electric stapler, so as to improve the automation, convenience and precision of minimally invasive surgery. Methods The clamping, firing and turning mechanism of the new electric stapler was innovatively designed to realize the electric drive of minimally invasive surgical anastomosis on the basis of traditional mechanical stapler. The motion process of electric clamping, firing and double-screw turning mechanism was analyzed in detail, and the equations for motion function of three mechanisms were solved, providing a theoretical basis for the intelligent control algorithm of electric stapler. Results The electric clamping and firing process was simulated using ADAMS software to verify the equation of motion. The prototype of the new electric stapler was made, and the anastomosis experiment and blasting pressure experiment of the in vitro small intestine tissues were carried out. The range of anastomotic blasting pressure was between 3.7 kPa and 11.67 kPa, meeting the basic requirements in clinic. Conclusions The structure of the new electric stapler can meet the requirements of electric pressing and firing in minimally invasive surgery, contributing to achieve tissue anastomosis more conveniently, quickly and effectively.
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Objective To compare and analyze the relationship between geometric parameters of the needle of different insulin pens and their puncture force, flow rate, and pressing force. Methods The human skin tissue model and needle model were established, and the finite element simulation analysis of needle puncture was performed. Using a test platform, 25 kinds of needles with different geometric parameters were tested for the puncture force, pushing pressure, flow rate and other parameters. The influence of geometric parameters on the performance of the needles were analyzed. Results The puncture force of the needle was closely related to its section design. Compared with the three-section needle, the five-section needle increases the secondary inclination angle and the condyle angle, increases the contact area between the needle and the tissue, and make the change of the contact angle more smoothly, which reduce the needle penetration force. The smaller the outer diameter of the needle, the smaller the penetrating power. The larger the inner diameter of the needle, the greater the fluid flow rate, the smaller the pushing pressure, and the higher the injection accuracy. Conclusions Five-section, ultra-thin-walled or ultra-thin-walled needles have more excellent performance. On the basis of ensuring the strength of the needle, the needle's geometry can be optimized to reduce the puncture force. The results of this study can provide theoretical basis and experimental basis for the design of needles for insulin pens.
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Objective To analyze influences of the braiding angle and material on performance of ventricular septal defect (VSD) occluders, so as to provide theoretical basis and guidance for their design. Methods The finite element models of occluders with different braiding angles (30°, 45° and 60°) were developed respectively. The radial supporting and axial bending performances of nickel titanium (NiTi) occlude and poly-p-dioxanone (PPDO) occlude were then compared. Results Under 5 kPa radial loading, radial stiffness of the 30°, 45° and 60° NiTi occluder waists were 8.60, 1.51 and 0.99 mN/mm3,respectively, while that of 45° PPDO occluder waist was 7.35 mN/mm3. Under axial bending of 0.5 rad, the maximum radial deformation of the 30°, 45°, 60° NiTi occluder waists were 1.17, 1.24 and 0.22 mm, while that of the 45° PPDO was 0.54 mm. Conclusions Under the condition of using the same material, occluders with braiding angle of 60° show the lowest radial stiffness, indicating they have the best radial supporting ability. Furthermore, they also show the smallest maximum radial deformation, indicating they have the best axial bending ability and the compliance. On the other hand, under the condition of using the same braiding angle, NiTi occluders show lower radial stiffness, indicating they have better radial supporting ability. However, PPDO occluders show lower maximum radial deformation, indicating they have better axial bending ability and compliance.
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Objective To explore the value of new and fused conventional texture features extracted from mammograms using improved local ternary patterns (LTP) in predicting risk of breast cancer.Methods Mammograms were segmented.Based on improved LTP,the new and conventional texture features were extracted from segmented mammograms of bilateral breasts.Then the features of bilateral breasts were merged.The high dimensional characteristics were reduced with principal component analysis (PCA).Finally,the new texture features were classified with k-nearest neighbor (KNN),and the fusion features were clustered with logistic alternating decision tree (LADTree) algorithm.Results The area under ROC curve (AUC) of new texture features for predicting breast cancer was 0.732 4 ±0.042 8,and the sensitivity,specificity and prediction accuracy was 72.04％ (67/93),74.51％ (76/102) and 73.33％ (143/195),respectively.Furthermore,AUC of fusion features was 0.865 5± 0.014 8,the sensitivity,specificity and prediction accuracy was 84.95％ (79/93),88.23％ (90/102) and 86.67％ (169/195),respectively.Conclusion The new texture features based on improved LTP have high prediction accuracy for breast cancer,and the prediction efficacy can be improved after fusion with conventional features.
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Simulations can mimic the environment that refers to the surgery operation to improve the technical skills of the trainees. In this paper, we designed a new cardiac surgery simulative training system. The isolated pig heart was selected as the heart model. A mechanical device was designed to achieve the beating of heart model. At the same time, adjusting frequencies of mechanical movement could change the rating of heartbeat. In order to validate the rationality of the system, 12 non-medical specialty students and 12 medical specialty students were divided into two groups, which consecutively accepted seven-days of training for off-pump coronary artery bypass grafting using the cardiac surgery simulative training system. The time for completing bypass grafting before and after training were recorded. And the bridging outcomes of each trainee were assessed by 3 surgery cardiac surgeons using the object structured assessments of technical skill (OSATS) criteria. After training, each trainee could finish the bypass suturing in a shorter time than before training, and the scores of each trainee assessed by OSATS criteria were also improved. The results showed that the cardiac surgery simulative training system had better training effect in improving the surgical techniques, operation skills and proficiency of surgical instruments of trainees.
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Objective To investigate the value of improving the prediction accuracy of near-term risk for developing breast cancer by transforming the original mammography image and fusing the different types of image features using the algorithm of machine learning.Methods The craniocaudal (CC) full-field digital mammography (FFDM) of 185 women were downloaded from the clinical database at the university of Pittsburgh medical center.Firstly,the original gray images were segmented and transformed into virtual optical density images.Then the asymmetry features were separately extracted from original gray images and virtual optical density images.Two decision tree classifiers of the first stage were trained based on the features extracted from two types of image.And the scores output from the two classifiers were used as input to train the second stage of one decision tree classifier.Leave-one-case-out method was used to validate the prediction performance of near-term risk of breast cancer.Results Using two-stage decision tree fusion method to predict breast cancer,the area under the ROC curve (AUC) was 0.9612±0.0132.And the sensitivity,specificity and prediction accuracy were 96.63％(86/89),91.67％(88/96) and 94.05％(174/185).Conclusion The features extracted from virtual optical density image have higher discriminatory power of predicting breast cancer.Fusing the two kinds of image features twice by two-stage decision tree method can help to improve the prediction accuracy of near-term risk of breast cancer.