Finite element analysis of braided dense-mesh stents for carotid artery stenosis.

When braided dense-mesh stents are used to treat carotid stenosis, the structural mechanics of vascular stents, the contact mechanics with blood vessels, and the fluid mechanics in the blood environment need to be studied in depth to reduce the damage of stents to blood vessels and the incidence of in-stent restenosis. Three types of braided stents with 8, 16, and 24 strands and laser-cut stents with the corresponding size parameters were designed, and the bending behavior of each of these types of stent, deployment, and fluid dynamic analysis of the 24-strand braided stent were simulated. The results show that the bending stress of the 8-, 16-, and 24-strand braided stents is 46.33%, 50.24%, and 31.86% of that of their laser-cut counterparts. In addition, higher strand density of the braided stents was associated with greater bending stress; after the 24-strand braided stent was expanded within the stented carotid artery, the carotid stenosis rate was reduced from 81.52% to 46.33%. After stent implantation, the maximum stress on the vessel wall in a zero-pressure diastolic environment decreased from 0.34 to 0.20 MPa, the maximum pressure on the intravascular wall surface decreased from 4.89 to 3.98 kPa, the area of high-pressure region decreased, the wall shear force of the stenotic segment throat decreased, and blood flow increased in the stenosis segments. The braided stent had less bending stress and better flexibility than the laser-cut stent under the same stent size parameters; after the 24-strand braided stent was implanted into the stented vessel, it could effectively dilate the vessel, and the blood flow status was improved.

[Design and analysis of shoulder type exoskeleton stretcher for individual soldier].

For the transportation process of rescuing wounded personnel on naval vessels, a new type of shoulder type exoskeleton stretcher for individual soldier was designed in this paper. The three-dimensional model of the shoulder type exoskeleton stretcher for individual soldier was constructed using three dimensional modeling software. Finite element analysis technique was employed to conduct statics simulation, modal analysis, and transient dynamics analysis on the designed exoskeleton stretcher. The results show that the maximum stress of the exoskeleton stretcher for walking on flat ground is 265.55 MPa, which is lower than the allowable strength of the fabrication material. Furthermore, the overall deformation of the structure is small. Modal analysis reveals that the natural frequency range of the exoskeleton stretcher under different gait conditions is 1.96 Hz to 28.70 Hz, which differs significantly from the swing frequency of 1 Hz during walking. This indicates that the designed structure can effectively avoid resonance. The transient dynamics analysis results show that the maximum deformation and stress of exoskeleton stretcher remain within the safety range, which meets the expected performance requirements. In summary, the shoulder type exoskeleton stretcher for individual soldier designed in this study can solve the problem of requiring more than 2 people to carry for the existing stretcher, especially suitable for narrow spaces of naval vessels. The research results of this paper can provide a new solution for the rescue of wounded personnel on naval vessels.

Algae: A Robust Living Material Against Cancer.

Cancer is the second leading cause of death worldwide. Its incidence has been increasing in recent years, and it is becoming a major threat to human health. Conventional cancer treatment strategies, including surgery, chemotherapy, and radiotherapy, have faced problems such as drug resistance, toxic side effects and unsatisfactory therapeutic efficacy. Therefore, better development and utilization of biomaterials can improve the specificity and efficacy of tumor therapy. Algae, as a novel living material, possesses good biocompatibility. Although some reviews have elucidated several algae-based biomaterials for cancer treatment, the majority of the literature has focused on a limited number of algae. As a result, there is currently a lack of comprehensive reviews on the subject of anticancer algae. This review aims to address this gap by conducting a thorough examination of algal species that show potential for anticancer activity. Furthermore, our review will also elucidate the engineering strategies of algae and discuss the challenges and prospects associated with their implementation.

Clinical value of video-assisted single-lumen endotracheal intubation and application of artificial intelligence in it.

Visualization techniques and artificial intelligence (AI) are currently used for intubation device. By providing airway visualization during tracheal intubation, the technologies provide safe and accurate access to the trachea. The ability of AI to automatically identify airways from images of intubation device makes it attractive for use in intubation devices. The purpose of this review is to introduce the state of application of visualization techniques and AI in certain intubation devices. We reviewed the evidence of clinical implications of the use of video-assisted intubation device in the intubation time, first attempt success rate, and intubation of the difficult airway. Especially, VivaSight single-lumen tube with an incorporated optics allows direct viewing of the airway. VivaSight single-lumen tube has more advantages in tracheal intubation. AI has been applied to fiberoptic bronchoscopy (FOB) and video laryngoscope with automatic airway image recognition, and has achieved certain accomplishment. Further, we discussed the possibility of applying AI to the VivaSight single-lumen tube and proposed future directions of research and application.

Design and evaluation of a multimodal balance training system.

OBJECTIVE: Current balance training systems are designed exclusively for one particular type of training and assessment. Additionally, they comprise monotonous training programs. Therefore, patients in different stages of rehabilitation must use different balance training models from different manufacturers, resulting in high treatment cost. Furthermore, large spaces are required to accommodate the balance training machines, and doctors and physiotherapists have to learn to operate multiple machines. We aimed to design a multimodal balance training and assessment system that can accommodate the assessment and training of static, dynamic, reactive and proactive balance to satisfy individual needs. METHODS: The difficulty associated with combining static, dynamic, reactive and proactive balance training in a single system was to use radial and circumferential driving mechanisms together with a clutch mechanism, whereby circumferential and radial drivers were installed in the base of the system to drive a compound foot plate system with interchangeable springs, in order to adjust stiffness using the clutch. Based on the kinematic equation, the influence of system parameters on the change of the body's center of gravity were evaluated. The parameters included the radial offset of the driving mechanism (r), circumferential angle of rotation (θ), height of the base of the balance training system (h), horizontal distance between the body's standing center of gravity and the center of the foot plate (R), thickness of the padding mat (ΔH) and inclination angle (α). RESULTS: The difficulties associated with combining static, dynamic, reactive and proactive balance training models in a single system were solved using radial and circumferential driving mechanisms together with a clutch mechanism. The foot plate can swing back and forth within ±20° around the X-axis, swing left and right within ±20° around the Y-axis, swing diagonally within ±20°, swing 360° around the Z-axis, and adjust the height along the Z-axis. Furthermore, the inclination angle α, circumferential angle of rotation θ, and speed (dα/dt and dθ/dt) of the system can be controlled in real time. CONCLUSION: The developed balance training system is suitable for patients in different stages of rehabilitation. By providing multiple functionalities, this system can ensure high use rates, reduce costs and save space.

[Material design and temperature field simulation analysis of tumor radiofrequency ablation needle].

To solve the problems of small one-time ablation range and easy charring of the tissue around the electrode associated with the tumor radiofrequency ablation needle, based on the multiphysical field coupling analysis software COMSOL, the effects of needle material, the number of sub needles and the bending angle of sub needles on the ablation effect of radiofrequency ablation electrode needle were studied. The results show that compared with titanium alloy and stainless steel, nickel titanium alloy has better radiofrequency energy transmission efficiency and it is the best material for electrode needle. The number of sub needles has a great influence on the average necrosis depth and the maximum necrosis diameter. Under the same conditions, the more the number of sub needles, the larger the volume of coagulation necrosis area. The bending angle of the needle has a great effect on the maximum diameter of the coagulated necrotic area, but has little effect on the average necrotic depth. Under the same other conditions, the coagulation necrosis area formed by ablation increased with the increase of the bending angle of the sub needle. For the three needles with bending angles of 60 °, 90 ° and 120 ° analyzed in this paper, the one with bending angle of 120 ° can obtain the largest coagulation necrosis area. In general, the design of nickel titanium alloy with 120 ° bending 8-pin is the optimal. The average depth of radiofrequency ablation necrosis area is 32.40 mm, and the maximum necrosis diameter is 52.65 mm. The above optimized design parameters can provide guidance for the structure and material design of tumor radiofrequency ablation needle.

Biomechanical analysis of mandibular defect reconstruction based on a new base-fixation system.

Buccal titanium plate fixation is a common method for repairing mandibular defects. However, the method presents certain problems: the requirement of a large volume of titanium plate, a large number of fixation screws, a lengthy duration of the surgical operation, and exposure of the fixation plate which easily causes wound infection. In this study, a new base-fixation system was designed. Mandibular reconstruction was performed using the three-dimensional reconstruction package Mimics. In order to compare the newly designed base-fixation system and the common buccal-fixation system, the stress distributions and the displacement distributions of the whole model under two loading conditions were studied, based on the finite element analysis package ANSYS. The safety of the base-fixation titanium plate was evaluated. The results showed that although the maximum stress of the base-fixation titanium plate was higher than that of the buccal-fixation titanium plate, it was still less than the yield strength of titanium. Therefore, under the condition of applying 300 N of vertical occlusal loading, the base-fixation titanium plate displayed superior fixation ability without permanent deformation (and concomitant fixation failure). The results of the fatigue simulation analysis showed that the safety factor of the base-fixation titanium plate in the working state was 3.8 (>1.0), indicating that its fatigue performance met the application requirements. Compared with traditional buccal fixation, the novel base-fixation system has obvious advantages, suggesting its suitability as a new treatment method for clinical mandibular defect reconstruction.

Finite element analysis of fixation effect for femoral neck fracture under different fixation configurations.

In this study, the biomechanical differences among three internal fixation configurations for treatment of Pauwels type II and III femoral neck fractures were analyzed. Using finite element analysis, the femur displacement and stress distributions of the internal fixation device and fracture section were obtained for different patients and movement conditions. The results show that patients with osteoporosis are more prone to femoral varus and femoral neck shortening, and the fracture probability of the device for these patients is higher than that for patients with normal bone. The treatment effect of the inverted-triangle screw (ITS) fixation and proximal femoral nail anti-rotation (PFNA) fixation is better than that of dynamic hip screw (DHS) fixation. The ITS fixation is more suitable for the treatment of the normal bone patients with Pauwels II femur neck fracture. However, the PFNA fixation has better biomechanical advantages and better capability for anti-femoral neck shortening. Therefore, it is suitable for the treatment of femoral neck fracture patients with osteoporosis.

Multifunctional testing system design for varicose vein therapy apparatus.

Varicose veins of lower extremity can be treated effectively with varicose vein therapy apparatus. In order to ensure its therapy effect, it is necessary to test the air tightness of pneumatic circuit and other related performance parameters. The traditional manual testing method has some problems, such as large error, low efficiency and so on. This paper developed a multifunctional testing system based on LabVIEW software to overcome these shortcomings. The system is a combination of software and hardware, which can realise key components calibration, pneumatic circuit air tightness testing, gasbag pressure-resistance performance testing, pressure sensor performance testing and air pump performance testing. The multifunctional testing system realises the goal of automated human-computer interaction testing, which has a bright future in the aspects of application prospect.

A novel fast solving method for targeted drug-delivery capsules in the gastrointestinal tract.

BACKGROUND: As an innovative technique without cable connection, targeted drug-delivery capsules improve diagnostic and therapeutic capabilities in the gastrointestinal (GI) tract. OBJECTIVE: To fast track targeted drug-delivery capsules in the GI tract, a tracking method based on the multiple alternating magnetic sources with adaptive adjustment of the excitation intensity has been investigated. METHODS: The functional prototype of the tracking system has been developed. The tracking model between the magnetic field strength and the capsule's location has been established, which shows a nonlinear equation group with multiple local extremum. Particularly, an improved back-propagation (BP) neural network by particle swarm optimization (PSO) is investigated to solve the tracking problem in real time. The PSO is introduced at an early stage to optimize the weights and thresholds of the BP neural network to improve the generalizability and global search ability. Consequently, the Levenberg-Marquardt (LM) algorithm is used as the learning rule to obtain a higher accuracy and convergence rate. RESULTS: The performance on the PSO-BP neural network is experimentally analyzed by comparing it with the standard BP network and the LM-BP network. CONCLUSIONS: The tracking experiments show that the PSO-BP neural network can solve the tracking problem successfully. The PSO-BP network can get the solution faster than iterative search algorithms.

A novel and reproducible release mechanism for a drug-delivery system in the gastrointestinal tract.

To establish a reliable, reproducible and accurate release of the drug in the gastrointestinal tract, a novel release mechanism for a controllable drug-delivery system has been investigated. The release mechanism, consisting of a one-way valve for drug release, a drug chamber, two axially magnetized cylindrical permanent magnets and a multi-layer solenoid coil, is hosted in the capsule-shaped shell with diameter 11 mm and length 30 mm. To actuate the coil piston, the two static magnetic fields produced by the two magnets are aligned along the same axis, having the same magnitude, but opposite directions. Based on the principle of the electromagnetic force and the Bernoulli equation, the actuating force can be expressed as a function of the coil stroke and the excitation current, which was modeled and experimentally verified. Thus the actuating force can be controlled by adjusting the activated period and intensity of the coil, resulting in the reproducible release with different doses and mean rates. Then, a prototype of the drug-delivery system has been developed, which consists of a drug-delivery capsule, a radio frequency transmission module, an interface circuit, and an instruction setting and triggering platform. All the drug release parameters, including the release mode, times, dose and mean flow rate, can be set by the platform. The experiment verifies that the drug-delivery capsule can deliver a predetermined dose with different flow rates and dip angles of the capsule. The relative error of the releasing dose becomes larger with increasing releasing rate and decreasing releasing dose.

Safety and efficacy of a novel abluminal groove-filled biodegradable polymer sirolimus-eluting stent.

Late stent thrombosis (LST) following drug-eluting stent (DES) implantation in patients with coronary artery disease (CAD) is often associated with delayed vascular healing, resulting from vascular inflammation and hypersensitivity to durable polymers and drugs. Therefore, DES design, materials, and coatings have been technologically revolutionized. Herein, we designed a novel abluminal groove-filled biodegradable polymer sirolimus-eluting stent (AGF-BP-SES), with a sirolimus content of only about one-third of traditional DES. The mechanical performances of AGF-BP-SES during compression and expansion were investigated. The pharmacokinetic (PK) profile of sirolimus was studied in the swine model. The in vivo efficacy of AGF-BP-SES was compared with that of Xience PRIME® stent. The results showed that AGF-BP-SES exhibited mechanical properties similar to traditional DES, including the rebound ratio of radial contraction/direction, rebound ratio of axial contraction/direction, and inhomogeneity of compression/expansion. Despite utilizing a reduced dose of sirolimus, AGF-BP-SES delivered sirolimus to the coronary artery in a controlled and efficient manner. The stent maintained a safe and effective local drug concentration without local or systemic risks. In the swine model, histopathological indicators predicted safety and biocompatibility of AGF-BP-SES. In conclusion, AGF-BP-SES maintained similar mechanical properties as other stents while reducing the drug-loading capacity, and showed a favorable safety and efficacy profile of the targeted DES.

[Testing system design and analysis for the execution units of anti-thrombotic device].

In an anti-thrombotic pressure circulatory device, relays and solenoid valves serve as core execution units. Thus the therapeutic efficacy and patient safety of the device will directly depend on their performance. A new type of testing system for relays and solenoid valves used in the anti-thrombotic device has been developed, which can test action response time and fatigue performance of relay and solenoid valve. PC, data acquisition card and test platform are used in this testing system based on human-computer interaction testing modules. The testing objectives are realized by using the virtual instrument technology, the high-speed data acquisition technology and reasonable software design. The two sets of the system made by relay and solenoid valve are tested. The results proved the universality and reliability of the testing system so that these relays and solenoid valves could be accurately used in the antithrombotic pressure circulatory equipment. The newly-developed testing system has a bright future in the aspects of promotion and application prospect.

[Design of a testing system for antithrombotic pressure circulatory equipment].

A new type of testing system used for antithrombotic pressure circulatory equipment has been developed, which realized a new method for the calibration of pressure sensor. Multi-path control and acquisition functions are achieved by this method based on human-computer interaction testing system. The precision of pressure sensor is ob tained by polynomial fitting for each test point using linear interpolation method. The result showed that the precision test of pressure sensor could be realized easily and efficiently, using the developed testing system, and the parameters of pressure sensor could be calibrated effectively, so that it could be accurately used in the antithrombotic pressure circulatory equipment. The developed testing system has a prosperous future in the aspects of promotion and application.