A 3D non-human primate digital model for pharmacokinetic prediction of intra-cerebrospinal fluid drug neuraxial dispersion

Pulsatile flow simulation in arterial vascular segments with intravascular ultrasound images

Simulation and integration of geometric and rigid body kinematics errors for assembly variation analysis

The influence of wall motion on the hemodynamic characteristics of the human femoral bifurcation and its effects on the development of peripheral artery disease has not been previously investigated. This study aimed in investigating the hemodynamics of a compliant patient-specific femoral artery bifurcation model by a fluid structure interaction (FSI) scheme. The complex physiological geometry of the femoral artery bifurcation was reproduced from sequentially obtained transverse CT scan images. Velocity waveforms derived from phase contrast MR images were extracted and mapped to define boundary conditions. Equations governing blood flow and wall motion were solved using an FSI framework that utilizes commercial codes: FLUENT for computational fluid dynamics and ANSYS for computational structural dynamics. The results showed that wall compliance decreased flow velocities at the relatively high curvature geometries including common and superficial femoral artery (SFA), and it created strong recirculation in the profunda femoris artery close to the bifurcation. In the SFA region near the apex, time averaged wall shear stress (TAWSS) differences up to 25% between compliant and rigid models were observed. The compliant model also exhibited lower TAWSS and oscillatory shear at the superior section of the common femoral artery close to the bifurcation. The presence of wall motion, however, created minor differences in the general flow-field characteristics. We conclude that wall motion does not have significant influence on the global fluid dynamic characteristics of the femoral artery bifurcation. Longer arterial segments need to be simulated to see the effect of wall motion on tortuousity which was previously cited as an important factor in the development of atherosclerosis at the femoral artery.

Inflatable penile prosthesis (IPP) implantation is a well-established treatment for erectile dysfunction. A comprehensive understanding of the mechanical interactions between the IPP and penile tissues is crucial for improving surgical outcomes and device performance. This study aims to develop and validate preclinical testbeds, including a polymer-based benchtop model and a finite element (FE) model, to replicate the biomechanical behaviour of penile tissues during IPP inflation. A polymer-based benchtop model was developed using porous and non-porous polyvinyl alcohol (PVA) hydrogels, with the porous PVA mimicking the spongy corpus cavernosum (CC) and the non-porous PVA representing the tunica albuginea and fascial layers. IPP inflation tests were conducted on three benchtop models and three human penile tissue segments. Additionally, 3D FE simulations of IPP inflation were performed on both the benchtop and human tissue models for comparative analysis. The experimental results demonstrated strong agreement between the human penile tissues, the benchtop model, and the FE simulations, validating the preclinical testbeds. Parametric studies using the FE model revealed that CC layer size and stiffness significantly influence IPP inflation mechanics, highlighting the importance of these factors in device performance. These validated preclinical testbeds provide a robust platform for optimising IPP design, guiding surgical procedures, and mitigating associatedpost-implantation complications. The developed benchtop and FE models effectively replicate human penile tissue responses to IPP inflation and can serve as valuable preclinical tools for device manufacturers and clinicians. Their use may enhance surgical decision-making and improve long-term IPP outcomes.

Purpose Inflatable penile prosthesis (IPP) implantation is a well-established treatment for erectile dysfunction (ED). A comprehensive understanding of the mechanical interactions between the IPP and penile tissues is crucial for improving surgical outcomes and device performance. This study aims to develop and validate preclinical testbeds, including a polymer-based benchtop model and a finite element (FE) model, to replicate the biomechanical behaviour of penile tissues during IPP inflation. Methods A polymer-based benchtop model was developed using porous and non-porous polyvinyl alcohol (PVA) hydrogels, with the porous PVA mimicking the spongy corpus cavernosum (CC) and the non-porous PVA representing the tunica albuginea (TA) and fascial layers. IPP inflation tests were conducted on three benchtop models and three human penile tissue segments. Additionally, 3D FE simulations of IPP inflation were performed on both the benchtop and human tissue models for comparative analysis. Results The experimental results demonstrated strong agreement between the human penile tissues, the benchtop model, and the FE simulations, validating the preclinical testbeds. Parametric studies using the FE model revealed that CC layer size and stiffness significantly influence IPP inflation mechanics, highlighting the importance of these factors in device performance. These validated preclinical testbeds provide a robust platform for optimising IPP design, guiding surgical procedures, and mitigating post-implantation complications associated. Conclusion The developed benchtop and FE models effectively replicate human penile tissue responses to IPP inflation and can serve as valuable preclinical tools for device manufacturers and clinicians. Their use may enhance surgical decision-making and improve long-term IPP outcomes.

Development of a 3D Printed Benchtop Model of the Pulmonary System to Assist in the Development of Device to Treat Large Pulmonary Thrombo-embolic Disease

The impact of compliance on Stage 2 uni-ventricular heart circulation: An experimental assessment of the Bidirectional Glenn

Clearly, the assumption that all bodies are perfectly rigid, hence the introduction of singular distributions in the modeling of collisions has the advantage of providing an attractive framework of impact dynamics. Note however that bodies that collide do possess a certain compliance, so that the collision duration is strictly positive (1) and local deformations occur near the point of impact. Actually global (vibrational) deformations are also created, and they may play a major role in the dynamics. They may even play a much more important role than the local deformations. Consequently, rigid body dynamics may be considered as a limit case only, which however does not preclude its practical as well as theoretical utility (the pros and cons of rigid and flexible body approaches are not the topic of this chapter). One may therefore choose to work with continuous-dynamics models of collision, such that the bodies deform during the impact, and the collision dynamics are treated as continuous time dynamic phenomena (restricted to local deformations in most of the studies). Historically, it has very often been difficult to certain scientists to accept the idea of perfect rigidity [979]. For instance Leibniz himself [509] [510] (and Bernoulli after him [77]) refused this idea because rigidity yields violation of the “law of continuity” in nature. A strong scientific debate motivated by the London Royal Society in 1668 also concerned the concept of “hardness” (which is to be understood as rigidity in this context): is a hard body able to rebound? Or is it necessary that the bodies possess some “springiness”? Wallis and Mariotte concluded that springs are necessary, while Huygens, Wren and Malebranche thought that hardness is sufficient [979]. We know now the difference between a model of nature and nature itself. We also have many more mathematical tools at our disposal to accept perfect rigidity and to study accurately the relationship between compliant and rigid models (2). Moreover the very short collision durations allow one to safely work with two timescales in many practical cases. And it is possible to lump the deformations effects in one single coefficient while keeping the attractiveness of rigid body models, see section 4.2 and subsection 4.2.10.KeywordsContact ForceInteraction ForceExternal ActionCompliant ModelUnilateral ConstraintThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Quantifying the forces needed for ureteral stent removal: Initial evaluation of magnetic stent removal devices on benchtop and porcine models

Benign prostatic hyperplasia (BPH) is a disease of the lower urinary tract which often requires surgical treatment. Recently, there has been a deluge of new treatment options, rarely validated or compared to current treatments on a benchtop model. The purpose of this review is to examine the literature and report which benchtop models are currently being used, which therapies have been tested on them, and what outcomes are being studied on each model. There are various benchtop models to choose from, each with their unique benefits and drawbacks. Perfused porcine kidney models are used to assess bleeding on the benchtop, ex-vivo human prostate helps to see specific interactions of devices with the prostatic tissue, and all other models have evaluated tissue ablation rates and depth of coagulation. There are currently no synthetic or non-animal tissues being used for this purpose, and surgical techniques such as enucleation, water-jet ablation, prostate stents, and water vapor thermal therapy have no representation in these benchtop tests. Benchtop testing serves an important role in the evaluation and comparison of surgical treatments for BPH. This testing allows these therapies to be objectively compared to one another, helping novel medical devices in their path to market and urologists make treatment decisions. Future directions may include further validation of the animal models currently being used and development of synthetic models which mimic the prostate on the benchtop.

Multiple surgical virtual reality (VR) simulators are currently available; however, there is lack of comparison between performance after practice on these simulators compared to bench top models. Utilizing the Intuitive Data recorder (IDR) and Objective performance indicators (OPI), we aim to objectively assess robotic surgical skills using a dry lab model. We hypothesize that practicing surgical skills will improve OPIs and that those who practice on the dry lab model will have a greater improvement in their OPIs compared to those who practice with Fundamentals of Robotic Surgery (FRS) SimNow VR. The IDR was used to record kinematics as each participant went through five basic surgery tasks on a dry lab benchtop model to record baseline performance. Participants were then randomized to practice on the dry lab model or the corresponding SimNow Virtual reality (VR) tasks. The participants repeated the tasks again on the benchtop model. Statistical analysis was performed using paired samples t tests, independent samples t tests, and ANOVA tests. Twenty-seven surgeons participated in our study ranging from interns to attendings. Randomization to VR vs benchtop practice resulted in 11 and 13 participants in each group. For the rollercoaster, backhand suturing, railroad, and knot tying tasks, a significant improvement in kinematic profiles was observed. Bimanual dexterity, angular motion, and smoothness metrics improved most consistently across the tasks after practice. Kinematic profiles between those practicing on VR versus benchtop had no significant differences. This study shows that OPIs can be used to benchmark surgical trainees. VR appears to be non-inferior to dry lab model for practice for trainees. We identified patterns in OPI improvement that can be tailored to specific skills depending on the trainees needs. Our study is the first step in developing a standardized training and assessment tool to assess competency in robotic surgery training.

For lower limb rehabilitation robot, the precise man-machine dynamics model is the basis for effective and reliable rehabilitation training. The traditional man-machine system dynamic model is a rigid body model with simplified link structure, which is difficult to realize man-machine synchronization movement without any interference, As well as, the safety of human motion cannot be guaranteed. To solve this problem, An adaptive UKF based parameter estimation of compliant man-machine dynamic model for lower limb rehabilitation robot is put forward. Firstly, according to the compliance of the human body movement, the human dynamic model described in the structure of “connecting rod parallel viscoelastic unit” is established based on the mechanism of human lower limb movement. In addition, the dynamic model of lower limb rehabilitation robot is established. Then, on this basis, the man-machine combined dynamics model is established according to the interaction relationship between human and the rehabilitation robot. Next, the parameters of man-machine dynamic model, which reflect the compliance of human movement, are estimated online by adaptive UKF algorithm. Finally, the compliant man-machine dynamic model is simulated and analyzed. The simulation results show that the adaptive UKF based parameter estimation of compliant man-machine dynamic model is scientific and reasonable.

A breast stabilization device or breast cradle has been developed for use in interventional procedures. The device is a three-dimensional collapsible linkage that, when actuated, lightly compresses the breast while pulling it away from the chest wall. The compression provides the pressure needed to hold the breast firm during needle biopsy, ablation, or other procedures while being more comfortable than bilateral compression plates. By collapsing radially in an open configuration, the cradle provides nearly full access to the breast, as compared to the restrictive two-dimensional layout of grid-based bilateral compression plates. By pulling the breast away from the chest wall, the breast cradle may reduce the incidence of lung puncture or other medical errors. Several iterations of the device were developed, including rigid-joint models and a compliant-joint model. The rigid models more precisely show the kinematics of the device, but the manufacturability and assembly of the joints may be tedious in a production environment. Conversely, the compliant model may be more easily mass-produced, although the design would be more complex and costly. To provide a proof-of-concept for the compliant-joint design, a rapid prototyping machine was used to quickly produce several models that could be produced by other means (i.e. vacuum forming or injection molding) in full production. These models will be tested with breast phantoms in a magnetic resonance imaging (MRI) environment to ensure compatibility. Other tests will be performed to ensure patient comfort amongst various breast sizes and shapes.

Patients with end stage renal disease require some form of vascular access for treatment, with Arterio-Venous Fistulas (avf) being the preferred form available due to better patency rates. However, they continue to present complications after creation, leading to early or late failure. While many studies are examining the flow in patient-specific fistulas, they often neglect the influence of vessel compliance on its hemodynamics. The objective of this study is to investigate the effect of wall compliance on the complex hemodynamics of a patient-specific brachio-cephalic avf and how it differs from a rigid fistula. Particle Image Velocimetry (piv) was used to capture the flow pattern within the fistula for both steady (Re = 1817) and pulsatile (Reav=1817, Remax=2232) flow conditions. The results were compared to rigid model measurements performed under the same Reynolds number. The streamline plots and coefficient of variation results did not differ significantly between the models; however, the non-dimensional velocity and directional variability results did vary between the two fistulas. A difference of approximately 8% was seen between the two models for both steady and pulsatile flow. The findings of this study suggest that to determine the bulk flow, a rigid model is adequate, but to capture the finer details of the flow, a compliant model is necessary.

In this paper, we attempt to study the influence of the bushings (compliant joints) on the static behavior of the guiding system used for the rear axle of the vehicles. In fact, we are interested to determine the difference in behavior between the compliant model (with bushings) and the rigid model (bushings modeled as spherical joints) of the axle guiding mechanism. The static model, in which the car body is attached to ground, is a constrained, multi-body spatial mechanical system, in which the bodies are connected through geometric constraints, compliant joints, and force elements. The external loading is made by vertical forces applied to the wheels, in stationary regime. The study is made for the general groups of guiding mechanisms, with M=1 and M=2 degrees of mobility, by using the MBS (Multi-Body Systems) environment ADAMS of MSC Software.