1,706 research outputs found

    Investigating the Effects of Biochemical and Biophysical Signals on Vascular Smooth Muscle Cell Differentiation

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    In blood vessel engineering, an optimal bioartifical scaffold can be characterized as a 3D tubular structure with high porosity for nutrient diffusion and enough mechanical strength to sustain in vivo dynamic environment. The luminal surface of the scaffold is supposed to have a continuous layer of endothelial cell that is ideally non-immunogenic and non-thrombogenic while the media layer of the construct is assigned for the ingrowth of vascular smooth muscle cell which can provide structural integrity and contractility. While reconstructing endothelial cell layer has been at the center of interest in most polymeric vascular replacements related research, growing VSMCs has had less attention due to the high risk of their excessive proliferation and unexpected phenotype shifts that can result in vessel restenosis. In addition, finding a reliable source of VSMC can be a formidable task. As such, we believe that if VSMCs can be modulated to remain quiescent and functional over time after they are obtained from an alternative source, they might eventually be considered to incorporate into artificial vascular substitute. To achieve this goal, first we investigated the potential of using stem cell to differentiate into functional VSMCs. Next, we designed a 3D culture construct to mimic blood vessel with distinct layers and analyzed the effect of combining different biochemical and biomechanical signals on modulating VSMCs behavior. Finally, we developed a biomechanical model that can incorporate the mechanical property of differentiated cell and distinct layers with geometrical information acquired from confocal images to predict cellular behavior under different conditions. The results of these studies provide insights from a basic science prospective about the potential of using stem cell to obtain functional VSMCs and the impact of environmental factors on VSMCs behavior. Researchers may use these results to optimize the culture condition of VSMCs in order to modulate its proliferation, phenotype and mechanical property. The model developed in this study might be used to predict cellular behavior under different culture environments without repetitive experiments

    On the Application of Mechanical Vibration in Robotics-Assisted Soft Tissue Intervention

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    Mechanical vibration as a way of transmitting energy has been an interesting subject to study. While cyclic oscillation is usually associated with fatigue effect, and hence a detrimental factor in failure of structures and machineries, by controlled transmission of vibration, energy can be transferred from the source to the target. In this thesis, the application of such mechanical vibration in a few surgical procedures is demonstrated. Three challenges associated with lung cancer diagnosis and treatment are chosen for this purpose, namely, Motion Compensation, tumor targeting in lung Needle Insertion and Soft Tissue Dissection: A robotic solution is proposed for compensating for the undesirable oscillatory motion of soft tissue (caused by heart beat and respiration) during needle insertion in the lung. An impedance control strategy based on a mechanical vibratory system is implemented to minimize the tissue deformation during needle insertion. A prototype was built to evaluate the proposed approach using: 1) two Mitsubishi PA10-7C robots, one for manipulating the macro part and the other for mimicking the tissue motion, 2) one motorized linear stage to handle the micro part, and 3) a Phantom Omni haptic device for remote manipulation. Experimental results are given to demonstrate the performance of the motion compensation system. A vibration-assisted needle insertion technique has been proposed in order to reduce needle–tissue friction. The LuGre friction model is employed as a basis for the study and the model is extended and analyzed to include the impact of high-frequency vibration on translational friction. Experiments are conducted to evaluate the role of insertion speed as well as vibration frequency on frictional effects. In the experiments conducted, an 18 GA brachytherapy needle was vibrated and inserted into an ex-vivo soft tissue sample using a pair of amplified piezoelectric actuators. Analysis demonstrates that the translational friction can be reduced by introducing a vibratory low-amplitude motion onto a regular insertion profile, which is usually performed at a constant rate. A robotics-assisted articulating ultrasonic surgical scalpel for minimally invasive soft tissue cutting and coagulation is designed and developed. For this purpose, the optimal design of a Langevin transducer with stepped horn profile is presented for internal-body applications. The modeling, optimization and design of the ultrasonic scalpel are performed through equivalent circuit theory and verified by finite element analysis. Moreover, a novel surgical wrist, compatible with the da Vinci® surgical system, with decoupled two degrees-of-freedom (DOFs) is developed that eliminates the strain of pulling cables and electrical wires. The developed instrument is then driven using the dVRK (da Vinci® research kit) and the Classic da Vinci® surgical system

    Acute effects of dynamic stretching on flexibility and agonist-antagonist muscle activity

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    Flexibility is an important determinant of health and important in sport performance. ADS and SPST are the methods most often used in training flexibility for sport. Although ADS appears to dominate SPST in measures of power and agility, the mechanisms are unclear. The purpose of this study was to delineate the effects of ADS on AROM and agonist-antagonist mean and peak EMG. The ADS protocol involved three sets of ten repetitions of leg kicks while in the supine position with the pelvis and contralateral limb fixed in extension. Participants moved the leg at the hip in a kicking motion to a point of mild discomfort while maintaining knee extension. Surface EMG (Telemyo DTS; Noraxon U.S.A. Inc.) was used to assess mean and peak activation of the RF and BF during the final 5 degrees of HF as well as calculate Cl. Integrated Webcam ( v. 6.1.7601.18208; Microsoft Corporation; 30Hz) was used to monitor HF. Peak Motion Analysis (v. 9.0; Vicon) was used to interpolate HF to 60Hz and digitize the video record to obtain HF during the first and tenth repetition of each set. Separate 1x6 repeated measures one-way ANOVAs revealed significant differences in HF, RF(subscript mean), RF(subscript peak), and BF(subscript peak). HF increased at every time-point following the first repetition despite decreasing significantly from set one to set two. A within-set increase in RF( subscript mean) and RF(subscript peak) was observed although returned to baseline following each set. HF, RF(subscript mean), RF(subscript peak), BF(subscript mean), and BF(subscript peak) increased over the course of the protocol, although BF(subscript mean) was non- significant. No significant alterations was observed in Cl. These findings support the limited association between flexibility and opposing muscle activity as well as a diminishing effect of stretching in AROM. --Leaf iv

    Subject-specific Human Knee FEA Models for Transtibial Amputees Vs Control Tibial Cartilage Pressure in Gait, Cycling and Elliptical Training

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    Millions of individuals around the globe are impacted by osteoarthritis, which is the prevailing type of arthritis. This condition arises as a result of gradual deterioration of the protective cartilage that safeguards the ends of the bones. This is especially true of transtibial amputees, who have a significantly higher incidence of osteoarthritis of the knee in their intact limb than non-amputees. Engaging in regular physical activity, managing weight effectively, and undergoing specific treatments can potentially slow down the advancement of the disease and enhance pain relief and joint function. Nevertheless, the relationship between the type of exercise and its impact on cartilage stress remains uncertain. In order to address this question, tibiofemoral finite element analysis (FEA) models were developed. The models incorporated more realistic material properties for cartilage, hexahedral elements, and non-linear springs for ligaments. To ensure their accuracy, the models were validated against experimental data obtained from cadaveric studies. The contact loads and flexion angles of two individuals with amputations and one individual without amputation, which were obtained in a previous study conducted at Cal Poly, were implemented in the FEA models for gait, cycling, and elliptical exercises. The FEA models were used to extract the maximum stress values experienced in the tibial contact areas, specifically in the medial and lateral compartments of the knee. In cycling, the normalized contact pressure on the tibial articular cartilage, relative to body weight, was generally higher for the two participants with amputations compared to the control participant, except for the medial compartment. Furthermore, when comparing different exercises, cycling resulted in the lowest contact pressure values, with elliptical and walking exercises producing similar maximum values. The findings indicated that individuals with amputations are at a greater risk of developing OA, regardless of the type of exercise performed. However, among the different exercises studied, cycling was found to exert the lowest levels of compression stress on the tibial cartilage

    Aerospace Medicine and Biology: A continuing bibliography, supplement 216

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    One hundred twenty reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1981 are listed. Topics include: sanitary problems; pharmacology; toxicology; safety and survival; life support systems; exobiology; and personnel factors

    Exploring Low to Moderate Velocity Motor Vehicle Rear Impacts as a Viable Injury Mechanism in the Lumbar Spine

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    Epidemiological research suggests that up to 50% of individuals involved in low speed rear impact collisions develop acute onset low back pain. Given that little information is known about the low back injury mechanisms as a result of these collisions the overarching goal of this thesis was to explore low to moderate velocity rear-end collisions as a potential low back injury mechanism. Using a combination of data mining, in vivo and in vitro mechanical testing of porcine functional spinal units, the global purposes of this thesis were to (i) explore the types of low to moderate velocity collisions that frequently result in claims of low back pain and injury (ii) explore the influence of low velocity rear impact collisions on peak in vivo joint loading, occupant pain reporting and passive tissue response of the lumbar spine, and (iii) characterize the effects of these mechanical exposures and explore facet joint capsule injury as a potential source of injury and pain generating pathways following low to moderate severity impacts. In-line with these global purposes, four independent studies were conducted, each with their own focused objectives. Study I - Exploring Low Velocity Collision Characteristics Associated with Claimed Low Back Pain Background: Up to fifty percent of individuals involved in low to moderate velocity collisions report low back pain. However, our understanding of the specific collision or occupant characteristics that result in such claims of low back pain remains limited. Objectives: The primary objective of this study was to define the circumstances of low velocity motor vehicle collisions that result in litigation in Ontario with claims of low back injury. Methods: Data for this investigation were obtained from a forensic engineering firm based in Toronto, Ontario, Canada. The database was searched and only cases with an evaluation of the injuries sustained in passenger vehicle to vehicle collisions, with a collision severity of 24 km/hour or less were included in this analysis. Each identified case was reviewed for collision characteristics, pre-existing medical conditions and injuries claimed. Descriptive statistics (mean, SD and ranges) across low back injury claims were computed for documented variables. Results: Out the 83 cases reviewed, 77% involved a claim of low back injury. Specific to those who claimed low back injury, examination of the medical history revealed that pre-existing low back pain (LBP) or evidence of lumbar disc degeneration were particularly common with 63% of claimants either having had a history of LBP or evidence of lumbar disc degeneration, or both. Of all low back injury claims, 97% were accompanied by a whiplash and/or whiplash associated disorder claim. For low back injury claims, a rear-end impact was the most common configuration (70% of all low back injury claims involved a rear-end collision). The majority of all low back injury claimants experienced a change in velocity of 13 km/hour or less (69%), with 42% of all low back injury claims falling between collision severities of 10 – 12 km/hour. Conclusions: Results indicate that rear-end collision severities of 10 – 12 km/hour appear to be particularly common with respect to low back injury reporting; more severe collisions were not associated with greater low back injury reporting. This result contrasts with previously published neck injury risk data, which demonstrated the risk of neck injury symptom reporting increases with collision severity. Evidence of lumbar disc degeneration was particularly common across claimants with low back injury claims. Study II - Characterizing Trunk Muscle Activations During Simulated Low Speed Rear Impact Collisions Background: The internal forces generated by the musculature of the lumbar region create most of the mechanical load placed on the spine. Thus, despite the anticipated low external forces generated between the occupant and the automobile seatback during a low speed rear impact collision, increased muscle tension may influence the resultant peak joint loads experienced in the lumbar spine. Consequently, the risk of low back injury may be altered by muscle activation. Objective: The purpose of this study was to evaluate the activation profiles of muscles surrounding the lumbar spine during unanticipated and braced simulated rear-end collisions. Methods: Twenty-two low speed sled tests were performed on eleven human volunteers (△v = 4 km/h). Each volunteer was exposed to one unanticipated impact and one braced impact. Accelerometers were mounted on the test sled and participants’ low back. Six bilateral channels of surface electromyography (EMG) were collected from the trunk during impact trials. Peak lumbar accelerations, peak muscle activation delay, muscle onset time and peak EMG magnitudes, normalized to maximum voluntary contractions (MVC), were examined across test conditions. Results: While not statistically significant, bracing for impact tended to reduce peak lumbar acceleration in the initial rearward impact phase of the occupant’s motion by approximately 15%. The only trunk muscles with peak activations exceeding 10% MVC during the unanticipated impact were the thoracic erector spinae. Time of peak muscle activation was slightly longer for the unanticipated condition (unanticipated = 296 ms; braced = 241 ms). Conclusions: Results from this investigation demonstrate that during an unanticipated low speed rear-end collision, the peak activation of muscles in the lumbar spine are low in magnitude. As such, muscle activation likely has minimal contribution to the internal joint loads that are experienced in the lumbar intervertebral joints during low speed rear impact collisions. Study III - Characterizing In Vivo Mechanical Exposures of the Lumbar Spine During Simulated Low Velocity Rear Impact Collisions Background: Historically, there has been a lack of focus on the lumbar spine during rear impacts because of the perception that the automotive seat back should protect the lumbar spine from injury. As a result, there have been no studies involving human volunteers to address the risk of low back injury in low velocity rear impact collisions. Objectives: The primary objectives of this study were to explore lumbar kinematics and joint reaction forces in human volunteers during simulated rear impact collisions and to examine the influence of lumbar support on the peak motion and forces experienced in the lumbar spine. A secondary objective was to evaluate lumped passive stiffness changes and low back pain reporting after a simulated rear impact collision Methods: Twenty-four participants (12 male, 12 female) were recruited. A custom-built crash sled was used to simulate unanticipated rear impact collisions, with a change in velocity of approximately 8 km/h. Randomized collisions were completed with and without lumbar support. Measures of passive stiffness and flexion-relaxation-ratio (FRR) were obtained prior to impact (Pre), immediately post impact (Post) and 24 hours post impact (Post-24). LBP reporting was monitored over the next 24 hours leading up to the final Post-24 measures. For collision simulations inverse dynamics analyses were conducted, and outputs were used to generate estimates of peak L4/L5 joint compression and shear. From the passive trials, lumbar flexion/extension moment-angle curves were generated to quantify time-varying changes in the passive stiffness of the lumbar spine, Post and Post-24 relative to Pre. FRRs were computed as the ratio of thoracic erector spinae and lumbar erector spinae muscle activation in an upright posture to muscle activation in a flexed position Results: Average [± standard deviation] peak L4/L5 compression and shear reaction forces were not significantly different without lumbar support (Compression = 498.22 N [±178.0]; Shear = 302.2 N [± 98.5]) compared to with lumbar support (Compression = 484.5 N [±151.1]; Shear = 291.3 N [±176.8]). Lumbar flexion angle at the point of peak shear was 36 degrees [±12] without and 33 degrees [±11] with lumbar support, respectively, with 0 degrees being the lumbar posture in upright standing. No participants developed clinically significant levels of LBP after impact. Time was a significant factor for the length of the low stiffness flexion and extension zone (p = 0.049; p = 0.035), the length of the low stiffness zone was longer in the Post and Post-24 trial for low stiffness flexion and longer in the Post-24 for low stiffness extension. Conclusions: Findings demonstrate that during a laboratory-simulation of an unanticipated 8 km/hour rear-impact collision, young healthy adults do not develop LBP. Lumbar support did not significantly influence the estimated L4/L5 joint reaction forces. Changes in the low stiffness portion of the passive flexion/extension curves were observed following impact and persisted for 24 hours. Changes in passive stiffness may lead to changes in the loads and load distributions within the passive structures such as the ligaments and intervertebral discs following impacts. Study IV - Exploring the Interaction Effects of Impact Severity and Posture on Vertebral Joint Mechanics Background: To date, no in vitro studies have been conducted to explore lumbar soft tissue injury potential and altered mechanical properties from exposure to impact forces. Typically, after a motor vehicle collision, the cause of a reported acute onset of low back pain is difficult to identify with potential soft tissue strain injury sites including the facet joint and highly innervated facet joint capsule ligament (FCL). Objectives: The purpose of this investigation was to quantify intervertebral translation and facet joint capsule strain under varying postures and impact severities. A secondary objective was to evaluate flexion-extension and shear neutral zone changes pre and post impact. Methods: A total of 72 porcine cervical FSUs were included in the study. Three levels of impact severity (4g, 8g, 11g), and three postures (Neutral Flexion and Extension) were examined using a full-factorial design. Impacts were applied using a custom-built impact track which simulated impact parameters similar to those experienced in low to moderate speed motor vehicle collisions. Passive flexion-extension and shear neutral zone testing were completed immediately prior to and immediately post impact. Intervertebral translation and the strain tensor of the facet capsule ligament were measured during impacts. Results: A significant main effect (p > 0.001) of collision severity was observed for peak intervertebral translation and peak FCL shear strain (p = 0.003). A significant two-way interaction was observed between pre-post and impact severity for flexion-extension neutral zone length (p = 0.031) and stiffness (p>0.001) and anterior-posterior shear neutral zone length (p = 0.047) and stiffness (p>0.001). This was a result of increased neutral zone range and decreased neutral zone stiffness pre-post for the 11g severity impact (regardless of posture). Conclusions: This investigation provides evidence that overall the peak vertebral translations observed across 4g to 11g impacts are below previously published ultimate shear failure displacements. FSU’s exposed to the highest severity impact (11g) had significant NZ changes, with increases in joint laxity in flexion-extension and shear testing and decreased stiffness, suggesting that soft tissue injury may have occurred. Despite observed main effects of impact severity, no influence of posture was observed. This lack of influence of posture and small FCL strain magnitudes suggest that the FCL does not appear to undergo injurious or permanent mechanical changes in response to low to moderate MVC impact scenarios. Study V - Characterizing the Mechanical Properties of the Facet Joint Capsule Ligament Background: The facet joint capsule ligament (FCL) is a structure in the lumbar spine that constrains motions of the vertebrae. Previous work has demonstrated that under physiological motion the FCL is subjected to significant deformation with FCL strains increasing in magnitude with increasing flexion and extension moments. Thus, it is important to characterize the mechanical response of the FCL for investigations into injury mechanisms. Sub failure loads can produce micro-damage resulting in increased laxity, decreased stiffness and altered viscoelastic responses. Thus, the objective of this investigation was to determine the mechanical and viscoelastic properties of the FCL under various magnitudes of strain from control samples and samples that had been exposed to an impact. Objectives: The purpose of this investigation was to quantify the mechanical properties and viscoelastic response of control and impacted FCL. Methods: 200 tissue samples were excised from the right and left FCL of 80 porcine cervical functional spinal units (FSU’s). Tissue samples were excised from FSU’s obtained from Study 4. Twenty FCL tissue samples served as the control group. The remaining 180 FCL tissue samples were randomly obtained from FSU’s that had been exposed to one of nine impact conditions (impacted tissue). Each specimen was loaded uniaxially, collinear with the primary fiber orientation. The loading protocol was identical for all specimens: preconditioning with 5 cycles of loading/unloading to 5% strain, followed by a 30 second rest period, 5 cycles of 10% strain and 1 cycle of 10% strain with a hold duration at 10% strain for 240 seconds. The same protocol followed for 30% (cyclic-30% & 30%-hold) and 50% strain (cyclic-50% & 50%-hold). All loading and unloading were performed at a rate of 2%/sec. All impacted FCL properties were compared back to controls. Measures of stiffness, hysteresis and force-relaxation were computed for the 30% and 50% strain conditions. Results: No significant differences in stiffness were observed for impacted specimens in comparison to control (30% Control = 2.64 N/mm; 4 g = 2.20 N/mm, 8 g = 2.07 N/mm, 16 g = 2.16 N/mm)(50% Control = 5.06 N/mm; 4g = 4.60 N/mm, 8 g = 4.07 N/mm, 16 g =4.64 N/mm). Impacted specimens from the 8g Flexed and 11 g Flexed and Neutral conditions exhibited greater hysteresis during the cyclic-30% and cyclic-50%, in comparison to controls. In addition, specimens from the 8g and 11g Flexed conditions resulted in greater force relaxation for the 50%-hold conditions. Conclusions: Results from this study demonstrate viscoelastic changes in FCL samples exposed to moderate and highspeed impacts in the flexed posture. However, it is interesting that these viscoelastic changes were not accompanied by changes in stiffness. Findings from this investigation provide novel insight and provide mechanical and viscoelastic properties of the FCL both in control and impacted scenarios. Global Summary: Findings from this thesis demonstrate that (i) rear-end collision severities of 10 – 12 km/hour appear to be particularly common with respect to low back injury reporting (ii) during a laboratory-simulation of an unanticipated 8 km/hour rear-impact collision, young healthy adults do not develop LBP, however, changes in the low stiffness portion of the passive flexion/extension curves were observed following impact and persisted for 24 hours and (iii) the observed peak displacements in porcine functional spinal units exposed to varying impact severities are below ultimate shear failure displacements and does not support a lumbar spine injury mechanism resulting in acute traumatic bone fractures and/or acute traumatic IVD herniations in previously “healthy” tissues. Overall, the small FCL strain magnitudes during impacts and unchanged FCL mechanical properties post-impact suggest that the FCL does not undergo injurious or permanent mechanical changes in response to low to moderate MVC impact scenarios. Collectively, the findings from this thesis indicate that there are no direct mechanical changes that would indicate the high incidence of low back pain reporting following low to moderate severity rear-end motor vehicle impacts. However, changes in passive tissue properties were observed, and if persistent over time, may predispose individuals to secondary pain pathways. It is also important to note that this thesis tested healthy conditions and the results do not directly apply to pre-existing LBP cases being exposed to the same impacts

    Robotics-Assisted Needle Steering for Percutaneous Interventions: Modeling and Experiments

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    Needle insertion and guidance plays an important role in medical procedures such as brachytherapy and biopsy. Flexible needles have the potential to facilitate precise targeting and avoid collisions during medical interventions while reducing trauma to the patient and post-puncture issues. Nevertheless, error introduced during guidance degrades the effectiveness of the planned therapy or diagnosis. Although steering using flexible bevel-tip needles provides great mobility and dexterity, a major barrier is the complexity of needle-tissue interaction that does not lend itself to intuitive control. To overcome this problem, a robotic system can be employed to perform trajectory planning and tracking by manipulation of the needle base. This research project focuses on a control-theoretic approach and draws on the rich literature from control and systems theory to model needle-tissue interaction and needle flexion and then design a robotics-based strategy for needle insertion/steering. The resulting solutions will directly benefit a wide range of needle-based interventions. The outcome of this computer-assisted approach will not only enable us to perform efficient preoperative trajectory planning, but will also provide more insight into needle-tissue interaction that will be helpful in developing advanced intraoperative algorithms for needle steering. Experimental validation of the proposed methodologies was carried out on a state of-the-art 5-DOF robotic system designed and constructed in-house primarily for prostate brachytherapy. The system is equipped with a Nano43 6-DOF force/torque sensor (ATI Industrial Automation) to measure forces and torques acting on the needle shaft. In our setup, an Aurora electromagnetic tracker (Northern Digital Inc.) is the sensing device used for measuring needle deflection. A multi-threaded application for control, sensor readings, data logging and communication over the ethernet was developed using Microsoft Visual C 2005, MATLAB 2007 and the QuaRC Toolbox (Quanser Inc.). Various artificial phantoms were developed so as to create a realistic medium in terms of elasticity and insertion force ranges; however, they simulated a uniform environment without exhibiting complexities of organic tissues. Experiments were also conducted on beef liver and fresh chicken breast, beef, and ham, to investigate the behavior of a variety biological tissues

    Non linear force feedback enhancement for cooperative robotic neurosurgery enforces virtual boundaries on cortex surface

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    Surgeons can benefit from the cooperation with a robotic assistant during the repetitive execution of precise targeting tasks on soft tissues, such as brain cortex stimulation procedures in open-skull neurosurgery. Position-based force-to-motion control schemes may not be satisfactory solution to provide the manipulator with the high compliance desirable during guidance along wide trajectories. A new torque controller with non-linear force feedback enhancement (FFE) is presented to provide augmented haptic perception to the operator from instrument-tissue interaction. Simulation tests were performed to evaluate the system stability according to different non-linear force modulation functions (power, sigmoidal and arc tangent). The FFE controller with power modulation was experimentally validated with a pool of non-expert users using brain-mimicking gelatin phantoms (8%-16% concentration). Besides providing hand tremor rejection for a stable holding of the tool, the FFE controller was proven to allow for a safer tissue contact with respect to both robotic assistance without force feedback and freehand executions (50% and 75% reduction of the indentation depth, respectively). Future work will address the evaluation of the safety features of the FFE controller with expert surgeons on a realistic brain phantom, also accounting for unpredictable tissue's motions as during seizures due to cortex stimulation

    Probing nano-scale viscoelastic response in air and in liquid with dynamic atomic force microscopy

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    We perform a comparative study of dynamic force measurements using an Atomic Force Microscope (AFM) on the same soft polymer blend samples in both air and liquid environments. Our quantitative analysis starts with calibration of the same cantilever in both environments. Intermodulation AFM (ImAFM) is used to measure dynamic force quadratures on the same sample. We validate the accuracy of the reconstructed dynamic force quadratures by numerical simulation of a realistic model of the cantilever in liquid. In spite of the very low quality factor of this resonance, we find excellent agreement between experiment and simulation. A recently developed moving surface model explains the measured force quadrature curves on the soft polymer, in both air and liquid

    Models for force control in telesurgical robot systems

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    Surgical robotics is one of the most rapidly developing fields within robotics. Besides general motion control issues, control engineers often find it challenging to design robotic telesurgery systems, as these have to deal with complex environmental constrains. The unique behavior of soft tissues requires special approaches in both robot control and system modeling in the case of robotic tissue manipulation. Precise control depends on the appropriate modeling of the interaction between the manipulated tissues and the instruments held by the robotic arm, frequently referred to as the tool–tissue interaction. Due to the nature of the physiological environment, the mechatronics of the systems and the time delays, it is difficult to introduce a universal model or a general modeling approach. This paper gives an overview of the emerging problems in the design and modeling of telesurgical systems, analyzing each component, and introducing the most widely employed models. The arising control problems are reviewed in the frames of master–slave type teleoperation, proposing a novel oft tissue model and providing an overview of the possible control approaches
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