Visual Illusion Created by a Striped Pattern through Augmented Reality for the Prevention of Tumbling on Stairs

A fall on stairs can be a dangerous accident. An important indicator of falling risk is the foot clearance, which is the height of the foot when ascending stairs or the distance of the foot from the step when descending. We developed an augmented reality system with a holographic lens using a visual illusion to improve the foot clearance on stairs. The system draws a vertical striped pattern on the stair riser as the participant ascends the stairs to create the illusion that the steps are higher than the actual steps, and draws a horizontal striped pattern on the stair tread as the participant descends the stairs to create the illusion of narrower stairs. We experimentally evaluated the accuracy of the system and fitted a model to determine the appropriate stripe thickness. Finally, participants ascended and descended stairs before, during, and after using the augmented reality system. The foot clearance significantly improved, not only while the participants used the system but also after they used the system compared with before.

One-DOF Wire-Driven Robot Assisting Both Hip and Knee Flexion Motion

Gait assistance robots are used to improve gait performance ability or perform gait motion with an assistance for several articular motions. The sparing use of a gait assistance robot to decrease the duration of the robot’s assistance is important for keeping the ability to perform a movement when the robot assists walking. In previous research, methods of ensuring a compliance mechanism and control method have been studied, and assistance for articular motions has been conducted independently using actuators corresponding to each articular motion. In this paper, we propose a wire-driven gait assistance robot to aid both hip and knee articular flexion motions by applying just one force to assist motion in the swing phase. We focused on a force that assists hip and knee flexion motion, and designed a robot with a compensation mechanism for the wire length. We used an assistance timing detection method for the robot, conducting tensile force control based on information from the hip, knee, and ankle angles. We carried out an experiment to investigate the controlled performance of the proposed robot and the effect on hip and knee angular velocity. We confirmed that the proposed robotic system can aid both hip and knee articular motion with just one force application.

Using Brain Activation to Evaluate Arrangements Aiding Hand-Eye Coordination in Surgical Robot Systems

GOAL

To realize intuitive, minimally invasive surgery, surgical robots are often controlled using master-slave systems. However, the surgical robot's structure often differs from that of the human body, so the arrangement between the monitor and master must reflect this physical difference. In this study, we validate the feasibility of an embodiment evaluation method that determines the arrangement between the monitor and master. In our constructed cognitive model, the brain's intraparietal sulcus activates significantly when somatic and visual feedback match. Using this model, we validate a cognitively appropriate arrangement between the monitor and master.

METHODS

In experiments, we measure participants' brain activation using an imaging device as they control the virtual surgical simulator. Two experiments are carried out that vary the monitor and hand positions.

CONCLUSION

There are two common arrangements of the monitor and master at the brain activation's peak: One is placing the monitor behind the master, so the user feels that the system is an extension of his arms into the monitor; the other arranges the monitor in front of the master, so the user feels the correspondence between his own arm and the virtual arm in the monitor.

SIGNIFICANCE

From these results, we conclude that the arrangement between the monitor and master impacts embodiment, enabling the participant to feel apparent posture matches in master-slave surgical robot systems.

Evaluation of Compensatory Movement by Shoulder Joint Torque during Gain Adjustment of a Powered Prosthetic Wrist Joint

Powered prostheses with low degree of freedom (DoF) have been developed for people with disabilities to assist daily tasks. These prostheses neglect the user's compensatory movements caused by the low degree of freedom. We assume that the movements can be reduced by well-designed controller of the devices. This paper explores an optimal control gain of the powered prosthesis to prevent the user from compensatory movements through experiments. In the experiments, we developed 1-DoF hand prosthesis with a position-controlled servo, which includes the constant gain as a feed-forward term. The compensatory movements are regarded as a joint torque at a shoulder (abduction/adduction). 4 intact subjects performed a pick-and-place task, using the prosthesis with several control gains. The empirical results show that there was the optimal gain for each subject, which reduces their compensatory movement.

Accuracy to detection timing for assisting repetitive facilitation exercise system using MRCP and SVM

This paper presents a feasibility study of a brain–machine interface system to assist repetitive facilitation exercise. Repetitive facilitation exercise is an effective rehabilitation method for patients with hemiplegia. In repetitive facilitation exercise, a therapist stimulates the paralyzed part of the patient while motor commands run along the nerve pathway. However, successful repetitive facilitation exercise is difficult to achieve and even a skilled practitioner cannot detect when a motor command occurs in patient’s brain. We proposed a brain–machine interface system for automatically detecting motor commands and stimulating the paralyzed part of a patient. To determine motor commands from patient electroencephalogram (EEG) data, we measured the movement-related cortical potential (MRCP) and constructed a support vector machine system. In this paper, we validated the prediction timing of the system at the highest accuracy by the system using EEG and MRCP. In the experiments, we measured the EEG when the participant bent their elbow when prompted to do so. We analyzed the EEG data using a cross-validation method. We found that the average accuracy was 72.9% and the highest at the prediction timing 280 ms. We conclude that 280 ms is the most suitable to predict the judgment that a patient intends to exercise or not.

Change detection technique for muscle tone during static stretching by continuous muscle viscoelasticity monitoring using wearable indentation tester

Static stretching is widely performed to decrease muscle tone as a part of rehabilitation protocols. Finding out the optimal duration of static stretching is important to minimize the time required for rehabilitation therapy and it would be helpful for maintaining the patient's motivation towards daily rehabilitation tasks. Several studies have been conducted for the evaluation of static stretching; however, the recommended duration of static stretching varies widely between 15-30 s in general, because the traditional methods for the assessment of muscle tone do not monitor the continuous change in the target muscle's state. We have developed a method to monitor the viscoelasticity of one muscle continuously during static stretching, using a wearable indentation tester. In this study, we investigated a suitable signal processing method to detect the time required to change the muscle tone, utilizing the data collected using a wearable indentation tester. By calculating a viscoelastic index with a certain time window, we confirmed that the stretching duration required to bring about a decrease in muscle tone could be obtained with an accuracy in the order of 1 s.

Timing of intermittent torque control with wire-driven gait training robot lifting toe trajectory for trip avoidance

Gait training robots are useful for changing gait patterns and decreasing risk of trip. Previous research has reported that decreasing duration of the assistance or guidance of the robot is beneficial for efficient gait training. Although robotic intermittent control method for assisting joint motion has been established, the effect of the robot intervention timing on change of toe clearance is unclear. In this paper, we tested different timings of applying torque to the knee, employing the intermittent control of a gait training robot to increase toe clearance throughout the swing phase. We focused on knee flexion motion and designed a gait training robot that can apply flexion torque to the knee with a wire-driven system. We used a method of timing detecting for the robot conducting torque control based on information from the hip, knee, and ankle angles to establish a non-time dependent parameter that can be used to adapt to gait change, such as gait speed. We carried out an experiment in which the conditions were four time points: starting the swing phase, lifting the foot, maintaining knee flexion, and finishing knee flexion. The results show that applying flexion torque to the knee at the time point when people start lifting their toe is effective for increasing toe clearance in the whole swing phase.

A novel optimal coordinated control strategy for the updated robot system for single port surgery

BACKGROUND

Research into robotic systems for single port surgery (SPS) has become widespread around the world in recent years. A new robot arm system for SPS was developed, but its positioning platform and other hardware components were not efficient. Special features of the developed surgical robot system make good teleoperation with safety and efficiency difficult.

METHODS

A robot arm is combined and used as new positioning platform, and the remote center motion is realized by a new method using active motion control. A new mapping strategy based on kinematics computation and a novel optimal coordinated control strategy based on real-time approaching to a defined anthropopathic criterion configuration that is referred to the customary ease state of human arms and especially the configuration of boxers' habitual preparation posture are developed.

RESULTS

The hardware components, control architecture, control system, and mapping strategy of the robotic system has been updated. A novel optimal coordinated control strategy is proposed and tested.

CONCLUSIONS

The new robot system can be more dexterous, intelligent, convenient and safer for preoperative positioning and intraoperative adjustment. The mapping strategy can achieve good following and representation for the slave manipulator arms. And the proposed novel control strategy can enable them to complete tasks with higher maneuverability, lower possibility of self-interference and singularity free while teleoperating.

Development of angle information system to facilitate the adjustment of needle-holding posture

PURPOSE

Our purpose is to develop a system based on image processing methods that can inform users of the angular relationship between the needle and the forceps. The user thereby adjusts their needle grasping posture according to the angle information, which leads to an improvement in suturing accuracy.

METHODS

The system prototype consists of a camera and an image processing computer. The image captured by the camera is input to the computer, and then, the angular relationship between the forceps and needle is calculated via image processing. Then, the system informs the user of the calculated angular relationship between the needle and forceps in real time. To evaluate whether the system improves suturing accuracy, we invited 12 participants to enroll in an experiment based on a suturing task.

RESULTS

The experimental results illustrate that the system allows participants to easily adjust the positional relationship between the needle and the forceps and that this adjusted angular relationship leads to higher suturing accuracy.

CONCLUSIONS

Adjustment to holding the needle at a right angle before insertion has a critical effect on suturing quality. Therefore, we developed a system that informs the user of the angular relationship between the needle and the forceps. The results of the evaluation show that the system significantly improves the suturing accuracy of participants via informing them of the angle.

Relationship between magnitude of applied torque in pre-swing phase and gait change for prevention of trip in elderly people

Elderly people are at risk of tripping because of their narrow range of articular motion. To avoid tripping, gait training that improves their range of articular motion would be beneficial. In this study we propose a gait-training robot that applies a torque during the pre-swing phase to achieve this goal. We investigated the relationship between magnitude of applied torque and change in the range of knee-articular motion while walking before and after the application of this torque. We developed a wearable robot and carried out an experiment on human participants in which a motor pulls a string embedded on the robotic frame, applying torque in the pre-swing phase for a period of 20 [s]. Before and after applying torque the participant walked normally for 15 [s] without interference from the robot. We found that knee flexion angle increased after applying the torque if the torque was within the range of approximately 6-8 [Nm]. Therefore, we were able to verify that a new range of knee articular motion can be learned through application of torque.

Simple empirical model for identifying rheological properties of soft biological tissues

Understanding the rheological properties of soft biological tissue is a key issue for mechanical systems used in the health care field. We propose a simple empirical model using fractional dynamics and exponential nonlinearity (FDEN) to identify the rheological properties of soft biological tissue. The model is derived from detailed material measurements using samples isolated from porcine liver. We conducted dynamic viscoelastic and creep tests on liver samples using a plate-plate rheometer. The experimental results indicated that biological tissue has specific properties: (i) power law increase in the storage elastic modulus and the loss elastic modulus of the same slope; (ii) power law compliance (gain) decrease and constant phase delay in the frequency domain; (iii) power law dependence between time and strain relationships in the time domain; and (iv) linear dependence in the low strain range and exponential law dependence in the high strain range between stress-strain relationships. Our simple FDEN model uses only three dependent parameters and represents the specific properties of soft biological tissue.

A robotic gait training system integrating split-belt treadmill, footprint sensing and synchronous EEG recording for neuro-motor recovery

This paper presents a robotic gait training system for neuro-motor rehabilitation of hemiplegic stroke survivors. The system is composed of a treadmill consisting of two separated belts, footprint array sensor attached below each belt for gait data acquisition, and an electroencephalography (EEG) device for monitoring brain activities during gait training. The split belt treadmill allow physical therapists to set different treadmill belt velocities to modify physical workload of the patients during walking, thus being able to better improve the symmetry of gait phases between affected and unaffected (sound) legs in comparison with conventional treadmills where there is only one single belt. In contrast to in-shoe pressure sensors, the under-belt footprint sensor array designed in this study not only reduces the preparation complexity of gait training but also collects more gait data for motion analysis. Recorded EEG is segmented synchronously with gait-related events. The processed EEG data can be used for monitoring brain-activities during gait training, providing a neurological approach for motion assessment. One subject with simulated stroke using an ankle-foot orthosis participated in this study. Preliminary results indicate the feasibility of the proposed system to improve gait function and monitor neuro-motor recovery.

Virtually transparent surgical instruments in endoscopic surgery with augmentation of obscured regions

PURPOSE

We developed and evaluated a visual compensation system that allows surgeons to visualize obscured regions in real time, such that the surgical instrument appears virtually transparent.

METHODS

The system consists of two endoscopes: a main endoscope to observe the surgical environment, and a supporting endoscope to render the region hidden from view by surgical instruments. The view captured by the supporting endoscope is transformed to simulate the view from the main endoscope, segmented to the shape of the hidden regions, and superimposed to the main endoscope image so that the surgical instruments look transparent. A prototype device was benchmarked for processing time and superimposition rendering error. Then, it was evaluated in a training environment with 22 participants performing a backhand needle driving task with needle exit point error as the criterion. Lastly, we conducted an in vivo study.

RESULTS

In the benchmark, the mean processing time was 62.4 ms, which was lower than the processing time accepted in remote surgeries. The mean superimposition error of the superimposed image was 1.4 mm. In the training environment, needle exit point error with the system decreased significantly for experts compared with the condition without the system. This change was not significant for novices. In the in vivo study, our prototype enabled visualization of needle exit points during anastomosis.

CONCLUSION

The benchmark suggests that the implemented system had an acceptable performance, and evaluation in the training environment demonstrated improved surgical task outcomes in expert surgeons. We will conduct a more comprehensive in vivo study in the future.

Method for estimating the temperature distribution associated with the vessel cooling effect in radio frequency ablation

Recently, radio frequency ablation (RFA) has become one of the most popular thermal treatments for liver cancer. RFA is minimally invasive and effective in inducing tumor coagulation, however, because use the procedure depends on the experience of the physician, consistent accuracy cannot be guaranteed. In particular, when the tumor is close to a large vessel, a suboptimal ablation margin can result in tumor recurrence. To improve the accuracy of RFA treatment, we have developed an RFA supporting system, which was constructed by using finite element method and operated by means of a model-based control method. In this study, we focused on the cooling effect of flow volume inside a large vessel during RFA, and analyzed heat transfer between the large vessel and liver tissue using a model. We derived the heat transfer parameter (the Nusselt number (Nu)) between the large vessel and liver tissue during RFA by using a finite-element method (FEM). When the Nu for FEM analysis had a value of 3, the FEM analysis model was representative of the actual ablation objective, and the maximum error between FEM analysis and the measurement results was within 2.0[°C]. Thus, it was suggested that the Nu was effective for FEM analysis regarding heat transfer between a large vessel and tissue. However, according to the differences between the results of FEM analysis and measurements concerning the three livers, the heat transfer volume was determined by the Nu, which is different individually in common with other thermal properties. In conclusion, it is necessary to consider the individual differences in the heat transfer volume parameter for FEM analysis.

Visual and somatic sensory feedback of brain activity for intuitive surgical robot manipulation

This paper presents a method to evaluate the hand-eye coordination of the master-slave surgical robot by measuring the activation of the intraparietal sulcus in users brain activity during controlling virtual manipulation. The objective is to examine the changes in activity of the intraparietal sulcus when the user's visual or somatic feedback is passed through or intercepted. The hypothesis is that the intraparietal sulcus activates significantly when both the visual and somatic sense pass feedback, but deactivates when either visual or somatic is intercepted. The brain activity of three subjects was measured by the functional near-infrared spectroscopic-topography brain imaging while they used a hand controller to move a virtual arm of a surgical simulator. The experiment was performed several times with three conditions: (i) the user controlled the virtual arm naturally under both visual and somatic feedback passed, (ii) the user moved with closed eyes under only somatic feedback passed, (iii) the user only gazed at the screen under only visual feedback passed. Brain activity showed significantly better control of the virtual arm naturally (p<;0.05) when compared with moving with closed eyes or only gazing among all participants. In conclusion, the brain can activate according to visual and somatic sensory feedback agreement.

Effect of the thickness and nonlinear elasticity of tissue on the success of surgical stapling for laparoscopic liver resection

Recently, the range of applications of surgical staplers has been extended to include laparoscopic liver resection because manipulation of a surgical stapler is very simple. Revealing the causes of stapling failure and suggesting a method to solve stapling failure are important for safe laparoscopic liver resection. Surgeons say that tissues make stapling more likely to fail if they are thick and brittle. However, the combinatorial effect of the thickness and stiffness of tissues on the success of surgical stapling for laparoscopic liver resection has not been investigated. Therefore, the objective of the present study was to investigate the effect of tissue thickness and tissue stiffness on the success rate (SR) of surgical stapling. From ex vivo stapling experimental results using pig livers, it is suggested that the effect of tissue thickness is greater than the effect of tissue stiffness on the SR of stapling. If tissue thickness is 5 mm, the SR of stapling is high regardless of the magnitude of the tissue-stiffness parameter. However, if tissue thickness is >10 mm, the SR of stapling has a relationship with nonlinear viscoelastic parameters. Therefore, the SR of stapling could be predicted from tissue thickness and nonlinear elastic parameters.

Real-time temperature control system based on the finite element method for liver radiofrequency ablation: effect of the time interval on control

Radiofrequency (RF) ablation is increasingly being used to treat liver cancer because it is minimally invasive. However, it is difficult for operators to control the size of the coagulation zones precisely, because no method has been established to form an adequate and suitable ablation area. To overcome this limitation, we propose a new system that can control the coagulation zone size. The system operates as follows: 1) the liver temperature is estimated using a temperature-distribution simulator to reduce invasiveness; 2) the output power of the RF generator is controlled automatically according to the liver temperature. To use this system in real time, both the time taken to calculate the temperature in the simulation and the control accuracy are important. We therefore investigated the relationship between the time interval required to change the output voltage and temperature control stability in RF ablation. The results revealed that the proposed method can control the temperature at a point away from the electrode needle to obtain the desired ablation size. It was also shown to be necessary to reduce the time interval when small tumors are cauterized to avoid excessive treatment. In contrast, such high frequency feedback control is not required when large tumors are cauterized.

Study on method to simulate light propagation on tissue with characteristics of radial-beam LED based on Monte-Carlo method

In biomedical, Monte-carlo simulation is commonly used for simulation of light diffusion in tissue. But, most of previous studies did not consider a radial beam LED as light source. Therefore, we considered characteristics of a radial beam LED and applied them on MC simulation as light source. In this paper, we consider 3 characteristics of radial beam LED. The first is an initial launch area of photons. The second is an incident angle of a photon at an initial photon launching area. The third is the refraction effect according to contact area between LED and a turbid medium. For the verification of the MC simulation, we compared simulation and experimental results. The average of the correlation coefficient between simulation and experimental results is 0.9954. Through this study, we show an effective method to simulate light diffusion on tissue with characteristics for radial beam LED based on MC simulation.

Brain activation in parietal area during manipulation with a surgical robot simulator

PURPOSE

we present an evaluation method to qualify the embodiment caused by the physical difference between master-slave surgical robots by measuring the activation of the intraparietal sulcus in the user's brain activity during surgical robot manipulation. We show the change of embodiment based on the change of the optical axis-to-target view angle in the surgical simulator to change the manipulator's appearance in the monitor in terms of hand-eye coordination. The objective is to explore the change of brain activation according to the change of the optical axis-to-target view angle.

METHODS

In the experiments, we used a functional near-infrared spectroscopic topography (f-NIRS) brain imaging device to measure the brain activity of the seven subjects while they moved the hand controller to insert a curved needle into a target using the manipulator in a surgical simulator. The experiment was carried out several times with a variety of optical axis-to-target view angles.

RESULTS

Some participants showed a significant peak (P value = 0.037, F-number = 2.841) when the optical axis-to-target view angle was 75°.

CONCLUSIONS

The positional relationship between the manipulators and endoscope at 75° would be the closest to the human physical relationship between the hands and eyes.

Evaluation of Hand-Eye Coordination Based on Brain Activity

Surgical robots have improved considerably in recent years, but their intuitive operability, and thus their user interoperability, has yet to be quantitatively evaluated. Thus, we propose a method for measuring a user’s brain activity while operating such a robot, to better enable the design of a robot with intuitive operability. The objective of this study was to determine the angle and radius between an endoscope and manipulator that best allows the user to perceive the manipulator as being part of their own body. In the experiments, a subject operated a hand controller to position the tip of a virtual slave manipulator onto a target in a surgical simulator while his/her brain activity was measured using a brain imaging device. The experiment was carried out several times with the virtual slave manipulator configured in a variety of ways. The results show that the amount of brain activity is significantly greater with a particular slave manipulator configuration. We concluded that the hand-eye coordination between the body image and the robot should be closely matched in the design of a robot having intuitive operability.

Functional electrical stimulation based on a pelvis support robot for gait rehabilitation of hemiplegic patients after stroke

More and more stroke survivors are suffering from physical motor impairments. Current therapeutic interventions have various limits to the efficient recovery of normal motor function of the lower limbs. Therefore, we propose a novel gait rehabilitation system for hemiplegic patients after stroke. It integrates functional electrical stimulation (FES) with a pelvis-supporting robotic system. A corresponding relationship between the gait phase and the active lateral movement of the pelvis is first constructed from experiments on simulated hemiplegic patients. By estimating the gait phase from the lateral motion of the pelvis based on this relationship, the timing of FES sent to the muscles of the lower limbs can be automatically determined during a gait cycle. After experiments on simulated hemiplegic stroke survivors with the FES control algorithm, the proposed algorithm and the gait rehabilitation system are verified to be feasible and promising.

A study of viscoelasticity index for evaluating muscle hypotonicity during static stretching

Static stretching is widely used as a preventative treatment for musculoskeletal disabilities by providing muscle hypotonicity, which results from changes in muscle tissue structure. However, the quantitative evaluation of hypotonicity during stretching has had limited success owing to the confounding factor of mechanical stress relaxation. To resolve this problem, we propose a new evaluation method for hypotonicity based on a viscoelastic muscle model using fractional calculus, which is known to be effective for biomaterials. We made continuous measurements of rectus skin indentation during static stretching as an indicator of reaction force in the rectus femoris muscle. The viscoelastic ratio and modulus were computed from the indentation trace. Both viscoelastic parameters decreased significantly between the early and final phases of stretching. The results suggest that our method is useful for quantitative evaluation of muscle hypotonicity during stretching.

Modeling of lung's electrical impedance using fractional calculus for analysis of heat generation during RF-ablation

Recently, Radio Frequency Ablation (RFA) is becoming a popular therapy for various cancers such as liver, breast, or lung cancer. RFA is one kinds of thermal therapy. However, it has been often reported about excessive ablation or non-ablation due to difficult control of ablation energy. In order to solve these difficulties, we have been proposed robotized RF-ablation system for precise cancer treatment. We have been tried to control heat energy by control of electromagnetic-wave frequency. In this paper, we reported about relation among electrical impedance of lung, lung's internal air volumes, and heat energy by use of electromagnetic-wave. In case of RFA for lung cancer, heat energy depends on electrical impedance and lung's internal air volumes. Electrical impedance has the dependence of electromagnetic-wave frequency and the dependence of lung's internal air volumes. Therefore, firstly we considered about fractional calculus model between lung's internal air volumes and electrical impedance. Secondly, we measured electric impedance frequency characteristic of lung with change of lung's internal air volumes. The measured and modeled results showed that use of fractional calculus realized high accurate model for electrical impedance of lung. And, from the results of numerical analysis of heat energy, it is supposed that control of electromagnetic-wave frequency has a small effectiveness for lung tissue ablation even if lung includes abundant air.

Method for estimation of structural composition of skin layers based on light propagation simulation for liposuction applications

Skin surface irregularity is the most common side effect after liposuction. To reduce this, it is necessary to devise a systematic method to provide structural composition details of skin layers, such as fat thickness and fat boundary tilt angle, for the plastic surgeon. Several commercial portable devices are available to measure skin layer information, working on the principle of a near-infrared technique using the light penetration properties of tissue in optical windows. However, these can only measure general fat thickness and not the structural compositions of skin layers with irregularities. Therefore, our goal in this paper is to propose a method to estimate the structural compositions of skin layers by analyzing and validating the relationship between light distribution and structural composition from simulation data based on specific structural conditions.

Development and testing of an endoscopic pseudo-viewpoint alternating system

Purpose

   An endoscopic system is needed that presents informative images irrespective of the surgical situation and the number of degrees of freedom in endoscopic manipulation. This goal may be achieved with a virtual reality view for a region of interest from an arbitrary viewpoint. An endoscopic pseudo-viewpoint alternation system for this purpose was developed and tested.

Method

   Surgical experts and trainees from an endoscopic surgery training course at the minimally invasive surgery training center of Kyushu University were enrolled in a trial of a virtual reality system. The initial viewpoint was positioned to approximate the horizontal view often seen in laparoscopic surgery, with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$20^{\circ }$$\end{document}20∘ between the optical axis of the endoscope and the task surface. A right-to-left suturing task with right hand, based on a task from the endoscopic surgery training course, was selected for testing. We compared task outcomes with and without use of a new virtual reality-viewing system.

Result

   There was a 0.37 mm reduction in total error (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p = 0.02$$\end{document}p=0.02) with use of the proposed system. Error reduction was composed of 0.1 mm reduction on the y-axis and 0.27 mm reduction on the x-axis. Experts benefited more than novices from use of the proposed system. Most subjects worked at a pseudo-viewpoint of around 34\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^\circ $$\end{document}∘.

Discussion

   Suturing performance improved with the new virtual reality endoscopic display system. Viewpoint alternation resulted in an overview that improved depth perception and allowed subjects to better aim the marker. This suggests the proposed method offers users better visualization and control in endoscopic surgery.

Development of an Exoskeleton to Support Eating Movements in Patients with Essential Tremor

Essential tremor is a disorder that causes involuntary oscillations in patients both while they are engaged in actions and when maintaining a posture. Such patients face serious difficulties in performing such daily living activities as eating, drinking, and writing. We have been developing an electromyogram-controlled exoskeleton to suppress tremors and support the eating movements of these patients. This exoskeleton is designed to suppress tremors and support voluntary movement at the elbow in terms of flexion and extension: movement of the elbow is essential in eating movements. In this study, we examined the effectiveness of our prototype exoskeleton at suppressing tremors. Our goal was to answer two questions: To what extent are the oscillations suppressed when wearing the exoskeleton? Is the exoskeleton able to suppress the oscillations sufficiently to allow eating movements? We were able to confirm experimentally that our exoskeleton can effectively suppress tremors to support eating movements.

Boundary condition generating large strain on breast tumor for nonlinear elasticity estimation

We describe a robotic palpation system that determines whether a breast tumor is benign or malignant by measuring its nonlinear elasticity. Two indenters compress the breast from different directions to generate sufficient strain on the inner tumor, which simply represents clinical dynamic testing. The nonlinear elasticity of the inner tumor is estimated by correcting the reaction force data of the surrounding soft tissue. Here, we present the basic concept of our study and simulation results considering geometric conditions of the indenters using a finite element breast model. Indenters with variable width are applied to the breast at several contact positions in a simulation for comparison. Our results indicate that when the spring stiffness between the contact position of one indenter and the center of the tumor equals the spring stiffness between the contact position of the other indenter and the center of the tumor, a larger contact area (i.e., larger spring stiffness) provides larger strain acting on the inner tumor.

Development of a 6-DOF manipulator driven by flexible shaft for minimally invasive surgical application

This paper presents a 6-DOF manipulator which consists of four parts, 1-DOF translational joint, two 2-DOF bending joints (segment1 and segment2), and 1-DOF rotational gripper. The manipulator with "flexible shaft and Double Screw Drive (DSD) mechanism" structure can obtain omni-directional bending motion through rotation of flexible shafts. In the first prototype, the flexible shafts were connected directly with the actuators in the manipulator. Compared with the first prototype, in the second prototype, flexible shafts for power transmission are connected to the base of the manipulator. Universal joints are used for power transmission to realize distal motion. The improvement done with the design of the second prototype reduced the torque necessary to drive the flexible shafts during motion in surgical interventions. Experiment results show that the manipulator has enough range of movement for surgical intervention.

Derivation of the relationship between the rate of temperature rise and viscoelasticity for constructing a coagulation model for liver radio frequency ablation

Radio frequency ablation (RFA) is usually conducted using ultrasound (US) imaging to monitor the insertion procedure and the coagulation extent of liver tissue which is contiguous to the RFA electrode. However, when RFA surgery is started, the US image becomes unclear because of water vapor. This disadvantage of RFA can lead to excessive and insufficient RFA thereby diminishing the advantages of the procedure. In the present study, we proposed a simulation system which shows the progress status of coagulation for liver RFA. To derive the coagulation characteristics in liver RFA, we used the viscoelasticity of liver tissue as the coagulation indicator to investigate coagulation development for liver RFA. This paper shows the acquisition procedures for analyzing the relationship between the rate of temperature and viscoelasticity. We measured the complex modulus of porcine liver tissue under different rate of temperature in RFA by controlling the output power. We showed that the viscoelasticity of liver tissue depended on temperature previous temperature increase above 60°C. This result indicates that in RFA, controlling the output power is important to completely coagulate the tumor.

Intuitive Operability Evaluation of Robotic Surgery Using Brain Activity Measurements to Clarify Immersive Reality

Surgical robots have undergone considerable improvement in recent years. But intuitive operability, which represents user interoperability, has not been quantitatively evaluated. With the aim of designing a robot with intuitive operability, we thus propose a method for measuring brain activity to determine intuitive operability. The purpose of this paper is to clarify the master configuration against the position of the monitor that best allows user to perceive the manipulator as part of his own body. We assume that the master configuration provides immersive reality to user as if he puts own arm into the monitor. In our experiments, subjects controlled the hand controller to position the tip of the virtual slave manipulator on a target in the surgical simulator and we measured brain activity using brain imaging devices. We carried out experiments a number of times with themastermanipulator configured in a variety of ways and the position of the monitor fixed. We found that the brain was significantly activated in all subjects when the master manipulator was located behind the monitor. We concluded that the master configuration produces immersive reality through body images related to visual and somatic sensory feedback.

Development of a temperature distribution simulator for lung RFA based on air dependence of thermal and electrical properties

Radio frequency ablation (RFA) for lung cancer has increasingly been used over the past few years, because it is a minimally invasive treatment. As a feature of RFA for lung cancer, lung contains air. Air is low thermal and electrical conductivity. Therefore, RFA for this cancer has the advantage that only the cancer is coagulated, because the heated area is confined to the immediate vicinity of the heating point. However, it is difficult for operators to control the precise formation of coagulation zones due to inadequate imaging modalities. We propose a method using finite element method to analyze the temperature distribution of the organ in order to overcome the current deficiencies. Creating an accurate thermal physical model was a challenging problem because of the complexities of the thermal properties of the organ. In this study, we developed a temperature distribution simulator for lung RFA using thermal and electrical properties that were based on the lung's internal air dependence. In addition, we validated the constructed simulator in an in vitro study, and the lung's internal heat transfer during RFA was validated quantitatively.

Validation of accuracy of liver model with temperature-dependent thermal conductivity by comparing the simulation and in vitro RF ablation experiment

Radiofrequency (RF) ablation is increasingly used to treat cancer because it is minimally invasive. However, it is difficult for operators to control precisely the formation of coagulation zones because of the inadequacies of imaging modalities. To overcome this limitation, we previously proposed a model-based robotic ablation system that can create the required size and shape of coagulation zone based on the dimensions of the tumor. At the heart of such a robotic system is a precise temperature distribution simulator for RF ablation. In this article, we evaluated the simulation accuracy of two numerical simulation liver models, one using a constant thermal conductivity value and the other using temperature-dependent thermal conductivity values, compared with temperatures obtained using in vitro experiments. The liver model that reflected the temperature dependence of thermal conductivity did not result in a large increase of simulation accuracy compared with the temperature-independent model in the temperature range achieved during clinical RF ablation.

Algorithm for selecting appropriate transfer support equipment and a robot based on user physical ability

In this present paper, we propose an algorithm for selecting appropriate transfer support equipment and robot based on the physical ability of the user. In addition, we describe the relationship between physical human features and the burden during standing when using a standing support robot. Although a number of care support devices have been developed, assistive robots are not yet popular because users do not know which devices are appropriate for their needs or physical abilities. In this study, we focus on a transfer support device and propose an algorithm for selecting transfer support equipment and a robot that suits the user's physical ability. We investigated the relationship between standing support equipment including a robot and the physical burden during standing, which is a basic transfer motion. Experimentally, we analyzed and calculated the knee and ankle joint moments and discussed the relationship between standing support equipment and knee and ankle joint moments during standing; we also investigated and the relationship between physical human features and the knee joint moment during standing. Our results identified standing support equipment that was appropriate to the user's physical ability. We found that it was effective to provide an up/down seat to persons having low residual ability; a standing support robot is appropriate for people having less residual ability in the knees, and a railing is suitable for people having low residual ability in the ankles.

The relation between temperature distribution for lung RFA and electromagnetic wave frequency dependence of electrical conductivity with changing a lung's internal air volumes

Radio frequency ablation (RFA) for lung cancer has increasingly been used over the past few years because it is a minimally invasive treatment. As a feature of RFA for lung cancer, lung contains air during operation. Air is low thermal and electrical conductivity. Therefore, RFA for this cancer has the advantage that only the cancer is coagulated, and it is difficult for operators to control the precise formation of coagulation lesion. In order to overcome this limitation, we previously proposed a model-based robotic ablation system using finite element method. Creating an accurate thermo physical model and constructing thermal control method were a challenging problem because the thermal properties of the organ are complex. In this study, we measured electromagnetic wave frequency dependence of lung's electrical conductivity that was based on lung's internal air volumes dependence with in vitro experiment. In addition, we validated the electromagnetic wave frequency dependence of lung's electrical conductivity using temperature distribution simulator. From the results of this study, it is confirmed that the electromagnetic wave frequency dependence of lung's electrical conductivity effects on heat generation of RFA.

Path tracking control of an omni-directional walker considering pressures from a user

An omni-directional walker (ODW) is being developed to support the people with walking disabilities to do walking rehabilitation. The training paths, which the user follows in the rehabilitation, are defined by physical therapists and stored in the ODW. In order to obtain a good training effect, the defined training paths need to be performed accurately. However, the ODW deviates from the training path in real rehabilitation, which is caused by the variation of the whole system's parameters due to the force from the user. In this paper, the characteristics of pressures from a user are measured, based on which an adaptive controller is proposed to deal with this problem, and validated in an experiment in which a pseudo handicapped person follows the ODW. The experimental results show that the proposed method can control the ODW to accurately follow the defined path with or without a user.

Pilot Study of Split Belt Treadmill Based Gait Rehabilitation System for Symmetric Stroke Gait

A split belt treadmill for gait rehabilitation was developed to improve the symmetry of the stance phase time of patients with stroke. The system, which increases the stance phase time of the affected leg and then realizes a well-balanced gait, is divided into two components. First, the stance phases of the sound and affected legs were measured and presented visually in real time to the patient and physical therapist as biofeedback. Second, using stance phase biofeedback, the physical therapist sets two different velocities of treadmill belts for sound and affected legs. In an experiment, 11 patients with chronic stroke participated in a short-term intervention trial (20 gait cycles) of the developed treadmill system. Three of the five subjects who had lost balance between the stance phase of the sound leg and that of the affected one improved their gait balance in the intervention trial. In addition, one subject kept the well-balanced gait after the intervention.

Gait Phase Detection Using Foot Acceleration for Estimating Ground Reaction Force in Long Distance Gait Rehabilitation

In gait rehabilitation, achieving a gait analysis method using a simple system during long-distance walking is important. This method is required to measure all gait parameters in a single measurement. In addition, it is required that the measurement system is not spatially constrained. Therefore, we have been developing a gait tracking system with acceleration sensors for long-distance gait rehabilitation. In this paper, we describe a gait phase detection method using foot acceleration data for estimating ground reaction force during long-distance gait rehabilitation. To develop this method, we focused on the jerk of each foot in vertical axis direction. Using two accelerometers mounted on the left and right feet, we carried out three experiments. First, we measured the jerk of each foot during a free gait to verify the relation with the walking speed. Second, we measured the jerk of each foot during walking faster than normal for each subject. We then compared these results with the results of first experiments. Finally, we measured the jerk of each foot during left-right asymmetrical walking. The results confirmed that gait phase could be detected using the jerk of each leg, calculated from acceleration data in vertical axis direction. In particular, the timing of Heel-contact / Toe-off could be obtained with an average error of 0.03 s. And as a preliminary study, we estimated the ground reaction force using the one of the results.