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.

Brain activation measurement for motion gain decision of surgical endoscope manipulation.

BACKGROUND: Robotic surgery improves minimally invasive interventions. However, it is challenging to determine the best gain settings for control of the endoscope. Providing the surgeon with the ability to manipulate the endoscope at an appropriate speed will likely improve the surgery by reducing the surgeon's stress. In this study, we validated the feasibility of a gain-tuning method in which the operator's brain activity is measured and used to evaluate stress levels. METHODS: We developed an endoscope-manipulation simulator and used functional near-infrared spectroscopy to measure the prefrontal cortical activity, while participants controlled the simulator at different gain values. RESULTS: The brain activation levels in the prefrontal cortex exhibited significant differences under different viewpoint motion gain conditions. CONCLUSIONS: The stress-related brain activity was significantly reduced at specific gains, indicating that the brain activity evaluation would be useful to determine the parameters related to the operator's feelings.

Non-minimum phase viscoelastic properties of soft biological tissues.

Understanding the viscoelastic properties of biological tissues is important because they can reveal tissue structure. This study analyzes the viscoelastic properties of soft biological tissues using a fractional dynamics model. We conducted a dynamic viscoelastic test on several porcine samples, i.e., liver, breast, and skeletal muscle tissues, using a plate-plate rheometer. We found that some soft biological tissues have non-minimum phase properties, i.e., the relationship between compliance and phase delay is not uniquely related to the non-integer derivative order in the fractional dynamics model. The experimental results show that the actual phase delay is larger than that estimated from compliance. We propose an empirical model to represent these non-minimum phase properties; a fractional Maxwell model with the fractional Hilbert transform term is proposed. The model and experimental results were highly correlated in terms of compliance and phase diagrams, and complex mechanical impedance. We also show that the amount of additional phase delay, defined as the increase in actual phase delay compared to that estimated from compliance, differs with tissue type.

State-of-the-art of intelligent minimally invasive surgical robots.

A number of developed countries are rapidly turning into super-aged societies. Consequently, the demand for reduced surgical invasiveness and enhanced efficiency in the medical field has increased due to the need to reduce the physical burden on older patients and shorten their recovery period. Intelligent surgical robot systems offer high precision, high safety, and reduced invasiveness. This paper presents a review of current intelligent surgical robot systems. The history of robots and three types of intelligent surgical robots are discussed. The problems with current surgical robot systems are then analyzed. Several aspects that should be considered in designing new surgical systems are discussed in detail. The paper ends with a summary of the work and a discussion of future prospects for surgical robot development.

Prediction Algorithm of Parameters of Toe Clearance in the Swing Phase.

The adaptive control of gait training robots is aimed at improving the gait performance by assisting motion. In conventional robotics, it has not been possible to adjust the robotic parameters by predicting the toe motion, which is considered a tripping risk indicator. The prediction of toe clearance during walking can decrease the risk of tripping. In this paper, we propose a novel method of predicting toe clearance that uses a radial basis function network. The input data were the angles, angular velocities, and angular accelerations of the hip, knee, and ankle joints in the sagittal plane at the beginning of the swing phase. In the experiments, seven subjects walked on a treadmill for 360 s. The radial basis function network was trained with gait data ranging from 20 to 200 data points and tested with 100 data points. The root mean square error between the true and predicted values was 3.28 mm for the maximum toe clearance in the earlier swing phase and 2.30 mm for the minimum toe clearance in the later swing phase. Moreover, using gait data of other five subjects, the root mean square error between the true and predicted values was 4.04 mm for the maximum toe clearance and 2.88 mm for the minimum toe clearance when the walking velocity changed. This provided higher prediction accuracy compared with existing methods. The proposed algorithm used the information of joint movements at the start of the swing phase and could predict both the future maximum and minimum toe clearances within the same swing phase.

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.

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.

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.

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.

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.

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.

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.

The effect of forceps manipulation for expert pediatric surgeons using an endoscopic pseudo-viewpoint alternating system: the phenomenon of economical slow and fast performance in endoscopic surgery.

PURPOSE: Endoscopic surgery is performed under a horizontal view in comparison to the vertical view that is associated with open surgery. We developed an endoscopic pseudo-viewpoint alternation system with out any scope action. We investigate the effect of this novel system on forceps manipulation among expert pediatric surgeons. METHODS: Six expert pediatric surgeons performed a Nissen wrap in a fundoplication simulator either with or without this system. The constructed Nissen wrap was evaluated. The total path length and the average velocity of the forceps were also analyzed. RESULTS: The times required either with or without this system were 587.5 ± 122.7 and 634.0 ± 212.4 s (p = 0.45), respectively. The total path lengths of right and left forceps either with or without this system were 12,309 ± 2495.5 and 15,726 ± 5649.6 mm (p = 0.07), 10,091 ± 2439.2 and 12,575 ± 5511.1 mm (p = 0.11), respectively. The average velocity of the right and left forceps with or without this system were 26.9 ± 5.29 and 31.6 ± 1.62 mm/s (p = 0.04), 21.6 ± 2.48 and 25.5 ± 6.48 mm/s (p = 0.15), respectively. There was no significance in the suture balance and suture interval. CONCLUSION: The endoscopic pseudo-viewpoint alternation system thus made it possible for expert pediatric surgeons to carry out slow and economical forceps manipulation. These effects make it possible for surgeons to perform safe and precise surgery, thus leading to a shortening of operation time.

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.

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.

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.