Yoshihiro Kuroda

Construction of Training Environment for Surgical Exclusion with a Basic Study of Multi-finger Haptic Interaction

Virtual reality based surgical simulator allows a repetitive training without spoiling patients. Exclusion is an important surgical manipulation of pushing aside organ to make a hidden tissue visible. The authors propose an organ exclusion training simulator with multi-finger haptic interaction and stress visualization. The system equips FEM-based soft tissue deformation and exoskeletal haptic device CyberForce. Real-time simulation was achieved with a prototype system. Results of training trial suggested effectiveness of stress visualization especially in early training days. Subjective evaluation by surgeons cleared its potential. Results of a basic study showed decrease of required refresh rate in multi-finger interaction compared with single finger interaction. It suggested the system can keep realism even if calculation time is increased by multi-finger interaction

A Non-grounded and Encountered-type Haptic Display Using a Drone

Encountered-type haptic displays recreate realistic haptic sensations by producing physical surfaces on demand for a user to explore directly with his or her bare hands. However, conventional encountered-type devices are fixated in the environment thus the working volume is limited. To address the limitation, we investigate the potential of an unmanned aerial vehicle (drone) as a flying motion base for a non-grounded encountered-type haptic device. As a lightweight end-effector, we use a piece of paper hung from the drone to represent the reaction force. Though the paper is limp, the shape of paper is held stable by the strong airflow induced by the drone itself. We conduct two experiments to evaluate the prototype system. First experiment evaluates the reaction force presentation by measuring the contact pressure between the user and the end-effector. Second experiment evaluates the usefulness of the system through a user study in which participants were asked to draw a straight line on a virtual wall represented by the device.

Development of a spatially transparent electrotactile display and its performance in grip force control

An important function for a tactile navigation system of a handheld tool, such as a surgical scalpel, is the spatial transparency of the device. This paper proposed a new tactile display that can augment touch sensation at the finger pulps without the need for a stimulator between the tool and the finger pulps. We utilized transcutaneous electrical nerve stimulation at the middle phalanx of a finger to separate the stimulated and the perceived areas. In order to verify the effects of the spatial transparency, the performances of grip force control were examined. The results indicated that the proposed display was effective in helping the user to maintain the stable control of the grip force when using a handheld tool.

Tactile mapping approach using electrical stimulus pattern

The fine concavo-convex shape of the object surface is a critical component that determines its texture. A previous electrotactile display could not tactually present fine concavo-convex objects but only a line pattern on the plane. In this study, the authors proposed a physiology-based tactile mapping method by formulating nerve activities that stem from a mechanical stimulus. The proposed electrical stimulus allows a human to perceive a concavo-convex shape. A stimulus frequency coded the skin displacement given by a concavo-convex shape and represented the adaptation of receptors with exponential approximation. As an example of tactually presenting a concavo-convex shape, roughness was introduced by using a Brownian surface, which enables a user to touch a surface of varying degrees of roughness with a developed tactile display mounted on a computer mouse. The results of subjective experiments showed a statistical difference among the perceived roughness of displayed rough surfaces. This study concluded that the proposed tactile mapping method was effective to present a touch sensation for concavo-convex shapes corresponding to a stimulus frequency below 100 Hz.

Evaluation of deformable image registration between external beam radiotherapy and HDR brachytherapy for cervical cancer with a 3D‐printed deformable pelvis phantom

Purpose In this study, we developed a 3D‐printed deformable pelvis phantom for evaluating spatial DIR accuracy. We then evaluated the spatial DIR accuracies of various DIR settings for cervical cancer. Methods A deformable female pelvis phantom was created based on patient CT data using 3D printing. To create the deformable uterus phantom, we first 3D printed both a model of uterus and a model of the internal cavities of the vagina and uterus. We then made a mold using the 3D printed uterus phantom. Finally, urethane was poured into the mold with the model of the internal cavities in place, creating the deformable uterus phantom with a cavity into which an applicator could be inserted. To create the deformable bladder phantom, we first 3D printed models of the bladder and of the same bladder scaled down by 2 mm. We then made a mold using the larger bladder model. Finally, silicone was poured into the mold with the smaller bladder model in place to create the deformable bladder phantom with a wall thickness of 2 mm. To emulate the anatomical bladder, water was poured into the created bladder. We acquired phantom image without applicator for EBRT. Then, we inserted the applicator into the phantom to simulate BT. In this situation, we scanned the phantom again to obtain the phantom image for BT. We performed DIR using the two phantom images in two cases: Case A, with full bladder (170 ml) in both EBRT and BT images; and Case B with full bladder in the BT image and half‐full bladder (100 ml) in the EBRT image. DIR was evaluated using Dice similarity coefficients (DSCs) and 31 landmarks for the uterus and 25 landmarks for the bladder. A hybrid intensity and structure DIR algorithm implemented in RayStation with four DIR settings was evaluated. Results On visual inspection, reasonable agreement in shape of the uterus between the phantom and patient CT images was observed for both EBRT and BT, although some regional disagreements in shape of the bladder and rectum were apparent. The created phantom could reproduce the actual patients uterus deformation by the applicator. For both Case A and B, large variation was seen in landmark error among the four DIR parameters. In addition, although DSCs were comparable, moderate differences in landmark error existed between the two different DIR parameters selected from the four DIR parameters (i.e., DSC = 0.96, landmark error = 13.2 ± 5.7 mm vs. DSC = 0.97, landmark error = 9.7 ± 4.0 mm). This result suggests that landmark error evaluation might thus be more effective than DSC for evaluating DIR accuracy. Conclusions Our developed phantom enabled the evaluation of spatial DIR accuracy for the female pelvic region for the first time. Although the DSCs are high, the spatial errors can still be significant and our developed phantom facilitates their quantification. Our results showed that optimization is needed to identify suitable DIR settings. For determining suitable DIR settings, our method of evaluating spatial DIR accuracy using the 3D‐printed phantom may prove helpful.

HapSticks: A novel method to present vertical forces in tool-mediated interactions by a non-grounded rotation mechanism

Force feedback in tool-mediated interactions with the environment is important for successful performance of complex tasks in our daily life as well as in specialized fields like medicine. Stylus-based haptic devices are studied and used extensively, and most of these devices require either grounding or attachment to the body of the user. Recently, non-grounded haptic devices are getting an increasing attention. In this paper, we propose a novel method to represent the vertical forces that are applied on the tip of a tool: a non-grounded rotation mechanism that mimics the cutaneous sensation that is caused by these tool-tip forces. To evaluate this method, we developed a novel ungrounded haptic device - HapSticks - that renders the sensation of manipulating objects using chopsticks. First, we present the novel mechanism, and test the pressure that it applies on the hand of the user when rendering a force at the tip of the tool in comparison to applying a real force at the tip of the tool. Next, we used the mechanism to build the HapSticks device as an example of an application of the proposed method, and present a psychophysical evaluation of this device in a virtual weight discrimination task.

Material Roughness Modulation via Electrotactile Augmentation

Tactile exploration of a materials texture using a bare finger pad is a daily human activity. However, modern tactile displays do not allow users to experience the natural sensations of a material when artificial sensations are presented. We propose an electrotactile augmentation technique capable of superimposing vibrotactile sensations in a finger pad, thereby allowing the texture modulation of real materials. Users attach two stimulus electrodes to the middle phalanx of a finger and a grounded electrode at the base of the finger in order to evoke nerve activity. This paper evaluates the proposed electrotactile augmentation for roughness modulation of real materials. First, we introduce the principle of the electrotactile display, which presents artificial sensations at the finger pad. We then confirm that the perceived frequency of mechanical vibration at the finger pad can be shifted using electrotactile augmentation. Finally, we discuss a user study, wherein participants rated the roughness of real materials explored using the proposed system. Experimental results indicate that fine- and macro-roughness perceptions of real materials can be altered using electrotactile augmentation.

HapticDrone: An Encountered-Type Kinesthetic Haptic Interface with Controllable Force Feedback: Initial Example for 1D Haptic Feedback

We present HapticDrone, a concept to generate controllable and comparable force feedback for direct haptic interaction with a drone. As a proof-of-concept study this paper focuses on creating haptic feedback only in 1D direction. To this end, an encountered-type, safe and un-tethered haptic display is implemented. An overview of the system and details on how to control the force output of drones is provided. Our current prototype generates forces up to 1.53 N upwards and 2.97 N downwards. This concept serves as a first step towards introducing drones as mainstream haptic devices.

Roughness Modulation of Real Materials Using Electrotactile Augmentation

In this paper, we present a roughness modulation technique that employs electrotactile augmentation to alter material texture perception, which is conducted through mechanically unconstrained touch. A novel electrotactile augmented reality system that superimposes modulating nerve activity onto afferent nerves at the middle phalanx of a finger is described. We conducted a user study in which participants were requested to rate the roughness of real materials that were explored using the system. The results indicated that participants could perceive the modulated fine- and macro-roughness via the electrotactile augmentation.

Prior estimation of motion using recursive perceptron with sEMG: A case of wrist angle

Muscle activity is followed by myoelectric potentials. Prior estimation of motion by surface electromyography can be utilized to assist the physically impaired people as well as surgeon. In this paper, we proposed a real-time method for the prior estimation of motion from surface electromyography, especially in the case of wrist angle. The method was based on the recursive processing of multi-layer perceptron, which is trained quickly. A single layer perceptron calculates quasi tensional force of muscles from surface electromyography. A three-layer perceptron calculates the wrists change in angle. In order to estimate a variety of motions properly, the perceptron was designed to estimate motion in a short time period, e.g. 1ms. Recursive processing enables the method to estimate motion in the target time period, e.g. 50ms. The results of the experiments showed statistical significance for the precedence of estimated angle to the measured one.