Discriminating Tissue Stiffness with a Haptic Catheter: Feeling the Inside of the Beating Heart

Magnetic Levitation Haptic Augmentation for Virtual Tissue Stiffness Perception

Haptic-based tissue stiffness perception is essential for palpation training system, which can provide the surgeon haptic cues for improving the diagnostic abilities. However, current haptic devices, such as Geomagic Touch, fail to provide immersive and natural haptic interaction in virtual surgery due to the inherent mechanical friction, inertia, limited workspace and flawed haptic feedback. To tackle this issue, we design a novel magnetic levitation haptic device based on electromagnetic principles to augment the tissue stiffness perception in virtual environment. Users can naturally interact with the virtual tissue by tracking the motion of magnetic stylus using stereoscopic vision so that they can accurately sense the stiffness by the magnetic stylus, which moves in the magnetic field generated by our device. We propose the idea that the effective magnetic field (EMF) is closely related to the coil attitude for the first time. To fully harness the magnetic field and flexibly generate the specific magnetic field for obtaining required haptic perception, we adopt probability clouds to describe the requirement of interactive applications and put forward an algorithm to calculate the best coil attitude. Moreover, we design a control interface circuit and present a self-adaptive fuzzy proportion integration differentiation (PID) algorithm to precisely control the coil current. We evaluate our haptic device via a series of quantitative experiments which show the high consistency of the experimental and simulated magnetic flux density, the high accuracy (0.28 mm) of real-time 3D positioning and tracking of the magnetic stylus, the low power consumption of the adjustable coil configuration, and the tissue stiffness perception accuracy improvement by 2.38 percent with the self-adaptive fuzzy PID algorithm. We conduct a user study with 22 participants, and the results suggest most of the users can clearly and immersively perceive different tissue stiffness and easily detect the tissue abnormality. Experimental results demonstrate that our magnetic levitation haptic device can provide accurate tissue stiffness perception augmentation with natural and immersive haptic interaction.

Robotic catheter cardiac ablation combining ultrasound guidance and force control

Cardiac catheters allow physicians to access the inside of the heart and perform therapeutic interventions without stopping the heart or opening the chest. However, conventional manual and actuated cardiac catheters are currently unable to precisely track and manipulate the intracardiac tissue structures because of the fast tissue motion and potential for applying damaging forces. This paper addresses these challenges by proposing and implementing a robotic catheter system that uses 3D ultrasound image guidance and force control to enable constant contact with a moving target surface in order to perform interventional procedures, such as intracardiac tissue ablation. The robotic catheter system, consisting of a catheter module, ablation and force sensing end effector, drive system, and image-guidance and control system, was commanded to apply a constant force against a moving target using a position-modulated force control method. The control system uses a combination of position tracking, force feedback, and friction and backlash compensation to achieve accurate and safe catheter–tissue interactions. The catheter was able to maintain a 1 N force on a moving motion simulator target under ultrasound guidance with 0.08 N RMS error. In a simulated ablation experiment, the robotic catheter was also able to apply a consistent force on the target while maintaining ablation electrode contact with 97% less RMS contact resistance variation than a passive mechanical equivalent. In addition, the use of force control improved catheter motion tracking by approximately 20%. These results demonstrate that 3D ultrasound guidance and force tracking allow the robotic system to maintain improved contact with a moving tissue structure, thus allowing for more accurate and repeatable cardiac procedures.

Evaluation of Construction Robot Telegrasping Force Perception Using Visual, Auditory and Force Feedback Integration

Construction robot telegrasping operation provides considerable challenges in postdisaster recovery missions. This paper presents an evaluation of construction robot telegrasping force perception, which integrates the use of visual, auditory and force feedback systems. The integration of graphically-presented feedback force is proposed to help operators visually monitor changes in grasping force. Auditory feedback is used simultaneously to provide rapid warnings, while force feedback enhances grasping sense. Sensitivity to each type of feedback is measured by using psychophysical tests, and manipulation tests are conducted to observe effects on the gripping risk index, task completion time and subjective workload. Results validate the need for multimodal sensory feedback, for accurately controlling the grasping process, and for avoiding unnecessary action due to human error.