The role of tactile feedback in grip force during laparoscopic training tasks.

BACKGROUND: Laparoscopic minimally invasive surgery has revolutionized surgical care by reducing trauma to the patient, thereby decreasing the need for medication and shortening recovery times. During open procedures, surgeons can directly feel tissue characteristics. However, in laparoscopic surgery, tactile feedback during grip is attenuated and limited to the resistance felt in the tool handle. Excessive grip force during laparoscopic surgery can lead to tissue damage. Providing additional supplementary tactile feedback may allow subjects to have better control of grip force and identification of tissue characteristics, potentially decreasing the learning curve associated with complex minimally invasive techniques. METHODS: A tactile feedback system has been developed and integrated into a modified laparoscopic grasper that allows forces applied at the grasper tips to be felt by the surgeon's hands. In this study, 15 subjects (11 novices, 4 experts) were asked to perform single-handed peg transfers using these laparoscopic graspers in three trials (feedback OFF, ON, OFF). Peak and average grip forces (newtons) during each grip event were measured and compared using a Wilcoxon ranked test in which each subject served as his or her own control. RESULTS: After activating the tactile feedback system, the novice subject population showed significant decreases in grip force (p < 0.003). When the system was deactivated for the third trial, there were significant increases in grip force (p < 0.003). Expert subjects showed no significant improvements with the addition of tactile feedback (p > 0.05 in all cases). CONCLUSION: Supplementary tactile feedback helped novice subjects reduce grip force during the laparoscopic training task but did not offer improvements for the four expert subjects. This indicates that tactile feedback may be beneficial for laparoscopic training but has limited long-term use in the nonrobotic setting.

Ultrasound imagery for dental implant diagnosis and treatment planning in a porcine model.

STATEMENT OF PROBLEM: Currently, there is no commercially available method to provide non-invasive, non-ionizing, real-time imaging of the gingival form and bony architecture of implant sites, before, during, and after implant placement. PURPOSE: The purpose of this study was to demonstrate the feasibility of 2-dimensional (2-D) ultrasound imaging of soft and hard tissues for implant diagnosis and treatment planning. MATERIAL AND METHODS: A sector scanning ultrasound system was applied. Five representative clinical features (implant in an edentulous ridge, single implant tooth replacement, implant dehiscence, tooth dehiscence, and mental foramina) were created or identified in each of the 5 porcine jaws, which were then covered with soft tissue and imaged in an acoustic water tank. RESULTS: All of the 5 model features, in all 5 jaws, were clearly visible with the ultrasound. Most objects were visible over a large range of positions and angles. Each of the features, as well as the soft tissue and bone surfaces, were recognized by specific acoustic signatures, with the same signature recurring for each object type among all 5 of the jaw specimens. All implants were highly reflective and clearly visualized. CONCLUSIONS: A 2-D sector scanning ultrasound system was demonstrated to be capable of imaging representative features for implant treatment planning in a porcine model; these included implants placed in edentulous ridges; implants placed for single tooth replacement; implants with simulated dehiscences; teeth with simulated dehiscences; and mental foramina. Specific acoustic signatures for these features were defined. Qualitative differences between ultrasound and other dental imaging techniques were described.

A prototype stimulator system for noninvasive Low Intensity Focused Ultrasound delivery.

A prototype Low Intensity Focused Ultrasound (LIFU) stimulator system was developed to evaluate non-invasive neuromodulation in a large animal model. We conducted a feasibility study on a Göttingen minipig, demonstrating reversible, targeted transcranial neuromodulation. The hypothalamus of the minipig was repeatedly stimulated with LIFU which evoked temporally correlated increases in both heart rate and blood pressure.

A transurethral catheter-based ultrasound system for multi-modal fusion.

Current methods of prostate cancer diagnosis and therapy rely on accurate imaging of the prostate using real-time ultrasound. Transurethral ultrasound (TUUS) may improve upon the current gold standard through improved 3D visualization and co-registration (fusion) with CT and MRI. A prototype transurethral ultrasound (TUUS) catheter-based transducer array and system was developed, featuring 32 elements with a diameter of 18F (6mm). A robust, multi-channel ultrasound transceiver was also developed to enable TUUS imaging using pulse-echo and frequency-based signal processing methods. The feasibility of a TUUS imaging system suitable for multi-modal image fusion and novel ultrasound signaling techniques was demonstrated.

Applications of tactile feedback in medicine.

A tactile feedback system has been developed in order to provide augmentative sensory feedback for a number of medical applications. The key component to the system is a pneumatic balloon-based tactile display, which can be scaled and adapted for a variety of configurations. The system also features pneumatic and electronic control system components, a commercial force sensor modified to fit the desired application. To date, this technology has been successfully applied to medical robotics, minimally invasive surgery, and rehabilitation medicine.

Terahertz imaging of biological tissues.

A reflective THz imaging system sensitive to small variations in water concentrations has been developed. Biological tissues such as skin, eyes and teeth were imaged to ascertain the systems response to tissue hydration. Difference in water concentrations translated to contrast in the THz images. Contrast was also seen in THz images of skin cancer and burns suggesting the potential diagnostic capability of THz imaging system in clinical settings. All specimens analyzed were freshly excised ex-vivo tissues. These encouraging preliminary results have motivated us to explore the in vivo potential of our imaging system.

Quantification of intraocular surgery motions with an electromagnetic tracking system.

Motion tracking was performed during a combined phacoemulsification (PKE) and pars plana vitrectomy (PPV) procedure on a pig eyeball. The UCLA Laparoscopic Training System (UCLA-LTS), which consists of electromagnetic sensors attached to the surgical tools to measure three-dimensional spatial vectors, was modified to enable quantification of intraocular surgery motions. The range of motion and time taken to complete the given task were successfully recorded.

Characterization of a pneumatic balloon actuator for use in refreshable Braille displays.

Many existing refreshable Braille display technologies are costly or lack robust performance. A process has been developed to fabricate consistent and reliable pneumatic balloon actuators at low material cost, using a novel manufacturing process. This technique has been adapted for use in refreshable Braille displays that feature low power consumption, ease of manufacture and small form factor. A prototype refreshable cell, conforming to American Braille standards, was developed and tested. The cell was fabricated from molded PDMS to form balloon actuators with a spin-coated silicone film, and fast pneumatic driving elements and an electronic control system were developed to drive the Braille dots. Perceptual testing was performed to determine the feasibility of the approach using a single blind human subject. The subject was able to detect randomized Braille letters rapidly generated by the actuator with 100% character detection accuracy.

Development and testing of a tactile feedback system for robotic surgery.

A tactile feedback system has been developed using silicone-based pneumatic balloon actuators and piezoelectric force sensors, paired with a pneumatic control system. This system has been fitted directly onto the da Vinci surgical robotic system, allowing the forces applied at the robotic end-effectors to be felt on the fingers of surgeons or other system operators. Preliminary system tests have been performed to evaluate the efficacy of the system and to validate the tactile feedback approach. The actuators and pneumatic system had a sufficiently low footprint such that they did not hinder movements during surgical task performance. Preliminary studies using a pressure-indicating phantom suggested that grip force may be reduced with direct tactile-to-tactile feedback. An additional study found that a six element tactile sensing array can effectively provide spatial information to the fingers. The results of these studies are summarized in this paper.

A prototype surgical manipulator for robotic intraocular micro surgery.

A prototype manipulator system was developed for ophthalmologic microsurgery. The system, consisting of two parallel X-Y stages, can mechanically maintain a fixed-point of rotation at the surface of the eye, potentially reducing trauma during surgical procedures. The initial prototype was designed to function in concert with the da Vinci Surgical System for gross positioning. Robotic tests demonstrated the mechanical fitness of the prototype while an in vitro surgical sclerectomy was performed to demonstrate functionality of the approach.

Towards medical terahertz sensing of skin hydration.

Terahertz imaging has shown promise as a tool for noninvasive in-vivo detection of skin abnormalities, including skin cancer, burns, scars, and wounds due to its low non-ionizing photon energy and ability to penetrate clothing and gauze. This study examines whether low-level bulk differences in the water content between hyperhydrated and dehydrated skin can be detected using a scanning, reflective THz imaging system. Our results show an 8.7 x difference in the THz reflectivity between hyperhydrated and dehydrated specimens of chicken skin. The results provide further evidence that water concentration is the primary contrast mechanism in reflective THz biomedical imaging.

Tissue mimicking materials for dental ultrasound.

While acoustic tissue mimicking materials have been explored for a variety of soft and hard biological tissues, no dental hard tissue mimicking materials have been characterized. Tooth phantoms are necessary to better understand acoustic phenomenology within the tooth environment and to accelerate the advancement of dental ultrasound imaging systems. In this study, soda lime glass and dental composite were explored as surrogates for human enamel and dentin, respectively, in terms of compressional velocity, attenuation, and acoustic impedance. The results suggest that a tooth phantom consisting of glass and composite can effectively mimic the acoustic behavior of a natural human tooth.

Towards THz medical imaging; reflective imaging of animal tissues.

A reflective THz imaging system has been developed, and features a photoconductive switch and zero-bias Schottky diode detector. The system was used to image deli meats and can distinguish between muscle and adipose tissue based on water content. This capability is a step towards the development of THz medical imaging systems.

A flexible, conformal ultrasound array for medical imaging.

An ultrasound imaging system is under development that features a flexible transducer that can be wrapped conformally around curved surfaces of the body. The device is intended to deliver high image quality without the need for mechanical scanning, and will benefit medical personnel with limited ultrasound training. A 2 x 8 element piezoelectric transducer prototype and 15.5 MHz imaging system have been built, and the system concept has been demonstrated by imaging a soft tissue phantom. The transducer design, imaging procedure, and preliminary image processing techniques are presented.

A prototype haptic feedback system for lower-limb prostheses and sensory neuropathy.

Lower-limb sensory loss as a result of peripheral neuropathy or amputation results in sub-optimal movement and an increased incidence of injury. While the adoption of lower-limb prostheses and therapeutic footwear can reduce tissue injury and support movement, the fundamental problem of sensory loss continues to exist. A prototype haptic feedback system has been developed to aid in the recovery of lower-limb sensation due to these causes. Thin-film force sensors placed at the critical points for gait and balance functions collect essential force data, which is delivered to the user via pneumatically controlled balloon inflation. It is postulated that the use of this system will increase the tactile awareness of a patient's lower-limb or prosthesis, and when used in concert with modern rehabilitation techniques will create a method that will reduce the duration and improve the quality of lower-limb rehabilitation, especially in gait and balance functions.

Penetration of radiopaque dental restorative materials using a novel ultrasound imaging system.

PURPOSE: To determine whether a novel ultrasound imaging system could detect 25 microm thick cracks beneath gold, silver amalgam, and porcelain restorations on tooth phantoms. METHODS: Tooth phantoms were constructed using acoustically-matched composite to simulate dentin, with 25 microm thick water-filled cracks located approximately 1 mm inside the simulated dentin. Porcelain and gold restorations were bonded using resinous cement, and an amalgam restoration was attached using mechanical retention. A portion of the gold restoration was left unattached to simulate cement washout. A novel monostatic pulse-echo ultrasound system with a 19 MHz single-element PLZT transducer, custom transmit/receive electronics and signal processing with a Ga-In alloy couplant was used to measure the relative return echo amplitude from restoration surfaces, simulated dentin/restoration interfaces, and cracks. Extracted teeth were also used to demonstrate that the system was capable of detecting cracks in real teeth. RESULTS: Cracks were detected beneath porcelain and amalgam, and within a human molar. Cracks were not detected in simulated dentin beneath gold; however, simulated cement washout directly beneath gold was identified. The ability to detect defects in the phantom was dependent on the acoustic reflection coefficient between interfaces, the attenuation of each material, acoustic clutter within the phantom, and geometry. Gold restorations transmitted minimal acoustic energy due to their large acoustic impedance; however, the ability to distinguish the gold/cement interface from the gold/washout interface indicated that ultrasound can detect density changes immediately below restorations, such as caries, fractures, or debonding. The ability to penetrate resin-composite was also demonstrated.

A pneumatic haptic feedback actuator array for robotic surgery or simulation.

Robot-assisted minimally invasive surgery (MIS) offers improved range of motion over standard laparoscopic techniques, but is characterized by a total loss of haptic feedback, requiring surgeons to rely solely on visual cues. Pneumatic tactile displays have many advantages, including low mass, low cost, compact size, and adaptability. A pneumatic haptic feedback actuator array has been developed that is suitable for mounting unto surgical robotic tools. The balloon actuators consist of spin-coated thin-film silicone membranes and molded substrates with cylindrical channels. Human perceptual tests were conducted on balloon diameters ranging from 0.75 to 2.0 mm to determine the optimal size that can be effectively detected. The control system was programmed to sequentially inflate a single balloon to one of the three levels, 100% (full hemispherical deformation), zero, 50% (half deformation), and 0% (no inflation). Blinded subjects (n=5) were asked to determine which of the two inflation levels was higher. Test results suggest that balloon diameters greater than 1.0 mm can deliver high detection accuracy. This indicates that pneumatic balloon-based actuation is a viable solution for generating haptic feedback. In addition to surgical applications, many other fields such as virtual reality-based simulators and neuroprosthetics can benefit from this technology.

Wearable Ultrasound Array for Point-of-Care Imaging and Patient Monitoring.

A versatile, flexible piezoceramic array has been developed for a variety of ultrasound applications. The transducer can be configured as a linear or curvilinear transducer array, or mounted directly onto the body as a patch or wearable device. Results using a prototype 16-element array demonstrated equivalence to commercial linear array probes in accuracy of vessel diameter measurements in vascular phantoms. The ability to view needle insertion for peripherally inserted central catheter (PICC) procedures was also demonstrated. Opportunities for wearable ultrasound devices include point-of-care imaging, combat casualty care, ultrasound therapy, patient monitoring, and personal health.

Integrated Self-Management System for Improved Treatment of Asthma.

A mobile, affordable product that provides clinicians and patients with comprehensive asthma assessment is needed to improve asthma control. Our solution is an integrated system consisting of a portable, inexpensive, easy-to-use spirometer and a mobile application that communicates wirelessly with the spirometer. Results demonstrated that the wireless asthma management solution meets recommended American Thoracic Society (ATS) and European Respiratory Society (ERS) standards. The device is expected to empower patients to accurately self-assess their asthma for better self-management at home, work, or leisure.

Robotic ultrasound systems in medicine.

Robots ultrasound (RUS) can be defined as the combination of ultrasound imaging with a robotic system in medical interventions. With their potential for high precision, dexterity, and repeatability, robots are often uniquely suited for ultrasound integration. Although the field is relatively young, it has already generated a multitude of robotic systems for application in dozens of medical procedures. This paper reviews the robotic ultrasound systems that have been developed over the past two decades and describes their potential impact on modern medicine. The RUS projects reviewed include extracorporeal devices, needle guidance systems, and intraoperative systems.