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.

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.

In vivo terahertz imaging of rat skin burns.

A reflective, pulsed terahertz (THz) imaging system was used to acquire high-resolution (d(10-90)/λ~1.925) images of deep, partial thickness burns in a live rat. The rat's abdomen was burned with a brass brand heated to ~220°C and pressed against the skin with contact pressure for ~10 sec. The burn injury was imaged beneath a Mylar window every 15 to 30 min for up to 7 h. Initial images display an increase in local water concentration of the burned skin as evidenced by a marked increase in THz reflectivity, and this likely correlates to the post-injury inflammatory response. After ~1 h the area of increased reflectivity consolidated to the region of skin that had direct contact with the brand. Additionally, a low reflecting ring of tissue could be observed surrounding the highly reflective burned tissue. We hypothesize that these regions of increased and decreased reflectivity correlate to the zones of coagulation and stasis that are the classic foundation of burn wound histopathology. While further investigations are necessary to confirm this hypothesis, if true, it likely represents the first in vivo THz images of these pathologic zones and may represent a significant step forward in clinical application of THz technology.

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.

Ultrasound imaging of dental implants.

Accurate measurement of soft tissue thickness is needed prior to dental implant placement and prior to surgical uncovering of the implant. Ultrasonography has many potential advantages for use in dental implant surgery, but has not yet been made suitable for clinical use. A 2D ultrasound imaging system and a mechanical positioning system were used to scan dental implants embedded in a porcine jaw, covered by soft tissue, submerged in a water tank. Results indicated that ultrasound can be used to accurately detect, locate, and measure dental implant fixtures and measure the thickness of the overlying soft tissue in an ex vivo environment.

Fabrication of a thin-film capacitive force sensor array for tactile feedback in robotic surgery.

Although surgical robotic systems provide several advantages over conventional minimally invasive techniques, they are limited by a lack of tactile feedback. Recent research efforts have successfully integrated tactile feedback components onto surgical robotic systems, and have shown significant improvement to surgical control during in vitro experiments. The primary barrier to the adoption of tactile feedback in clinical use is the unavailability of suitable force sensing technologies. This paper describes the design and fabrication of a thin-film capacitive force sensor array that is intended for integration with tactile feedback systems. This capacitive force sensing technology could provide precise, high-sensitivity, real-time responses to both static and dynamic loads. Capacitive force sensors were designed to operate with optimal sensitivity and dynamic range in the range of forces typical in minimally invasive surgery (0-40 N). Initial results validate the fabrication of these capacitive force-sensing arrays. We report 16.3 pF and 146 pF for 1-mm(2) and 9-mm(2) capacitive areas, respectively, whose values are within 3% of theoretical predictions.

Terahertz sensing in corneal tissues.

This work introduces the potential application of terahertz (THz) sensing to the field of ophthalmology, where it is uniquely suited due to its nonionizing photon energy and high sensitivity to water content. Reflective THz imaging and spectrometry data are reported on ex-vivo porcine corneas prepared with uniform water concentrations using polyethylene glycol (PEG) solutions. At 79% water concentration by mass, the measured reflectivity of the cornea was 20.4%, 14.7%, 11.7%, 9.6%, and 7.4% at 0.2, 0.4, 0.6, 0.8, and 1 THz, respectively. Comparison of nine corneas hydrated from 79.1% to 91.5% concentration by mass demonstrated an approximately linear relationship between THz reflectivity and water concentration, with a monotonically decreasing slope as the frequency increases. The THz-corneal tissue interaction is simulated with a Bruggeman model with excellent agreement. THz applications to corneal dystrophy, graft rejection, and refractive surgery are examined from the context of these measurements.

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.

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.

THz Medical Imaging: in vivo Hydration Sensing.

The application of THz to medical imaging is experiencing a surge in both interest and federal funding. A brief overview of the field is provided along with promising and emerging applications and ongoing research. THz imaging phenomenology is discussed and tradeoffs are identified. A THz medical imaging system, operating at ~525 GHz center frequency with ~125 GHz of response normalized bandwidth is introduced and details regarding principles of operation are provided. Two promising medical applications of THz imaging are presented: skin burns and cornea. For burns, images of second degree, partial thickness burns were obtained in rat models in vivo over an 8 hour period. These images clearly show the formation and progression of edema in and around the burn wound area. For cornea, experimental data measuring the hydration of ex vivo porcine cornea under drying is presented demonstrating utility in ophthalmologic applications.

Remote tactile sensing glove-based system.

A complete glove-based master-slave tactile feedback system was developed to provide users with a remote sense of touch. The system features a force-sensing master glove with piezoresistive force sensors mounted at each finger tip, and a pressure-transmitting slave glove with silicone-based pneumatically controlled balloon actuators, mounted at each finger tip on another hand. A control system translates forces detected on the master glove, either worn by a user or mounted on a robotic hand, to discrete pressure levels at the fingers of another user. System tests demonstrated that users could accurately identify the correct finger and detect three simultaneous finger stimuli with 99.3% and 90.2% accuracy, respectively, when the subjects were located in separate rooms. The glove-based tactile feedback system may have application to virtual reality, rehabilitation, remote surgery, medical simulation, robotic assembly, and military robotics.

Terahertz sensing of corneal hydration.

An indicator of ocular health is the hydrodyanmics of the cornea. Many corneal disorders deteriorate sight as they upset the normal hydrodynamics of the cornea. The mechanisms include the loss of endothelial pump function of corneal dystophies, swelling and immune response of corneal graft rejection, and inflammation and edema, which accompany trauma, burn, and irritation events. Due to high sensitivity to changes of water content in materials, a reflective terahertz (300 GHz and 3 THz) imaging system could be an ideal tool to measure the hydration level of the cornea. This paper presents the application of THz technology to visualize the hydration content across ex vivo porcine corneas. The corneas, with a thickness variation from 470 - 940 µm, were successfully imaged using a reflective pulsed THz imaging system, with a maximum SNR of 50 dB. To our knowledge, no prior studies have reported on the use of THz in measuring hydration in corneal tissues or other ocular tissues. These preliminary findings indicate that THz can be used to accurately sense hydration levels in the cornea using a pulsed, reflective THz imaging system.

A review of tissue substitutes for ultrasound imaging.

The characterization and calibration of ultrasound imaging systems requires tissue-mimicking phantoms with known acoustic properties, dimensions and internal features. Tissue phantoms are available commercially for a range of medical applications. However, commercial phantoms may not be suitable in ultrasound system design or for evaluation of novel imaging techniques. It is often desirable to have the ability to tailor acoustic properties and phantom configurations for specific applications. A multitude of tissue-mimicking materials and phantoms are described in the literature that have been created using a variety of materials and preparation techniques and that have modeled a range of biological systems. This paper reviews ultrasound tissue-mimicking materials and phantom fabrication techniques that have been developed over the past four decades, and describes the benefits and disadvantages of the processes. Both soft tissue and hard tissue substitutes are explored.

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.