Helical Needle Suture Inserter Provides Increased Suture Retention Force Compared to a Straight Needle

This paper presents an evaluation of the effect of needle geometry on the strength of a tether made using a barbed suture inserted into phantom tissue using a unique device. This tether is designed to secure an intrauterine device (IUD) to uterine fundus, with the aim of improving retention of IUDs inserted in the immediate postpartum period. A factorial experiment was designed to evaluate the effect of needle geometry on tether strength. Tether strength was characterized by the peak retention force of a suture subjected to a uniaxial tensile load. Experiments were performed using phantom tissue. Two needle geometries and three suture sizes were evaluated. Sutures deposited in phantom tissue with the helical needle had up to 132% increase in retention forces compared to sutures inserted with a straight needle, with more advantage at greater active length. The helical needle provides increased suture retention force and is a suitable tether delivery mechanism for this application.

Towards a Miniaturized 3D Receiver WPT System for Capsule Endoscopy

The optimization, manufacturing, and performance characterization of a miniaturized 3D receiver (RX)-based wireless power transfer (WPT) system fed by a multi-transmitter (multi-TX) array is presented in this study for applications in capsule endoscopy (CE). The 200 mm outer diameter, 35 μm thick printed spiral TX coils of 2.8 g weight, is manufactured on a flexible substrate to enable bendability and portability of the transmitters by the patients. The 8.9 mm diameter—4.8 mm long, miniaturized 3D RX—includes a 4 mm diameter ferrite road to increase power transfer efficiency (PTE) and is dimensionally compatible for insertion into current endoscopic capsules. The multi-TX is activated using a custom-made high-efficiency dual class-E power amplifier operated in subnominal condition. A resulting link and system PTE of 1% and 0.7%, respectively, inside a phantom tissue is demonstrated for the proposed 3D WPT system. The specific absorption rate (SAR) is simulated using the HFSSTM software (15.0) at 0.66 W/kg at 1 MHz operation frequency, which is below the IEEE guidelines for tissue safety. The maximum variation in temperature was also measured as 1.9 °C for the typical duration of the capsule’s travel in the gastrointestinal tract to demonstrate the patients’ tissues safety.

The feasibility of using compression bioimpedance measurements to quantify peripheral edema

The accurate assessment of body fluid volume is important in many clinical situations, especially in the determination of “dry weight” in a dialysis setting. Currently, no clinically applicable diagnostic system exists to determine the mechanical properties that accurately characterize peripheral edema in an objective and quantitative manner. We have developed a method for quantifying the impact of compression on the electrical properties of tissue by measuring stress-induced changes in bioimpedance (BIS). Using this method, we simultaneously measured the impedance and mechanical response of a tissue mimicking material (tofu) under both quasi-static and dynamic loading conditions. Our results demonstrate a temporal quantification of viscoelastic properties using a viscoelastic phantom tissue model.

Analysis of Tissue Phantom Ratio of the Megavoltage Photon Beams

Iso-centric beam data, phantom tissue ratios (TPR) are a dosimetric quantity commonly used to describe the change in dose with depth in tissue. Measurement of this is time-consuming and has the possibility of lose the consistency. The value of this quantity of any filed size in any depth is possible to calculate conveniently by the newly developed formula using only percentage depth dose (PDD) data of two fields. PDD for square fields ranging from 2 to 30 cm and various depths in increment of 0.4 cm up to maximum 30 cm have been measured in water at a fixed source surface distance (SSD) of 90 cm for 4, 6 and 15 MV photon beams in Ahsania Mission Cancer & General Hospital (AMCGH), Dhaka, Bangladesh. TPR values calculating for these energies of the same field sizes, depths and SSD by using the developed formula compared with those determined from the measured PDD data using a standard formula and had the good agreement. Mean error less than 1% observed between these TPR values.

Adaptive Control of a Robot-Assisted Tele-Surgery in Interaction With Hybrid Tissues

In a haptic teleoperation system, which interacts with unknown and hybrid environments, it is important to achieve stability and transparency. In medical usages, the utilization of knowledge on the tissues behavior in a controller design can improve the performance of the surgery in a robot-assisted telesurgery. Simultaneous interaction with hard and soft tissues makes it difficult to achieve stability and transparency. To deal with this difficulty, two controller schemes are designed. At first, a nonlinear mathematical model (inspired by the Hunt-Crossley (HC) model), which has the properties of soft and hard tissues, is combined with the slave side dynamic. In the second approach, the reaction force applied by hybrid tissues during the transition between tissues of different properties is modeled as an unknown force acting on the slave side. In a four-channel (4-CH) architecture, nonlinear adaptive controllers are designed without any knowledge about the parameters of the master, the slave robot, and the environment. For both control schemes, Lyapunov candidate functions provide a way to ensure the stability and transparency in the presence of uncertainties. The testbed comprises two Novint Falcon robots functioning as master and slave robots. Moreover, the experiments are performed on various objects, including a soft cube, a hard cube, and a phantom tissue. This paper rigorously evaluates the performances of the proposed methods, comparing them with each other and other previous schemes. Experimental and numerical results demonstrate the effectiveness of the proposed control schemes.

Vibration-Assisted Slicing of Soft Tissue for Biopsy Procedures

Skin cancer represents one of the most common forms of cancer in the U.S. This and other skin disorders can be effectively diagnosed by performing a punch biopsy to obtain full-thickness skin specimens. Their quality depends on the forces exerted by the punch cannula during the cutting process. The reduction of these forces is critical in the extraction of high quality tissue samples from the patient. During skin biopsy, the biopsy punch (BP) is advanced into the lesion while it is rotated alternately clockwise and counterclockwise generating, therefore, a rotary vibrational motion. No previous studies analyzed whether this motion is effective in soft tissue cutting and if it could be improved. In this study, the BP procedure is investigated in detail. First, the steady cutting motion of the BP is analyzed. Then, the superimposition of several vibrational motions onto the rotary motion of the BP is investigated. Analytical models, based on a fracture mechanics approach, are adopted to predict the cutting forces. Experimental studies are performed on phantom tissue, usually adopted in medical investigations. The results demonstrate that the application of rotary vibrational motions determines the increase of the force and penetration depth necessary to fracture soft tissue, while the implementation of axial vibrations can lead to 30% decrease of the axial force. The outcome of this study can benefit several clinical procedures in which a cannula device is used to cut and collect soft tissue samples.

Surgical Robot With Variable Remote Center of Motion Mechanism Using Flexible Structure

Remote center of motion (RCM) mechanisms are often used in surgical robots for laparoscopic surgery. In this paper, a RCM mechanism for holding a robotic forceps that facilitates adjustment using a flexible structure is proposed. The flexible structure is designed and manufactured with polypropylene-like resin material using a three-dimensional (3D) printer. Super elastic NI-Ti rods are inserted in the structure to have elasticity for bending and have rigidity for twisting. The structure achieves pitch motion around the remote center with two pneumatic cylinders. One cylinder drives the position and the other cylinder controls the bending radius of the structure. Therefore, the location of the remote center can be variable. This allows easier adjustment of the remote center before or during operation. The holder robot including the mechanism has four degrees-of-freedom (DOFs) in total, consisting of the pitch, a rotation around yaw axis, a translation in the direction of forceps insertion and a rotation of the forceps. Pneumatic rotary actuators are used for rotations and a cylinder is used for the translational motion. The model of the flexible structure is derived experimentally to design a controller for the pitch motion. A pneumatically driven robotic forceps is mounted on the holder to construct a master–slave control system. Experimental results show that the proposed control law achieves the desired rotational pitch motion. We compare the holder with a rigid link RCM holder and confirm the robustness of the proposed holder for variable remote center. Finally, the effectiveness of the system is confirmed with suturing tasks using a phantom tissue.

LesionAir: An Automated, Low-Cost Vision-Based Skin Cancer Diagnostic Tool

Current techniques for diagnosing skin cancer lack specificity and sensitivity, resulting in unnecessary biopsies and missed diagnoses. Automating tissue palpation and morphology quantification will result in a repeatable, objective process. LesionAir is a low-cost skin cancer diagnostic tool that measures the full-field compliance of tissue by applying a vacuum force and measuring the precise deflection using structured light three-dimensional (3D) reconstruction. The technology was tested in a benchtop setting on phantom skin and in a small clinical study. LesionAir has been shown to measure deflection with a 0.085 mm root-mean-square (RMS) error and measured the stiffness of phantom tissue to within 20% of finite element analysis (FEA) predictions. After biopsy and analysis, a dermatopathologist confirmed the diagnosis of skin cancer in tissue that LesionAir identified as noticeably stiffer and the regions of this stiffer tissue aligned with the bounds of the lesion. A longitudinal, full-scale study is required to determine the clinical efficacy of the device. This technology shows initial promise as a low-cost tool that could rapidly identify and diagnose skin cancer.