Porcine Subject Research Articles

Automated, Transferable, and Ethanol-Free Radiosynthesis of [11C]Butanol.

Cerebral blood flow and blood-brain barrier permeability assessment are crucial hemodynamic parameters to measure under neurological conditions. In conjunction with positron emission tomography (PET), oxygen-15-labeled water has emerged as a gold standard for measuring cerebral perfusion; however, at higher flow rates, [15O]water extraction becomes nonlinear. In such a scenario, freely diffusible [11C]butanol can provide a truer estimate. Radiosyntheses of [11C]butanol reported to date are protracted, are not automated, or require ethanol in the final formulation. By using a flow-based, captive solvent approach on a commercially available radiosynthesizer, we automated and reduced the synthesis time to 28 min. Forgoing cartridge-based purification for an aqueous high-performance liquid chromatography method, we obtained high purity [11C]butanol in ethanol-free phosphate buffered saline in sufficient yields for clinical PET studies. We here report our expedited, automated, and ethanol-free radiosynthesis of [11C]butanol along with preliminary imaging of a porcine subject.

Thermal Safety Boundaries for Laser Power and Irrigation Rate During Ureteroscopy: In Vivo Porcine Assessment With a Ho:YAG Laser

To map thermal safety boundaries during ureteroscopy (URS) with laser activation in two in vivo porcine subjects to better understand the interplay between laser power, irrigation rate, and fluid temperature in the collecting system. URS was performed in two in vivo porcine subjects with a prototype ureteroscope containing a thermocouple at its tip. Up to 6 trials of 60seconds laser activation were carried out at each selected power setting and irrigation rate. Thermal dose was calculated for each trial, and laser power-irrigation rate parameter pairs were categorized based on number of trials that exceeded a thermal dose of 120 equivalent minutes. The collecting fluid temperature was increased with greater laser power and slower irrigation rate. In the first porcine subject, 25W of laser power could safely be applied if irrigation was at least 15mL/min, and 48W with at least 30mL/min. Intermediate values followed a linear curve between these bounds. For the second subject, where the calyx appeared larger, 15W laser power required 9mL/min irrigation, 48W required 24mL/min, and intermediate points also followed a near-linear curve. This study validates previous bench research and provides a conceptual framework for selection of safe laser lithotripsy settings and irrigation rates during URS with laser lithotripsy. Additionally, it provides insight and guidance for future development of thermal mitigation strategies and devices.

Subject-specific modelling of pneumoperitoneum: model implementation, validation and human feasibility assessment

PurposeThe aim of this study is to propose a model that simulates patient-specific anatomical changes resulting from pneumoperitoneum, using preoperative data as input. The framework can assist the surgeon through a real-time visualisation and interaction with the model. Such could further facilitate surgical planning preoperatively, by defining a surgical strategy, and intraoperatively to estimate port positions.MethodsThe biomechanical model that simulates pneumoperitoneum was implemented within the GPU-accelerated NVIDIA FleX position-based dynamics framework. Datasets of multiple porcine subjects before and after abdominal insufflation were used to generate, calibrate and validate the model. The feasibility of modelling pneumoperitoneum in human subjects was assessed by comparing distances between specific landmarks from a patient abdominal wall, to the same landmark measurements on the simulated model.ResultsThe calibration of simulation parameters resulted in a successful estimation of an optimal set parameters. A correspondence between the simulation pressure parameter and the experimental insufflation pressure was determined. The simulation of pneumoperitoneum in a porcine subject resulted in a mean Hausdorff distance error of 5–6 mm. Feasibility of modelling pneumoperitoneum in humans was successfully demonstrated.ConclusionSimulation of pneumoperitoneum provides an accurate subject-specific 3D model of the inflated abdomen, which is a more realistic representation of the intraoperative scenario when compared to preoperative imaging alone. The simulation results in a stable and interactive framework that performs in real time, and supports patient-specific data, which can assist in surgical planning.

A pre-operative planning framework for global registration of laparoscopic ultrasound to CT images

PurposeLaparoscopic ultrasound (LUS) enhances the safety of laparoscopic liver resection by enabling real-time imaging of internal structures such as vessels. However, LUS probes can be difficult to use, and many tumours are iso-echoic and hence are not visible. Registration of LUS to a pre-operative CT or MR scan has been proposed as a method of image guidance. However, the field of view of the probe is very small compared to the whole liver, making the registration task challenging and dependent on a very accurate initialisation.MethodsWe propose the use of a subject-specific planning framework that provides information on which anatomical liver regions it is possible to acquire vascular data that is unique enough for a globally optimal initial registration. Vessel-based rigid registration on different areas of the pre-operative CT vascular tree is used in order to evaluate predicted accuracy and reliability.ResultsThe planning framework is tested on one porcine subject where we have taken 5 independent sweeps of LUS data from different sections of the liver. Target registration error of vessel branching points was used to measure accuracy. Global registration based on vessel centrelines is applied to the 5 datasets. In 3 out of 5 cases registration is successful and in agreement with the planning. Further tests with a CT scan under abdominal insufflation show that the framework can provide valuable information in all of the 5 cases.ConclusionsWe have introduced a planning framework that can guide the surgeon on how much LUS data to collect in order to provide a reliable globally unique registration without the need for an initial manual alignment. This could potentially improve the usability of these methods in clinic.

Performance Evaluation of an Ultra-Wideband Transmit Diversity in a Living Animal Experiment

To realize implant communications with a high data rate, ultra-wideband (UWB) transmission has gathered a lot of attention as a promising candidate. However, due to high operation frequency, the UWB communication link suffers from large attenuation. This represents the difficulty to achieve reliable communications. To mitigate such a problem, spatial diversity techniques have been proposed in the literature, where some of them work without any frequency extension. In contrast, the implant side diversity technique has been rarely discussed because of the difficulty in miniaturizing the size of the transmitter antenna. In this paper, we designed a UWB transmitter diversity antenna and evaluated its performance numerically and experimentally. First, we analyzed the antenna performance using a finite-difference time-domain simulation and physical experiment in a liquid phantom. Thereafter, we measured the path loss performance in an implant communication link using a liquid phantom and a living porcine subject. Finally, we evaluated the impact of the implant side polarization diversity system with the developed antenna on the communication performance. Based on the measured isolation between the polarization channels, our measurements show that a signal-to-noise power ratio improvement of 7 dB can be in principle achieved with a predicted outage rate of 0.01 and a range of 15 cm in typical body environments.

Circumferential Three-Dimensional–Printed Tracheal Grafts: Research Model Feasibility and Early Results

Methods for tracheal graft research have presented persistent challenges to investigators, and three-dimensional (3D)-printed biosynthetic grafts offer one potential development platform. We aimed to develop an efficient research platform for customizable circumferential 3D-printed tracheal grafts and evaluate feasibility and early structural integrity with a large-animal model. Virtual 3D models of porcine subject tracheas were generated using preoperative computed tomography scans. Two designs were used to test graft customizability and the limits of the construction process. Designs I and II used 270-degree and 360-degree external polycaprolactone scaffolds, respectively, both encompassing a circumferential extracellular matrix collagen layer. The polycaprolactone scaffolds were made in a fused-deposition modeling 3D printer and customized to the recipient's anatomy. Design I was implanted in 3 pigs and design II in 2 pigs, replacing 4-ring tracheal segments. Data collected included details of graft construction, clinical outcomes, bronchoscopy, and gross and histologic examination. The 3D-printed biosynthetic grafts were produced with high fidelity to the native organ. The fabrication process took 36 hours. Grafts were implanted without immediate complication. Bronchoscopy immediately postoperatively and at 1 week demonstrated patent grafts and appropriate healing. All animals lived beyond a predetermined 1-week survival period. Bronchoscopy at 2 weeks showed significant paraanastomotic granulation tissue, which, along with partial paraanastomotic epithelialization, was confirmed on pathology. Overall survival was 17 to 34 days. We propose a rapid, reproducible, resource efficient method to develop various anatomically precise grafts. Further graft refinement and strategies for granulation tissue management are needed to improve outcomes.

Frequency-Selective Computed Tomography: Applications During Periodic Thoracic Motion.

We seek to use computed tomography (CT) to characterize regional lung parenchymal deformation during high-frequency and multi-frequency oscillatory ventilation. Periodic motion of thoracic structures results in artifacts of CT images obtained by standard reconstruction algorithms, especially for frequencies exceeding that of the X-ray source rotation. In this paper, we propose an acquisition and reconstruction technique for high-resolution imaging of the thorax during periodic motion. Our technique relies on phase-binning projections according to the frequency of subject motion relative to the scanner rotation, prior to volumetric reconstruction. The mathematical theory and limitations of the proposed technique are presented, and then validated in a simulated phantom as well as a living porcine subject during oscillatory ventilation. The 4-D image sequences obtained using this frequency-selective reconstruction technique yielded high-spatio-temporal resolution of the thorax during periodic motion. We conclude that the frequency-based selection of CT projections is ideal for characterizing dynamic deformations of thoracic structures that are ordinarily obscured by motion artifact using conventional reconstruction techniques.

Evaluation of a Steerable Tube Thoracostomy System Compatible with a Flexible Bronchoscope

Tube thoracostomy is effective at draining the pleural space; however, when fluid or air is loculated, drainage may be compromised. For this reason, a steerable chest tube with a redirecting stylet was developed. This tube also allows use of a flexible bronchoscope in the pleural space without significant limitations in mobility as seen in prior studies.Methods:We tested the ability of a steerable tube thoracostomy system in a porcine subject to change position, drain fluid, and utilize a flexible bronchoscope in the pleural space. Fiducial markers were implanted into the parietal pleura to demonstrate maneuverability of the bronchoscope and the ability to take forceps biopsies.Results:Bronchoscope positions in the pleural space were confirmed fluoroscopically: apical, medial, lateral, anterior diaphragm, and posterior diaphragm. All fiducial markers and tissue along the parietal pleura were located and biopsied via flexible forceps with the bronchoscope. The tube was repositioned into all dependent areas where fluid collected.Conclusions:This steerable tube and a flexible bronchoscope can access and visualize the pleural space, locate and biopsy implanted markers on the parietal pleural surface, and drain fluid from the pleural space. Further studies will be needed to evaluate the usefulness of this procedure in the clinical setting.

Design of a Subtarsal Ultrasonic Transducer for Mild Hyperthermia Treatment of Dry Eye Disease

Dry eye disease is a disorder of the ocular surface that causes pain and low vision in a significant portion of the adult population. A common cause is obstructive Meibomian gland dysfunction, whereby the Meibomian glands secrete abnormal meibum with a melting point elevated by 3°C–4°C; hence, hyperthermia is the typical treatment. A design is proposed for an ultrasound hyperthermia device made of a transducer contained inside a contact lens with an internal air gap. The transducer heats the posterior of the tarsus, and the air gap provides an air backing to the transducer, preventing direct heating of the cornea. A prototype device was built, and hyperthermia experiments were performed on a porcine subject in vivo. A therapeutic temperature rise of 5°C–7°C was achievable in 10–15 min. The temperature of the cornea did not rise more than 2°C during any of the experiments.

Polarised stereo endoscope and narrowband detection for minimal access surgery.

Polarisation imaging has the potential to provide enhanced contrast based on variations in the optical properties, such as scattering or birefringence, of the tissue of interest. Examining the signal at different wavebands in the visible spectrum also allows interrogation of different depths and structures. A stereo endoscope has been adapted to allow snapshot acquisition of orthogonal linear polarisation images to generate difference of linear polarisation images. These images are acquired in three narrow bands using a triple-bandpass filter and pair of colour cameras. The first in vivo results, acquired during a surgical procedure on a porcine subject, are presented that show wavelength dependent variations in vessel visibility and an increase in contrast under polarised detection.

New bipolar tissue ligator combines constant tissue compression and temperature guidance: histologic study and implications for treatment of hemorrhoids

BackgroundSeveral minimally invasive technologies are available to treat common soft tissue lesions including symptomatic hemorrhoids. The use of energy to deliver heat and coagulate target lesions is commonly practiced. This study compares the histologic effects produced on intestinal tissues by two energy-based systems which employ different approaches of heat delivery.MethodsTwo heat delivery systems were evaluated in vivo in a single porcine subject: infrared coagulator and bipolar tissue ligator utilizing constant tissue compression and temperature guidance. Eighteen treatment sites divided into three groups of six were assessed. Treatment site temperature was measured and the effects of thermal treatment in the mucosa, submucosa, submucosal vessels, and muscularis layer were scored. Lateral thermal spread beyond the energy application site was also assessed.ResultsTreatment site temperatures were much lower in the bipolar ligator group than in the infrared coagulator group. The mucosal and submucosal tissue changes observed in tissues treated with infrared energy and bipolar energy at 55°C were similar. Both the mucosal and submucosal tissue changes with bipolar energy at 50°C were significantly less.ConclusionBoth devices achieved similar histologic results. However, the unique design of the bipolar ligator, which allows consistent capture, constant compression, and temperature monitoring of target tissue, accomplished the desired histologic changes with less muscular damage at much lower temperatures than the infrared coagulator. The use of bipolar ligation could offer clinical advantages such as reduced patient pain and a minimized chance of heat-related collateral tissue damage.

A NOVEL IN VITRO PLATFORM FOR THE SIMULATION OF SURGICAL PROCEDURES FOR HEART VALVE REPAIR IN PORCINE HEARTS

New surgical techniques for heart valve repair and new transcatheter valves can be effectively supported by in vitro tests [Jimenez, 2005]. Moreover, in order to maintain the structural continuity of the natural heart tissues and properly replicate the physiological and/or surgical scenarios, the integration of biological samples into in vitro mock loops is fundamental [Notzold, 2005]. A mock loop able to house an entire explanted porcine heart and subject it to pulsatile fluiddynamic conditions was developed. The system allows the performance of surgical procedures for heart valve repair, the implant of transcatheter heart valves and the acquisition of both echographic and endoscopic images of the cardiac structures.

MARVEL IN VIVO WIRELESS VIDEO SYSTEM

This article describes the design, optimization, and prototype testing of a Miniature Anchored Robotic Videoscope for networked Expedited Laparoscopy (MARVEL), which is a camera module (CM) that features wireless communications and control and is designed to decrease the surgical-tool bottleneck experienced by surgeons in state-of-the art Laparoscopic Endoscopic Single-Site (LESS) minimally invasive abdominal surgery. Software simulation is utilized to characterize the internal human body (in vivo) wireless channel to optimize the antenna, transceiver architecture, and communication protocols between multiple CMs. A CM research platform has been realized that includes: a near-zero latency video wireless communications link; a pan/tilt camera platform, actuated by two motors, which provides surgeons a full hemisphere field of view inside the abdominal cavity; a small wireless camera; an illumination control system; wireless controlled focus; digital zoom; and a wireless human– machine interface (HMI) to control the CM. An in vivo experiment on a porcine subject has been carried out to test the performance of the system and features, with the exception of recently added autofocus and digital zoom. MARVEL is a research platform for a broad range of experiments for faculty and students in the Colleges of Engineering and Medicine at USF and at Tampa General Hospital.

ORAL PRESENTATION

ORAL PRESENTATION

Evaluation of Cardiovascular Stents as Antennas for Implantable Wireless Applications

In this study, we explore the use of stents as radiating structures to support transcutaneous wireless telemetry for data transfer of internal measurements from within the circulatory system. The implant location is chosen for the specific application of heart failure detection by monitoring internal pressure measurements of the pulmonary artery. The radiative properties of the single stent are quantified in free space within an anechoic chamber and compared with measurements taken while implanted in a live porcine subject. The in vivo studies of our 2.4-GHz stent-based transmitter, implanted at a depth of 3.5 cm within the chest, showed a 32-35-dB power reduction at a receive distance of 10 cm for both co- and cross-polarizations. The approximate far-field H-plane antenna pattern is quantified at a distance of 50 cm both in free space within an anechoic chamber and while implanted within a porcine chest. These results are used to explore the accuracy of a high-fidelity simulation model developed using Ansoft's High Frequency Structural Simulator and components of their Human Body Model to provide a model that is validated with empirical data. This study provides insight into the effects of tissue on high-frequency electromagnetic transcutaneous transmission and develops a high-fidelity model that can be used for further design and optimization.

Surface Current Density Mapping for Identification of Gastric Slow Wave Propagation

The magnetogastrogram (MGG) records clinically relevant parameters of the electrical slow wave of the stomach noninvasively. Besides slow wave frequency, gastric slow wave propagation velocity is a potentially useful clinical indicator of the state of health of gastric tissue, but it is a difficult parameter to determine from noninvasive bioelectric or biomagnetic measurements. We present a method for computing the surface current density from multichannel MGG recordings that allows computation of the propagation velocity of the gastric slow wave. A moving dipole source model with hypothetical as well as realistic biomagnetometer parameters demonstrates that while a relatively sparse array of magnetometer sensors is sufficient to compute a single average propagation velocity, more detailed information about spatial variations in propagation velocity requires higher density magnetometer arrays. Finally, the method is validated with simultaneous MGG and serosal electromyography measurements in a porcine subject.

Comparison of wound-healing and tissue effects using the Gyrus PlasmaKnife with monopolar, Coblation, and Harmonic Scalpel methodologies

The aim of this study was to assess the histological and thermal effects of different dissection technologies on tissue around incision and to consider their comparative wound healing profiles. The technologies used were Gyrus PlasmaKnife, monopolar electrode, Coblation wand, and Harmonic Scalpel. Single incisions were made using each device on the internal peritoneal surface at four test sites per porcine subject. The incision sites were assessed to determine the extent of tissue and thermal damage around the incision site in the first animal and the formation of wound cover and degree of inflammation 14 days post-procedure in the second. The PlasmaKnife was easier to handle and more controllable than the other devices and resulted in a precise incision with only localised thermal damage. The other technologies produced either deep lesions extending into the muscle and/or considerable lateral damage across the mesothelial surface. Of all the devices only the PlasmaKnife resulted in compact well-organised wound cover showing vascularisation and neo-collagenesis. The notably better wound healing profile and reduced inflammatory response seen suggest that use of the PlasmaKnife in the clinical setting may lead to reductions in both wound healing times and post-operative pain.

Evaluation of cross-sectional geometry and mass density distributions of humans and laboratory animals using computerized tomography

The purpose of this study was to determine the cross-sectional geometry and mass density distribution of a young porcine subject using the X-ray computerized tomographic (CT) method and to perform a comparative study of anatomical features of this subject and a 3 yr old female child specimen. The cross-sectional CT scans of the porcine subject were obtained at 1 cm intervals. The outlines of each cross section and of selected anatomical components within each section were obtained by standard picture processing techniques. The mass and inertia tensor for each cross section and for each anatomical structure in a section were computed based on the CT numbers. The porcine subject was then sacrificed, frozen, sectioned and photographed. These sectional photographs were then compared with those obtained from the CT method. Tabulated cross-sectional mass and inertia tensor obtained from CT scans of the porcine subject were also used to compare with similar results derived from previously completed CT scans of the 3 yr old female child specimen. In particular, the comparisons were made on the location of the center of gravity and the inertia tensor in the head, neck, head and neck and cervical spine regions. Some immediate applications of this data are inputs to finite element models, lumped parameter biodynamic models, computer simulation of vehicle crash victims, and dummy design.