Electrosurgical vessel sealing

Electrosurgical vessel sealing devices have been demonstrated to reduce patient blood loss and operative time during surgery. Whilst the benefits of such devices are widely reported there is still a large variation in the quality of the seal produced, with factors such as vessel size known to effect seal quality. The study aimed to investigate parameters affecting device performance and improve the seal quality. The burst pressure test was used to assess the seal quality and tissue adhesion was measured using a peel test. Additionally histology techniques were used to quantify vessel morphology and found that with an increase in elastin content there was a reduction in seal quality. A number of device modifications were made, testing a selection of non-stick coatings and surface features of the shims. No coating reduced the level of tissue adhesion to the device, but results found that with a greater level of adhesion there was a reduction in seal quality. Considering the different surface features one design, a combination of longitudinal and transverse grooves, resulted in a seal failure rate of 0.0%, a significant improvement in device performance. Two FEM’s were produced to further investigate the device modifications; one in FEBio investigating the mechanical aspects of vessel sealing and the second a multiphysics model to investigate the thermal aspects of vessel sealing. Results from both FEM’s showed a difference in shim performance, with the addition of surface features effecting the stress distribution within the vessel wall and the heat distribution. Additionally DIC was used to capture the vessel sealing process, with results showing each seal was produced in a different way with different levels of tissue contraction. Research conducted demonstrated a number of significant relationships between seal quality and vessel properties, but did not find an explanation for all variation occurring

Laser-induced forward transfer (LIFT) of water soluble polyvinyl alcohol (PVA) polymers for use as support material for 3D-printed structures

The additive microfabrication method of laser-induced forward transfer (LIFT) permits the creation of functional microstructures with feature sizes down to below a micrometre [1]. Compared to other additive manufacturing techniques, LIFT can be used to deposit a broad range of materials in a contactless fashion. LIFT features the possibility of building out of plane features, but is currently limited to 2D or 2½D structures [2–4]. That is because printing of 3D structures requires sophisticated printing strategies, such as mechanical support structures and post-processing, as the material to be printed is in the liquid phase. Therefore, we propose the use of water-soluble materials as a support (and sacrificial) material, which can be easily removed after printing, by submerging the printed structure in water, without exposing the sample to more aggressive solvents or sintering treatments. Here, we present studies on LIFT printing of polyvinyl alcohol (PVA) polymer thin films via a picosecond pulsed laser source. Glass carriers are coated with a solution of PVA (donor) and brought into proximity to a receiver substrate (glass, silicon) once dried. Focussing of a laser pulse with a beam radius of 2 µm at the interface of carrier and donor leads to the ejection of a small volume of PVA that is being deposited on a receiver substrate. The effect of laser pulse fluence , donor film thickness and receiver material on the morphology (shape and size) of the deposits are studied. Adhesion of the deposits on the receiver is verified via deposition on various receiver materials and via a tape test. The solubility of PVA after laser irradiation is confirmed via dissolution in de-ionised water. In our study, the feasibility of the concept of printing PVA with the help of LIFT is demonstrated. The transfer process maintains the ability of water solubility of the deposits allowing the use as support material in LIFT printing of complex 3D structures. Future studies will investigate the compatibility (i.e. adhesion) of PVA with relevant donor materials, such as metals and functional polymers. References: [1] A. Piqué and P. Serra (2018) Laser Printing of Functional Materials. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA. [2] R. C. Y. Auyeung, H. Kim, A. J. Birnbaum, M. Zalalutdinov, S. A. Mathews, and A. Piqué (2009) Laser decal transfer of freestanding microcantilevers and microbridges, Appl. Phys. A, vol. 97, no. 3, pp. 513–519. [3] C. W. Visser, R. Pohl, C. Sun, G.-W. Römer, B. Huis in ‘t Veld, and D. Lohse (2015) Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer, Adv. Mater., vol. 27, no. 27, pp. 4087–4092. [4] J. Luo et al. (2017) Printing Functional 3D Microdevices by Laser-Induced Forward Transfer, Small, vol. 13, no. 9, p. 1602553

Design and Development of Non-Equilibrium Plasmas for the Medical Field

There is great interest in the plasma research community on the potential medical applications of non-equilibrium plasmas, called cold atmospheric plasma (CAP), yet currently no such plasma device is approved by the US Food and Drug Administration (FDA). This dissertation seeks to take a holistic look at five novel plasma systems with potential use in the medical field. These systems are all analyzed from an engineering point of view to characterize the plasma and basic biocompatibility from an electrical and thermal approach. The overall design life-cycle for these devices is also examined, with an emphasis on deciding an approval pathway through the Food and Drug Administration, where the intended use of the device is the driving factor. The first device considered is a nanosecond puling circuit devised for skin electroporation. An electrode is developed to help maximize the electric field applied to a substrate and ensure user safety. Voltage and current traces and optical emission spectroscopy are used to characterize the plasma generated for various substrates, showing the non-equilibrium behavior of the plasma for a wide operating range. The second device considered is an existing FDA-cleared electrosurgical device power supply and hand piece, which has been modified for use as a CAP source. By varying the tube length the plasma can be operated in a non-equilibrium state. The third device is a direct write system for depositing thin films in a controlled pattern. This system consists of a dielectric barrier discharge jet attached to a three-dimensional printer head for spatially controlling the plasma location. Various methods of depositing material are used, including directly onto biological substrates. The final two devices are for improving the strength of additively manufactured parts intended for use in custom printed prosthetics. The first is a nanosecond pulsed discharge onto a printed part, which shows 100% strength improvement from the plasma treatment. The second is a planar dielectric barrier discharge mounted onto the head of a three-dimensional printer, which is able to print parts with the same strength as injection molded parts

Thermal Fusion for Sutureless Closure: Devices, Composition, Methods

As minimally invasive surgical techniques progress, the demand for reliable ligation is pronounced. The surgical advantages of energy-based vessel sealing exceed those of traditional, compression-based ligatures in procedures sensitive to duration, foreign bodies, and recovery time alike. While the use of energy-based devices to seal or transect vasculature and connective tissue bundles is widespread, the breadth of heating strategies and energy dosimetry used between devices underscores an uncertainty as to the molecular nature of the sealing mechanism and induced tissue bond. Further, energy-based techniques (e.g., tissue “fusion” or tissue “welding”) exhibit promise for the closure, repair and functional recovery of soft and connective tissues in the orthopaedic, colorectal and dermal domains. To optimize and progress the use of energy-based tissue fusion, a constitutive theory of molecular bonding forces that arise in response to supraphysiological temperatures is required. While rapid tissue bonding may arise from dehydration and water transport, dipole interactions, covalent crosslinks or the coagulation of cellular proteins, long-term tissue repair requires that the reaction to thermal damage be tailored to accelerate and mimic the onset of biological healing and remodeling. The aim of this work is to supplement the findings of published thermal fusion research by exploring the contributions of primary and secondary tissue constituents to the formation of energy-based fusion bonds. Results of this work and their associated implications to the theory of energy-based surgical adhesion will encourage a molecular approach to characterization of the prevalent and promising energy-based tissue bond

Smart knives: controlled cutting schemes to enable advanced endoscopic surgery

With the backdrop of the rapidly developing research in Natural Orifice Transluminal Endoscopic Surgery (NOTES), analysis of the literature supported the view that inventing new, controlled tissue dissection methods for flexible endoscopic surgery may be necessary. The literature also confirmed that white space exists for research into and the development of new cutting tools. The strategy of “deconstructing dissection” proposed in this thesis may provide dissection control benefits, which may help address the unique manoeuvring challenges for tissue dissection at flexible endoscopy. This assertion was supported by investigating six embodiments of the strategy which provided varying degrees of enhanced tissue dissection control. Seven additional concepts employing the strategy which were not prototyped also were offered as potential solutions that eventually might contribute evidence in defence of the strategy. One concept for selective ablation — dye-mediated laser ablation — was explored in-depth by theoretical analysis, experimentation and computation. The ablation process was found to behave relatively similar to unmediated laser ablation, but also to depend on cyclic carbonisation for sustained ablation once the dye had disappeared. An Arrhenius model of carbonisation based on the pyrolysis and combustion of wood cellulose was used in a tissue ablation model, which produced reasonable results. Qualitative results from four methods for dye application and speculation on three methods for dye removal complete the framework by which dye-mediated laser ablation might deliver on the promise offered by “deconstructing dissection”. Overall, this work provided the “deconstructing dissection” strategic framework for controlled cutting schemes and offered plausible evidence that the strategy could work by investigating embodiments of the scheme. In particular, dye-mediated laser ablation can provide selective ablation of tissue, and a theoretical model for the method of operation was offered. However, some practical hurdles need to be overcome before it can be useful in a clinical setting

Inflammation and Corrosion in Total Hip Prostheses: The Generation and Interaction of Reactive Oxygen Species with CoCrMo Metallic Biomaterial Surfaces

There are many molecules, species and mechanisms that contribute to the overall wear and degradation of biometallic alloys like cobalt-chromium-molybdenum (CoCrMo). Following implantation, orthopaedic alloys are subject to an encompassing inflammatory response that will either lead to foreign body giant cell formation and attachment to the surface or the fibrous tissue encapsulation, forming an inflamed periprosthetic joint. In addition to the inflammatory response, tribocorrosion-based processes of alloy-on-alloy or alloy-on-polymer couples release polymeric wear debris, oxides, hydroxides, and metal ions in response to excessive wear, loading and corrosion. It is hypothesized that these processes, biological and triboelectrochemical, are linked together in a feedback-loop, and there is reason to believe that there exists a common catalyst, reactive oxygen species (ROS), that accelerates the cycle. This dissertation explains how ROS are generated in physiological conditions and how they affect electrochemical properties, under what circumstances ROS are consumed intracellularly, how different cell types respond to ROS-rich conditions, and how ROS interact with solution components native to synovial fluid, with a decisive effort and focus on defining their presence and role in the inflamed joint space. By fluorescently labeling individual ROS like hydroxyl radicals (OH·) and hydrogen peroxide (H2O2), we were able to correlate ROS concentrations against time of applied voltage (-1V vs. Ref) as well as against applied voltage for 2 hours. It was found that there exist thresholds for both the production and consumption of ROS, and there is a voltage range for which ROS are produced in measurable quantities. Under similar electrochemical conditions, different cell types (pre-osteoblast-like MC3T3-E1, monocyte macrophage-like U937) were cultured and exposed to an influx of ROS through cathodic excursions. It was found that cells possess a unique ‘electrochemical zone of viability’ per phenotype with reduced glutathione (GSH) activity, a ROS scavenger molecule produced within inflammatory cells, hypothesized to be the oxidative stress suppressor in the U937 cells. This hypothesis was later confirmed when exposing macrophages (RAW 264.7) to simulated synovial fluid, where it was found that ROS (H2O2) had a significant (p \u3c 0.05) effect on intracellular GSH activity (fluorescent intensity). In addition to influencing cell behavior and response, ROS production and exposure was found to alter electrochemical properties of CoCrMo surfaces. Using nearfield electrochemical impedance spectroscopy (NEIS), CoCrMo retrievals and CoCrMo surfaces damaged by electrocautery and ROS-rich solutions were shown to have significantly (p \u3c 0.05) decreased corrosion resistance (RP) with increased constant phase element capacitance (CPE Q) and open circuit potentials (OCPs), indicating that ROS are major contributors in corrosion susceptibility. By interpreting these observations and results, we were able to demonstrate that ROS are influential in several aspects of the inflammatory reaction to metallic biomaterials. The development of new diagnostics and predictive models centered around ROS can lead to safer practices involving orthopaedic alloys and further support our understanding of an inflamed joint space

Elektromagnetische velden in arbeidssituaties

NB Nederlandstalige versie verschenen onder nummer 610015001N De EU heeft richtlijn 2004/40/EG uitgevaardigd om de werknemer te beschermen tegen gezondheidsrisico's door blootstelling aan elektromagnetische velden op het werk. Deze richtlijn moet uiterlijk 30 april 2008 zijn omgezet in nationale wetgeving. Ter voorbereiding hiervan heeft het RIVM in opdracht van het Ministerie van SZW de blootstelling in Nederlandse arbeidssituaties geinventariseerd en geanalyseerd. Het doel van dit rapport is de werkgevers een handreiking te geven om vast te stellen of aan de eisen uit de richtlijn wordt voldaan en om de risico-inventarisatie en -evaluatie (RI&E) voor elektromagnetische velden op te stellen. Totdat er geharmoniseerde Europese normen van het Europees Comiti voor elektrotechnische normalisatie (CENELEC) beschikbaar zijn voor alle situaties die moeten worden beoordeeld, gemeten en berekend, mag dit rapport als richtsnoer gebruikt worden. Gebruik van dit rapport is dus geen verplichting. Voor de meeste werkgevers is het voldoende om de eerste twee hoofdstukken door te nemen. De volgende drie hoofdstukken bevatten voor een aantal arbeidssituaties informatie over de blootstelling, de rekenregels waarmee de situatie kan worden ingeschat en de mogelijke beheersmaatregelen. Het laatste hoofdstuk geeft een overzicht van de kosten die met invoering van de richtlijn samenhangen. Om te kunnen toetsen of de blootstelling onder de limieten van de richtlijn blijft, moeten CENELEC-normen worden gebruikt, voor zover ze bestaan. Deze normen zijn zonder specialistische kennis niet eenvoudig toe te passen. Ook hoeft niet alle apparatuur even uitgebreid beoordeeld te worden of zijn even zware maatregelen nodig. Om de beoordeling te vergemakkelijken geeft dit rapport een beoordelingsschema en tabellen met een indeling van alle relevante werkomgevingen in drie categorieen. Voor iedere categorie geldt een ander beoordelingstraject.The EU has issued Directive 2004/40/EC on the protection of workers from health and safety risks arising from exposure to electromagnetic fields in the workplace. This directive must be implemented in national legislation no later than 30 April 2008. To prepare for implementation, RIVM has, on commission of the Ministry of Social Affairs and Employment, investigated and analysed the exposure in Dutch working environments. The purpose of this report is to provide assistance to employers to assess whether compliance is met and to carry out the inventory and evaluation of risks (RI&E) due to electromagnetic fields. Until harmonised European standards from CENELEC cover all relevant assessment, measurement and calculation situations, this report may serve as a guide. It is not mandatory to use this report. It will be sufficient for most of the employers to confine themselves to the first two chapters. Subsequent chapters deal with the exposure found in several working environments and provide guidelines for assessing risks and possible measures in these working environments. Costs for implementing the directive are discussed in the last chapter. CENELEC standards, if available, are mandatory for assessing whether exposure occurs below the limits in the directive. However, these standards are not easy to use without specialist knowledge. Furthermore, not all equipment needs to be assessed to the same extent nor are the same measures needed. A flow chart and tables of relevant working environments, classified into three categories, are provided to facilitate the assessment. Each category has its own assessment path.SZ

NASA Tech Briefs, March 2002

Topics include: a special section on data acquisition, software, electronic components and systems, materials, computer programs, mechanics, machinery/automation, manufacturing, biomedical, physical sciences, book and reports, and a special section of Photonics Tech Briefs

Aptameric Formulation for Enhanced Biopharmaceutical Delivery

This research work developed a novel polymeric carrier system for targeted drug delivery to specific body sites. It utilized unique molecular probes called aptamers that navigate the complexity of mammalian cell systems and present drug molecules to desired locations. The aptamer molecules were tagged onto polymer drug carriers as binding ligands to direct an efficient path towards targeted delivery, avoiding unwanted effects on nontargeted cells and potentially addressing side effects of chemotherapy