Jaime C. Fonseca

Nanostructured hollow tubes based on chitosan and alginate multilayers

The design and production of structures with nanometer-sized polymer films based on layer-by-layer (LbL) are of particular interest for tissue engineering since they allow the precise control of physical and biochemical cues of implantable devices. In this work, a method is developed for the preparation of nanostructured hollow multilayers tubes combining LbL and template leaching. The aim is to produce hollow tubes based on polyelectrolyte multilayer films with tuned physical-chemical properties and study their effects on cell behavior. The final tubular structures are characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), microscopy, swelling, and mechanical tests, including dynamic mechanical analysis (DMA) in physiological simulated conditions. It is found that more robust films could be produced upon chemical cross-linking with genipin. In particular, the mechanical properties confirms the viscoelastic properties and a storage and young modulus about two times higher. The water uptake decreases from about 390% to 110% after the cross-linking. The biological performance is assessed in terms of cell adhesion, viability, and proliferation. The results obtained with the cross-linked tubes demonstrate that these are more suitable structures for cell adhesion and spreading. The results suggest the potential of these structures to boost the development of innovative tubular structures for tissue engineering approaches.

Adhesive nanostructured multilayer films using a bacterial exopolysaccharide for biomedical applications

Medical adhesives and sealants often require that long-term adhesiveness is achieved. In this work, nanostructured coatings consisting of chitosan and the adhesive bacterial exopolysaccharide levan are fabricated using layer-by-layer (LbL) assembly. Taking advantage of the electrostatic self-assembly mechanism of LbL, the charges of both chitosan and a phosphonate-derivatized levan (Ph-levan) are measured and the feasibility of constructing hybrid films is monitored and confirmed using a quartz crystal microbalance with dissipation monitoring (QCM-D). The adhesive properties between two identical bonded films with a total of 100 layers are compared to control films in which Ph-levan is replaced by alginate, revealing that the detachment force of the former is about 3 times higher than the control. Scanning electron microscopy of the films surface shows that the surface of Ph-levan films is smooth and homogeneous. Cell adhesion tests were conducted using a L929 cell line. Early cell adhesion is significantly higher in chitosan/Ph-levan films when compared to chitosan/alginate controls. These findings establish levan derivatives as bioinspired ingredients for conceiving medical adhesive devices that allow achieving enhanced mechanical and biological performance.

Collecting System Percutaneous Access Using Real-Time Tracking Sensors: First Pig Model In Vivo Experience

PURPOSE Precise needle puncture of the renal collecting system is an essential but challenging step for successful percutaneous nephrolithotomy. We evaluated the efficiency of a new real-time electromagnetic tracking system for in vivo kidney puncture. MATERIALS AND METHODS Six anesthetized female pigs underwent ureterorenoscopy to place a catheter with an electromagnetic tracking sensor into the desired puncture site and ascertain puncture success. A tracked needle with a similar electromagnetic tracking sensor was subsequently navigated into the sensor in the catheter. Four punctures were performed by each of 2 surgeons in each pig, including 1 each in the kidney, middle ureter, and right and left sides. Outcome measurements were the number of attempts and the time needed to evaluate the virtual trajectory and perform percutaneous puncture. RESULTS A total of 24 punctures were easily performed without complication. Surgeons required more time to evaluate the trajectory during ureteral than kidney puncture (median 15 seconds, range 14 to 18 vs 13, range 11 to 16, p=0.1). Median renal and ureteral puncture time was 19 (range 14 to 45) and 51 seconds (range 45 to 67), respectively (p=0.003). Two attempts were needed to achieve a successful ureteral puncture. The technique requires the presence of a renal stone for testing. CONCLUSIONS The proposed electromagnetic tracking solution for renal collecting system puncture proved to be highly accurate, simple and quick. This method might represent a paradigm shift in percutaneous kidney access techniques.

Fuzzy logic speed control of an induction motor

Abstract This paper describes the use of fuzzy logic techniques to control the speed of a three-phase induction motor. The use of Matlab/Simulink and fuzzyTECH MCU96 as software development tools for system design is emphasised. Hardware implementation is based on a standard 16/32-bit microcontroller, without the need of any additional components for the fuzzy logic controller. The system performance is evaluated in comparison with a traditional PI control scheme. Both simulation and experimental results are presented.

Kidney Targeting and Puncturing During Percutaneous Nephrolithotomy: Recent Advances and Future Perspectives

BACKGROUND AND PURPOSE Precise needle puncture of the kidney is a challenging and essential step for successful percutaneous nephrolithotomy (PCNL). Many devices and surgical techniques have been developed to easily achieve suitable renal access. This article presents a critical review to address the methodologies and techniques for conducting kidney targeting and the puncture step during PCNL. Based on this study, research paths are also provided for PCNL procedure improvement. METHODS Most relevant works concerning PCNL puncture were identified by a search of Medline/PubMed, ISI Web of Science, and Scopus databases from 2007 to December 2012. Two authors independently reviewed the studies. RESULTS A total of 911 abstracts and 346 full-text articles were assessed and discussed; 52 were included in this review as a summary of the main contributions to kidney targeting and puncturing. CONCLUSIONS Multiple paths and technologic advances have been proposed in the field of urology and minimally invasive surgery to improve PCNL puncture. The most relevant contributions, however, have been provided by the application of medical imaging guidance, new surgical tools, motion tracking systems, robotics, and image processing and computer graphics. Despite the multiple research paths for PCNL puncture guidance, no widely acceptable solution has yet been reached, and it remains an active and challenging research field. Future developments should focus on real-time methods, robust and accurate algorithms, and radiation free imaging techniques.

Non-contact 3D acquisition system based on stereo vision and laser triangulation

This paper proposes a novel contact 3D acquisition system based on stereo vision and laser triangulation. The system is composed by several software modules for data acquisition purposes, data calibration, data processing and data reconstruction of 3D scenes. Different 3D image techniques, such as, polynomial determination, cubic spline interpolation and hierarchical space decomposition were used. To validate this method, a simple laboratory prototype machine was built for the purpose of road profile acquisition, road macro and mega texture characterization. In this paper, only the results and discussion of road profile acquisition are presented.

Off-Line Robot Programming Framework

The industrial robot programming is a work for specialist in robotics. Today, this work is very hard because there are many robot manufacturers with different languages and different programming environments. Although, off-line programming is an way that can reduce drastically the machines stop time to maintenance. With the use of object oriented design patterns, it is possible minimize the time spent in robot programming. In this work is proposed a off-line programming environment. This tool is based in one abstract model to program robots, encapsulate in Java classes. This way has the main advantage of best source code utilization. Grouping the business classes in modules by functionalities, we can reduce complexity between low matching. Recognized patterns like facade and template method will construct the base to develop this programming framework. The programming robot languages tested in this work was Rapid, Karel and Melfa Basic IV, respectively languages used by ABB, Fanuc and Mitsubishi constructors

Accuracy Comparison of Implant Impression Techniques: A Systematic Review

BACKGROUND Several studies link the seamless fit of implant-supported prosthesis with the accuracy of the dental impression technique obtained during acquisition. In addition, factors such as implant angulation and coping shape contribute to implant misfit. PURPOSE The aim of this study was to identify the most accurate impression technique and factors affecting the impression accuracy. MATERIAL AND METHODS A systematic review of peer-reviewed literature was conducted analyzing articles published between 2009 and 2013. The following search terms were used: implant impression, impression accuracy, and implant misfit. A total of 417 articles were identified; 32 were selected for review. RESULTS All 32 selected studies refer to in vitro studies. Fourteen articles compare open and closed impression technique, 8 advocate the open technique, and 6 report similar results. Other 14 articles evaluate splinted and non-splinted techniques; all advocating the splinted technique. Polyether material usage was reported in nine; six studies tested vinyl polysiloxane and one study used irreversible hydrocolloid. Eight studies evaluated different copings designs. Intraoral optical devices were compared in four studies. CONCLUSIONS The most accurate results were achieved with two configurations: (1) the optical intraoral system with powder and (2) the open technique with splinted squared transfer copings, using polyether as impression material.

An image processing application for liver tumour segmentation

Liver cancer is one of the leading causes of death worldwide. Consequently, the development of accurate and reliable segmentation techniques is indispensable for tumour volume measurement and staging analysis. An interactive algorithm for liver tumour segmentation was developed, allowing the user to quickly paint the object of interest in the image using an intelligent paintbrush. This technique was based on an image partitioning into homogeneous primitives regions by applying a pseudo-watershed algorithm on an image gradient magnitude. Outcome of this initial segmentation was the input of an efficient region merging process to find the best image partitioning, based on the minimum description length principle. The algorithm was evaluated on Computed Tomography (CT) and Magnetic Resonance (MR) data using the dice similarity coefficient (DSC) as a statistical validation metric. This led to a DCS mean scores of 87% and 84% on the CT and MR studies, respectively.

Automatic 3D aortic annulus sizing by computed tomography in the planning of transcatheter aortic valve implantation

BACKGROUND Accurate imaging assessment of aortic annulus (AoA) dimension is paramount to decide on the correct transcatheter heart valve (THV) size for patients undergoing transcatheter aortic valve implantation (TAVI). We evaluated the feasibility and accuracy of a novel automatic framework for multidetector row computed tomography (MDCT)-based TAVI planning. METHODS Among 122 consecutive patients undergoing TAVI and retrospectively reviewed for this study, 104 patients with preoperative MDCT of sufficient quality were enrolled and analyzed with the proposed software. Fully automatic (FA) and semi-automatic (SA) AoA measurements were compared to manual measurements, with both automated and manual-based interobserver variability (IOV) being assessed. Finally, the effect of these measures on hypothetically selected THV size was evaluated against the implanted size, as well as with respect to manually-derived sizes. RESULTS FA analysis was feasible in 92.3% of the cases, increasing to 100% if using the SA approach. Automatically-extracted measurements showed excellent agreement with manually-derived ones, with small biases and narrow limits of agreement, and comparable to the interobserver agreement. The SA approach presented a statistically lower IOV than manual analysis, showing the potential to reduce interobserver sizing disagreements. Moreover, the automated approaches displayed close agreement with the implanted sizes, similar to the ones obtained by the experts. CONCLUSION The proposed automatic framework provides an accurate and robust tool for AoA measurements and THV sizing in patients undergoing TAVI.