ReSCon '09, Research Student Conference: Book of Abstracts

The second SED Research Student Conference (ReSCon2009) was hosted over three days, 22-24 June 2009, in the Lecture Centre at Brunel University. The conference consisted of technical presentations, a poster session and social events. The abstracts and presentations were the result of ongoing research by postgraduate research students from the School of Engineering and Design at Brunel University. The conference is held annually, and ReSCon plays a key role in contributing to research and innovations within the School

Nanophotonic Interconnect Architectures For Many-Core Microprocessors

Nanophotonics is an emerging technology that has the potential to improve the performance and energy consumption of inter- and intra-die communication in future chip multiprocessors. To date, the successful demonstration of a working large-scale system has been hampered by integration challenges and temperature sensitivity of the optical building blocks. Moreover, current approaches to interfacing with these devices are either CMOS incompatible or degrade the potential Tb/s modulation capability to only tens of Gb/s. At first glance it may seem like all of these challenges hint at today's nanophotonic devices being too impractical. However, using a combination of proposed solutions at the device and architectural level, a rich tradeoff space begins to emerge that is still largely untouched due to the knowledge gap between nanophotonic researchers on both sides of the spectrum. To this end, this dissertation attempts to fill this gap by targeting both device and system level research in an integrated fashion. We begin with an extended background and related work section that presents the relevant parameters and functionality of key optical devices for designing interconnection networks at the architecture level. Following this, we give a detailed discussion on the system level implications of optics including communication methods and summaries of recent network architectures for both on-chip and off-chip signaling with important takeaways for designing future systems. The lack of a comprehensive and accurate modeling strategy for optical com- ponents in the architecture community has lead to potentially inaccurate, and inflated, power and performance estimates. Since better representation of optical devices in architectural level simulations is essential to producing trustworthy results, we present a comprehensive, mathematical model for all of the major optical building blocks. To our knowledge, this is the first comprehensive model of all relevant optical devices specifically tailored to system level design for architects. An interesting aspect of architectural research in the field of optics is that there is not a natural progression of scaling parameters that will necessarily dictate future designs as is the case in CMOS. Because nanophotonics is an emerging technology, the potential is limitless for creating new devices that solve previous challenges. Optical packet switching is a promising approach for overcoming the performance and power limitations of bus-based on-chip networks. We present two variations of Phastlane, the first proposed nanophotonic packet switched architecture. In our evaluation, we demonstrate the potential improvements in system performance and power consumption across a range of modulator and receiver parameters. We also augment this analysis with projections for current optical devices using our mathematical device model. Finally, we propose alternatives for overcoming some of the limitations of both Phastlane architectures in the event that future optical components stagnate at current performance and power consumption. Also, we use our device model to explore a less aggressive approach to nanophotonics that judiciously combines electrical and optical interconnect

A continuum robotic platform for endoscopic non-contact laser surgery: design, control, and preclinical evaluation

The application of laser technologies in surgical interventions has been accepted in the clinical domain due to their atraumatic properties. In addition to manual application of fibre-guided lasers with tissue contact, non-contact transoral laser microsurgery (TLM) of laryngeal tumours has been prevailed in ENT surgery. However, TLM requires many years of surgical training for tumour resection in order to preserve the function of adjacent organs and thus preserve the patient’s quality of life. The positioning of the microscopic laser applicator outside the patient can also impede a direct line-of-sight to the target area due to anatomical variability and limit the working space. Further clinical challenges include positioning the laser focus on the tissue surface, imaging, planning and performing laser ablation, and motion of the target area during surgery. This dissertation aims to address the limitations of TLM through robotic approaches and intraoperative assistance. Although a trend towards minimally invasive surgery is apparent, no highly integrated platform for endoscopic delivery of focused laser radiation is available to date. Likewise, there are no known devices that incorporate scene information from endoscopic imaging into ablation planning and execution. For focusing of the laser beam close to the target tissue, this work first presents miniaturised focusing optics that can be integrated into endoscopic systems. Experimental trials characterise the optical properties and the ablation performance. A robotic platform is realised for manipulation of the focusing optics. This is based on a variable-length continuum manipulator. The latter enables movements of the endoscopic end effector in five degrees of freedom with a mechatronic actuation unit. The kinematic modelling and control of the robot are integrated into a modular framework that is evaluated experimentally. The manipulation of focused laser radiation also requires precise adjustment of the focal position on the tissue. For this purpose, visual, haptic and visual-haptic assistance functions are presented. These support the operator during teleoperation to set an optimal working distance. Advantages of visual-haptic assistance are demonstrated in a user study. The system performance and usability of the overall robotic system are assessed in an additional user study. Analogous to a clinical scenario, the subjects follow predefined target patterns with a laser spot. The mean positioning accuracy of the spot is 0.5 mm. Finally, methods of image-guided robot control are introduced to automate laser ablation. Experiments confirm a positive effect of proposed automation concepts on non-contact laser surgery.Die Anwendung von Lasertechnologien in chirurgischen Interventionen hat sich aufgrund der atraumatischen Eigenschaften in der Klinik etabliert. Neben manueller Applikation von fasergeführten Lasern mit Gewebekontakt hat sich die kontaktfreie transorale Lasermikrochirurgie (TLM) von Tumoren des Larynx in der HNO-Chirurgie durchgesetzt. Die TLM erfordert zur Tumorresektion jedoch ein langjähriges chirurgisches Training, um die Funktion der angrenzenden Organe zu sichern und damit die Lebensqualität der Patienten zu erhalten. Die Positionierung des mikroskopis chen Laserapplikators außerhalb des Patienten kann zudem die direkte Sicht auf das Zielgebiet durch anatomische Variabilität erschweren und den Arbeitsraum einschränken. Weitere klinische Herausforderungen betreffen die Positionierung des Laserfokus auf der Gewebeoberfläche, die Bildgebung, die Planung und Ausführung der Laserablation sowie intraoperative Bewegungen des Zielgebietes. Die vorliegende Dissertation zielt darauf ab, die Limitierungen der TLM durch robotische Ansätze und intraoperative Assistenz zu adressieren. Obwohl ein Trend zur minimal invasiven Chirurgie besteht, sind bislang keine hochintegrierten Plattformen für die endoskopische Applikation fokussierter Laserstrahlung verfügbar. Ebenfalls sind keine Systeme bekannt, die Szeneninformationen aus der endoskopischen Bildgebung in die Ablationsplanung und -ausführung einbeziehen. Für eine situsnahe Fokussierung des Laserstrahls wird in dieser Arbeit zunächst eine miniaturisierte Fokussieroptik zur Integration in endoskopische Systeme vorgestellt. Experimentelle Versuche charakterisieren die optischen Eigenschaften und das Ablationsverhalten. Zur Manipulation der Fokussieroptik wird eine robotische Plattform realisiert. Diese basiert auf einem längenveränderlichen Kontinuumsmanipulator. Letzterer ermöglicht in Kombination mit einer mechatronischen Aktuierungseinheit Bewegungen des Endoskopkopfes in fünf Freiheitsgraden. Die kinematische Modellierung und Regelung des Systems werden in ein modulares Framework eingebunden und evaluiert. Die Manipulation fokussierter Laserstrahlung erfordert zudem eine präzise Anpassung der Fokuslage auf das Gewebe. Dafür werden visuelle, haptische und visuell haptische Assistenzfunktionen eingeführt. Diese unterstützen den Anwender bei Teleoperation zur Einstellung eines optimalen Arbeitsabstandes. In einer Anwenderstudie werden Vorteile der visuell-haptischen Assistenz nachgewiesen. Die Systemperformanz und Gebrauchstauglichkeit des robotischen Gesamtsystems werden in einer weiteren Anwenderstudie untersucht. Analog zu einem klinischen Einsatz verfolgen die Probanden mit einem Laserspot vorgegebene Sollpfade. Die mittlere Positioniergenauigkeit des Spots beträgt dabei 0,5 mm. Zur Automatisierung der Ablation werden abschließend Methoden der bildgestützten Regelung vorgestellt. Experimente bestätigen einen positiven Effekt der Automationskonzepte für die kontaktfreie Laserchirurgie

Development of a portable time-domain system for diffuse optical tomography of the newborn infant brain

Conditions such as hypoxic-ischaemic encephalopathy (HIE) and perinatal arterial ischaemic stroke (PAIS) are causes of lifelong neurodisability in a few hundred infants born in the UK each year. Early diagnosis and treatment are key, but no effective bedside detection and monitoring technology is available. Non-invasive, near-infrared techniques have been explored for several decades, but progress has been inhibited by the lack of a portable technology, and intensity measurements, which are strongly sensitive to uncertain and variable coupling of light sources and detector to the scalp. A technique known as time domain diffuse optical tomography (TD-DOT) uses measurements of photon flight times between sources and detectors placed on the scalp. Mean flight time is largely insensitive to the coupling and variation in mean flight time can reveal spatial variation in blood volume and oxygenation in regions of brain sampled by the measurements. While the cost, size and high power consumption of such technology have hitherto prevented development of a portable imaging system, recent advances in silicon technology are enabling portable and low-power TD-DOT devices to be built. A prototype TD-DOT system is proposed and demonstrated, with the long-term aim to design a portable system based on independent modules, each supporting a time-of-flight detector and a pulsed source. The operation is demonstrated of components that can be integrated in a portable system: silicon photodetectors, integrated circuit-based signal conditioning and time detection -- built using a combination of off-the-shelf components and reconfigurable hardware, standard computer interfaces, and data acquisition and calibration software. The only external elements are a PC and a pulsed laser source. This thesis describes the design process, and results are reported on the performance of a 2-channel system with online histogram generation, used for phantom imaging. Possible future development of the hardware is also discussed