Projective camera model in biomedical navigation applications

Surgical interventions pose very high demands on the spatial sense of surgeons. Especially in complex surgeries, navigation support is an important factor for the success of an operation. With the introduction of computers in surgical navigation, the field of computer assisted surgery was born. In difference to former mechanical constructions, these systems are highly adaptive and enable the development of versatile medical applications. This thesis examines different aspects of integrating a camera into surgical 3D navigation systems. Depending on the context, a camera can perform a self-localization or has to be tracked. In either case, this information is used to build intuitive visualization interfaces, where the operation planning and the reality are fused in a spatially correct manner. The accuracy and reliability of such augmented reality navigation applications is a major concern in this thesis. However, besides the high level incorporation of existing algorithms, this thesis also investigates the projective transformation at its core. It is shown that the position and behavior of a controllable tilting mirror can be described compactly with the projective camera model

PATTERN EVALUATION FOR IN-PLANE DISPLACEMENT MEASUREMENT OF THIN FILMS

The term Gossamer is used to describe ultra-lightweight spacecraft structures that solve the aerospace challenge of obtaining maximum performance while reducing the launch costs of the spacecraft. Gossamer structures are extremely compliant, which complicates control design and ground testing in full scale. One approach is to design and construct smaller test articles and verify their computational models experimentally, so that similar computational models can be used to predict the dynamic performance of full-scale structures. Though measurement of both in-plane and out-of-plane displacements is required to characterize the dynamic response of the surface of these structures, this thesis lays the groundwork for dynamic measurement of the in-plane component. The measurement of thin films must be performed using non-contacting sensors because any contacting sensor would change the dynamics of the structure. Moreover, the thin films dealt with in this work are coated with either gold or aluminum for special applications making the film optically smooth and therefore requiring a surface pattern. A Krypton Fluoride excimer laser system was selected to fabricate patterns on thin-film mirror test articles. Parameters required for pattern fabrication were investigated. Effects of the pattern on the thin-film dynamics were studied using finite element analysis. Photogrammetry was used to study the static in-plane displacement of the thin-film mirror. This was performed to determine the feasibility of the photogrammetric approach for future dynamic tests. It was concluded that photogrammetry could be used efficiently to quantify dynamic in-plane displacement with high-resolution cameras and sub-pixel target marking

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

The applicability of robot-guided laser osteotomy in a clinical environment and the interaction of laser light and bone tissue

Laser is an integral part of diagnostics and therapy in modern medicine. However, removing hard tissue with laser became successful only recently. The advantages of laser osteotomy are high precision and complete freedom in designing the cutting geometry. Nevertheless, these can be fully realized only when the laser system is guided by a robot. The most important challenges here are the miniaturization and the ergonomic design of the entire system. In this dissertation, I presented our first experience with a computer-assisted, integrated and miniaturized laser system, which is driven by a surgical robot. An Er:YAG laser source was integrated into a housing with an optical system and attached to the surgical robot arm. Pre-operatively generated planning data was imported and used to execute the osteotomies. Intraoperatively, a navigation system performed the positioning. In the actual operation room environment, the laser osteotome was used to produce different defect geometries in the mandibular bones of six minipigs. On the contralateral side of the mandible, surgeons used a PZE osteotome to create the same defects for comparison. The performance of the laser osteotome was analyzed in terms of the workflow, ergonomics, bone healing, user-friendliness, and safety. We were able to demonstrate that the laser osteotome could be ergonomically integrated into the operation room environment. It showed a high precision and the complex cutting geometries were transferred as planned. We expect that the computer-assisted and robot-guided laser osteotome will routinely used in the future, whenever special incision and high precision are required in osteotomies

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Optical Methods in Sensing and Imaging for Medical and Biological Applications

The recent advances in optical sources and detectors have opened up new opportunities for sensing and imaging techniques which can be successfully used in biomedical and healthcare applications. This book, entitled ‘Optical Methods in Sensing and Imaging for Medical and Biological Applications’, focuses on various aspects of the research and development related to these areas. The book will be a valuable source of information presenting the recent advances in optical methods and novel techniques, as well as their applications in the fields of biomedicine and healthcare, to anyone interested in this subject

Towards Image-Guided Pediatric Atrial Septal Defect Repair

Congenital heart disease occurs in 107.6 out of 10,000 live births, with Atrial Septal Defects (ASD) accounting for 10\% of these conditions. Historically, ASDs were treated with open heart surgery using cardiopulmonary bypass, allowing a patch to be sewn over the defect. In 1976, King et al. demonstrated use of a transcatheter occlusion procedure, thus reducing the invasiveness of ASD repair. Localization during these catheter based procedures traditionally has relied on bi-plane fluoroscopy; more recently trans-esophageal echocardiography (TEE) and intra-cardiac echocardiography (ICE) have been used to navigate these procedures. Although there is a high success rate using the transcatheter occlusion procedure, fluoroscopy poses radiation dose risk to both patient and clinician. The impact of this dose to the patients is important as many of those undergoing this procedure are children, who have an increased risk associated with radiation exposure. Their longer life expectancy than adults provides a larger window of opportunity for expressing the damaging effects of ionizing radiation. In addition, epidemiologic studies of exposed populations have demonstrated that children are considerably more sensitive to the carcinogenic effects radiation. Image-guided surgery (IGS) uses pre-operative and intra-operative images to guide surgery or an interventional procedure. Central to every IGS system is a software application capable of processing and displaying patient images, registration between multiple coordinate systems, and interfacing with a tool tracking system. We have developed a novel image-guided surgery framework called Kit for Navigation by Image Focused Exploration (KNIFE). This software system serves as the core technology by which a system for reduction of radiation exposure to pediatric patients was developed. The bulk of the initial work in this research endevaour was the development of KNIFE which itself went through countless iterations before arriving at its current state as per the feature requirements established. Secondly, since this work involved the use of captured medical images and their use in an IGS software suite, a brief analysis of the physics behind the images was conducted. Through this aspect of the work, intrinsic parameters (principal point and focal point) of the fluoroscope were quantified using a 3D grid calibration phantom. A second grid phantom was traversed through the fluoroscopic imaging volume of II and flat panel based systems at 2 cm intervals building a scatter field of the volume to demonstrate pincushion and \u27S\u27 distortion in the images. Effects of projection distortion on the images was assessed by measuring the fiducial registration error (FRE) of each point used in two different registration techniques, where both methods utilized ordinary procrustes analysis but the second used a projection matrix built from the fluoroscopes calculated intrinsic parameters. A case study was performed to test whether the projection registration outperforms the rigid transform only. Using the knowledge generated were able to successfully design and complete mock clinical procedures using cardiac phantom models. These mock trials at the beginning of this work used a single point to represent catheter location but this was eventually replaced with a full shape model that offered numerous advantages. At the conclusion of this work a novel protocol for conducting IG ASD procedures was developed. Future work would involve the construction of novel EM tracked tools, phantom models for other vascular diseases and finally clinical integration and use

The interaction of an electrothermal plasma with JA2 solid propellant

Electrothermal plasmas are being studied as an ignition mechanism for solid propellants in large caliber guns. Benefits of electrothermal plasma ignition over conventional primer charge ignition include a reduction of ignition delay and delay jitter (bootstrapping) and compensation for the variable burn rate of propellants at different initial temperatures. When JA2 solid propellant is exposed to plasma radiation alone, significant decomposition results. This radiative interaction is a possible mechanism that causes the bootstrapping and temperature compensation. In addition, the effects of plasma radiation exposure have the potential to increase the propellant burn rate. To characterize this radiation interaction, PLIF imaging of NO, a JA2 decomposition product, was conducted at the propellant surface. Also, simultaneous high speed video of the propellant surface and scattering of ejected particles has been performed. During the radiation interaction scattering particles and NO appeared between 100 and 150 µs after the beginning of the discharge and propagated away from the propellant surface. This ejected material appeared in identifiable structures that are irregular in shape and distribution. This suggests that the material was ejected at semi-discrete locations on the surface rather than diffused uniformly from the surface. During the plasma firing the propellant surface changed markedly by forming irregularly shaped decomposition structures that grew in size over the course of the discharge. No correlation was observed between the structure of the ejected material and the decomposition structures formed on the propellant surface during the discharge. After the plasma discharge, the propellant continued to react, with bubbles forming on the surface up to 9 ms after the discharge finished. These bubbles are probably the largest decomposition structures in images taken of the propellant surface minutes after radiation exposure. The delayed reaction of the propellant produced the majority of ejected particles after the plasma firing. This raises concerns that the potential burning rate increase by the effects of the radiation might not be completely realized in a plasma ignition event. Regions of the propellant exposed to plasma radiation could be consumed by the burning surface before all of the observed effects of the radiative interaction took place.Aerospace Engineering and Engineering Mechanic

Robust artificial clock transition by continuous dynamical decoupling in multi-ion calcium crystals

Optical atomic clocks reach astonishingly low frequency uncertainties. Therefore, they are a valuable tool for applications even beside time determination. Predicted extensions of the standard model of particle physics can be tested using these clocks. For this reason, they can help to uncover unresolved discrepancies between these models and the observed universe. A low frequency uncertainty also enables height measurements according to general relativity. Clock comparisons over long distances might be used to refine geodetic models of the earth’s gravitational potential. A variety of atomic species and techniques are in competition for realizing the most accurate clock. The aluminium single ion clock is, at the moment, the most accurate clock. But it is impeded by long averaging times due to the quantum projection noise limit. For some of the aforementioned applications, this is a serious drawback. Larger ion crystals offer an increased signal-to-noise ratio, but maintaining their frequency accuracy is demanding, as the strong confinement potentials shift the atomic resonance. This thesis reports on the experimental realization of a continuous dynamical decoupling technique. Designed coupling of Zeeman sub-levels by radio-frequency fields is used to mitigate major frequency shifts in 40Ca+ crystals. The obtained artificial clock transition has the potential to compete with more promising clock transitions of different atomic species regarding its low sensitivity to magnetic field fluctuations as well as suppressed quadrupole and tensorial ac-Stark shifts. Long coherence times in multi-ion 40Ca+ crystals are obtained for the artificial transition. Thus, the system’s potential for a low statistical uncertainty makes it promising as a replacement for a lattice clock in a compound clock or for applications where frequency differences must be determined on a short timescale.Optische Atomuhren erreichen außergewöhnlich niedrige Frequenzunsicherheiten. Daher sind sie selbst für Anwendungen neben der Zeitbestimmung ein nützliches Werkzeug. Erweiterungen des Standardmodells der Teilchenphysik können durch sie getestet werden und somit können sie helfen, ungelöste Diskrepanzen dieser Modelle mit dem beobachteten Universum aufzudecken. Außerdem werden Höhenmessungen nach Vorhersage der allgemeinen Relativitätstheorie ermöglicht. Uhrenvergleiche über lange Distanzen können verwendet werden, um geodätische Modelle des Gravitationspotentials der Erde zu verbessern. Viele Atomarten und Techniken konkurrieren um die Realisierung der genauesten Uhr. Derzeit hat die Aluminium- Einzelionenuhr die höchste Genauigkeit. Aufgrund ihrer Limitierung durch Quanten-Projektions-Rauschen sind lange Mittelungszeiten erforderlich. Dies ist ein großer Nachteil für einige der oben genannten Anwendungen. Mehrionenkristalle bieten ein größeres Signal-zu-Rauschverhältnis, die Erhaltung ihrer Frequenzgenauigkeit wird jedoch durch die starken Einschlusspotentiale erschwert, welche die atomare Resonanz verschieben. Diese Arbeit beinhaltet die experimentelle Realisierung einer kontinuierlich dynamischen Entkopplungstechnik. Maßgeschneiderte Radiofrequenzfelder werden zur Kopplung von Zeeman- Zuständen genutzt, um einige Frequenzverschiebungen in 40Ca+ Kristallen abzuschwächen. Der künstlich erzeugte Uhrenübergang hat das Potenzial, zu vielversprechenderen Übergängen anderer Atomarten aufzuschließen. Dies gilt in Hinblick auf seine geringe Empfindlichkeit gegenüber Magnetfeldfluktuationen, sowie der unterdrückten Quadrupol- und tensoriellen,dynamischen Stark-Verschiebung. Für den künstlichen Übergang werden lange Kohärenzzeiten in Mehrionen 40Ca+ Kristallen erreicht. Der Austausch von Gitteruhren in einer Hybriduhr durch große Ionenkristalle wird aufgrund der langen Kohärenzzeiten ihres künstlichen Übergangs denkbar. Außerdem ist der künstliche Übergang für Anwendungen interessant, bei denen Frequenzunterschiede auf einer kurzen Zeitskala bestimmt werden müssen