A NOVEL POSITIONAL SENSOR FOR 3D VASCULAR RECONSTRUCTION

Intravascular ultrasound (IVUS) is a device that is surgically inserted into a femoral artery, or vein, to aid in the diagnosis of cardiovascular disease. Correctly locating the IVUS tip facilitates accurate 3D vascular reconstruction. Researchers are actively investigating different methods, such as: stereo X-rays, radio triangula- tion, computer-aided tomography (CAT) scans, etc., to produce quality 3D graphical vascular images. Each of these methods has their pros and cons, however they all require external sensors and some are bulky and complicated to operate. This research investigates an accelerometer, constructed from a multi-mode fiber- optic cable, and studies its performance with multi-mode fiber interferometry tech- nology (speckle-gram analysis) and presents experimental evidence to support its suitability for tracking an IVUS sensor in vivo, leading to real-time 3D reconstruc- tion of internal arterial segments. The system resulting from this study is expected to be simple, small, and economically feasible, to bridge the diagnostic/treatment time gap and eliminate the need for external tracking equipment. Non-linear models and analysis of variance methodologies are presented to verify that the fiber-optic accelerometer is functioning within experimental error which can provide accurate spatial tracking. The results from this study show that the fiber accelerometer is per- forming as well as a micro-electromechanical machine system (MEMS) accelerometer and, unlike the MEMS, it is immune to environmental noise. The potential system is expected to reduce the computation necessary to perform 3D vascular reconstruction from IVUS data, leading to improvements in, and the reduction of, the diagnos- tic/treatment time-line. Also, the performance and sensitivity of this novel positional sensor is expected to improve with appropriate changes in the craftsmanship of the fiber accelerometer and testing apparatus

Head Worn Display System for Equivalent Visual Operations

Head-Worn Displays or so-called, near-to-eye displays have potentially significant advantages in terms of cost, overcoming cockpit space constraints, and for the display of spatially-integrated information. However, many technical issues need to be overcome before these technologies can be successfully introduced into commercial aircraft cockpits. The results of three activities are reported. First, the near-to-eye display design, technological, and human factors issues are described and a literature review is presented. Second, the results of a fixed-base piloted simulation, investigating the impact of near to eye displays on both operational and visual performance is reported. Straight-in approaches were flown in simulated visual and instrument conditions while using either a biocular or a monocular display placed on either the dominant or non-dominant eye. The pilot's flight performance, visual acuity, and ability to detect unsafe conditions on the runway were tested. The data generally supports a monocular design with minimal impact due to eye dominance. Finally, a method for head tracker system latency measurement is developed and used to compare two different devices

Characterization of a Contact-Stylus Surface Digitization Method Using Collaborative Robots: Accuracy Evaluation in the Context of Shoulder Replacement or Resurfacing

Total shoulder arthroplasty (TSA) is the third most common joint replacement. While robot-assisted hip and knee replacement technologies have enjoyed extensive development, this has been limited in the upper limb. This work focused on quantifying the localization accuracy of a robotic system, and evaluating its efficacy in the context of TSA. A collaborative robot was fitted with a stylus tip to perform manual surface digitizations using the robot’s encoder output. In the first experiment, two precision-machined master cubes, representing the working volume around a glenoid structure, were used for system validation. Next, cadaveric glenoids were digitized and compared to a ‘gold standard’ laser scanner. Digitization errors were 0.37±0.27 mm, showing that collaborative robotics can be used for osseous anatomy digitization. This thesis presents two novel concepts: 1) use of collaborative robotics for manually operated surface digitizing, and 2) optical fiducial technique, allowing registration between a laser scanner and stylus digitizer

Development of a Near-Field Magnetic Projectile Location System

Near-field magnetic principles and properties have been well studied and are used in a plethora of modern applications, ranging from medical applications to audio and video processing, and magnetic tracking. Current tracking applications are based in either AC or Pulsed-DC systems. Generally, AC systems have high resolution and accuracy, but perform very poorly in the presence of conducting magnetic materials. Pulsed-DC tracking has the benefit of not inducing large eddy currents in proximity to magnetic materials, thus increasing its overall accuracy. It has been suggested that pure DC systems are not feasible because they are unable to account for the presence of the Earth\u27s magnetic field.;It was the purpose of this research to propose and create a system, and develop an algorithm, that has the ability to determine the three-dimensional position and orientation of a permanent magnetic source; the position and orientation to be determined by information reported by a network of single-axis magnetic sensors. Methodology to account for the Earth\u27s magnetic field before, during, and after operation in order to remove ambient and environmental magnetic noise, much like a pulsed-DC system does, was also to be considered.;A center-finding algorithm was developed to determine position (x- and y-axis) based on the unique geometry of the B-field of the magnetic source at any point in three-dimensional space. Two degrees of orientation, elevation and rotation, were calculated from the position and the reported values of the magnetic sensors. The z-axis position was then determined given the analytical model and the other calculated values. In addition to the computed position, a six input Kalman tracker-estimator was developed and implemented using three dimensions of position and velocities to aid in predicting the path the magnetic source will take, based solely on kinematics, to reduce position-based sensor error.;The contribution of this research shows that is it not necessary to obtain three-axis magnetic data to track a magnetic source in three-dimensional space. When the distribution of the magnetic flux density is known, it is possible to determine three-dimensional position and orientation with only single-axis information.;Experimental testing verified the theoretical predictions of this statement. A rotational test apparatus was used to verify two-dimensional position and orientation, while a linear test apparatus verified position in three dimensions. The same magnetic source was used, while changing the orientation for each test. Initial findings allow the magnetic source to be tracked on the rotational testing apparatus to within a radial error of 3.9% (mean) and less than 6.4% (worst case) for predictions. The linear apparatus is able to track the z-axis component of the source which can be determined within 0.19% (mean) and 0.24% (worst case), and mean three-dimensional position of the magnetic source within 1.4% error. These results suggest that the novel method presented in this document is credible method for magnetic detection and tracking

New Mechatronic Systems for the Diagnosis and Treatment of Cancer

Both two dimensional (2D) and three dimensional (3D) imaging modalities are useful tools for viewing the internal anatomy. Three dimensional imaging techniques are required for accurate targeting of needles. This improves the efficiency and control over the intervention as the high temporal resolution of medical images can be used to validate the location of needle and target in real time. Relying on imaging alone, however, means the intervention is still operator dependent because of the difficulty of controlling the location of the needle within the image. The objective of this thesis is to improve the accuracy and repeatability of needle-based interventions over conventional techniques: both manual and automated techniques. This includes increasing the accuracy and repeatability of these procedures in order to minimize the invasiveness of the procedure. In this thesis, I propose that by combining the remote center of motion concept using spherical linkage components into a passive or semi-automated device, the physician will have a useful tracking and guidance system at their disposal in a package, which is less threatening than a robot to both the patient and physician. This design concept offers both the manipulative transparency of a freehand system, and tremor reduction through scaling currently offered in automated systems. In addressing each objective of this thesis, a number of novel mechanical designs incorporating an remote center of motion architecture with varying degrees of freedom have been presented. Each of these designs can be deployed in a variety of imaging modalities and clinical applications, ranging from preclinical to human interventions, with an accuracy of control in the millimeter to sub-millimeter range

Ultraschallbasierte Navigation für die minimalinvasive onkologische Nieren- und Leberchirurgie

In der minimalinvasiven onkologischen Nieren- und Leberchirurgie mit vielen Vorteilen für den Pa- tienten wird der Chirurg häufig mit Orientierungsproblemen konfrontiert. Hauptursachen hierfür sind die indirekte Sicht auf die Patientenanatomie, das eingeschränkte Blickfeld und die intra- operative Deformation der Organe. Abhilfe können Navigationssysteme schaffen, welche häufig auf intraoperativem Ultraschall basieren. Durch die Echtzeit-Bildgebung kann die Deformation des Organs bestimmt werden. Da viele Tumore im Schallbild nicht sichtbar sind, wird eine robuste automatische und deformierbare Registrierung mit dem präoperativen CT benötigt. Ferner ist eine permanente Visualisierung auch während der Manipulation am Organ notwendig. Für die Niere wurde die Eignung von Ultraschall-Elastographieaufnahmen für die bildbasierte Re- gistrierung unter Verwendung der Mutual Information evaluiert. Aufgrund schlechter Bildqualität und geringer Ausdehnung der Bilddaten hatte dies jedoch nur mäßigen Erfolg. Die Verzweigungspunkte der Blutgefäße in der Leber werden als natürliche Landmarken für die Registrierung genutzt. Dafür wurden Gefäßsegmentierungsalgorithmen für die beiden häufigsten Arten der Ultraschallbildgebung B-Mode und Power Doppler entwickelt. Die vorgeschlagene Kom- bination beider Modalitäten steigerte die Menge an Gefäßverzweigungen im Mittel um 35 %. Für die rigide Registrierung der Gefäße aus dem Ultraschall und CT werden mithilfe eines bestehen- den Graph Matching Verfahrens [OLD11b] im Mittel 9 bijektive Punktkorrespondenzen definiert. Die mittlere Registrierungsgenauigkeit liegt bei 3,45 mm. Die Menge an Punktkorrespondenzen ist für eine deformierbare Registrierung nicht ausreichend. Das entwickelte Verfahren zur Landmarkenverfeinerung fügt zwischen gematchten Punkte weitere Landmarken entlang der Gefäßmittellinien ein und sucht nach weiteren korrespondierenden Gefäß- segmenten wodurch die Zahl der Punktkorrespondenzen im Mittel auf 70 gesteigert wird. Dies erlaubt die Bestimmung der Organdeformation anhand des unterschiedlichen Gefäßverlaufes. Anhand dieser Punktkorrespondenzen kann mithilfe der Thin-Plate-Splines ein Deformationsfeld für das gesamte Organ berechnet werden. Auf diese Weise wird die Genauigkeit der Registrierung im Mittel um 44 % gesteigert. Die wichtigste Voraussetzung für das Gelingen der deformierbaren Registrierung ist eine möglichst umfassende Segmentierung der Gefäße aus dem Ultraschall. Im Rahmen der Arbeit wurde erstmals der Begriff der Regmentation auf die Segmentierung von Gefäßen und die gefäßbasierte Registrie- rung ausgeweitet. Durch diese Kombination beider Verfahren wurde die extrahierte Gefäßlänge im Mittel um 32 % gesteigert, woraus ein Anstieg der Anzahl korrespondierender Landmarken auf 98 resultiert. Hierdurch lässt sich die Deformation des Organs und somit auch die Lageveränderung des Tumors genauer und mit höherer Sicherheit bestimmen. Mit dem Wissen über die Lage des Tumors im Organ und durch Verwendung eines Markierungs- drahtes kann die Lageveränderung des Tumors während der chirurgischen Manipulation mit einem elektromagnetischen Trackingsystem überwacht werden. Durch dieses Tumortracking wird eine permanente Visualisierung mittels Video Overlay im laparoskopischen Videobild möglich. Die wichtigsten Beiträge dieser Arbeit zur gefäßbasierten Registrierung sind die Gefäßsegmen- tierung aus Ultraschallbilddaten, die Landmarkenverfeinerung zur Gewinnung einer hohen Anzahl bijektiver Punktkorrespondenzen und die Einführung der Regmentation zur Verbesserung der Ge- fäßsegmentierung und der deformierbaren Registrierung. Das Tumortracking für die Navigation ermöglicht die permanente Visualisierung des Tumors während des gesamten Eingriffes