7 research outputs found

    Navigated Ultrasound in Laparoscopic Surgery

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    Electromagnetic Tracking for Medical Imaging

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    This thesis explores the novel use of a wireless electromagnetic: EM) tracking device in a Computed Tomography: CT) environment. The sources of electromagnetic interference inside a Philips Brilliant Big Bore CT scanner are analyzed. A research version of the Calypso wireless tracking system was set up inside the CT suite, and a set of three Beacon transponders was bonded to a plastic fixture. The tracking system was tested under different working parameters including orientation of tracking beacons, the gain level of the frontend amplifier, the distance between the transponders and the sensor array, the rotation speed of the CT gantry, and the presence/absence of the CT X-ray source. The performance of the tracking system reveals two obvious factors which bring in electromagnetic interference: 1) metal like effect brought in by carbon fiber patient couch and 2) electromagnetic disturbance due to spinning metal inside the CT gantry. The accuracy requirements for electromagnetic tracking in the CT environment are a Root Mean Square: RMS) error of \u3c2 mm in stationary position tracking. Within a working volume of 120×120×120 mm3 centered 200 mm below the sensor array, the tracking system achieves the desired clinical goal

    ELECTROMAGNETIC TRACKER CHARACTERIZATION AND OPTIMAL TOOL DESIGN (WITH APPLICATIONS TO ENT SURGERY)

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    Electromagnetic tracking systems prove to have great potential for serving as the tracking component of image guided surgery (IGS) systems. However, despite their major advantage over other trackers in that they do not require line-of-sight to the sensors, their use has been limited primarily due to their inherent measurement distortion problem. Presented here are methods of mapping the measurement field distortion and results describing the distortion present in various environments. Further, a framework for calibration and characterization of the tracking system’s systematic error is presented. The error maps are used to generate polynomial models of the distortion that can be used to dynamically compensate for measurement errors. The other core theme of this work is related to optimal design of electromagnetically tracked tools; presented here are mathematical tools for analytically predicting error propagation and optimally configuring sensors on a tool. A software simulator, using a model of the magnetic field distortion, is used to further design and test these tools in a simulation of actual measurement environments before ever even being built. These tools are used to design and test a set of electromagnetically tracked instruments, specifically for ENT surgical applications

    Enhancement of spatial awareness in natural orifice transluminal endoscopic surgery

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    Natural orifice transluminal endoscopic surgery (NOTES) represents a challenging concept to pursue in minimally invasive procedures, with a promise of becoming even less invasive, but with the additional issues of being team dependent and more technology intensive. The safety of patients undergoing any surgical procedure is of principal importance. When a surgeon performs laparoscopic procedures, he only has a two dimensional field of view and as a result, his spatial awareness is diminished. A surgeon operating under conditions of reduced spatial awareness poses an increased risk to a patient. Spatial awareness is deemed a necessary skill for the safe deployment of NOTES procedures. Understanding the surgeon’s situational and spatial awareness during NOTES investigation is therefore of paramount importance for the safe performance of this type of procedures. Enhancing scene visualisation, for instance by means of additional viewpoints or electromagnetic tracking, seems a feasible strategy for augmenting spatial awareness in NOTES. This study aims to propose novel approaches involving electromagnetic tracking and additional off-axis visualisation in an attempt to assess, as well as enhance spatial awareness of the operating field in NOTES. The original contributions of this thesis include: • Validation of an outlining approach to characterise spatial awareness in minimally invasive surgery particularly in NOTES • Qualitative and quantitative assessment of spatial awareness n NOTES • Identification of certain navigation behavioural patterns in NOTES • Design and evaluation of spatial awareness enhancement tool for NOTES The value of the research presented in this thesis, as well as the potential for further development is also discussed in the context of spatial awareness in MIS in general

    Desarrollo de un nuevo sistema de navegación en Implantología basado en unidades de medición inercial

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    La colocación de implantes dentales mediante cirugía guiada por ordenador tiene numerosas ventajas frente a la realizada a mano alzada, especialmente mayor precisión, mayor seguridad y menor invasividad. Pero también, tanto los sistemas estáticos o férulas, como los dinámicos o navegación, presentan dificultades de uso y un mayor coste, por lo que su utilización actual es limitada. Se elabora una revisión de los distintos sistemas de guiado de la cirugía de colocación de implantes, de su uso, precisión y fuentes de error. Describimos la unidad de medición inercial o IMU y sus primeras aplicaciones en cirugía general, como una alternativa versátil, simple y económica a las tecnologías existentes. Por medio de un prototipo que integra los sensores IMU en una interfaz computerizada, se colocan implantes guiados por estos sensores, y también por férulas CAD-CAM. Los resultados medios comparados que obtenemos entre ambos sistemas de guiado, son similares estadísticamente. Las desviaciones medias han sido en coronal 1.48 ± 0.2 (SD 0.58; 95% CI 1.27 - 1.69) y 1.42 ± 0.2 (SD 0.61; 95% CI 1.2 - 1.64) mm, en apical 2.00 ± 0.33 (SD 0.93; 95% CI 1.67 - 2.33) y 2.07 ± 0.35 (SD 0.97; 95% CI 1.72 - 2.42) mm, y las angulares 7.13º ± 1.47º (SD 4.1; 95% CI 5.66 - 8.6) y 5.63º ± 1.41º (SD 3.94; 95% CI 4.22 - 7.04), para IMU y Férulas Estereolitográficas (FE) respectivamente. Estos resultados son consistentes con la precisión reportada en la literatura para la cirugía guiada, tanto estática como dinámica. Se valora igualmente la percepción del operador y su comodidad de uso, encontrando que el manejo del sistema requiere un entrenamiento previo y que se facilitaría al mejorar la interfaz gráfica. Se abre así una vía de investigación para adaptar este nuevo sistema de navegación al uso clínico rutinario. Para ello, es necesaria la mejora in vitro de sus condiciones de manejo, así como ulteriores estudios sobre pacientes.Computer-guided dental implant placement is considered to be safer, more accurate and less invasive compared to freehand implant surgery. Currently two types of surgical guiding systems are available, static templates and dynamic navigation. Both make intervention more complex and costly and this could be the reason why their current use remains limited. A "state of the art" of the different implant placement guiding systems, their use, precision and sources of error has been conducted. The Inertial Measurement Unit (IMU) and its early applications in general surgery are described. The IMU was shown to be a versatile, simple and economical alternative to existing surgical guidance technologies. A prototype surgical handpiece was assembled with IMU sensors integrated with a computerized interface to guide implant placement. Implants were placed in models using this prototype and the standard CAD-CAM splints. Similar statistical average results were obtained using either of the two systems. The mean deviations were 1.48 ± 0.2 (SD 0.58; 95% CI 1.27 - 1.69) and 1.42 ± 0.2 (SD 0.61; 95% CI 1.2 - 1.64) mm coronal, 2.00 ± 0.33 (SD 0.93; 95% CI 1.67 - 2.33) and 2.07 ± 0.35 (SD 0.97; 95% CI 1.72 - 2.42) mm apical, and 7.13º ± 1.47º (SD 4.1; 95% CI 5.66 - 8.6) y 5.63º ± 1.41º (SD 3.94; 95% CI 4.22 - 7.04) angular, for IMU’s and splints respectively. These results are consistent with the precision reported in the literature for guided surgery, both current static and dynamic modalities. When operator’s perceptions and comfort of use were addressed, it was found that the system’s handling requires going through a learning curve and that it would be facilitated by improving the graphic interface. The present study opens a path of investigation to adapt this new surgical navigation system to routine clinical use. To this end, the system has to be improved to make the operator’s control easier before further studies on patients can be carried out

    Méthode de correction des erreurs de mesure appliquée à un système FASTRAK 3SPACE

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    La méthode de correction développée au LIO permet de réduire l’erreur de mesure en translation et en rotation produites par des distorsions électromagnétiques et qui affectent la précision des capteurs Fastrak. La méthode permet la caractérisation des erreurs de mesure d’un champ électromagnétique et l’étalonnage d’un volume de 0,458 m3 en moins de 35 secondes. Il est possible de réduire l’erreur moyenne d’un ensemble de mesures, sans en augmenter la variabilité, pour autant que l’erreur de mesure ne dépasse pas 35 mm en translation. Nous avons réussi à réduire cette erreur à 6,1 mm +/- 3,0 mm en translation et à 0,49° +/- 0,17° en rotation avec seulement 1000 étalons sur un ensemble de 712 mesures. La méthode fonctionne sur un nombre illimité de mesures pouvant se situer jusqu’à 115 cm de l’émetteur. Le nombre de mesures étalons utilisées à montrer qu’il influence les performances de la méthode de correction, ce nombre se situant entre 100 et 1000 mesures. À 115 cm de l’émetteur, les meilleurs résultats ont été obtenus en divisant le volume global d’étalonnage en deux sous volumes distinctes. Dans ce cas, le calcul des polynômes se fait donc sur les sections plus petites, ce qui permet d’éliminer les distorsions aux frontières du volume d’étalonnage dans les conditions optimales de la méthode de correction du LIO. Pour des distances inférieures à 75 cm de l’émetteur, l’utilisation d’un seul ensemble de polynômes est possible

    Advances in Biomedical Applications and Assessment of Ultrasound Nonrigid Image Registration.

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    Image volume based registration (IVBaR) is the process of determining a one-to-one transformation between points in two images that relates the information in one image to that in the other image quantitatively. IVBaR is done primarily to spatially align the two images in the same coordinate system in order to allow better comparison and visualization of changes. The potential use of IVBaR has been explored in three different contexts. In a preliminary study on identification of biometric from internal finger structure, semi-automated IVBaR-based study provided a sensitivity and specificity of 0.93 and 1.00 respectively. Visual matching of all image pairs by four readers yielded 96% successful match. IVBaR could potentially be useful for routine breast cancer screening and diagnosis. Nearly whole breast ultrasound (US) scanning with mammographic-style compression and successful IVBaR were achieved. The image volume was registered off-line with a mutual information cost function and global interpolation based on the non-rigid thin-plate spline deformation. This Institutional Review Board approved study was conducted on 10 patients undergoing chemotherapy and 14 patients with a suspicious/unknown mass scheduled to undergo biopsy. IVBaR was successful with mean registration error (MRE) of 5.2±2 mm in 12 of 17 ABU image pairs collected before, during or after 115±14 days of chemotherapy. Semi-automated tumor volume estimation was performed on registered image volumes giving 86±8% mean accuracy compared with a radiologist hand-segmented tumor volume on 7 cases with correlation coefficient of 0.99 (p<0.001). In a reader study by 3 radiologists assigned to mark the tumor boundary, significant reduction in time taken (p<0.03) was seen due to IVBaR in 6 cases. Three new methods were developed for independent validation of IVBaR based on Doppler US signals. Non-rigid registration tools were also applied in the field of interventional guidance of medical tools used in minimally invasive surgery. The mean positional error in a CT scanner environment improved from 3.9±1.5 mm to 1.0±0.3 mm (p<0.0002). These results show that 3D image volumes and data can be spatially aligned using non-rigid registration for comparison as well as quantification of changes.Ph.D.Applied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64802/1/gnarayan_1.pd
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