Modern image-guided surgery aids minimally-invasive, high-precision procedures that increase efficacy of treatment. This thesis investigates two research aims to improve precision and integration of intraoperative cone-beam CT (CBCT) imaging in guidance of head and neck (H&N) surgery. First, marker configurations were examined to identify arrangements that minimize target registration error (TRE). Best arrangements minimized the distance between the configuration centroid and surgical target while maximizing marker separation. Configurations of few markers could minimized TRE with more markers providing improved uniformity. Second, an algorithm for automatic registration of image and world reference frames was pursued to streamline integration of CBCT with real-time tracking and provide automatic updates per scan. Markers visible to the tracking and imaging systems are automatically co-localized and registered with equivalent accuracy and superior reproducibility compared to conventional registration. Such work helps the implementation of CBCT in H&N surgery to maximize surgical precision and exploit intraoperative image guidance.

This thesis presents the first work, to our knowledge, to evaluate the potential of Optical Coherence Tomography (OCT) as an intravascular imaging modality to characterize and guide interventions on chronic total occlusions (CTOs) in arteries. An ex vivo imaging study using OCT is presented that characterizes various pathologies associated with peripheral CTOs and illustrates the ability to differentiate between the vessel wall and the occluded lumen. We also found that, while OCT could image approximately 1mm through tissue, it was effective for imaging deeper through clarified microchannels seen within the occluded lumen. While others had reported observing such microchannels within the lumen before, little was known about the global architecture of these channels. This motivated a study of the global morphology of microchannels in occlusions using micro computed tomography (microCT). In this microCT study, we found that microchannels within the occluded lumen of the artery appeared to be continuous over several millimeters. However, these channels also exited the artery frequently, suggesting the need for some form of imaging guidance. As a potential intravascular imaging set-up, a forward-viewing OCT catheter was built. This catheter uses a novel scanning mechanism that combines high voltage and a dissipative polymer to achieve fast compact actuation. Doppler OCT results are presented using this catheter to image flow in the forward direction. Doppler OCT imaging of microchannels in vivo is also shown in a surgically exposed occluded artery in situ.

This thesis presents the first work, to our knowledge, to evaluate the potential of Optical Coherence Tomography (OCT) as an intravascular imaging modality to characterize and guide interventions on chronic total occlusions (CTOs) in arteries. An ex vivo imaging study using OCT is presented that characterizes various pathologies associated with peripheral CTOs and illustrates the ability to differentiate between the vessel wall and the occluded lumen. We also found that, while OCT could image approximately 1mm through tissue, it was effective for imaging deeper through clarified microchannels seen within the occluded lumen. While others had reported observing such microchannels within the lumen before, little was known about the global architecture of these channels. This motivated a study of the global morphology of microchannels in occlusions using micro computed tomography (microCT). In this microCT study, we found that microchannels within the occluded lumen of the artery appeared to be continuous over several millimeters. However, these channels also exited the artery frequently, suggesting the need for some form of imaging guidance. As a potential intravascular imaging set-up, a forward-viewing OCT catheter was built. This catheter uses a novel scanning mechanism that combines high voltage and a dissipative polymer to achieve fast compact actuation. Doppler OCT results are presented using this catheter to image flow in the forward direction. Doppler OCT imaging of microchannels in vivo is also shown in a surgically exposed occluded artery in situ.

Modern image-guided surgery aids minimally-invasive, high-precision procedures that increase efficacy of treatment. This thesis investigates two research aims to improve precision and integration of intraoperative cone-beam CT (CBCT) imaging in guidance of head and neck (H&N) surgery. First, marker configurations were examined to identify arrangements that minimize target registration error (TRE). Best arrangements minimized the distance between the configuration centroid and surgical target while maximizing marker separation. Configurations of few markers could minimized TRE with more markers providing improved uniformity. Second, an algorithm for automatic registration of image and world reference frames was pursued to streamline integration of CBCT with real-time tracking and provide automatic updates per scan. Markers visible to the tracking and imaging systems are automatically co-localized and registered with equivalent accuracy and superior reproducibility compared to conventional registration. Such work helps the implementation of CBCT in H&N surgery to maximize surgical precision and exploit intraoperative image guidance.

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Image guidance is a common methodology of minimally invasive procedures. Depending on the type of intervention, various imaging modalities are available. Common imaging modalities are computed tomography, magnetic resonance tomography, and ultrasound. Robotic systems have been developed to enable and improve the procedures using these imaging techniques. Spatial and technological constraints limit the development of versatile robotic systems. This paper offers a brief overview of the developments of robotic systems for image-guided interventions since 2015 and includes samples of our current research in this field.

La réalisation de gestes percutanés dans l’IRM ouvre la voie à des pratiques médicales prometteuses. En revanche, l’utilisation de l’IRM reste à ce jour limitée, et ce malgré l’intérêt en terme de qualité d’image. Cela est dû principalement à l’étroitesse du tunnel et à la complexité des gestes réalisés. Pour rendre accessibles de telles pratiques, une assistance robotique semble très pertinente. Pour le concepteur, la réalisation d’un système robotisé compatible IRM n’est pas une tâche facile, étant donné l’espace disponible et la présence d’un champ magnétique intense. C'est dans ce contexte que nous avons développé un assistant robotique, MRGuide, dédié aux traitements du cancer de la prostate dans l’IRM. Il s'agit d'un manipulateur à câbles avec un actionnement déporté. Dans ce travail, de nombreuses contributions menant à la réalisation de ce prototypes ont présentées. Parmi celles‐ci, une instrumentation originale pour estimer la tension des câbles est proposée. Cette instrumentation est basée sur l’utilisation d’une structure en treillis, de mécanismes compliants et de capteurs de déplacement à technologie optique pour assurer la compatibilité avec le scanner. Pour optimiser la géométrie du robot et faciliter son intégration dans l'IRM, une démarche de conception des robots à câbles instrumentés est développée. Cette démarche est basée sur une approche par intervalles. D'autres contributions relatives à la caractérisation de l'espace de travail des robots à câbles instrumentés, à l'étalonnage des capteurs de tension et au développement d'une stratégie de commande adaptée au dispositif sont décrites. / Performing medical gestures under MRI is a promising medical approach. Todate, using MRI for interventions is still limited, despite the quality of the provided images. This limitation is mainly due to the confined physical space inside the tunnel and the complexity of the gestures. To make accessible such practices, a robotic assistance seems very relevant. However, it’s a challenge for the designer, given the limited space and the strong magnetic field inside the bore. In this context, we have developed an MR-‐compatible robotic assistant, named MRGuide, for prostate interventions. The robot is based on an original cable-­‐ driven manipulator with a remote actuation. In this work, many contributions leading to the development of MRGuide are presented. One of these contributions lies in the use of an original instrumented structure to evaluate the cables tensions. This instrumentation is based on the use of a truss structure, compliant mechanisms and optical displacement sensors for MRcompatibility. In order to optimize the size of the robot and facilitate its integration in the scanner, a new design methodology using interval analysis has been developed. Other contributions related to the workspace characterization of instrumented cable-­‐driven robots, the tension sensor calibration and the development of a new control strategy adapted to the device are described.