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Haptic feedback system design for MR-guided needle intervention [electronic resource]

Advances in imaging are leading to new opportunities for medical diagnosis and treatment, including the possibility to perform procedures such as biopsies while a patient is undergoing imaging. Along with these new opportunities come new challenges. In particular, for patients undergoing magnetic resonance (MR) imaging, the geometry of the MR machine makes it difficult to perform procedures. One solution is to provide robotic or teleoperated equipment that can fit in the remaining space between a patient and the inner walls of the MR bore and manipulate tools such as biopsy needles. A physician stands near the MR machine, viewing live images and controlling the robotic equipment within. However, in this scenario the physician lacks the tactile sensitivity that she would have if manipulating a needle with her own hands. This thesis presents technology to provide haptic feedback to a physician operating a master device that controls a robotic system for MR-guided procedures. The first part of the solution is a new biopsy needle instrumented with optical fibers with Bragg gratings. The needle is equipped with features to enhance its sensitivity to forces applied at the tip of the needle. The optical fibers are unaffected by the intense MR field, and the needle produces no imaging artifacts beyond those of a standard biopsy needle. The second part of the thesis introduces two different types of haptic displays that present the radial and axial forces, respectively, from the instrumented needle. The radial forces provide guidance to users attempting to target small, compliantly-supported objects (e.g. tumors) in tissue. The axial forces provide users with the ability to detect when the tip of the needle has contacted bone or punctured a membrane. In both cases, the displays use materials and actuators that are MR-compatible. Controlled experiments confirm that human subjects can use the information provided by the displays to improve targeting accuracy and to detect membrane contact. An additional experiment shows that force information provided by the needle can reveal changes in tissue texture, for example, when passing through healthy or fibrotic liver tissue.