PhD Thesis Defense

Zoom Link: https://caltech.zoom.us/j/8246433520

Medical electronic devices are an integral part of the healthcare system today. Significant advances have been made over the past few decades to yield ultra-low power and highly miniaturized form-factors for such devices. A key feature that is central to the use of medical devices in many applications is the capability to locate them precisely inside the body. Location sensing is crucial in several areas: tracking pills in the GI tract, navigation during precision surgeries, endovascular procedures, robotic and minimally invasive surgery, and targeted therapy. The current gold-standard solutions for these procedures include invasive techniques such as endoscopy, or procedures that require repeated use of potentially harmful X-ray radiation such as CT scans. These techniques also require frequent evaluation in a hospital setting and are not conducive for non-clinical environments.

In this dissertation, we present a radiation-free system for high-precision localization and tracking of miniaturized wireless devices in-vivo, using harmless magnetic field gradients. First, we demonstrate our system for application in precision surgeries. We designed highly miniaturized, wireless and battery-less microdevices, capable of measuring and transmitting their local magnetic field. Planar electromagnetic coils are designed for creating monotonically varying magnetic fields in X, Y and Z, resulting in field gradients that uniquely encode the spatial position of the microdevices. The system is tested in-vitro to demonstrate a localization accuracy of <100mm in 3D, the highest reported to the best of our knowledge. Second, we perform localization and tracking of ingestible microdevices in the GI tract in real time and in non-clinical settings, with mm-scale spatial resolution, and without using any X-ray radiation. The system functionality is demonstrated in-vivo in large animals under different chronic conditions and disease models. This could be of significant clinical benefit for diagnosis and treatment of GI disorders such as constipation, incontinence, motility disorders, medication adherence monitoring, and quantitative assessment of GI transit-time. Third, in order to further miniaturize our medical devices and to reduce the power consumption, we present a monolithic 3D magnetic sensor in 65nm CMOS technology that measures 4mm2 and consumes 14.8µW while achieving <10μTrms noise. Our novel 3D magnetic sensor overcomes the challenges faced by traditional magnetic sensors by being fully CMOS compatible and achieves high sensitivity with only µW-level power. We demonstrate the use of our sensor for tracking catheters and guidewires during endovascular procedures, and show potential towards minimally invasive surgeries, targeted radiotherapy, and preoperative planning.