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On-chip magnetic sensor and readout design for 3D position tracking in image-guided interventions
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Date
2025
Authors
Srivastava, Manish
Journal Title
Journal ISSN
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Publisher
University College Cork
Published Version
Abstract
Electromagnetic tracking (EMT) technology is integral to complex medical procedures, providing precise real-time tracking of surgical instruments while reducing dependence on radiation-based imaging. EMT is particularly beneficial in various image-guided interventions, enhancing accuracy and safety. Despite its advantages, EMT has not been widely adopted in common procedures such as laparoscopic surgery and non-robotic endoscopy due to the prohibitive cost of the sensors, which range from approximately $25 for 5-degrees-of-freedom (DoF) devices to around $250 for 6-DoF devices. This thesis proposes a cost-effective solution using compact 0.5 mm wide and 2.3 mm long on-chip magnetic sensors. The on-chip magnetic sensor includes a state-of-the-art low-noise analog-front-end (2.07 nV/√Hz) and a low-area continuous-time delta-sigma analog-to-digital converter (ADC) (0.07 mm2). The readout circuit also incorporates essential power management blocks such as a bandgap reference (BGR) and a low-dropout regulator (LDO), along with a low-voltage differential signaling (LVDS) driver for minimal signal distortion and an on-chip clock source. These integrated components reduce the pin count and contribute to the compactness of the on-chip sensor. This on-chip magnetic sensor is employed for 5-DoF magnetic tracking (x, y,z, yaw, and pitch). These sensors are both affordable and practical for real-world applications. The proposed on-chip sensor’s small size and cost-effectiveness facilitate seamless integration into existing magnetic navigation systems without significant modifications, reducing the scalable cost to an estimated $1.50, compared to approximately $25 for existing discrete 5-DoF sensors. Furthermore, the on-chip sensor offers a digital readout, enhancing robustness compared to wire-wound sensors with analog readouts. This work also presents 6-DoF tracking (x, y, z, yaw, pitch, and roll angles) that combines low-cost on-chip sensors with wire-wound sensors featuring ferromagnetic core devices. This hybrid system provides a cost-effective, compact, and competitive solution in terms of form factor. Utilising low-frequency magnetic fields to detect the position and orientation
of instruments, this sensor provides a viable alternative to X-rays in image-guided surgery. Fabricated using 65 nm CMOS technology and occupying an area of 1.06 mm2, the 5-DoF system navigates with a precision of 1.1 mm within a 15×15×15 cm3 volume of interest, while the 6-DoF system achieves a navigation accuracy of 0.8 mm and an angular error of 1.1◦. The prototype sensor successfully demonstrated its ability to accurately track positions for in vivo settings, with a worst-case registration accuracy of 5.8 mm, primarily due to patient motion artifacts rather than tracking inaccuracies. These advancements significantly enhance the precision and cost-effectiveness of electromagnetic tracking in medical procedures, offering new possibilities for improving patient care.
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Keywords
Electromagnetic tracking , On chip magnetic sensor , Image guided interventions , Analog front end readout , CCIA , Adder-Less Continuous-Time ΔΣ Modulator
Citation
Srivastava, M. 2025. On-chip magnetic sensor and readout design for 3D position tracking in image-guided interventions. PhD Thesis, University College Cork.