Structure and 3-D Model of a Solid State Thin-Film Magnetic Sensor

Vector 3-D magnetic sensors form the basis of measurement devices for magnetic field mapping and magnetic tracking. Typically, such sensors utilize specific constructions based on split Hall structures (SHS). An SHS-based 3-D magnetic sensor is a bulk semiconductor integrated structure with 8 or more contacts. Combining current flow directions through the contacts and measuring the corresponding voltages, one defines projections BX, BY, BZ of the magnetic field vector. This work presents a novel design of 3-D solid state magnetic sensors that requires no insulation by p-n junctions and can be implemented by thin-film technology traditionally used for fabrication of Hall sensors including those based on InSb films. Besides, a SPICE model of the 3-D magnetic sensor is provided, which helps design the proposed sensor and refine techniques of its calibration.

Towards Tracking of Deep Brain Stimulation Electrodes Using an Integrated Magnetometer

This paper presents a tracking system using magnetometers, possibly integrable in a deep brain stimulation (DBS) electrode. DBS is a treatment for movement disorders where the position of the implant is of prime importance. Positioning challenges during the surgery could be addressed thanks to a magnetic tracking. The system proposed in this paper, complementary to existing procedures, has been designed to bridge preoperative clinical imaging with DBS surgery, allowing the surgeon to increase his/her control on the implantation trajectory. Here the magnetic source required for tracking consists of three coils, and is experimentally mapped. This mapping has been performed with an in-house three-dimensional magnetic camera. The system demonstrates how magnetometers integrated directly at the tip of a DBS electrode, might improve treatment by monitoring the position during and after the surgery. The three-dimensional operation without line of sight has been demonstrated using a reference obtained with magnetic resonance imaging (MRI) of a simplified brain model. We observed experimentally a mean absolute error of 1.35 mm and an Euclidean error of 3.07 mm. Several areas of improvement to target errors below 1 mm are also discussed.