Wireless Electromagnetic Sensors for Image-Guided Cardiothoracic Procedures

Electromagnetic tracking (EMT) is essential in surgical navigation without line of sight and to reduce the use of harmful radiation-based imaging. The inductive sensors used in current EMT systems are small, often less than a millimeter in diameter, but the need for a wired connection from the sensor to the control unit can cause obstructions and complicate the surgical field. This work introduces a novel wireless method of tracking electromagnetic (EM) sensors with immediate applications intended to streamline surgical workflows. Wireless EM 6-degree-of-freedom (DOF) sensor nodes were designed and manufactured with the intended use as a patient-mounted registration device. The battery-powered prototype device was shown to have a position and orientation trueness of 0.84 mm and 0.7 degrees, respectively, over a tracking volume of $40\times 40\times 35$ cm. The sensor node performs analog and digital signal processing and uses bluetooth low energy (BLE) to transmit the sensor data at a 25-Hz refresh rate. The Bluetooth-based wireless EM sensor nodes developed in this work have comparable performance to standard wired sensors and were tested in both a static volume characterization and a dynamic ex vivo lung model. The work in this article is based on the open-source Anser EMT system although the approach can be generalized to any tracking system. Wireless EMT offers the potential to introduce computer-assisted navigation in surgical procedures where wired sensors were previously infeasible.