RESUMO
OBJECTIVES: The puncture needle of an intelligent puncture robot must accurately reach the target location early in the diagnosis of benign and malignant nodules and in the puncture ablation of malignant tumors. To track the position and the orientation of the puncture needle tip, an electromagnetic tracking system based on adaptive adjustment of excitation intensity and lock-in amplification is proposed. METHODS: The system includes a time-sharing excitation device with multiple magnetic sources, a magnetic sensor, a signal processing device based on dual-phase lock-in amplifiers and a computing platform in the upper computer. With adaptive adjustment of excitation intensity, the time-sharing excitation device uses a microcontroller to control a direct digital synthesizer. Based on feedback from the magnetic sensor, the microcontroller time-shares the power amplifier to generate the required excitation current. Dual-phase lock-in amplifiers demodulate the magnetic sensor output after preamplification and filtering. Through analog-to-digital conversion and the serial interface, the digital signal is sent to the computing platform for solving by neighborhood particle swarm optimization algorithm, and the position and orientation of the puncture needle fixed with the magnetic sensor are obtained. RESULTS: The experimental results within a 300 mm×300 mm×300 mm space show average position errors of 0.4467 cm (X-axis), 0.4154 cm (Y-axis), and 0.3766 cm (Z-axis). The overall average position error is 0.4129 cm, with a root mean square error of 0.4970 cm. CONCLUSIONS: The proposed electromagnetic tracking system can track the needle position and orientation of puncture robots in real-time, thereby enhancing puncture success rates and reducing puncture times.
