A Virtual Ultrasonography Simulator for Skill Training Using Magnetic-Inertial Probe Tracking

Simulation-based ultrasonography training has been proven to be effective for novice practitioners to acquire operation skills. However, existing simulators are cumbersome, expensive, and sometimes fail to provide intuitive and interactive training experience. In this article, a compact, inexpensive, and interactive ultrasonography simulator is developed using magnetic-inertial 6-degree of freedom (DoF) probe pose tracking and virtual ultrasound image generation. Embedded with magnetic and inertial sensors, the sham ultrasound probe is tracked by fusing magnetic measurement of a single electromagnet embedded in the phantom and inertial measurement of the probe. Then the virtual scan plane is determined according to the estimated probe pose to slice the digital anatomical model for virtual image generation, providing visual feedback for skill training. The probe tracking accuracy is experimentally validated to be sufficiently accurate for correct image generation with the RMS position error of 3.67 mm and average orientation error of 0.74^\circ . The interactive performance of the simulator is evaluated by volunteer tests, showing shortened task completion time (40.68 s versus 50.46 s) and slightly improved accuracy of reaching target views compared to the slider control method. It is also shown that an inexperienced operator can learn to successfully acquire standard and diagnostic views of fetal hearts with congenital diseases. Due to intuitive freehand interaction, accurate probe tracking, and real-time visual guidance of ultrasound images and three-dimensional (3-D) virtual scene of the probe and anatomy, the proposed simulator can provide immersive training experience for quick ultrasound skill acquirement.