A quadratic particle swarm optimization method for magnetic tracking of tongue motion in speech disorders.

We have devised a new magnetic localization technique to accurately track 3-D tongue movements during speech and ingestion. A small permanent magnet secured on the tongue by tissue adhesives, is utilized as a tracer. The magnetic field variations due to tongue motion are detected by three 3-axis magneto-inductive sensor modules outside the mouth, and wirelessly transmitted to a computer for further processing. The tracer is modeled as a magnetic dipole, which position (x, y, z) and orientation (theta, y) are estimated using a quadratic particle swarm optimization (PSO) algorithm. This algorithm provides faster and more reliable computation compared to the linear PSO. Statistical analysis based on hundreds of simulation and experimental results show that using this method, calculations are accelerated by a factor of three and the tracer can be localized in real-time with approximately 1 mm resolution in position and 2 degrees in orientation.