Proposal of a Method for Estimating the Position of Ferromagnetic Markers under Magnetization Conditions

In the treatment of early-stage breast cancer, breast-conserving surgery is performed to remove only the tumor while preserving the original breast shape as much as possible. In a previous study by our research group, a hand-held magnetic probe [1] was developed to achieve high sensitivity by simultaneously measuring the magnetic field and enhancing magnetization with a permanent magnet in order to accurately determine the tumor location during surgery. However, the hysteresis curve of the magnetization of the magnetic marker to be enhanced changes from moment to moment in a complex manner according to the way the probe is moved and its history, making it difficult to estimate the position using the forward problem method. In this study, we propose a position estimation method that combines an inverse problem solution and a magnetization model, and show that the estimable distance can be extended within an error range of 1 mm in the presence of magnetization enhancement by a permanent magnet.