Magnetic characteristics of a magnetic marker for localized tumor excision with a handheld magnetic probe

Abstract

To excise the non-palpable breast lesion, conventionally surgeons estimate the excision margin by naked eyes subjectively with a localization tool such as a hook wire. By introducing a magnetic detection system, location of the magnetic marker injected intratumorally can be identified with a handheld magnetic probe. Detection ranges of existing magnetic markers are up to 30 mm, limiting applications on tumors located deeper down the skin. In this study, materials and designs of magnetic markers are evaluated to achieve an extended detection range. Stainless steel (SUS) 304 is magnetic and biocompatible for an implant device, and a SQUID measurement is performed to evaluate its magnetic properties. A numerical simulation tool has been developed to evaluate the magnetic field strength induced by the magnetic marker from any orientation. Based on a backward-facing hook shape design, magnetic field strength induced by the marker with varies hook length and separation angle between the hook and the main body is evaluated. At an extended distance of 40 mm, the detection of the magnetic marker with 8 mm hook length and 75° separation angle can be achieved on 57% of the orientations.