Abstract
Background : We thought that moving a small neodymium magnet would promote migration of the magnetic tracer to the sentinel lymph node (SLN). Higher monitoring counts on the skin surface before incision help us detect SLNs easily and successfully. The aim of the present study was to verify enhancement of the monitoring count on the skin surface in SLN detection by the magnet movement in sentinel lymph node biopsy (SNB) using superparamagnetic iron oxide (SPIO) nanoparticles. Methods: After induction of general anesthesia, superparamagnetic iron oxide nanoparticles were injected sub-dermally into the subareolar area or peritumorally. The neodymium magnet was moved over the skin from the injection site to the axilla to promote migration of the magnetic tracer without massage. A total of 62 patients were enrolled from February 2018 to November 2018; 13 cases were given 20 times magnet movement (Group A), 8 cases were given 1-min magnet movement (Group B), 26 cases were given a short (about 5 min) interval from injection to 1-min magnet movement (Group C), and 15 cases were given a long (about 25 min) interval before 1-min magnet movement by the magnetometer’s head (Group D). In all cases, sentinel node biopsy was conducted using both the radioisotope (RI) and SPIO methods. The monitoring counts on the skin surface were measured by a handheld magnetometer and compared among the 4 groups. Changes in the monitoring count by interval and by magnet movement were evaluated. Results: The identification rates of the SPIO and RI methods were 100% and 95.2%, respectively. The mean monitoring counts of Group A, B, C, and D were 2.39 μT, 2.73 μT, 3.15 μT, and 3.92μT, respectively (p<0.0001; Kruskal-Wallis test) . The monitoring counts were higher with longer magnet movement and with the insertion of an interval. Although there were no relationships between the monitoring count on the skin surface and clinicopathologic factors, magnet movement influenced strongly on the monitoring count on the skin surface. Conclusion: Moving a small neodymium magnet is effective for promoting migration of a magnetic tracer and increasing monitoring counts on the skin surface.
Pre-operative sentinel lymph node localization in breast cancer with superparamagnetic iron oxide MRI: the SentiMAG Multicentre Trial imaging subprotocol
