International Journal on Magnetic Particle Imaging IJMPI
Vol. 11 No. 1 Suppl 1 (2025): Int J Mag Part Imag
Evaluating Magnetic Staging Following Sentinel Lymph Node Biopsy: The LowMag Trial
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Copyright (c) 2025 Sadaf Salamzadeh, Anke Christenhusz, Heleen.S van Nie, Anneriet E. Dassen, Erik Krooshoop, Bennie ten Haken, Lejla Alic
This work is licensed under a Creative Commons Attribution 4.0 International License.
Abstract
Background: Accurate identification of metastatic lymph nodes (LNs) is essential for cancer prognosis and treatment planning. In the LowMag clinical trial [1], a magnetic sentinel lymph node biopsy (SLNB) procedure was introduced for patients with invasive breast cancer. Difference between metastatic and non-metastatic LNs was assessed using amount of iron captured in individual LNs and their respective AC susceptibility (ACS).
Methods: Two magnetic devices—the superparamagnetic quantifier (SPaQ) [1,2] and the differential magnetometer handheld (DMH) probe [1,3] —were used to measure iron content and ACS in individual LNs. Additionally, ex vivo LN imaging was performed using a low-field MRI system [1,4], followed by detailed histopathological analysis. A total of 33 LNs from 18 consecutive patients, including four metastatic nodes, were examined.
Results: The low-field MRI findings and histopathological analysis of iron levels were consistent with measurements obtained from SPaQ and DMH probe. A significant difference in iron content was observed between metastatic LNs (DMH: 203.12 ± 87.67 µg; SPaQ: 131.28 ± 53.38 µg) and non-metastatic LNs (DMH: 92.47 ± 89.8 µg; SPaQ: 42.45 ± 46.9 µg). Furthermore, combining two features extracted from the ACS curve—Full Width at Half Maximum (FWHM) and peak values—resulted in a sensitivity of 75.0%, a specificity of 96.6%, and an overall accuracy of 93.9%.
Conclusion: This study suggests that the DiffMag method may offer precise detection of non-metastatic LNs. Additionally, SPaQ in both DiffMag and ACS mode, exhibits higher specificity and greater accuracy than the DMH probe due to its unique design.
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References
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3. S. Waanders, et al, A handheld spio-based sentinel lymph node mapping device using differential magnetometry, Phys Med Bio, 2016.
4. A. Christenhusz, et al, Ex vivo lymph node staging by a portable low-field MRI scanner, In Proceedings of the Joint Annual Meeting ISMRM–ISMRT, Toronto, Canada, 2023.