International Journal on Magnetic Particle Imaging
Vol 8 No 1 Suppl 1 (2022): Int J Mag Part Imag

Short Abstracts

Assessing excitation field frequency for various magnetic nanoparticles

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Melissa M. Horstman - van de Loosdrecht  , Tamara Kahmann , Frank Ludwig  (Braunschweig University of Technology), Lejla Alic , Bennie ten Haken 


Magnetic detection is presently used in a handheld probe to identify metastasis bearing lymph nodes (LNs) fora variety of oncology applications. This approach utilises the underlying assumption that injected magneticnanoparticles (MNPs) will migrate to LNs with the shortest path to a tumor and therefore will generate a localizedmagnetic signal. Nonlinear magnetic detection is specific for magnetic nanoparticles and negates the influenceof human tissue and surgical instruments. Our nonlinear DiffMag principle uses a combination of an AC and DCmagnetic field to activate MNPs and records the consequent magnetic signal. MNP detection can be optimised tomaximise detection parameters, such as iron sensitivity and detection depth. Tuning the excitation field frequencyto physical properties of MNPs (such as particle diameter) leads to improved detection.This study assesses the magnetic properties of various MNPs (SHP15, SHP20, SHP25, SHP30) and compare thefindings to clinically available MNP (Magtrace®). Magnetization response of these MNPs was acquired using theSuperParamagnetic Quantifier (SPaQ) at various AC field frequencies (1, 2.5, 5, 7.5, 10, 12.5 and 15 kHz). Two featurescapturing magnetization response (maximum signal difference and full width at half maximum) were extracted tocompare MNPs. Additional acquisition captured AC susceptibility (ACS) in the range 10Hz-1MHz.SPaQ results show an optimal excitation frequency between 5 and 12.5 kHz for the various types of MNPs. ACSresults show small particles (SHP15) are Néel dominated, large MNPs (SHP30) are Brownian dominated and thesizes in between show a combination of Néel and Brownian relaxation. The larger, Brownian dominated MNPsperform best in nonlinear magnetic detection.

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