Magnetomotive Ultrasound: Magnet Design and Optimization for Broader Applications

Magnetomotive ultrasound (MMUS) is a contrast-enhanced imaging technique that uses magnetic nanoparticles (MNPs) as tracers. To identify labeled regions, MNPs bound to tissue are driven by a temporally modulated magnetic force, and the resulting tissue motion is detected via ultrasound. MMUS has shown promise for applications ranging from blood clot detection and elastometry to cancer diagnosis and drug delivery. However, challenges remain in magnet design and placement.

 

Implementations using small solenoids positioned opposite the ultrasound transducer and directly against the sample can produce strong signals but encroach on the imaging area, limiting sample size. In contrast, “open-air MMUS” configurations, which place solenoids on the transducer side, enable much larger imaging areas but at the cost of reduced signal strength.

 

This talk presents a finite element analysis (FEA) model developed to guide MMUS magnet design and optimization. Model results, supported by experimental validation, demonstrate multiple simple strategies for improving magnetic performance. For instance, adding two small, precisely positioned permanent magnets more than doubled the signal strength in an existing MMUS system. Further exploration is expected to produce new magnet configurations leading to further clinical applications for this exciting new imaging modality.