Combined Magnetomotive and Passive Cavitation Imaging Within Complex Ultrasound Flow Phantom

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown promise across a wide range of biomedical applications, including targeted drug delivery, magnetic hyperthermia, magnetic resonance imaging, and regenerative medicine. In the context of local tumor therapy (Magnetic Drug Targeting, MDT) SPIONs can be functionalized with chemotherapeutic agents and accumulated at tumor sites using an externally applied magnetic field. To achieve effective drug accumulation and therapeutic efficacy, precise positioning of the accumulation magnet relative to the tumor is essential. To address this need, we propose a dual-modality ultrasound imaging approach combining Magnetomotive Ultrasound (MMUS) and Passive Cavitation Mapping (PCM). MMUS detects magnetically induced tissue displacements, allowing localization of SPIONs embedded in tissue. However, MMUS is ineffective in vascular regions where no tissue displacement occurs. To overcome this, we use PCM to image circulating SPIONs, which are engineered to emit cavitation signals under focused ultrasound exposure. This complementary method enables SPIONs monitoring within tissue and flow. Validation was performed using standard phantoms and a custom-designed carotid bifurcation tumor flow phantom fabricated with 3D printing. Experimental results confirm that this hybrid strategy effectively images SPIONs in both tumor tissue and vasculature. This demonstrates the strong potential of complementary MMUS and PCM imaging for monitoring in preclinical and clinical MDT settings.