Coherence Factor Weighted Third Degree Delay Multiply and Sum Passive Cavitation Mapping for Magnetic Nanoparticle Visualization

Ultrasound-induced cavitation is a fundamental physical phenomenon for histotripsy, lithotripsy, and local drug delivery. Magnetic nanoparticles (MNPs) enable magnetically assisted cancer therapy (Magnetic Drug Targeting, MDT) and can be used as cavitation nuclei. While MDT has shown promising results in preclinical studies, there remains a need for a real-time monitoring system. Here, we introduce a GPU-accelerated passive cavitation mapping (PCM) method that pairs a third-degree delay-multiply-and-sum beamformer (DMAS3) with coherence-factor weighting (CFwDMAS3) to enhance spatial localization and suppress off-axis incoherent emissions. We evaluated the approach in a flow-channel phantom perfused with lauric-acid–coated MNPs under pulsed focused ultrasound, and complemented the experiments with simulations based on Vokurka’s bubble-dynamics model. Reconstructions using Delay and Sum (DAS), Delay Multiply and Sum (DMAS), and DMAS3, each with and without CF weighting, were assessed using ROC metrics (AUROC, sensitivity, specificity) and precision measures (PPV, F1-score). CF weighting consistently produced sharper maps and higher specificity; CFwDMAS3 achieved the best overall balance and supported real-time visualization (approximately 0.1 s per frame) on a GPU. These results indicate that CFwDMAS3 PCM is a practical solution for monitoring MNP-mediated cavitation during MDT and related therapeutic ultrasound procedures.