Multi-Amplitude Modulation Frequency in Harmonic Motion Imaging Guided Focused Ultrasound (HMIgFUS) on Ablated Lesion...

Harmonic Motion Imaging (HMI) is an ultrasound acoustic radiation-force (RF) based elasticity imaging technique, in which tissue displacement is induced at a specified frequency. HMI guided Focused Ultrasound (HMIgFUS) uses HMI to track FUS ablation induced changes in tissue displacement. In this study, we use a multi-frequency amplitude modulated (AM) signal to investigate the effect of AM frequency in HMIgFUS lesion monitoring.

HMI imaging was performed in a tissue-mimicking phantom with embedded inclusions to investigate the relationship between HMI AM frequency and inclusion size estimation. Multi-AM frequency HMIgFUS was performed in 15 4T1-luciferase model mice.

In phantom imaging, HMI displacement spatial distribution was found to vary in area across frequencies, such that lower AM frequencies required smaller cutoff thresholds (around -3 dB) for optimal lesion size estimation, while higher AM frequencies required larger thresholds (-4 to -8 dB). In the breast cancer mouse model, there was a significant positive correlation between HMIgFUS displacement percent change and HMI imaging percent change conducted prior to and post HMIgFUS, indicating that real-time HMIgFUS monitoring at selected AM frequencies can be used to predict FUS lesion development. HMI displacement imaging performed 1 week following HMIgFUS treatment showed a significant difference in displacement between treated and control mice, suggesting longitudinal tissue changes following HMIgFUS ablation. Finally, mice who received HMIgFUS treatment experienced slower tumor growth and longer survival time compared to control mice.

We developed a multi-AM frequency HMIgFUS technique for improved ablation lesion monitoring, and showed slower tumor growth and improved survival in mice treated with multi-AM frequency HMIgFUS.