Exploring the Postactivation Behavioral Patterns of Intratumorally Injected Theranostic Nanodroplets: An Ultrasound-Only Extravascular Monitoring Technique

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 71; no. 10; pp. 1186 - 1198
• Main Authors: Huang, Anqi, Jia, Ziyan, Wu, Haitao, Feng, Kangyi, Zhang, Chaonan, Wan, Mingxi, Zong, Yujin
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.10.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic postactivation behavioral patterns; Acoustics; Boiling points; Controllability; Foci; Frequency control; high-bulk-boiling-point phase-change nanodroplets (HBP PCNDs); Imaging; In vivo methods and tests; intratumoral injection; Monitoring; Pattern analysis; Pattern recognition; Pharmacology; Physiological effects; Probes; recondensation; Thermal stability; Tumors; Ultrasonic imaging; ultrasound extravascular monitoring
• ISSN: 0885-3010; 1525-8955; 1525-8955
• DOI: 10.1109/TUFFC.2024.3450885

Phase-change nanodroplets (PCNDs) are customizable and controllable theranostic agents of particular interest in extravascular therapies such as drug delivery and histotripsy. High-bulk-boiling-point (HBP) PCNDs are preferred for their enhanced thermal stability under physiological temperature to achieve on-demand therapeutic effects on target sites-mainly in tumor tissue. However, the behavioral patterns of high-concentration, heterogeneously distributed HBP PCNDs in vivo have rarely been explored-the foci of PCND-related therapies mostly fall on the final therapeutic effect rather than the detailed behaviors of PCNDs, which may hamper the development and improvement of in vivo treatments with PCNDs. To fill the gap, we demonstrate an ultrasound-only extravascular monitoring technique to analyze the underlying behavioral patterns of intratumorally injected HBP PCNDs. In our hypothesis, recondensation and coalescence are the two predominant patterns influencing the trend of the postactivation signal of PCNDs. A "blink map" method was, thus, proposed to separate the two parts of the signal by recognizing the unique signal pattern of stochastic recondensation, and four derivative metrics were calculated for further analysis. The results revealed the postactivation patterns of PCNDs at different activation-pulse durations and activation stages throughout the activation-imaging period, and several general trends were observed and explained by existing theories, suggesting the feasibility of our extravascular monitoring technique. Overall, this work enriches the knowledge of the characteristics of HBP PCNDs as extravascular theranostic agents, and the monitoring results have the potential to provide timely feedback on PCND-related treatments underway, which may help adjust the treatment strategy and improve the therapeutic efficacy.