Evaluation of the dual-frequency transducer for controlling thermal ablation morphology using frequency shift keying signal

• Published in: International journal of hyperthermia 2022-12, Vol.39 (1), p.1344-1357
• Main Authors: Huang, Wenchang, Ning, Chuanlong, Zhang, Rui, Xu, Jie, Chen, Beiyi, Li, Zhangjian, Cui, Yaoyao, Shao, Weiwei
• Format: Article
• Language: English
• Subjects: catheter-based ultrasound; FSK; heating effect; High intensity ultrasound; interventional therapy; thermal ablation
• ISSN: 0265-6736; 1464-5157
• DOI: 10.1080/02656736.2022.2130999

The catheter-based ultrasound (CBUS) can reach the target tissue directly and achieve rapid treatment. The frequency shift keying (FSK) signal is proposed to regulate and evaluate tumor ablation by a miniaturized dual-frequency transducer. A dual-frequency transducer prototype (3 × 7 × 0.4 mm) was designed and fabricated for the CBUS applicator (OD: 3.8 mm) based on the fundamental frequency of 5.21 MHz and the third harmonic frequency of 16.88 MHz. Then, the acoustic fields and temperature field distributions using the FSK signals (with 0, 25, 50, 75, and 100% third harmonic frequency duty ratios) were simulated by finite element analysis. Finally, tissue ablation and temperature monitoring were performed in phantom and ex vivo tissue, respectively. At the same input electrical power (20 W), the output acoustic power of the fundamental frequency of the transducer was 10.03 W (electroacoustic efficiencies: 50.1%), and that of the third harmonic frequency was 6.19 W (30.6%). As the third harmonic frequency duty ratios increased, the shape of thermal lesions varied from strip to droplet in simulated and phantom experimental results. The same trend was observed in ex vivo tests. Dual-frequency transducers excited by the FSK signal can control the morphology of lesions. The acoustic power deposition of CBUS was optimized to achieve precise ablation.