@inproceedings{guo_jiang_2015, title={Enhancement of ultrasonic cavitation yield by dual frequency sonication}, DOI={10.1115/imece2014-39641}, abstractNote={This paper reports the experimental study on the enhanced cavitation yield via dual-frequency ultrasonic sonication and the multi-frequency single-bubble cavitation bubble modeling. The cavitation yield was characterized using the PCD (passive cavitation detection) method. A dual-frequency (1.5 MHz/3 MHz) pulse ultrasound was used in the tests. It was found that the sonication of dual-frequency ultrasound can produce a significant increase in cavitation yield compared with single-frequency irradiation. The possible mechanisms of the enhanced effect were explained by the single-bubble cavitation model, where the calculated radiated pressure generated by acoustic bubble cavitation was found greater in dual-frequency cases. The findings from this paper are promising for the design of multi-frequency ultrasound system with enhanced cavitation for a number of biomedical, biological and chemical processing applications.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, 2014, vol 3}, author={Guo, S. J. and Jiang, X. N.}, year={2015} }
 @article{suo_guo_lin_jiang_jing_2015, title={Thrombolysis using multi-frequency high intensity focused ultrasound at MHz range: an in vitro study}, volume={60}, ISSN={["1361-6560"]}, DOI={10.1088/0031-9155/60/18/7403}, abstractNote={High intensity focused ultrasound (HIFU) based thrombolysis has emerged as a promising drug-free treatment approach for ischemic stroke. The large amount of acoustic power required by this approach, however, poses a critical challenge to the future clinical translation. In this study, multi-frequency acoustic waves at MHz range (near 1.5 MHz) were introduced as HIFU excitations to reduce the required power for treatment as well as the treatment time. In vitro bovine blood clots weighing around 150 mg were treated by single-frequency and multi-frequency HIFU. The pulse length was 2 ms for all experiments except the ones where the duty cycle was changed. It was found that dual-frequency thrombolysis efficiency was statistically better than single-frequency under the same acoustic power and excitation condition. When varying the acoustic power but fixing the duty cycle at 5%, it was found that dual-frequency ultrasound can save almost 30% power in order to achieve the same thrombolysis efficiency. In the experiment where the duty cycle was increased from 0.5% to 10%, it was shown that dual-frequency ultrasound can achieve the same thrombolysis efficiency with only half of the duty cycle of single-frequency. Dual-frequency ultrasound could also accelerate the thrombolysis by a factor of 2–4 as demonstrated in this study. No significant differences were found between dual-frequencies with different frequency differences (0.025, 0.05, and 0.1 MHz) and between dual-frequency and triple-frequency. The measured cavitation doses of dual-frequency and triple-frequency excitations were at about the same level but both were significantly higher than that of single-frequency.}, number={18}, journal={PHYSICS IN MEDICINE AND BIOLOGY}, author={Suo, Dingjie and Guo, Sijia and Lin, Weili and Jiang, Xiaoning and Jing, Yun}, year={2015}, month={Sep}, pages={7403–7418} }
 @article{guo_suo_jing_jiang_frank_lin_2014, title={Thrombolysis enhanced by dual-frequency high-intensity focused ultrasound}, ISSN={["1948-5719"]}, DOI={10.1109/ultsym.2014.0541}, abstractNote={It has been demonstrated that high-intensity focused ultrasound can be an efficient method to induce thrombolysis. Excessive thermal effect on neighboring tissue is however a concern. The goal of this work is to test the efficacy of dual-frequency ultrasound-induced thrombolysis, with the aim to reduce the acoustic power required to achieve the same lysis rate (mass loss of blood clots over time) as single-frequency ultrasound. In vitro clots of mouse blood were prepared and placed at the focus of two piezoelectric ultrasound transducers (center frequencies were 0.95 MHz and 1.5 MHz, respectively). 0.65 W ultrasound waves with 10% duty cycle were employed in both single- and dual-frequency ultrasound exposures. The mass losses of the clots were recorded to obtain the lysis rate after each test. It was found that dual-frequency results in more efficient thrombolysis. Cavitation bubble modeling was also conducted for both single- and dual-frequency ultrasound to explain the experimental founding.}, journal={2014 IEEE INTERNATIONAL ULTRASONICS SYMPOSIUM (IUS)}, author={Guo, Sijia and Suo, Dingjie and Jing, Yun and Jiang, Xiaoning and Frank, Jonathan and Lin, Weili}, year={2014}, pages={2173–2176} }
 @article{ma_guo_wu_geng_jiang_2013, title={Design, Fabrication, and Characterization of a Single-Aperture 1.5-MHz/3-MHz Dual-Frequency HIFU Transducer}, volume={60}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2013.2724}, abstractNote={High-intensity focused ultrasound (HIFU) treatment efficiency is critical in maximizing the hyperthermia and reducing the surgery time. In this paper, a single-aperture, 1.5 MHz/3 MHz dual-frequency HIFU transducer was designed, fabricated, and characterized for tissue ablation enhancement. Double PZT-2 layers were configured in serial and dual-frequency ultrasound waves can be concurrently generated by exciting one of the PZT-2 layers. Impulse responses from the prototype showed that the wave amplitudes at 1.5 and 3 MHz were about the same, and both are more than 12 dB larger than those of higher orders of harmonics. Tissue ablation tests demonstrated that higher temperature rise can be achieved with dual-frequency ultrasound than with single-frequency ablation at the same acoustic power.}, number={7}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Ma, Jianguo and Guo, Sijia and Wu, Di and Geng, Xuecang and Jiang, Xiaoning}, year={2013}, month={Jul}, pages={1519–1529} }
 @article{guo_jing_jiang_2013, title={Temperature Rise in Tissue Ablation Using Multi-Frequency Ultrasound}, volume={60}, ISSN={["1525-8955"]}, DOI={10.1109/tuffc.2013.2751}, abstractNote={High-intensity focused ultrasound (HIFU) is becoming an increasingly important noninvasive surgical tool, despite the challenges in temperature rise control and unwanted heating problems. In this study, experiments and simulations on tissue ablation effectiveness were performed using multi-frequency HIFU with frequency differences of more than 500 kHz (center frequencies are 950 kHz, 1.5 MHz, and 3.3 MHz). In the experiments, the temperature was recorded as chicken breast tissue was heated by single-frequency, dual-frequency, and tri-frequency HIFU configurations at controlled acoustic power and exposure time. 5% to 10% temperature rise differences were observed between single- and multi-frequency modes, indicating that multi-frequency HIFU is more effective at producing faster temperature rises. Cavitation detection tests were conducted to compare the cavitation pressure fields between single- and multi-frequency ultrasound. Moreover, simulations on single-frequency and multi-frequency acoustic fields as well as bio-heating-induced temperature fields were performed. With the comparison between experimental and simulation results, we believe that the more effective tissue ablation using multi-frequency ultrasound is likely attributed to the enhanced cavitation, a promising result for HIFU applications.}, number={8}, journal={IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL}, author={Guo, Sijia and Jing, Yun and Jiang, Xiaoning}, year={2013}, month={Aug}, pages={1699–1707} }
 @inproceedings{bakshi_guo_jiang_2012, title={Multi-frequency focused ultrasound for tissue ablation}, DOI={10.1115/imece2011-64076}, abstractNote={In this study, the effectiveness of tissue ablation was investigated using multi-frequency high intensity focused ultrasound (HIFU) transducers (950 kHz, 1.5 MHz). Temperature rise and lesion volume were recorded when chicken tissue was ablated by focused ultrasound (FUS) with controlled ultrasound power and exposure time using single frequency and multi-frequency modes. It was found that multi-frequency tissue ablation gives a higher maximum temperature accompanied by a faster rise, and a larger ablation lesion volume, compared with single frequency ablation, under the same input conditions of electrical power, exposure time and depth of focus. Also, it was concluded that the same desired tissue temperature and ablation lesion conditions can be attained by using less power for the multi-frequency ablation. These findings are promising because the multi-frequency ultrasound ablation using FUS with a greater frequency difference could result in promising imaging guided effective therapy using one multi-frequency probe.}, booktitle={Proceedings of the ASME International Mechanical Engineering Congress and Exposition, vol 2}, author={Bakshi, S. and Guo, S. J. and Jiang, X. N.}, year={2012}, pages={665–670} }