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Diagnostic Ultrasound
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Later a more elaborate way to push on tissue was developed. Here, the sound itself executes the push, by the effect known as acoustic radiation force. This is the result of the transfer of momentum from a sound wave in a medium, where the attenuation causes pressure and particle velocity to become out of phase. The result is a force in the propagation direction, which in a fluid is expressed as a flow (acoustic streaming), while in tissue it will be experienced as a displacement. Now, this displacement for a given sound intensity is dependent on the tissue elasticity. For example, the displacement in tumorous tissue would be smaller. Pulses used for imaging purposes do create a push as well, but it is too small to be used. Instead, a longer pulse, or even from a separate focused transducer is used.
A Perspective of Ultrasound-Related Micro/Nano Cancer Therapy
Published in Hala Gali-Muhtasib, Racha Chouaib, Nanoparticle Drug Delivery Systems for Cancer Treatment, 2020
Tingting Zheng, Yun Chen, Jiao Peng, Yu Shi, Jun Zhang, Haitao Xiao, Xiangmei Chen, Yongcan Huang, Tao Pei, Zhuxia Zhang, Xue Zhang, Xiaohe Bai, Li Liu, Jinrui Wang
Different from ultrasound thermal effect, which is about heat, ultrasound is believed to be able to transfer momentum to the tumor, and this is due to the existence of the pressure gradient [101–104]. As a result, this process would then lead to acoustic streaming and result in additional stoichiology effect for further tumor theranostics (Fig. 6.7) [105–110]. More so, the sonophoresis effect of acoustic radiation force (ARF) is well adopted in transdermal drug delivery applications [111, 112]. It has been suggested that ARF is able to enhance the tumoral uptake and effect of small-drug molecules [113–117]. On the other hand, it is best achieved with high intensities since ARF is determined by energy absorption.
Modeling of particle interaction dynamics in standing wave acoustic field
Published in Aerosol Science and Technology, 2019
Fengxian Fan, Xuan Xu, Sihong Zhang, Mingxu Su
This article presents an improved theoretical model developed to describe interaction dynamics between two neighboring particles within a horizontal standing wave acoustic field. Manifestation of three major acoustically induced interaction mechanisms—orthokinetic interaction, acoustic wake effect, and mutual scattering effect—was simultaneously considered in the proposed model. Additionally, effects of spatial variation in acoustic velocity on the three major interaction mechanisms were incorporated within the proposed model. Comparisons between simulation results obtained in this study against experimental data suggest that the proposed model is capable of accurately capturing physical phenomena associated with particle interaction dynamics, including particle velocity caused by acoustic entrainment, particle interaction pattern, and collision time. The effects of model improvements on PM2.5 interaction dynamics were also analyzed. We found interaction dynamics between differently sized particles may demonstrate remarkable changes upon inclusion of the mutual scattering effect. Additionally, the particle drift during orthokinetic interactions under standing wave conditions can only be observed via inclusion of spatial variations in acoustic velocity. Results obtained in this study demonstrate that in cases involving identically sized particles, the collision time reduces significantly with increase in particle size. When maintaining the size of a particle constant and increasing that of the other particle, the collision time tends to reduce in cases involving a small or moderate particle size difference. Once the size difference is large, the range of orientation angle values that leads to particle collision narrows down dramatically to zero. Thus, no collision occurs. This study addresses major issues concerning researches performed in particle interaction dynamics domain with special focus on acoustic agglomeration under standing wave conditions. However, the acoustic radiation force was not considered during investigations performed in this study. It should be noted that the acoustic radiation force becomes important as acoustic frequency increases for small particles in a standing wave. Further research must, therefore, be performed to facilitate inclusion of the acoustic radiation force in the proposed particle interaction model to examine particle interaction dynamics under high-frequency standing wave acoustic conditions.