CAREER: Dynamics of Holographic Acoustic Lenses for Nonlinear Ultrasound Focusing

聚焦超声（FU）是一种变革性技术，具有非侵入性治疗许多医学疾病的潜力。就像使用凸透镜将光束聚焦在一个点上一样，在FU中，声透镜用于将声能集中到身体深处的期望目标上。FU可用于加热、破坏或改变靶组织，并已被预测为非侵入性脑肿瘤消融、短暂血脑屏障破坏和神经调节的有效工具，可能导致脑肿瘤、癫痫、阿尔茨海默病和帕金森病的新治疗。然而，在这些应用中，具有非平坦几何形状的非均匀介质强烈地衰减、反射和扭曲超声波，这可能导致声能的低效和不准确的递送。这个教师早期职业发展计划（CAREER）项目将通过引入能够产生指定的高强度FU场的新一代声学透镜来增强最先进的波聚焦能力。透镜设计基于表征目标的形状和声学特性，通过后向传播模型施加期望的声场，计算透镜设计的唯一厚度图，并且最后使用前向传播模型来重建目标声场。这项研究有可能在FU的新兴治疗应用方面引领科学进步，实现患者特异性药物，其中镜片为每个特定患者定制和3D打印。沿着研究活动，教育计划包括夏令营，将服务，导师，并授权代表性不足的学生从历史上黑人学院和大学的主题超声触觉使用声学透镜。学生实习将获得独特的技能，建立专业网络，并获得跨文化的经验。这项研究将计算机全息技术的概念引入非线性声学。实验和建模方法旨在扩展声全息透镜的能力，以从单个元件换能器产生高强度可缩放声场。在较高的激励振幅下，非线性效应表现为谐波的产生、声波波形的失真以及可能的激波阵面的形成。这种现象影响声场的压力分布和衍射图案。因此，新的混合域算法，将非线性，向前和向后波传播，将被引入，以实现高强度场的有效和精确的图案。研究成果包括非线性波前整形的数学框架，推进了非线性声学逆问题的知识。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Focused ultrasound (FU) is a transformative technology with the potential to treat many medical disorders noninvasively. Like using a convex lens to focus light beams on a single point, in FU, acoustic lenses are used to concentrate acoustic energy onto the desired target deep in the body. FU can be used to heat up, destroy, or change the target tissue, and has been projected as an effective tool for non-invasive brain tumor ablation, transient blood-brain barrier disruption, and neuromodulation, potentially leading to novel treatments of brain tumors, epilepsy, and Alzheimer’s and Parkinson’s diseases. However, in these applications, the inhomogeneous medium with non-flat geometry strongly attenuates, reflects, and distorts ultrasound waves, which could lead to inefficient and inaccurate delivery of acoustic energy. This Faculty Early Career Development Program (CAREER) project will enhance the state-of-the-art wave focusing capabilities by introducing a new generation of acoustic lenses capable of generating specified high-intensity FU fields. The lens design is based on characterizing the shape and acoustic properties of the target, imposing the desired acoustic field by a backward propagation model, calculating the unique thickness map of the lens design, and finally using a forward propagation model for reconstructing the target acoustic field. This research has the potential to lead the progress of science in emerging therapeutic applications of FU, enabling patient-specific medicine, where lenses are customized and 3D printed for each specific patient. Along with the research activities, the educational plan includes summer camps that will serve, mentor, and empower underrepresented students from historically black colleges and universities on the topic of ultrasound haptics using acoustic lenses. The student interns will acquire unique skills, build professional networks, and gain cross-cultural experiences. The research introduces the concept of computer-generated holographic techniques to nonlinear acoustics. The experiments and modeling approaches aim to extend the capabilities of the acoustic holographic lenses to generate high-intensity scalable acoustic fields from a single element transducer. At higher excitation amplitudes, the nonlinear effects are exhibited by the generation of harmonics, distortion of the acoustic waveform, and possibly the formation of shock fronts. Such phenomena influence the pressure distribution and the diffraction pattern of the sound field. Therefore, new mix-domain algorithms that incorporate nonlinearities, for the forward and backward wave propagation, will be introduced to achieve efficient and precise patterning of high-intensity fields. The outcome of the research includes a mathematical framework for nonlinear wavefront shaping that advances the knowledge of inverse problems of nonlinear acoustics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.