CAREER: Dynamics of Holographic Acoustic Lenses for Nonlinear Ultrasound Focusing

聚焦超声(FU)是一种变革性的技术，有可能非侵入性地治疗许多医学疾病。就像使用凸透镜将光束聚焦在一个点上一样，在FU中，声透镜被用来将声能集中到身体深处想要的目标上。FU可用于加热、破坏或改变靶组织，已被认为是非侵入性脑肿瘤消融、一过性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疗法。然而，在这些应用中，具有非平坦几何形状的非均匀介质会对超声波产生强烈的衰减、反射和扭曲，这可能会导致声能量的低效和不准确的传输。该学院早期职业发展计划(CALEAR)项目将通过引入能够产生特定高强度FU场的新一代声学透镜来增强最先进的波聚焦能力。透镜设计的基础是表征目标的形状和声学特性，通过反向传播模型施加所需的声场，计算透镜设计的唯一厚度图，最后使用前向传播模型重建目标声场。这项研究有可能在FU的新兴治疗应用方面引领科学进步，使患者能够使用特定的药物，其中镜片是为每个特定的患者定制和3D打印的。除了研究活动，教育计划还包括夏令营，这些夏令营将服务、指导和增强来自历史上黑人学院和大学的未被充分代表的学生的能力，这些学生的主题是使用声透镜的超声波触觉。学生实习生将获得独特的技能，建立专业网络，并获得跨文化体验。该研究将计算全息技术引入到非线性声学中。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伸缩的声场。在较高的激励幅度下，非线性效应表现为谐波的产生，声波波形的失真，以及可能形成的冲击波阵面。这些现象会影响声场的压强分布和绕射图案。因此，将引入结合非线性的新的混合域算法，用于前向波和后向波的传播，以实现高强度场的高效和精确的图案化。这项研究的结果包括一个非线性波前整形的数学框架，它促进了非线性声学逆问题的知识。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.