Sound bullets for enhanced biomedical ultrasound systems

超声应用广泛，包括医学成像、无损评估、治疗性超声等。在所有这些情况下，通常需要形成图像或创建焦点区域。当前用于产生最佳声场的方法一般依赖于换能器内的线性过程。这种线性转换过程在空间分辨率和最大强度方面影响了结果的性质，并指出在这种焦点区域可以实现的空间分辨率和功率密度存在基本限制。在声学领域的最新工作中，已经证明了一种新型的声信号可以通过粒子链中的非线性效应来产生，粒子链作为一种波导。这些都是基于孤立波的传播。这些都是在低频率下的研究，但这项研究将着眼于将这些新结构用于生物医学超声的可能性。支持孤立波的材料不在标准的超声波工作中使用；关于它们的使用几乎没有发表，尽管性能可能会有阶梯变化的事实。在这项提议中，这种波将在含有多个孤立波链的超声源中产生，频率在500 kHz-5 MHz范围内。据我们所知，这之前从未被调查过。数组也是可能的，其中每个链形成单个元素。由于链将主要沿其长度耦合，而不是在每个链之间横向耦合，因此可以避免机械交叉耦合引起的问题。每条链的预压缩将改变其内部的传播速度，从而产生波束转向/聚焦。传播特性也会随着信号幅度的变化而变化，这导致了声学二极管的可能性。这些新的创新将在超声波增强的药物输送、用于肿瘤治疗的高强度聚焦超声(HIFU)和谐波成像等领域得到应用。

Ultrasound is used in many applications, including medical imaging, non-destructive evaluation, therapeutic ultrasound etc. In all these cases, there is usually a need for the formation of images or the creation of a focal region. Current methods for the generation of optimal acoustic fields generally rely on a linear process within the transducer. This linear transduction process influences the resultant properties in terms of spatial resolution and maximum intensity, noting that there are fundamental limits on the spatial resolution and power densities that can be achieved in such focal regions. In recent work in the area of acoustics, it has been demonstrated that a new type of acoustic signal can be generated via non-linear effects in chains of particles, which act as a kind of waveguide. These are based on the propagation of solitary waves. These have been studies at low frequencies, but this study will look at the posibility of using these new structures for use in biomedical ultrasound. Materials that support solitary waves are not used in standard ultrasonic work; little has been published on their use, despite the fact that a step change in performance may be possible. In this proposal, such waves will be generated within ultrasonic sources containing multiple solitary wave chains, at frequencies in the 500 kHz - 5 MHz range. To our knowledge, this has not been investigated before. Arrays are also possible, where each chain forms a single element. Because the chains would be primarily coupled along their length, but not laterally between each chains, issues arising from mechanical cross-coupling might be avoided. Pre-compression of each chain would alter the propagation velocity within it, so that beam-steering/focussing to be created. The propagation charaistics also change with signal amplitude, leading to the possibility of an acoustic diode. These new innovations would have applications in such areas as ultrasound-enhanced drug delivery, High Intensity Focussed Ultrasound (HIFU) for the treatment of tumours, and harmonic imaging.