A Novel Ultrasound Modulated Optical Tomography System

生物组织的光学成像能够提供结构和功能信息，这可能使早期发现异常，如肿瘤和组织氧合检测成为可能。然而，这种技术的一个缺点是难以对物体进行深度成像。相比之下，超声成像能够提供良好的深度图像分辨率，是一种成熟的临床成像方式。然而，超声成像是基于组织中机械特性的检测，它不像光学技术那样敏感，例如检测肿瘤。超声调制光学层析成像（UOT）是一种利用两种成像方式的综合优势的新技术。在UOT中，光被传输到目标组织中，同时超声波被聚焦到组织中来调制光。来自组织的散射光可以被测量，组织光学特性的图像可以重建，空间分辨率主要由超声定义。UOT作为医学成像工具的研究直到90年代才开始。虽然实验室的幻影和切除的组织已经产生了有希望的图像，但当前UOT技术的一个重大挑战是要测量的弱光调制信号。解决弱光信号问题的直接方法是最大限度地利用超声波调制所有通过超声聚焦的光。过去的研究表明，仅仅增加超声振幅可能是不够的，而且还会产生一些不良影响。在这个项目中，我们建议开发一种新的双频率超声激励的UOT系统，以最大限度地提高调制光信号。在这个试点研究中，将开发一个计算机模拟系统和一个实验系统，并将结果与传统的UOT系统进行比较。这个新系统有潜力显著提高UOT图像质量。

Optical imaging of biological tissue is able to provide structural and functional information, which potentially enables early detection of abnormalities such as tumours and detection of tissue oxygenation. However, one disadvantage of such technique is the difficulty to image objects at depth. By comparison, ultrasound imaging is able to provide good image resolution at depth and is an established clinical imaging modality. However, ultrasound imaging is based on the detection of the mechanical properties in tissues which is not as sensitive as optical techniques in e.g. detecting tumours.Ultrasound-modulated optical tomography (UOT) is a new technique to take advantage of the combined strengths of the two imaging modalities. In UOT, light is transmitted into the target tissue and at the same time an ultrasonic wave is focused into the tissue to modulate the light. The scattered light from the tissue can be measured and images of tissue optical properties can be reconstructed, with a spatial resolution primarily defined by ultrasound. Studies of UOT as a medical imaging tool only began in the 90s. Although promising images have been produced with laboratory phantoms and excised tissues, a significant challenge of the current UOT technique is the weak optical modulation signal to be measured. A direct way to tackle the problem of weak optical signal is to maximise the ultrasonic modulation of all light passing through the ultrasound focus. Past studies show that simply increasing the ultrasound amplitude may not be sufficient and also has some adverse effects. In this project, we propose to develop a novel UOT system with dual-frequency ultrasound excitation to maximise the modulated light signal. In this pilot study both a computer simulation system and an experimental system will be developed and results compared with the conventional UOT system. This new system has the potential to significantly improve UOT image quality.