Spatially resolved detection of the scattering coefficient and the capillary network of tissue by using a random laser

对于医学诊断，成像是指导和协助临床工作人员的基本技术。通常，物理学的最新发展允许研究新的方法和研究新的疾病相关参数来检测疾病。随机激光（RL）是一种新型的组织成像工具，通过将组织本身转变为RL，可以提供组织微观结构的空间分辨反馈。RL可以通过将散射介质与激光染料相结合来建立。在外部光泵浦下，产生随机激光。例如，组织或内毒素可以用罗丹明6G浸泡或混合。如果用倍频Nd：YAG激光泵浦这种混合物，将建立RL。所发射的光的光谱将允许关于所研究的介质的散射性质的结论。RL的这种简单设置使得能够利用稳健的设置来收集关于所研究的组织的信息。预期收集的光谱可用于导出两种类型的信息。首先，关于毛细血管网络的信息应该是可重构的，其次，可以重构所研究的组织的空间分辨散射系数。为此，计划中的研究重点是对生物组织中随机激光的行为有一个基本的了解。由于随机激光器的特性，预计可以特别分析较小的血管结构。因此，组织分类，特别是癌性病变，可以很容易地完成与随机激光。注射染料后，其灌注在注射和测量之间的不同时间间隔内发生变化。在本项目的范围内，研究和评价了不同荧光染料灌注量的影响，并借助组织模拟体模在受控环境中研究RL。这些不同的灌注量被用来重建组织的散射系数，并获得有关毛细血管网络的信息。与现有的光学技术相比，RL应该允许快速和精确的方法来测量毛细血管网络和散射系数。使用RL的新方法具有使用非常简单、可能非常稳健和快速设置的优点。此外，预计这两个参数的微小变化是可测量的。因此，应该能够研究早期疾病（如癌症）中组织的变化，以了解疾病的发展，并且RL应该允许其检测。

For medical diagnostics, imaging is an essential technique to guide and assist the clinical staff. Often, recent developments in physics allow the investigation of new methodologies and the investigation of new disease related parameters to detect diseases. In this study, the random laser (RL) will be studied for the usage as a new tool for tissue imaging with the aim to provide the spatial resolved feedback about the micro structure of the tissue under investigation by turning the tissue itself into a RL.A RL can be set-up by combining a scattering medium with a laser dye. With external optical pumping, the random laser is generated. For example, tissue or intralipid can be soaked or mixed with Rhodamin 6G. If this mixture is pumped with a frequency doubled Nd:YAG Laser, a RL will be built. The spectrum of the emitted light will allow conclusions on the scattering properties of the medium under investigation. This easy set-up of the RL enables to collect information about the tissue under investigation with a robust set-up. It is expected that the collected spectra can be used to derive two types of information. First, information about the capillary network should be reconstructable and, second, the spatially resolved scattering coefficient of the tissue under investigation can be reconstructed. To do so, the planned research focuses on getting a fundamental understanding of the behaviour of random lasers in biological tissue. Due to the behaviour of the random laser, it is expected that especially the smaller vessel structures can be analysed. Therefore, tissue classification especially for cancerous lesions might be easily done with a random laser. After injection of the dye, its perfusion changes for different time spans between injection and measurement. Within the scope of this project, the effects of different amount of perfusion of the fluorescence dye are investigated and evaluated with the help of tissue mimicking phantoms to study the RL in a controlled environment. These different amounts of perfusion are used to reconstruct the scattering coefficient of the tissue and to derive information about the capillary network.Compared to established optical technologies, the RL should allow a fast and precise way for measuring capillary networks and scattering coefficients. The new approach with a RL has the advantage of using a very simple, potentially very robust and fast set-up. Moreover, small changes of both parameters are expected to be measurable. Therefore, the changes of tissue in early stage diseases like carcinomas should be able to be studied for understanding the development of the disease as well as the RL should allow its detection.