Advanced laser methods have recently been used in human and animal head tissues for functional and molecular imaging. Combining these approaches with various probes and nanostructures gives up a new path for theranostic applications in brain tissues. The diverse optical properties of head tissues such as the scalp, skull, cerebrospinal fluid, and brain tissues result in considerable photon scattering and absorption. Diffusion of photons inside head tissues decreases the optical imaging quality and limits the optical resolutions of cellular and neural treatments. Tissue optical clearing (TOC) was set up more than a century ago to make tissue transparent by immersing it in liquids with a matching RI as the tissue. This approach has lately gained popularity in the field of brain imaging. The physical fundamentals of optical clearing (OC) procedures for brain tissue, such as RI matching with chemical agents, dehydration, delipidation, decalcification, hyperhydration, and innovative hybrid brain OC methods, are explored here. This study covers critical issues such as choosing the best brain OC methods and optimizing wavelength and laser energy to control tissue optical properties. Here, innovative ways for decreasing photon scattering based on immersion procedures and induced heating tunnels are discussed. In addition, simulation methods of photon migration in brain tissues (based on random approaches) are investigated, paving the way for the proper brain OC strategy. Finally, the limitations of this method for applications are discussed, as well as possible applications in cranial implants, optogenetics, laser brain stimulation, and functional optical imaging.

中文翻译：

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通过光学清除将激光辐射传输到大脑的进展：从模拟到现实

先进的激光方法最近已用于人类和动物头部组织的功能和分子成像。将这些方法与各种探针和纳米结构相结合，为脑组织的治疗诊断应用开辟了一条新途径。头皮、颅骨、脑脊液和脑组织等头部组织的不同光学特性导致大量的光子散射和吸收。头部组织内光子的扩散降低了光学成像质量并限制了细胞和神经治疗的光学分辨率。组织光学透明 (TOC) 是在一个多世纪前建立的，通过将组织浸入与组织相匹配的 RI 的液体中来使其透明。这种方法最近在脑成像领域受到欢迎。本文探讨了脑组织光学清除 (OC) 程序的物理基础，例如 RI 与化学试剂匹配、脱水、脱脂、脱钙、过度水化和创新的混合脑 OC 方法。这项研究涵盖了一些关键问题，例如选择最佳的脑 OC 方法以及优化波长和激光能量以控制组织光学特性。在这里，讨论了基于浸入程序和感应加热隧道的减少光子散射的创新方法。此外，还研究了脑组织中光子迁移的模拟方法（基于随机方法），为正确的脑 OC 策略铺平了道路。最后，讨论了这种方法的应用局限性，以及在颅骨植入、光遗传学、激光脑刺激和功能光学成像中的可能应用。