Veysset David, Ling Tong, Zhuo Yueming, Pandiyan Vimal Prabhu, Sabesan Ramkumar, Palanker Daniel
Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA.
Department of Ophthalmology, Stanford University, Stanford, CA 94305, USA.
Biomed Opt Express. 2022 Jan 13;13(2):728-743. doi: 10.1364/BOE.448803. eCollection 2022 Feb 1.
Precise control of the temperature rise is a prerequisite for proper photothermal therapy. In retinal laser therapy, the heat deposition is primarily governed by the melanin concentration, which can significantly vary across the retina and from patient to patient. In this work, we present a method for determining the optical and thermal properties of layered materials, directly applicable to the retina, using low-energy laser heating and phase-resolved optical coherence tomography (pOCT). The method is demonstrated on a polymer-based tissue phantom heated with a laser pulse focused onto an absorbing layer buried below the phantom's surface. Using a line-scan spectral-domain pOCT, optical path length changes induced by the thermal expansion were extracted from sequential B-scans. The material properties were then determined by matching the optical path length changes to a thermo-mechanical model developed for fast computation. This method determined the absorption coefficient with a precision of 2.5% and the temperature rise with a precision of about 0.2°C from a single laser exposure, while the peak did not exceed 8°C during 1 ms pulse, which is well within the tissue safety range and significantly more precise than other methods.
精确控制温度升高是进行适当光热治疗的前提条件。在视网膜激光治疗中，热量沉积主要由黑色素浓度决定，而黑色素浓度在整个视网膜以及不同患者之间会有显著差异。在这项工作中，我们提出了一种使用低能量激光加热和相分辨光学相干断层扫描（pOCT）来确定层状材料光学和热学性质的方法，该方法可直接应用于视网膜。该方法在一个基于聚合物的组织模型上得到了验证，用聚焦在埋于模型表面下方吸收层上的激光脉冲对其进行加热。使用线扫描光谱域pOCT，从连续的B扫描中提取由热膨胀引起的光程长度变化。然后通过将光程长度变化与为快速计算而开发的热机械模型相匹配来确定材料性质。该方法通过单次激光照射确定吸收系数的精度为2.5%，确定温度升高的精度约为0.2°C，在1 ms脉冲期间峰值不超过8°C，这完全在组织安全范围内，并且比其他方法精确得多。
