Zhu Timothy C, Altschuler Martin D, Hu Yida, Wang Ken, Finlay Jarod C, Dimofte Andreea, Cengel Keith, Hahn Stephen M
Department of Radiation Oncology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
Proc SPIE Int Soc Opt Eng. 2010 Jan;7551. doi: 10.1117/12.842968.
Singlet oxygen (O) is the major cytotoxic agent for type II photodynamic therapy (PDT). The production of O involves the complex reactions among light, oxygen molecule, and photosensitizer. From universal macroscopic kinetic equations which describe the photochemical processes of PDT, the reacted O concentration, [O], with cell target can be expressed in a form related to time integration of the product of O quantum yield and the PDT dose rate. The object of this study is to develop optimization procedures that account for the optical heterogeneity of the patient prostate, the tissue photosensitizer concentrations, and tissue oxygenation, thereby enable delivery of uniform reacted singlet oxygen to the gland. We use the heterogeneous optical properties measured for a patient prostate to calculate a light fluence kernel. Several methods are used to optimize the positions and intensities of CDFs. The Cimmino feasibility algorithm, which is fast, linear, and always converges reliably, is applied as a search tool to optimize the weights of the light sources at each step of the iterative selection. Maximum and minimum dose limits chosen for sample points in the prostate constrain the solution for the intensities of the linear light sources. The study shows that optimization of individual light source positions and intensities is feasible for the heterogeneous prostate during PDT. To study how different photosensitizer distributions as well as tissue oxygenation in the prostate affect optimization, comparisons of light fluence rate were made with measured distribution of photosensitizer in prostate under different tissue oxygenation conditions.
单线态氧（O）是II型光动力疗法（PDT）的主要细胞毒性剂。O的产生涉及光、氧分子和光敏剂之间的复杂反应。从描述PDT光化学过程的通用宏观动力学方程来看，与细胞靶点反应的O浓度[O]可以用一种与O量子产率和PDT剂量率乘积的时间积分相关的形式来表示。本研究的目的是开发优化程序，该程序要考虑患者前列腺的光学异质性、组织光敏剂浓度和组织氧合情况，从而能够向腺体输送均匀的反应单线态氧。我们使用为患者前列腺测量的非均匀光学特性来计算光通量核。采用多种方法来优化圆柱扩散光纤（CDF）的位置和强度。快速、线性且始终可靠收敛的奇米诺可行性算法被用作搜索工具，以在迭代选择的每个步骤中优化光源的权重。为前列腺中的采样点选择的最大和最小剂量限制约束了线性光源强度的解。研究表明，在PDT期间对异质性前列腺的单个光源位置和强度进行优化是可行的。为了研究前列腺中不同的光敏剂分布以及组织氧合如何影响优化，在不同组织氧合条件下，将光通量率与前列腺中光敏剂的测量分布进行了比较。
