Yuan J, Mahama-Relue P A, Fournier R L, Hampton J A
Department of Bioengineering, The University of Toledo, Ohio 43606, USA.
Radiat Res. 1997 Oct;148(4):386-94.
Photodynamic therapy (PDT) is a relatively new protocol for cancer treatment which has recently been approved for limited clinical use. Traditionally, the success of treatment with PDT has been compared on the basis of total light delivery. Using the mathematical model of Henning et al. (Radiat. Res. 142, 221-226, 1995), we have determined that when oxygen is not depleted from the tissue, the concentration of singlet oxygen that is generated is directly proportional to the product of the light fluence rate (phi) and the concentration of the photosensitizer (Cs). Therefore, phiCs is an appropriate parameter for comparing the potential success of PDT protocols under these conditions. For a treatment of time t, the observed photodynamic effect resulting from singlet oxygen exposure should be directly related to phiCst. For high phiCs, the model predicts that oxygen depletion occurs within the tumor tissue. As a result, the photodynamic effect is no longer proportional to phiCst. We have expanded the model of Henning et al. to include the changes in oxygen concentration which occur within the capillary as blood flows through the tissue. Our new predictions with the mathematical model for optimal PDT treatment conditions are significantly different from those predicted by the previous models. Predictions of the model are given using parameters relevant for treatment of solid tumors with Photofrin.
光动力疗法（PDT）是一种相对较新的癌症治疗方案，最近已被批准用于有限的临床应用。传统上，PDT治疗的成功与否是基于总光剂量进行比较的。利用亨宁等人（《辐射研究》142卷，221 - 226页，1995年）的数学模型，我们已经确定，当组织中的氧气未被耗尽时，产生的单线态氧浓度与光通量率（phi）和光敏剂浓度（Cs）的乘积成正比。因此，phiCs是在这些条件下比较PDT方案潜在成功性的一个合适参数。对于时间为t的治疗，由单线态氧暴露产生的观察到的光动力效应应该与phiCst直接相关。对于高phiCs，该模型预测肿瘤组织内会发生氧气耗尽。结果，光动力效应不再与phiCst成正比。我们扩展了亨宁等人的模型，以包括血液流经组织时毛细血管内发生的氧气浓度变化。我们用数学模型对最佳PDT治疗条件的新预测与先前模型的预测有显著差异。该模型的预测是使用与用卟吩姆钠治疗实体瘤相关的参数给出的。
