Bays R, Wagnières G, Robert D, Braichotte D, Savary J F, Monnier P, van den Bergh H
Institute of Environmental Engineering, Swiss Federal Institute of Technology, Lausanne, Switzerland.
Lasers Surg Med. 1997;20(3):290-303. doi: 10.1002/(sici)1096-9101(1997)20:3<290::aid-lsm8>3.0.co;2-l.
Photodynamic therapy (PDT) is an efficient technique to treat superficial early cancers in the pharynx, esophagus, and tracheo-bronchial tree. However, the lack of selectivity of some of the clinically used photosensitizers can result in significant damage to the healthy tissue during the treatment. In the esophagus, this may lead to medical complications such as stenosis and fistula. Insufficient selectivity may be compensated to some extent by accurate light dosimetry. Here, we present an approach to safer and more efficient PDT by improved light dosimetry in the esophagus.
STUDY DESIGN/MATERIALS AND METHODS: This includes the utilization of a suitable light distributor, the estimation of the radiant energy density in the tissue, and the knowledge of the esophagus morphology. The light distributor presently used in the clinic is described and several techniques to study light propagation in the esophageal wall have been investigated and are discussed. Thickness of different histological layers of the esophageal wall have been measured ex vivo and are presented.
Under these conditions and based on a simple model of the light distribution in the tissue, some basic and clinically useful notions of light dosimetry can be drawn. These notions, associated with measured value of tissue optical properties at the wavelengths of interest with the presently used photosensitizers, are discussed regarding the particular morphology of the esophageal wall. In particular, the importance of the illumination wavelength from the safety point of view is shown.
The proposed approach allows for improved safety and efficacy of PDT in the esophagus, particularly in the clinical tests of new photosensitizers.
光动力疗法（PDT）是治疗咽喉、食管及气管支气管树浅表早期癌症的一种有效技术。然而，一些临床使用的光敏剂缺乏选择性，可能导致治疗过程中对健康组织造成严重损伤。在食管中，这可能会引发诸如狭窄和瘘管等医学并发症。准确的光剂量测定在一定程度上可弥补选择性不足的问题。在此，我们提出一种通过改进食管光剂量测定来实现更安全、高效光动力疗法的方法。
研究设计/材料与方法：这包括使用合适的光分布器、估计组织中的辐射能量密度以及了解食管形态。描述了目前临床使用的光分布器，并研究和讨论了几种研究光在食管壁中传播的技术。已对食管壁不同组织学层的厚度进行了离体测量并给出结果。
在这些条件下，基于组织中光分布的简单模型，可以得出一些光剂量测定的基本且具有临床实用性的概念。结合目前使用的光敏剂在感兴趣波长下的组织光学特性测量值，针对食管壁的特定形态对这些概念进行了讨论。特别从安全角度展示了照明波长的重要性。
所提出的方法可提高食管光动力疗法的安全性和有效性，尤其在新光敏剂的临床试验中。
