DESIGN, FABRICATION, AND ANALYSIS OF MINIATURE REFLECTIVE OXYGEN MONITORING SYSTEM FOR USE IN PDT OF ESOPHAGEAL CARCINOMA

摘要

Photodynamic therapy (PDT) is an effective and minimally invasive treatment modality with relatively less side effects, which is approved by FDA for the treatment of esophageal cancer. Maximum therapeutic outcome of the PDT protocol for each individual patient requires optimization of the components of PDT operating at their highest efficacy. Tumor necrosis, the method of malignant tissue destruction by PDT, is carried out by the toxic singlet oxygen molecules that are being formed from the molecular oxygen in the tumor. The availability of molecular oxygen, hence being the rate limiting step for PDT plays a key role in the treatment protocol. Currently the PDT of esophageal carcinoma is rather a blind process since there is no method to monitor the tumor oxygen level during the treatment. In this paper we present an optical technique to monitor molecular oxygen level in the PDT milieu. The technique described herein is a reflection oximetry technique designed with small semiconductor lasers and a silicon photodiode. The light used for monitoring system comes from two semiconductor diode lasers of 650 nm and 940 nm wavelengths. The two lasers and the photodiode are mounted onto a small package which is to be imprinted onto a balloon catheter containing the PDT light delivery system. Lasers and the photodiode are powered and controlled by a control box that is connected via a cable. Light sources and the respective photodiode output are controlled by the LabVIEW virtual instrumentation. The sequential on and off light source and the respective reflective signal are processed with MATLAB. The latter code integrates with LabVIEW to make an automatic calculation of the corresponding light absorption by each chromophore and to calculate the change in oxygen level as well as the amount of blood and oxygen present in the treatment area. The designed system is capable of monitoring the change in oxygen level and the blood flow in any part of the human body where the package is possible to place.