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.
Photodynamic therapy (PDT) is an approved treatment modality for Barrett's and invasive esophageal
carcinoma. Proper Combination of photosentizing agent, oxygen, and a specific wavelength of light to
activate the photosentizing agents is necessary for the cytotoxic destruction of cancerous cells by PDT. As a
light source expensive solid-state laser sources currently are being used for the treatment. Inexpensive
semiconductor lasers have been suggested for the light delivery system, however packaging of semiconductor
lasers for optimal optical power output is challenging. In this paper, we present a multidirectional direct
water-cooling of semiconductor lasers that provides a better efficiency than the conventional unidirectional
cooling. AlGaAsP lasers were tested under de-ionized (DI) water and it is shown that the optical power output
of the lasers under the DI water is much higher than that of the uni-directional cooling of lasers. Also, in this
paper we discuss how direct DI water-cooling can optimize power output of semiconductor lasers. Thereafter
an optimal design of the semiconductor laser package is shown with the DI water-cooling system. Further, a
microwave antenna is designed which is to be imprinted on to a balloon catheter in order to provide local
heating of esophagus, leading to an increase in local oxygenation of the tumor to generate an effective level of
singlet oxygen for cellular death. Finally the optimal level of light energy that is required to achieve the
expected level of singlet oxygen is modeled to design an efficient PDT protocol.
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