Abstract
Photodynamic therapy (PDT) was proved to be a safe and promising alternative for the treatment of patients with superficial esophageal cancer and early gastric cancer who are poor risks for surgery. However, it is very difficult to irradiate enough energy for the proper portion of the lesion, because we can not clearly observe not only the cancerous region, but also the border of irradiation spot during photoradiation. In PDT, a conventional electronic endoscope is not applicable, because excessive amounts of red light at 630nm wavelength for irradiation, which radiate unsystematically, prevent the charge coupled device (CCD) chip from forming and transmitting an image. Then, we used a fiberscope in PDT, with being placed a green filter on the eyepiece of the fiberscope to protect the naked eye from being dazzled during laser irradiation. This method improved being dazzled, but the image of mucosa turned to a greenish one. We could not clearly observe the border of the cancerous lesion. We, therefore, designed an original device for photoradiation in PDT combined an electronic endoscope and a laser. The device consists of an electronic endoscope whose light source is an electric flash lamp instead of a xenon lamp, and a pulsed laser. An ideal combination is an electronic endoscope with 60 frames per second and a pulsed laser with 240 pulses per second. They are conducted so systematically that the laser irradiates at a pause during the electric flash lamp illuminates, and then the CCD chip forms and transmits the image. Furthermore, the CCD chip accepts the image of one pulse of the laser out of four. In conclusion, the new device allows as follows: 1. The laser beam does not prevent the CCD chip from forming and transmitting the image of the mucosa illuminated with an electric flash lamp; 2. The CCD chip can take an image of a spot of laser irradiation, then the image passes through a real-time image processor, and finally the image will be shown on a monitor lied upon the picture of the lesion such as a blue ring. We showed this system can be created theoretically. It is only a dream at present, but in the future when it will put into practice, it will be very useful for PDT to come into wide use, although there will be many difficulties in putting the theory into practice.
