Fig. 1. Schematic of PDT and PDD

Fig. 2.

Comparison of two types of video endoscopes during laser irradiation^[21]. (a) White screen is displayed by field sequential video endoscope; (b) laser spot can be distinguished clearly by simultaneous video endoscope

Fig. 3. Schematic of the tip of multi-channel endoscope (optical fiber enters the body through exit channel of the equipment)

Fig. 4. Illustration of flexible laser steering endoscope^[29]. (a) Schematic illustration of laser endoscope; (b) experimental setup

Fig. 5. Operating principle of SAFE-3000^[31]. (a) Operating principle of SAFE-3000 at white light mode, where a xenon lamp is used for excitation light for white light mode, infrared light is eliminated by an infrared cut filter and white light is collected by the lens and transmitted to the object through light guide of the videoendoscope; (b) operating principle of SAFE-3000 at autofluorescence, where a diode laser is used as an autofluorescence mode excitation light source,the objective lens eliminates excitation light and captures only autofluorescence from the target

Fig. 6. Treatment course of a metachronous superficial early gastric cancer located in greater curvature of gastric body after ESD^[21]. (a) Before PDT: 0-Ⅱa+Ⅱc (indicated by arrows) and a scar after ESD (circle); (b) during irradiation with an EDL using cylindrical fiber; (c) one week after PDT; (d) six months after PDT

Fig. 7. Composite-type optical fiberscope (COF)^[52]. (a) Tip of composite-type optical fiberscope with an external diameter of 1.0 mm, where the red arrows show the port of laser irradiation, the yellow arrows show the port of image transmission, and there are a lot of fibers that pass white light around the two ports; (b) composite-type optical fiberscope has a straight-type laser probe; (c) image of peripheral-type lung cancer lesion as visualized by composite-type optical fiberscope (the red arrow shows the tumor)