Photodynamic Therapy (PDT) of Gastrointestinal Tumours: A New Light Delivery System

Abstract.

The Paterson lamp is a convenient, low cost, portable, alternative light source to lasers for photodynamic therapy (PDT). A multiwavelength capability enables the clinician to vary the photosensitiser used. The Paterson lamp has been applied in the field of dermatology using a liquid light guide with distal optics for surface application. We now describe distal optics suitable for use with this light guide for intraluminal applications in the oesophagus and colorectum.

The geometry of the site (oesophagus and colorectum) requires distal optics such as a cylindrical diffuser or a side-fire diffuser. We have designed new probes that diffuse light radially from the guide axis (cylindrical diffusion). The tips have a frosted glass surface that scatters and effectively couples light radially into the tissue. An acrylic spacer is placed over the diffuser to position the tissue at a constant diameter from the probe. This is held in position by a silicone sheath placed over the distal one metre. For use in the oesophagus, a channel, to facilitate intubation over a guide wire, is included. The diameter of the entire probe is 8.4 mm and the power output can be adjusted from 0–500 mW. Pilot PDT of tubulovillous adenomas of the rectum and Barrett's oesophagus using this light delivery system is currently underway and has shown good early response in the treated area.