Walsh Medical Devices (Canada)

Cylindrical fiber diffusers are common tools in photodynamic therapy (PDT). However, large outer diameter and short length limit the indications to which they can be applied. Here a diffuser with an outer diameter of 250 microm and an active length exceeding 5 cm was developed. Diffusers based on photosensitive quartz optical fibers with a cladding diameter of 140 microm were developed using a structured beam from an excimer laser. A complete set of photometric characteristics, including longitudinal, polar, and azimuth radiance emission diagrams were collected. The longitudinal radiance emission is homogenous to within +/-10%. The ability to create custom designed longitudinal emission profiles was demonstrated. The variations of the polar and azimuth radiance emission diagrams were within +/- 15% from an ideal Lambertian emitter. The polar uniformity can be improved with a slight increase of the outer diameter using a diffusing recoating compound. The residual light leakage at the distal end of the fiber diffuser was suppressed to 2%. The minimal bending radius after recoating is approximately 5 mm. Maximum power distribution is > 0.5 W cm(-1).

The development and implementation of PDT dosimetry for deep-seated tumors, is limited by the availability of clinically acceptable sensors capable of monitoring all PDT- efficacy determining parameters throughout the treatment volume. Here we present a multitasking optical fiber probe, with 250 micrometers OD, for the detection of the fluence-rate, photosensitizer concentration and partial oxygen pressure at one to five positions along the length of the optical fiber. The performance characteristics and preliminary evaluation of these fiber probes are described. The fluence-rate can be measured to better than 10 percent of the true value with a detection limit of < 10 (mu) W cm<SUP>-1</SUP>. The detection limit for photosensitizer concentration is determined by the fluorescent quantum yield and the fluence rate at the sensor position. For typical PDT treatment conditions the detection limit for Photofrin is approximately 1 (mu) g ml<SUP>-1</SUP>. The partial oxygen can be quantified for pO<SUB>2</SUB> < 2 mmHg.