Multitasking optical fiber probes for fluence-rate and fluorescent drug monitoring in vivo

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-1. 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-1. The partial oxygen can be quantified for pO2 < 2 mmHg.