Fig. 1.

(a) Optical monitoring system in which light is collected at the distal tip of the interstitial probe (i) and transmitted along an optical fiber to an amplified photodetector (ii). The output voltage is reduced from 0–10V to 0–5V via a voltage divider (iii) and converted to a digital signal using a microcontroller (iv). The digital signal is read by a dedicated computer (v) running custom designed software (vi). (b) Detailed view of the four interstitial optical probe designs. Note, red arrows indicate directionality of light acceptance. (c) The experimental setup which was designed to match the clinical scenario where both the laser catheter and optical probe are inserted in parallel