A robotic multi-channel platform for interstitial photodynamic therapy.

A custom-made robotic multichannel platform for interstitial photodynamic therapy (PDT) and diffuse optical tomography (DOT) was developed and tested in a phantom experiment. The system, which was compatible with the operating room (OR) environment, had 16 channels for independent positioning of light sources and/or isotropic detectors in separate catheters. Each channel's motor had an optical encoder for position feedback, with resolution of 1.5 mm, and a maximum speed of 5 cm/s. Automatic calibration of detector positions was implemented using an optical diode beam that defined the starting position of each motor, and by means of feedback algorithms controlling individual channels. As a result, the accuracy of zero position of 0.1 mm for all channels was achieved. We have also employed scanning procedures where detectors automatically covered the appropriate range around source positions. Thus, total scan time for a typical optical properties (OP) measurement throughout the phantom was about 1.5 minutes with point sources. The OP were determined based on the measured light fluence rates. These enhancements allow a tremendous improvement of treatment quality for a bulk tumor compared to the systems employed in previous clinical trials.