An IR navigation system for real-time treatment guidance of Pleural PDT

Uniform light fluence distribution for patients undergoing photodynamic therapy (PDT) is critical to ensure predictable PDT outcome. However, common practice uses a point source to deliver light to the pleural cavity with the light uniformity monitored by 7 detectors placed within the pleural cavity. To improve the uniformity of light fluence rate distribution, we have used a real-time infrared (IR) tracking camera to track the movement of the light point source. The same tracking device is used to determine the surface contour of the treatment area. This study examines the light fluence (rate) delivered between the measurement and calculation in phantom studies. Isotropic detectors were used for in-vivo light dosimetry. Light fluence rate in the pleural cavity is calculated and compared with the in-vivo calculation. Phantom studies show that the surface contour can be determined with an accuracy of 2 mm, with maximum deviation of 5 mm. We can successfully match the calculated light fluence rates with the in-vivo measurements. Preliminary results indicate that the light fluence rate can have up to 50% deviation compared to the prescription in phantom experiments. The IR camera has been used successfully in pleural PDT patient treatment to track the motion of light source in real-time. We concluded that it is feasible to develop an IR camera based system to guide the motion of the light source to improve the uniformity of light distribution.