Validation of a real-time navigation system for pleural photodynamic therapy with 3D-printed lung phantom and various optical properties

Intraoperative photodynamic therapy (PDT) has proven effective in treating malignant pleural mesothelioma. Achieving uniform light dose delivery is vital for its efficiency. Currently, eight light detectors are placed inside the pleural cavity to monitor light distribution. To enhance this process, an updated navigation system, combined with a novel scanning system, has been developed to provide real-time guidance to physicians during pleural PDT, thereby improving light delivery. The scanning system incorporates two handheld three-dimensional (3D) scanners, enabling rapid and precise capture of the pleural cavity's surface topography before PDT. This allows for identification of the target surface for real-time calculation of light fluence distribution during treatment. An algorithm has been devised to further process the scanned volume, facilitating continuous tracking of the light source position within the pleural cavity throughout the treatment process. During PDT, real-time 3D and 2D visualizations of the light source position, scanned pleural cavity, and light fluence distribution across the entire cavity's surface are displayed, providing physicians with invaluable guidance to enhance overall treatment efficiency. To validate the system, phantom studies were conducted using three newly 3D-printed lung phantoms of varying volumes based on individual CT scans. A set of liquid tissue-simulating phantoms with different combinations of optical properties (mu a,mu s') was utilized for improved clinical simulation. These lung phantoms, designed to mimic surgical conditions, feature side openings similar to the actual surgery and are treated with eight isotropic detectors fixed on the inner surface at positions predetermined by the physician.