Physics in Medicine and Biology 2020 February 13 [Link]

Kim MM, Zhu TC, Ong YH, Finlay JC, Dimofte A, Singhal S, Glatstein E, Cengel KA


Pleural photodynamic therapy (PDT) is performed intraoperatively for the treatment of microscopic disease in patients with malignant pleural mesothelioma. Accurate delivery of light dose is critical to PDT efficiency. As a standard of care, light fluence is delivered to the prescribed fluence using 8 isotropic detectors in pre-determined discrete locations inside the pleural cavity that is filled with a dilute Intralipid solution. An optical infrared (IR) navigation system was used during light delivery to monitor the position of the light source within the treatment cavity. The light source is tracked using a modified and improved treatment delivery wand with reflective passive markers that are seen by the infrared camera-based navigation system. This information was used to calculate the light dose, incorporating a constant scattered light dose and using a dual correction method. Calculation methods were extensively compared for 8 detector locations and 7 patient case studies. The light fluence uniformity was also quantified by representing the unraveled three-dimensional geometry on a two-dimensional plane. Calculated light fluence at the end of treatment delivery was compared to measured values from isotropic detectors. Using a constant scattered dose for all detector locations along with a dual correction method, the agreement between calculated and measured values for each detector was less than 15%. Primary light dose alone does not fully account for the light delivered inside the cavity. This is useful in determining the light dose delivered to areas of the pleural cavity between detector locations, and can prove to improve treatment delivery with implementation in real-time in the surgical setting. We concluded that the standard deviation of light fluence uniformity for the Photofrin-mediated PDT is 10%.