Post written by Masayuki Suyama, MD, PhD, from the Department of Gastroenterology and Endoscopy, National Cancer Center Hospital East, Kashiwa, Japan.

This video case series presents the usefulness of oxygen saturation imaging for photodynamic therapy for esophageal cancer. Oxygen saturation (OS) imaging is a novel technique that directly measures and visualizes the tissue oxygen saturation (StO₂) at the surface of the gastrointestinal tract.

The one of the major modes of action of PDT is known as vascular shutdown effect; however, it cannot be visualized by ordinary white-light imaging (WLI) endoscopy in clinical practice. Changes in the laser illuminated area are very minor with WLI immediately after illumination and the day after PDT. Therefore, it is difficult to determine if the illuminated area is adequate during or after the PDT procedure.

OS imaging showed an extreme change to the hypoxic state of the illuminated area after illumination at 100 J/cm², although the change was invisible on WLI. After completion of the illumination, the lesion area was changed to blue color. The use of OS imaging allowed real-time visualization and easy confirmation of the illuminated area.

With OS imaging, it is possible to visualize the state and function of tissues that are difficult to grasp by morphology and color tone of white-light image.

The microenvironment of cancer is highly heterogeneous, and hypoxia is known to be strongly associated with the biological characteristics of cancer. Therefore, this endoscopic system is expected to contribute to the study of cancer microenvironment, as well as the prediction of efficacy of anti-cancer therapies including molecular targeted agents or radiotherapy in clinical.

Read the full article online.

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