Evolution of photodynamic medicine based on fluorescence image-guided diagnosis using indocyanine green and 5-aminolevulinic acid

New diagnostic techniques based on photodynamic medicine, such as near-infrared fluorescence using indocyanine green (NIR-ICG) and 5-aminolevulinic acid-mediated photodynamic diagnosis (ALA-PDD), are aiding navigation tasks across various fields of surgery. Specifically, NIR-ICG is being used for the intraoperative identification of sentinel lymph nodes or blood vessels in organ resection and for blood flow evaluation in surgery. These ICG-fluorescent imaging techniques could provide an additional and potentially valuable way to identify vascular and lymphatic structures in surrounding tissue. 5-Aminolevulinic acid is a precursor of a photosensitizing substance with affinity for tumors; thus, diagnostic laparoscopy using ALA-PDD in combination should improve the accuracy of detecting peritoneal dissemination in patients with advanced gastric cancer. The ability to overlay fluorescent imaging with conventional color images in real time using ALA-PDD and NIR with ICG would be of immense benefit to surgeons, providing good visualization and detection of target lesions not seen with the naked eye. A multi-center clinical study examining the safety and efficacy of ALA-PDD during laparoscopic examination for patients with advanced gastric cancer is currently underway in the form of doctor-initiated trials, and further verification studies will be conducted. Such imaging capability could have broad potential across cancer and vascular surgery.