Background: Various approaches and markers for marking the lungs prior to lung tumor resection have been reported. In clinical practice, the hook wire localization method is often used owing to the simplicity of the technique. However, although rare, this method is associated with air embolism, which can be lethal. Because vitamin B2 is harmless to the body and fluorescent, it was applied to various methods for thoracic surgery. Using a pig model, we aimed to examine whether a lung-marking method involving the injection of vitamin B2 to peripheral small lung lesions and observing them under black light irradiation could replace the hook wire localization method. Methods: We used a pig model to perform hook wire localization of the lungs and at the same time injected 1 mL of a vitamin B2 aqueous solution to the lung parenchyma at the hook wire puncture site under the visceral pleura. Subsequently, we measured the length of the fluorescent marked area and fluorescence intensity over time. Black light was used to assess the fluorescent marked area, and fluorescence intensity was quantified using image analysis software. Results: Lung-marking was successful in all five pigs and we visualized the vitamin B2-marked area under black light irradiation. Measurements were taken immediately after thoracotomy (0 min) and 60 and 120 min thereafter. No changes in the length of the marked area (1.3±0.3/1.2±0.3/1.1±0.3 cm, 0/60/120 min, P=0.21) and fluorescence intensity (162.8±55.1/157.2±63.1/165.2±62.2, 0/60/120 min, P=0.96) were observed over time. Compared to the non-marked area (normal lungs), the marked area showed significantly higher fluorescence intensity (P=0.01/0.01/0.01, 0/60/120 min). Conclusions: Vitamin B2 lung-marking was performed safely and accurately using the pig model, providing good visibility of the marked area. This approach may replace the hook wire localization method. In the near future, we plan to conduct clinical trials to evaluate the applicability of this method in humans.
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