Safety and feasibility of near-infrared fluorescence imaging with inhaled indocyanine green to assess the pulmonary parenchyma in six normal dogs.

Inhaled ICG enables safe, rapid real-time pulmonary fluorescence imaging in dogs.

This preclinical exploratory study evaluated the safety and feasibility of near-infrared fluorescence (NIRF) imaging using inhaled indocyanine green (ICG) to visualize pulmonary parenchyma in six normal dogs. Dogs underwent thoracoscopy and received inhaled ICG at doses of 0.1, 0.5, or 1.0 mg/kg. Real-time fluorescence visualization was achieved in all subjects, with administration times of 1-10 minutes and mean fluorescence onset of 1.5 minutes. Subjective fluorescence peaked at moderate levels for the 0.1 mg/kg dose and strong levels for higher doses. Quantitative fluorescence demonstrated dose-dependent increases, with 3-fold and 10-fold elevations above baseline at 20 minutes post-administration for 0.5 and 1.0 mg/kg doses, respectively. Critically, no histologic abnormalities or clinical respiratory compromise was observed during the 14-day monitoring period, with follow-up biopsies at 6 months showing no adverse changes. These findings support the safety and clinical utility of inhaled ICG for intraoperative pulmonary imaging, establishing a foundation for further investigation into identifying pathologic pulmonary lesions in veterinary patients.

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