Inhaled ICG shows early promise for canine lung imaging: full analysis

A newly published exploratory study in Veterinary Surgery suggests that near-infrared fluorescence imaging with inhaled indocyanine green may be a workable new way to visualize canine lung tissue during surgery. In six normal purpose-bred dogs, the technique produced rapid intraoperative fluorescence after thoracoscopic administration, with no detectable adverse clinical or histologic effects reported during follow-up. (researchgate.net)

The study is early-stage and intentionally narrow: it did not test dogs with lung tumors or other pulmonary lesions. Instead, the authors set out to answer a foundational question for image-guided thoracic surgery in veterinary medicine: can inhaled ICG safely and consistently label normal pulmonary parenchyma in dogs, and if so, at what dose and on what timeline? According to the abstract, dogs were randomized to 0.1, 0.5, or 1.0 mg/kg inhaled ICG, and the investigators also tracked respiratory function, quantitative fluorescence, and lung histology, including repeat peripheral biopsies six months later. (researchgate.net)

The technical results were encouraging. All six dogs showed real-time near-infrared fluorescence of the pulmonary parenchyma after inhalation. Administration took 1 to 10 minutes, mean time to first fluorescence was 1.5 minutes, and signal intensity increased with dose. Peak subjective fluorescence was described as strong at 0.5 and 1.0 mg/kg, compared with moderate at 0.1 mg/kg, while quantitative fluorescence increased about three-fold above baseline at 20 minutes with 0.5 mg/kg and about ten-fold with 1.0 mg/kg. The authors reported no histologic abnormalities and no clinical evidence of respiratory compromise. (researchgate.net)

This work fits into a broader, still developing body of fluorescence-guided thoracic surgery. In human medicine, a 2020 diagnostic study in JAMA Surgery found that inhaled ICG accumulated in healthy lung tissue but was rarely detected in tumor tissue, creating contrast that appeared useful for identifying tumor margins. The authors there also reported that inhalation used a much lower dose than intravenous delivery while producing better margin-detection efficiency in their models. That human literature helps explain why the canine study focused first on labeling normal lung: if normal parenchyma fluoresces reliably and diseased tissue does not, surgeons may gain a negative-contrast map during resection. (jamanetwork.com)

There is also relevant veterinary precedent, though mostly with intravenous, not inhaled, ICG. A 2023 Frontiers in Veterinary Science case series of 40 privately owned dogs with pulmonary masses found fluorescence in all resected nodules and reported that ICG fluorescence for lymph node metastasis had 100% sensitivity and 75.0% specificity in that cohort. But performance for assessing complete resection was more modest, with 67.7% sensitivity and 60.0% specificity. In other words, fluorescence imaging already shows promise in canine thoracic oncology, but the clinical value depends heavily on what question it's being used to answer. (frontiersin.org)

Why it matters: For veterinary professionals, especially surgeons and specialty hospitals investing in advanced imaging, this paper is less about immediate practice change and more about platform development. If inhaled ICG proves effective in dogs with pulmonary disease, it could expand intraoperative decision support for lesion localization, margin assessment, and possibly detection of additional nodules that are hard to appreciate visually or by palpation alone. It may also offer a different signal pattern than intravenous ICG, which has already shown utility but also limitations in specificity and margin interpretation. Still, this is a six-dog feasibility study in normal lungs, so it shouldn't be read as evidence that the method is ready for routine clinical use. (researchgate.net)

No independent expert commentary or institutional press release was readily available in the sources surfaced during this search, which suggests the paper is entering the field largely through the peer-reviewed literature rather than a broader commercial or regulatory rollout. The strongest outside reaction, for now, comes from adjacent human and veterinary studies that support the biological rationale for fluorescence-guided lung surgery, while also underscoring the need for lesion-specific validation. (jamanetwork.com)

What to watch: The next milestone will be prospective clinical studies in dogs with pulmonary masses to test whether inhaled ICG can improve lesion detection, surgical margins, or staging accuracy, and to define the dose, workflow, equipment requirements, and case selection that make the technique useful in real-world referral practice. (researchgate.net)