Near-infrared Intraoperative Imaging of Thoracic Sympathetic Nerves: From Preclinical Study to Clinical Trial

Abstract

The sympathetic nervous system controls and regulates the activities of the heart and other organs. Sympathetic nervous system dysfunction leads to disease. Therefore, intraoperative real-time imaging of thoracic sympathetic nerves (ITSN) would be of great clinical significance for diagnosis and therapy. The aim of this experimental study was to evaluate the feasibility and validity of intraoperative ITSN using indocyanine green (ICG).

Methods: ITSN using ICG was performed on 10 rabbits to determine its feasibility. Animals were allocated to two groups. The rabbits in one group received the same dose of ICG, but were observed at different times. The rabbits in the other group were administered different doses of ICG, but were observed at the same time. Signal to background ratio (SBR) was measured in regions of interest in all rabbits. Furthermore, fifteen consecutive patients with pulmonary nodules were intravenously injected with ICG 24 h preoperatively and underwent near-infrared (NIR) fluorescence imaging (FI) thoracoscopic surgeries between July 2015 and June 2016. A novel self-developed NIR and white-light dual-channel thoracoscope system was used. SBRs of thoracic sympathetic nerves were calculated in all patients.

Results: In the preclinical study, we were able to precisely recognize each rabbit's second (T2) to fifth (T5) thoracic ganglia on both sides of the spine using ITSN with ICG. In addition, we explored the relationship between SBR and the injection time of ICG and that between SBR and the dose of ICG. Using the novel dual-channel thoracoscope system, we were able to locate the ganglia from the stellate ganglion (SG) to the sixth thoracic ganglion (T6), as well as the chains between these ganglia in all patients with a high SBR value of 3.26 (standard deviation: 0.57). The pathological results confirmed our findings.

Conclusion: We were able to use ICG FI to distinguish thoracic sympathetic nerves during NIR thoracoscopic surgery. The technique may replace the rib-oriented method as standard practice for mapping the thoracic sympathetic nerves.

Trial registration: ClinicalTrials.gov NCT02084784.

Keywords: indocyanine green.; intraoperative fluorescence imaging; near-infrared; sympathetic nerves; thoracoscopic surgery.

Figure 1

(A) Photograph of the modified fluorescence microscope system. (B) Ex vivo imaging of the rabbit's thoracic sympathetic nerve, including color, fluorescence, and merged images. NIR CCD: near-infrared charge-coupled device.

Figure 2

(A) The relationship between SBR and the injection time in each rabbit in the timing group. (B) The relationship between SBR and the dose of ICG in each rabbit in the dose group. (C) Representative fluorescence image of a paraffin section of a rabbit's thoracic sympathetic nerves. (D) H&E-stained cross-section of the area marked by the dotted box in Fig. 2C. SBR: signal to background ratio.

Figure 3

(A) A picture of the dual-channel thoracoscope system. (B-D) In vivo thoracic sympathetic nerve images of a patient, including color, fluorescence, and merged images.

Figure 4

(A) The SBR values for SG to T6 for all patients. (B-D) Fluorescence, color and merged images of a paraffin section of the thoracic sympathetic nerve specimen from patient No. 11. (E) H&E-stained section of the area shown in Fig. 4C. SBR: signal to background ratio.