Intraoperative Real-Time Near-Infrared Image-Guided Surgery to Identify Necrotic Tissues.

Background and importance: The usefulness of intraoperative real-time fluorescence navigation using indocyanine green (ICG) for metastatic brain tumors, schwannomas, and meningiomas is well established. However, its application in cases of radiation-induced brain necrosis remains unexplored. Surgical intervention is performed in symptomatic and medically refractory cases; however, radiation-necrotic lesions often exhibit a diffuse pattern with unclear surgical boundaries, making it challenging for surgeons to identify the lesion during the surgery.

Methods: Four patients with intracranial necrotic tissues received 1.5 mg/kg ICG 1 hour before observation during the surgery. We used near-infrared fluorescence to identify the necrotic location.

Clinical presentation: Case 1: A 61-year-old man with lung cancer and metastatic brain tumor history exhibited left-sided weakness a year after craniotomy and radiotherapy. A new lesion required surgery, where ICG fluorescence imaging highlighted a significant contrast in the resection cavity, aiding in successful lesion removal without complications. Case 2: A 51-year-old man with resected glioblastoma developed paralysis. ICG fluorescence during surgery confirmed necrosis and enabled the lesion's removal despite potential inaccuracies due to brain shift, without ICG-related complications. Near-infrared fluorescence could visualize necrotic tissues in all 4 cases. The mean signal-to-background ratio of the necrotic tissues in delayed window ICG was 3.5 ± 0.7. The ratio of the gadolinium-enhanced T1 tumor signal to the brain (T1-weighted background ratio) was 2.3 ± 0.4.

Conclusion: This report is the first to demonstrate the efficacy of ICG intraoperative fluorescence imaging in identifying radiation-induced necrotic brain tissues.