Safety of Indocyanine Green Microdosing for Clinical Imaging of CSF Ventricular Dynamics and Extracranial Outflow.
Journal of neuroimaging : official journal of the American Society of Neuroimaging January 1, 2025 Miriam Zamorano, Banghe Zhu, Ahmed T Massoud et al.
Microdosing indocyanine green (ICG) directly into cerebrospinal fluid (CSF) appears safe based on cell culture, rat, and adult human data. In mixed primary CNS cell cultures, ICG caused transient toxicity only at a high concentration (1291 µM) after 1 hour, but not at or below 322 µM even after 24 hours. Juvenile rats receiving intraventricular ICG injections showed no behavioral differences (Novel Object Place Recognition, rotarod) or brain changes (TNF-α, oxidative DNA damage, microglial activation, neuronal density) compared to saline controls. In 10 brain-injured adults, intraventricular ICG concentrations from intravenous administration ranged from 0.17 to 7.93 µM with no adverse events. Microdosing 100 µg ICG into neonatal CSF yields maximal concentrations of 1.3 to 6.5 µM, well below toxic levels.