Noninvasive optical imaging of the subarachnoid space and cerebrospinal fluid pathways based on near-infrared fluorescence

Abstract
✓ The authors have developed a noninvasive optical method to image the subarachnoid space and cerebrospinal fluid pathways in vivo based on the near-infrared fluorescence of indocyanine green (ICG). The ICG was bound to purified lipoproteins (ICG—lipoprotein) and injected into the subarachnoid space of neonatal and adult rats. The ICG fluorescence was detected by a cooled charge-coupled device camera. After injection of ICG—lipoprotein into the cerebral subarachnoid space of the neonatal rat, ICG fluorescence was clearly detected at the injection site through the skull and skin. The ICG fluorescence was observed in the cerebellum and the lumbar spinal cord 1 and 8 hours postinjection, respectively. After injection of ICG—lipoprotein into the lumbar spinal subarachnoid space of an adult rat, ICG fluorescence was observed from the injection site to the thoracic levels along the spinal subarachnoid space. In addition, with the rat's head tilted downward, ICG fluorescence had extended to the cerebral subarach...