Imaging of cerebrospinal fluid space and movement in mice using near infrared fluorescence

We developed an optical method for imaging the cerebrospinal fluid (CSF) space and the movement of CSF in mice using a near infrared fluorescence imaging methodology. Indocyanine green bound to high-density lipoprotein (ICG-HDL) was injected into the lumber subarachnoid space of nude mice. The time course of CSF movement was followed over 48 h. The imaging system was configured for epi-fluorescence measurements at near infrared wavelengths using the illumination light and narrow band excitation filtration with central wavelength of 755 nm. Emission light was filtered with a longpass filter with a cutoff at 798 nm. After the injection of ICG-HDL, a strong fluorescence signal clearly delineated the cisterna magna, bilateral supracerebellar/cerebello-pontine angle cistern, and interhemispheric cistern. Much of the fluorescent tracer was washed out within 24 h after the injection. This study has therefore demonstrated that an optical method, employing near infrared fluorescence imaging, can determine the CSF space and the movement of CSF in nude mice.