NIR light penetration in unfrozen samples of rat brain gray matter

Optical tissue properties have been widely investigated and studied in human and animal tissue due to its importance in the medical laser applications. However, published data on the optical properties of neural tissue in rodents are rare. The aim of this study was to measure the penetration depth of light into the rat brain gray mater at NIR wavelengths. Sample preparation is an important factor in measurements of tissue optical properties. Although shock and slow freezing are standard procedures, they alter the optical properties of biological tissue. In this study, intact slices of gray matter were cut in the range of 300 to 1500 mum without prior freezing to the brain samples. We found the penetration depth in the rat gray matter to be 0.39plusmn0.036 mm. Compared to the data reported in literature for the human brain, the rat brain gray matter attenuates the NIR light much more strongly.