Short-wave Photoacoustic Lipid Imaging (SW-PALI) for Detection of early-onset Alzheimer's Disease

Deficiencies in lipid transport and metabolism in the brain have been shown to increase the risk factor of Alzheimer's disease (AD), indicating that structural changes of lipids in the brain may play a vital role in early-onset AD. It is henceforth important to have the capability of imaging these structural changes of lipids throughout different stages of disease. Currently, there is an unmet need for high spatial resolution (~100µm) mapping of lipids in the brain at depths greater than what is obtained using traditional optical methods (>1 mm). We have previously demonstrated the ability of a short-wave infrared (SWIR) photoacoustic (PA) system to spatially map lipid and water (L/W) content in tissue. Here we present the ability of the system to accurately map and predict lipid concentrations at depths of ~5mm. L/W mapping of a mouse brain predicts gray and white matter lipid concentrations of 30 ± 9% and 57 ± 3% respectively, which agree with generally accepted values. This work lends itself to the application of future in vivo studies of early-onset AD in mouse models, where noninvasive mapping of L/W would dramatically improve on existing methods for brain imaging of lipid content.