Optimizing Photoacoustic Measurement of Lymphatic Drainage of Cerebrospinal Fluid in Pigmented Mice for Microgravity Experiments

Non-invasive dynamic imaging techniques are needed to study the lymphatic drainage of cerebrospinal fluid, whose role in various diseases is actively being investigated. The optimized set of optical wavelengths and spectral unmixing algorithm is pursued in this study to accurately quantify the lymphatic drainage in pigmented mice by multispectral optoacoustic tomography. Several optical wavelength sets and spectral unmixing algorithms for multispectral photoacoustic tomography with a near-infrared tracer were compared. The combination of 11 wavelengths, selected based on absorption spectra of chromophores and exclusion of melanin from the linear regression unmixing algorithm, provided the best spatial similarity to reference images obtained using 151 wavelengths. Furthermore, the 11 wavelengths without melanin in linear regression unmixing algorithm showed the most accurate quantification of mean pixel intensity of the tracer in the neck lymph nodes and its change, compared to other sets of wavelengths and unmixing algorithms.