Glycerol In Oil-Based Phantom With Improved Performance For Photoacoustic Imaging

Photoacoustic imaging is a hybrid imaging modality where ultrasound signal is generated when laser pulses are absorbed by tissue. Tissue-mimicking phantom is a useful tool to characterizing new imaging methods. However, there is still a lack of development of phantoms applied to hybrid modalities such as photoacoustics. SEBS gel is a translucent material and present acoustic and elastic properties similar to tissue. Recently, we proposed using glycerol dispersion to further tune the acoustic properties of the phantom. Chromophores can be added to tune optical absorption, while additives such as intralipid and TiO2 can be incorporated to tune optical scattering. Most additives used to tune optical properties of phantoms are hydrophilic; therefore, not soluble in mineral oil and SEBS molten gel. To overcome this limitation, in this study we propose using the glycerol dispersion technique to incorporate hydrophilic additives to the phantom. Therefore, the influence of adding glycerol on the acoustic, mechanical and optical properties of SEBS gel was evaluated. We also evaluated the viability of using this material as phantoms for photoacoustic imaging. SEBS/glycerol gel was prepared using 10% w/w of polymer SEBS in mineral oil and glycerol was added in a fraction of 15% of the oil mass. The material's speed of sound; acoustic attenuation and Young's modulus were assessed. We prepared two phantoms of SEBS/glycerol gel, with TiO2 as optical scatterer, containing cylindrical inclusions with India ink and methylene blue as optical absorbers. Photoacoustic spectroscopy had a peak between 680-690 nm for the methylene blue inclusion; for the India ink case a flat PA signal magnitude in the range of 680-950 nm was obtained. In both cases, the PA spectroscopy was consistent with the absorption spectra. Finally, we observed that the strategy of mixing the chromofores with glycerol prevented them to diffuse to the background material.