Ultrasonic attenuation of biomaterials for compensation in photoacoustic imaging

Ultrasonic attenuation in biomaterials limits the quality and resolution of ultrasonic imaging. This work presents a simple and reliable method to investigate acoustic attenuation of biological tissue samples and liquids in order to improve reconstruction algorithms for photoacoustic imaging. For this purpose broadband high-frequency single transmission measurements were performed. The spectra of the acquired signals were compared to reference measurements in distilled water. Unfocused broadband piezoelectric transducers were used as ultrasound source and detector. Moreover, laser generated ultrasound, which provides more intensity and signals with higher bandwidth, was used to measure acoustic attenuation. Only few studies concerned with attenuation of fat tissue performed broadband high frequency measurements and to our knowledge none of those used the simple and reliable single transmission approach with unfocused ultrasound. Our results for acoustic attenuation in olive oil show good agreement with literature. Many studies indicate linear frequency increase of attenuation of fat tissue. However, we observed significant non-linear frequency behaviour of porcine subcutaneous fat tissue at room temperature with a power-law exponent of around 1.45.