Depth-dependent fluence compensation without a priori knowledge of tissue composition for quantitative...

Compensation for depth-dependent fluence without a priori knowledge of tissue composition is a crucial unmet need for quantitative photoacoustic imaging.

We developed a method for estimating the effective optical attenuation coefficient of bulk tissue with composition and optical properties that are not known in advance, through combined ultrasound/photoacoustic imaging during mechanical displacement of tissue.

Ultrasound/photoacoustic imaging was performed on a target embedded in biological media while applying tissue displacement to change the optical path. After compensation for geometry-dependent scattering of light from light source apertures, the change of photoacoustic amplitude against optical path length was used to estimate the effective optical attenuation coefficient.

Using the developed approach, the estimation of the effective optical attenuation coefficient of tissue-mimicking (milk/water) phantoms and ex vivo porcine muscle and chicken breast was accurate compared with ground-truth literature values.

Regardless of the varying geometries used for light delivery in photoacoustic imaging, it is feasible to perform ultrasound-guided photoacoustic imaging with simultaneous mechanical displacement of tissue to determine the effective optical attenuation coefficient of bulk tissue along the light path to the target.