Speaker
Description
Quantifying tissue composition is crucial for accurate medical diagnoses. Photoacoustic imaging, which uses pulsed light to generate sound waves from tissue, emerges as a promising technique for tissue quantification. It offers deep imaging capabilities, optical contrast, and acoustic resolution. Its integration with conventional ultrasound imaging leverages structural tissue information alongside the functional insights provided by photoacoustic imaging, enhancing diagnostic potential. However, the challenge lies in the complex interplay of light and sound propagation within tissues, making quantitative analysis difficult.
We present two strategies named Ultrasound-informed Quantitative Photoacoustic Imaging, utilizing ultrasound images to improve photoacoustic imaging quantification. The first method employs ultrasound-derived tissue boundaries to model light propagation. We present a fluence compensated dual-wavelength oxygen saturation imaging method, utilizing structural information from the ultrasound image, and prior knowledge of the optical properties of the tissue with a Monte-Carlo based light propagation model. This approach has been tested on phantoms, in-vivo experiments on mouse thigh tissues under an oxygen challenge, and applications on human volunteers. The proposed method was found to improve the oxygen saturation imaging accuracy. The second strategy uses arterial blood as an internal reference, using known values of oxygen saturation and hematocrit to estimate the optical properties of blood. This internal marker aids in accurately determining the optical properties of unknown chromophores within tissues. We implemented this prior information in a gradient-based iterative optical inversion method with diffusion approximation for light propagation modelling. We demonstrate this method in the context of carotid plaque imaging using simulated phantoms and present our preliminary experimental results.
Our findings underscore the potential of integrating ultrasound imagery with photoacoustic imaging for advanced tissue quantification. This synergy not only improves the accuracy of existing quantitative photoacoustic imaging methods but also opens new avenues for medical applications such as plaque composition analysis and oxygen saturation imaging.
