Quantitative photoacoustic examination of abnormal particles hidden in a mixture of particles with non-uniform sizes.

Noninvasive quantification of abnormal particles hidden in a granular mixture from deep tissue is still a challenge of medical examination. In this study, we have theoretically deduced the power spectrum of the photoacoustic signals from the random mixture of particles with non-uniform sizes. It is revealed that there is an approximate linear relationship between the content of abnormal particles and the spectral slope. This finding provides a parameter of equivalent diameter for the abnormal particle detection. The experimental studies sensitively differentiate and quantify a trace of big micro-particles mixed in small micro-particles. Since the abnormal particles are associated with many important physiological and pathological processes, this study might provide a noninvasive way to assess the related diseases, such as microthrombosis, through monitoring the abnormal particles.