An Analysis Scheme for Investigation of Effects of Various Parameters on Signals in Acoustic-Resolution Photoacoustic Microscopy of Mice Brain: a Simulation Study

Abstract

Purpose:Photoacoustic spectral analysis is a novel tool for studying various parameters affecting signals in Photoacoustic microscopy. But only observing frequency components of photoacoustic signals doesn’t make enough data for a desirable analysis. Thus a hybrid time-domain and frequency-domain analysis scheme has been proposed to investigate effects of various parameters like depth of microscopy, laser focal spot size and contrast agent concentration on Photoacoustic signals.
Methods:Photoacoustic microscopy of mouse brain mathematical phantom has been simulated using k-space method and both time-domain and frequency-domain analysis of photoacoustic signals are presented for evaluation of three parameters affecting signals; depth of microscopy, concentration of Indocyanine Green as an exogenous contrast agent and size of laser focal spot illuminating hemoglobin as an optical absorber. A novel method for study of effects of different optical absorber sizes on PA signals has been proposed.
Results:This work demonstrates that going deeper through the brain will decrease contrast and resolution of photoacoustic microscopy of mouse brain vasculature and this can be solved by using an exogenous contrast agent like Indocyanine Green. Also, by proposed analysis of photoacoustic signals, we demonstrated that using Indocyanine Green will increase both depth resolution and contrast of photoacoustic signals.
Conclusion:Simulations and analysis done on different sizes of irradiated hemoglobin absorbers demonstrated that there is a need to ultra-broadband transducers for achieving more precise analysis of photoacoustic signals, and this means that Acoustic-Resolution Photoacoustic Microscopes are less efficient for utilization in photoacoustic spectral analysis.