Multiparametric photoacoustic microscopy of the mouse brain with 300-kHz A-line rate

Enabling simultaneous high-resolution imaging of the total concentration of hemoglobin (C_Hb), oxygen saturation of hemoglobin (sO₂), and cerebral blood flow (CBF), multiparametric photoacoustic microscopy (PAM) holds the potential to quantify the cerebral metabolic rate of oxygen at the microscopic level. However, its imaging speed has been severely limited by the pulse repetition rate of the dual-wavelength photoacoustic excitation and the scanning mechanism. To address these limitations, we have developed a new generation of multiparametric PAM. Capitalizing on a self-developed high-repetition dual-wavelength pulsed laser and an optical-mechanical hybrid-scan configuration, this innovative technique has achieved an unprecedented A-line rate of 300 kHz, leading to a 20-fold increase in the imaging speed over our previously reported multiparametric PAM that is based on pure mechanical scanning. The performance of the high-speed multiparametric PAM has been examined both in vitro and in vivo. Simultaneous PAM of microvascular C_Hb, sO₂, and CBF in absolute values over a ∼3-mm-diameter brain region of interest can be accomplished within 10 min.