(A) AR-PAM system . PA imaging to probe changes in cortical blood volume (B) and oxygenation (C) without a labeling agent . (D) In vivo transcranial imaging of changes in HbT in single cerebral cortex vessels in small animals . (E) Cerebral hemodynamic responses to neuronal activities induced by direct cortical electrical stimulation in rats; V1, V2 – observed blood vessels . (F-G) A method to measure transverse blood flow was employed PA Doppler, showing the (F) speed and (G) velocity with directions .