Table 2.

The target depths and critical PRR for different types of PAI systems. PRR, pulse repetition rate; PAI, photoacoustic imaging; PACT, photoacoustic computed tomography; AR-PAM, acoustic-resolution photoacoustic microscopy; OR-PAM, optical-resolution photoacoustic microscopy; ${\mathit{v}}_{\mathit{s}}$, speed of sound in soft tissue.

	PACT	AR-PAM	OR-PAM
Optical focus regime	Diffusive	Quasi-diffusive	Ballistic regime
Effective imaging depth	≤ 5 cm	≤ 10 mm	≤ 1 mm
Critical PRR	30.8 kHz	154 kHz	1.54 MHz

(where $v_s=$ 1540 m/s).