Table 3.

Comparison of selected specifications of PAI, UMF, and USF imaging systems.

Imaging modality	Working mode	Resolution	Penetration depth	Depth-to-resolution ratio	Frame rate
PAI	OR-PAM	lateral 0.22μm axial 30μm	~1 mm	~200	Visual rate could be satisfied
	AR-PAM	≥7 μm	~10 mm
	PAT	~100 μm	<70 mm
UMF	Intensity or lifetime	~1 mm	~1 mm	~1	NR
USF	Intensity mode	~100 μm	<50 mm	~10	~10 mins
	Lifetime mode