Table 1.

Comparison of the performance of different imaging techniques

Variable	Ultrasound	Photoacoustic imaging	Fluorescence imaging	MRI	PET
Type of energy measured	High-frequency sound waves	High-frequency sound waves	Visible or near-infra- red light	Radio waves	High energy gamma rays
Spatial resolution	50–500 μm	50–500 μm	2–10 mm (depth dependent)	20–100 μm	1–2 mm
Time resolution	Seconds to minutes	Seconds to minutes	Seconds	Minutes to hours	Minutes
Sensitivity	Not well characterized	pM	nM	μM–mM	pM
Depth	< 5 cm	< 5 cm	< 5 mm	No limit	No limit
Type of contrast agents	Microbubble	Nanoparticle/micro-bubble	Small molecules nanoparticle	Small molecules nanoparticle	Small molecules nanoparticle
Cost	Low	Low	Medium	High	High

MRI, magnetic resonance imaging; PET, positron emission tomography.