Table 1. Characteristics of Various Nanoparticle-Based Imaging Modalities.

imaging modality	imaging probe	spatial resolution	molecular sensitivity	maximum penetration depth
magnetic resonance imaging (MRI)	para-/superpara-/ferromagnetic nanoparticles (Gd, Fe, Mn, etc.)	∼100 μm	μM–mM	no limit
computed tomography (CT)	nanoparticles of high-Z elements (Ba, I, Au, Ta, etc.)	∼100 μm	∼1 mM	no limit
anti-Stokes shift-based optical imaging	doped quantum dots, upconverting nanoparticles	<1 μm	<1 μM	<1 mm