Table 2.

Comparison of emerging molecular imaging technologies for precision medicine

Imaging Modalities	Spatial Resolution		Imaging Time	Depth of Penetration	Imaging Agents and Molecular Probes	Key Utilization
Multi-photon Microscopy		15-1000 nm	Secs	-	Fluorescent proteins, dyes, rhodamine amide, quantum dots	Visualization of cell structures
Atomic Force Microscopy		10-20 nm	Mins	-	Intermolecular forces	Mapping cell surface
Electron Microscopy		0.2-3 nm	Secs	-	Cyrofixation	Discerning protein structure
Ultrasound (US)	Superficial applications	50 μm, 0.01-0.1 mm	Secs	mm-cm	Microbubbles, nanoparticles	Vascular imaging
	Deeper applications	1-2 mm
CT	Preclinical	12-50 μm, 50-200 μm	Mins	Limitless	Iodine	Lung and bone tumor imaging
	Clinical	0.5-1 mm
MRI	Preclinical	4-100 μm, 25-100 μm	Mins-Hrs	Limitless	Gadolinium, dysprosium, iron oxide particles	Anatomical imaging
	Clinical	~1 mm				Functional
fMRI		~1 nm	Secs-Mins	-	Oxygenated hemoglobin	Functional imaging of brain activity
					(HbO2) deoxygenated hemoglobin (Hb)
MRS		~2 nm	Secs	-	N-acetylaspartate (NAA), creatine, choline, citrate	Detection of metabolites
PET	Preclinical	1-2 mm	Mins	Limitless	Fluorodeoxyglucose (FDG), 18F, 11C, 15O	Metabolic imaging
	Clinical	5-7 mm
SPECT	Preclinical	1-2 mm	Mins	Limitless	Tc-99m, In-111, I-131-labeled compounds, Ga-67, Tl-201, Peptide	Cardiovascular imaging, diagnosis of bone metastasis
	Clinical	8-10 mm
Optical fluorescence imaging (OFI)		2-3 mm	Secs-Mins	< 1 cm	Peptide, integrins, matrix metallo-proteinases, caspases	Characterization of cancer
Optical bioluminecence imaging (OBI)		3-5 mm	Secs-Mins	1-2 cm	Luciferins, coelenterazines, luminal, Peptide	Gene expression, cell & bacterial tracking
Surface-enhanced raman scattering (SERS) imaging		mm	Min-days	~5 mm	EGFR-SERS, EGFR affibody-gold-silica nanoparticles	Oligonucleotide targeting
Photoacoustic imaging (PAI)		~10 μm to 1 mm	Secs-Mins	6 mm to 5 cm	EGFR Antibody-gold nanoparticles [Nle4, d-Phe7]- -melanocyte-stimulating hormone-gold, hormone-gold nanocages	Functional imaging of blood oxygenation
Intravital microscopy (IVM)		1 μm	Secs-days	< 400-800 μm, ~700 μm	Photoproteins, fluorochromes	In development (endoscopy, skin)
Fluorescence reflectance imaging (FRI)		1 mm	Secs-Mins	< 1 cm	Photoproteins, fluorochromes	Rapid screening of molecular events in surface-based disease
Fluorescence mediated tomography (FMT)		1 mm	Mins	2-3 cm	Near Infrared, fluorochromes	Quantitative imaging of targeted or “smart” fluorochrome reporters