TABLE 3

Imaging Modalities

Modality	Signal/contrast	Translational	Preclinical	Sensitivity^*	Resolution	Depth	Quantitative	Target	Acquisition time (s)	Cost^†
PET	¹¹C, ¹³N, ¹⁵O, ¹⁸F, ⁶⁴Cu, ⁶⁸Ga, ⁸⁹Zr, ¹²⁴I	Yes	Yes	1	1–2 mm	No limit	Yes (very good)	Molecular	10–100	$$$
SPECT	^99mTc, ^123/125I, ²⁰¹Tl, ¹¹¹In, ¹⁷⁷Lu, ⁶⁷Ga, ¹³³Xe	Yes	Yes	10⁻¹–10⁻²	<1 mm	No limit	Yes (good)	Molecular	100–1,000	$$
MRI	Hydrogen, gadolinium, magnetic or paramagnetic particles	Yes	Yes	10⁻⁵	10–100 μm	No limit	Yes (fair)	Anatomic, molecular	100–1,000	$$$
MR spectroscopy	Hyperpolarization (¹³C, ¹⁵N, ¹²⁹Xe, ³He)	Yes	Yes	<10⁻⁵	5 mm	No limit	Yes (fair)	Molecular	100–1,000	$$$
Ultrasound	Echoes, microbubbles	Potential	Yes	10⁻³	50 μm	Centimeter	Yes (poor)	Anatomic, molecular	<1	$$
Bioluminescence	Luciferase (reporter gene)	No	Yes	1–10²^‡	<10 mm	Centimeter	Yes (poor to fair)^‡	Molecular	1–10	$$
Fluorescence	Fluorescent proteins, fluorochromes, quantum dots	Potential	Yes	10⁻²–1^‡	2–3 mm	<1 cm	Yes (poor to fair)^‡	Molecular	1–10	$

↵* Relative to that of PET.
↵† For high-resolution, small-animal imaging systems (clinical imaging systems differ). Cost is based on purchase price of imaging systems in United States. $=low cost; $$=intermediate cost; $$$=high cost.
↵‡ Depth-dependent.