Table 1.

Summary of the technical and functional capabilities of the 3 imaging modalities in this review. Approximate scan time and cost are listed as ranges depicting the approximate minimum and maximum values. Scan time generally increases with increased resolution (smaller in-plane resolution) and increasing the number of slices or acquisitions. The cost of scanning varies widely due to the institution, equipment used, use of a trained technician, and if the imaging time is designated as preclinical or clinical. Preclinical imaging time is traditionally much less expensive than time reserved for clinical imaging

Modality	In-plane resolution	Depth of penetration	Approximate scan time	Cost ($ per hour)	Imaging techniques sensitive to TERM outcome measures
					State	Biocompatibility	Function
Ultrasound	~0.1 mm	~cm	Real-time	50–300	B-Modea	Dopplera	Dopplera, elastographya
X-Ray/CT	~0.1 mm–~0.5 mm	Unlimited	Seconds – 10 minutes	200–1000	CTa, contrast agentsb	Cell labelingb	Contrast agentsb
MRI	~mm	Unlimited	1 minutes – 20 minutes	400–2000	Structural MRIa, relaxationa, UTEb	Perfusionb, UTEb, contrast agentsb	Relaxationa, CESTb, DTIb, elastographyb, taggingb, contrast agentsb

^aIndicates clinically oriented imaging technique.

^bIndicates research-oriented imaging technique.

TERM – Tissue engineering and regenerative medicine. CT – computed tomography. MRI – magnetic resonance imaging. UTE – ultrashort echo time. CEST – chemical exchange saturation transfer. DTI – diffusion tensor imaging.