Table 1.

Comparison of various imaging modalities in preclinical use.

	MRI	OPI	PAT	CT
Detection sources	• magnetic, • field, • radiowaves	• visible or near-infrared light	• short-pulsed laser beam	• X-ray
Advantages	• applicable for human, • high spatial resolution, • no tissue penetrating limit	• inexpensive • easy operation	• high resolution and contrast	• anatomical imaging, • applicable for humans
Disadvantages	• scan and processing, • relatively low sensitivity, • time and money consuming	• photobleaching, • surface-weighted, • autofluorescence disturbance, • relatively low spatial resolution • limited tissue penetrating depth	• high frequency or photoacoustic signals	• radiation risks, • not quantitative, • limit soft tissue resolution
Applications	• cell trafficking, • gene expression, • morphological reporter, • cerebral and coronary angiography in clinics	• trafficking or movement monitoring of reporter/gene, • cellular/intracellular expression	• endoscopy, • gene expression, • molecular imaging, • melanoma detection	• bone and tumor imaging, • fused image with other modalities