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| Imaging modality | Optical imaging | Computed tomography | Magnetic resonance imaging | Ultrasound | Radionuclide imaging |
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| Source of detection | visible or near-infrared light | X-ray | magnetic field, radiowaves | ultrasonic waves | γ-ray |
| Common imaging probes | fluorescent dyes, quantum dots | heavy atom-containing contrast agents, for example, iodine, barium and gadolinium salts | paramagnetic or superparamagnetic contrast agents, for example, gadolinium, manganese compounds and magnetofluids (Fe3O4) | microbubbles | Radionuclides (18F, 11C, 64Cu, , 111In, etc.)-labeled probes |
| Advantages | inexpensive, low-cost, easy operation | anatomical imaging, applicable for humans | high spatial resolution, combines morphological and functional imaging, no tissue penetrating limit, applicable for humans | safety, real-time, low cost, wide availability, easy handling | high sensitivity, quantitative, no penetration limit |
| Disadvantages | photobleaching, limited tissue penetrating depth, surface-weighted, relatively low spatial resolution, autofluorescence disturbance | radiation risks, limited soft tissue resolution, not quantitative | relatively low sensitivity, time-consuming scan and processing, high cost | limited resolution and sensitivity, low data reproducibility | low spatial resolution, radiation risks, high cost |
| Some practical applications | cellular/intracellular expression, trafficking or movement monitoring of reporter/gene | bone and tumor imaging, fused image with other modalities | cell trafficking, morphological reporter/gene expression, cerebral and coronary angiography in clinics | potential application in drug delivery and controlled release, echocardiography and intracranial neoplasm in clinics | noninvasive evaluation of pharmacokinetics and metabolism of drugs, cerebral, cardiac and tumor imaging in clinics |
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