Table 1.
Comparison of IVM with other in vivo imaging systems
| Methods | Spatial/temporal (preclinical) | Spatial/temporal (clinical) | Penetration depth | Physical principle | Imaging agent | Multi-channel imaging | Primary use | Advantages | Disadvantages |
|---|---|---|---|---|---|---|---|---|---|
| IVM | 100 nm-1 μm/Sub-seconds-Seconds | 1 μm/Sub-seconds-Seconds | [Confocal] <100 μm | Visible and near-infrared light | Photoproteins, Fluorochromes | Multiple | All below | - Microscopic resolution | - Small field of view |
| [Two-photon] <300 μm | - Live cell/molecule tracking | - Limited penetration depth | |||||||
| - Real-time monitoring | |||||||||
| CT | 400 nm (nano CT), 50-200 mm/Minutes | 500 μm/Seconds | No limit | X-rays | Iodinated molecules | No | Primarily for vascular, lung, and bone imaging | - High spatial resolution | - Limited sensitivity |
| - High penetration depth | - Radiation | ||||||||
| - Fast and cross-sectional images | - Relatively poor soft tissue contrast | ||||||||
| MRI | 10-100 μm/Minutes-Hours | 1 mm/Seconds-Minutes | No limit | Radio waves | Paramagnetic chelates, Magnetic particles | No | Versatile imaging with high soft tissue contrast | - High spatial resolution | - Low sensitivity |
| - Anatomical detail | - Long acquisition and Image process times | ||||||||
| - Functional information | - Low throughput | ||||||||
| PET | 1-2 mm/Seconds-Minutes | 4 mm/Seconds | No limit | High-energy g-rays | F-18, Cu-64, C-11, Ga-68 labeled compounds | No | Versatile imaging with many different tracers | - High sensitivity | - High cost of cyclotron |
| - High penetration depth | - Radiation | ||||||||
| - Limited spatial resolution | |||||||||
| SPECT | 0.25 mm (USPECT), 1-2 mm/Minutes | 6-8 mm/Seconds | No limit | Low-energy g-rays | Tc-99m, In-111, I-131-labeled compounds, Ga-67, Tl-201 | Two | Imaging labelled antibodies, proteins, and peptides | - High sensitivity (but lower than PET) | - Limited spatial resolution |
| - High penetration depth | - Radiation | ||||||||
| - No need for cyclotron | - Hard to quantify | ||||||||
| Ultrasound | 50-500 mm/Seconds-Minutes | 300-500 mm/Seconds | < 15 cm | High-frequency sound wave | Microbubbles (for contrast enhancement) | No | Vascular and interventional imaging | - Excellent sensitivity with microbubbles | - Poor penetration depth |
| - High temporal resolution | - Low spatial resolution | ||||||||
| - Inexpensive | - Low contrast and strong boundary effect |
The characteristics of IVM are compared to those of other imaging systems. Other in vivo imaging systems have no limitations in penetration depth and a larger field of view. On the other hand, IVM has higher spatial and temporal resolution and can be used for multiple-channel imaging. Also, the clinical adaption of IVM is still in development compared to other in vivo imaging systems. CT, Computed Tomography; MRI, Magnetic Resonance Imaging; PET, Positron Emission Tomography; SPECT, Single-Photon Emission Computed Tomography; IVM, Intravital Microscopy.