Optimal stem cell tracking probe characteristic | Optimal cellular probe | Examples | Probe disadvantages | Imaging modality |
---|---|---|---|---|
Absorbance/emission spectra within “optical window” | Fluorescence | Reporter genes (e.g. iRFP), quantum dots, exogenous probes (e.g. PKH26) | Requires genetic modification and excitation light, high background due to autofluorescence, signal loss with cell division, low depth of imaging, limited spatial resolution | FLI |
Bioluminescence | Reporter genes (e.g. fLuc) | Requires genetic modification and exogenous substrate administration | BLI | |
Photoacoustic | Reporter genes (e.g. LacZ, iRFP), endogenous labels (e.g. Hb, melanin) | Requires excitation light and may require genetic modification, expensive equipment | PAI | |
High signal sensitivity/intensity | Radionuclide | Reporter genes (e.g. hNIS), 99mTc, 111In, 18F FDG | Ionizing radiation, poor anatomical detail (but can be combined with magnetic resonance or x-ray), radioactive decay limits imaging time, cellular toxicity, may require genetic modification, expensive | SPECT, PET |
Electron density | Gold nanoparticles | Limited spatial/soft tissue resolution, ionizing, not indicative of cell viability, expensive | x-ray, CT | |
Fluorescence | As described above | As described above | FLI | |
Bioluminescence | As described above | As described above | BLI | |
Photoacoustic | As described above | As described above | PAI | |
High spatial resolution | Magnetic resonance | Iron oxides, microcapsules | Low signal intensity, not indicative of cell viability, expensive | MRI |
High temporal resolution/real time tracking | Echography | Microbubbles, perfluorocarbons | Low resolution, acoustic artefacts, subject to user bias | US |
Fluorescence | As described above | As described above | FLI | |
Bioluminescence | As described above | As described above | BLI | |
Photoacoustic | As described above | As described above | PAI | |
Radionuclide | As described above | As described above | SPECT, PET | |
High imaging depth | Photoacoustic | As described above | As described above | PAI |
Echography | As described above | As described above | US | |
Radionuclide | As described above | As described above | SPECT, PET | |
High cellular retention/signal retention upon cell division | Fluorescence | Reporter genes (e.g. iRFP) | As described above | FLI |
Bioluminescence | As described above | As described above | BLI | |
Photoacoustic | As described above | As described above | PAI | |
High anatomical detail | Magnetic resonance | As described above | As described above | MRI |
Electron density | As described above | As described above | x-ray, CT | |
Multimodal systems which include MRI or x-ray | ||||
Low cellular toxicity/non-ionizing | Echography | As described above | As described above | US |
Magnetic resonance | As described above | As described above | MRI | |
Fluorescence | As described above | As described above | FLI | |
Bioluminescence | As described above | As described above | BLI | |
Quantifiable signal | Fluorescence | As described above | As described above | FLI |
Bioluminescence | As described above | As described above | BLI | |
No cellular genetic modification | Echography | As described above | As described above | US |
Radionuclide | 99mTc, 111In, 18F FDG | As described above | SPECT, PET |