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Table 2 Stem cell tracking strategies for cardiovascular applications in vivo

From: Tracking of stem cells in vivo for cardiovascular applications

Physical principle Modality Cell labels Advantages Disadvantages
Tissue contrast based Magnetic field change CMR • Iron oxides • High spatial resolution • Low sensitivity
• Gad-chelates • Signal not linked to cell viability
• Microcapsules • High anatomic detail
• Reporter genes (enzyme-based, transporter-based) • Lack of CMR-compatible devices for interactivity
• No ionizing radiation
• Post-processing capabilities
• Not compatible for patients with implants
• Permits medium-term tracking
• Expensive
• Acoustic noise
Electron density change X-Ray/CT • Gold Nanoparticles • High sensitivity • Ionizing radiation
• Microcapsules • High potential of real-time interactivity • Limited spatial resolution
• Lacks soft tissue detail
Echogenicity change US • Liposomes • High potential of real-time interactivity • Difficultly with thin/obese patients
• Microbubbles
• Microcapsules • Highly operator dependent
• Perfluorocarbons • No ionizing radiation
• Interpretation has high learning curve
• Inexpensive
• Highly portable
• Limited resolution
• Acoustic artifacts may compromise image
Photon emission based Radionuclide imaging (High energy ionizing radiation) PET • Reporter genes, e.g. HSV-tk, hNIS • High sensitivity • Poor anatomic detail
• High translational capacity
• Poor interactivity
• Radionuclides, e.g. 18 F-FHBG, 124I FIAU, and 18 F-FDG • Ionizing radiation
• Temporal limitations (due to radioactive decay)
SPECT • Radionuclides, e.g. 111In oxine, 99mTc and18 F FDG • Concerns for label-induced cellular toxicity
• Biohazardous labels
• Expensive
Optical imaging (Low energy radiation) BLI • Reporter genes, e.g. luciferase • Permits longitudinal monitoring • Limited spatial resolution
• Lacks clinical relevance
• Low background
• No excitation light required • Biohazardous labels
Fluorescence • Fluorophores, e.g. GFP • High sensitivity • Photon attenuation w/cell division
• Multiplexing
• Near-infrared probes • No ionizing radiation • Autofluorescence yields high background
• Quantum dots • Low cost
• Small depth of high-resolution
• Permits short-term tracking
• Biohazardous labels
  1. BLI: Bioluminescence imaging; 18F FDG: Fluoro-2-deoxy-d-glucose; FHBG: Fluoro-3-hydroxymethylbutyl; GFP: green fluorescent protein; 111In: Indium; PET: Positron emission tomography; SPECT: Single photoelectron computed tomography; 99mTc: Technetium; US: Ultrasound.