Stem Cell Tracking Technologies for Neurological Regenerative Medicine Purposes

Table 1

Imaging modalities currently available for tracking neural stem cells.

Modality	Source of imaging	Type of probe	Spatial resolution	Temporal resolution	Tissue penetrating depth	Sensitivity	Clinical use	Advantages	Disadvantages
MRI
In vivo labeling	Radiowave	Para- (Gd3+/Mn2+), SPIO or ^19F	>25 μm	Min–hrs	No limit	mM–μM	Yes	No radiation, very good tissue contrast, high resolution	Low sensitivity, agent dilution
Ex vivo labeling	Radiowave	MR reporter genes						Long-term imaging, long-term imaging	Exogenous gene risk
PET
Direct labeling	High-energy γ-ray	Radionuclides (e.g., ^18F, ^11C)	>1 mm	Sec–min	No limit	pM	Yes	High sensitivity, high sensitivity, deep tissues	Radiation, radiotracer dilution
Indirect labeling	High-energy γ-ray	Reporter genes (e.g., HSV1-tk)						Long-term imaging, avoid false signal, nontoxicity	Exogenous gene risk
SPECT
Direct labeling	Low-energy γ-ray	Radionuclides (e.g., ^111In, ^99mTc)	>1 mm	Min	No limit	pM	Yes	High sensitivity, able to image deep tissues	Radiation, low resolution, radiotracer dilution
Indirect labeling	Low-energy γ-ray	Reporter genes						Long-term imaging, nontoxicity	Exogenous gene risk
Optical imaging
Fluorescence imaging	Visible light	Fluorescence near-infrared dye, QD light	>2 mm	Sec–min	<1 cm	nM-pM	No	Cheap, simple, high sensitivity, activatable	Deep tissue limited, low resolution, tissue damaging
BIL	Visible light	Reporter genes	>2 mm	Sec–min	<1 cm	nM	No	Simple, high sensitivity	Deep tissue limited, low resolution