Table 1.

Advantages and Disadvantages of Imaging Modalities of Islets

	Advantages	Disadvantages	Contrast Agent
MRI	High spatial resolution, Deep tissue penetration, Tomographic capability, No radiation, Repeatability	Low sensitivity, Toxicity of contrast agent, Difficulty of distinguishing between live and dead islets, Pre-labeling islets before transplantation	SPIO, Gd, Mn2+, Zn2+,19F
SPECT	High resolution, Deep tissue penetration, High sensitivity, Functional evaluation of islets	Low spatial and anatomical resolution, Ionizing radiation	99mTc, 111In, 123I, 131I
PET	High resolution, Deep tissue penetration, Higher sensitivity, Functional evaluation of islets	Low spatial and anatomical resolution, Ionizing radiation	11C, 18F, 68Ga, 64Cu
FI	High sensitivity, Quantitative evaluation of islets, No radiation	Short period of cancellation, Poor tissue penetration, Low spatial resolution	GFP, RFP, FITC, Cy-5.5
BLI	Long-term observation, High sensitivity, Quantitative evaluation of islets, No radiation	Susceptible to internal environment, Weak signal, Low spatial resolution	Luciferin
US	Simple operation, No radiation, Repeatability, No adverse effects	Operator dependency, Low sensitivity, Weak signal, cannot visualize single islets
MPI	No radiation, high temporal resolution, high spatial resolution and high sensitivity	No anatomical background.	Magnetic particle
PAI	High resolution, Deep tissue penetration, No ionizing radiation Diverse endogenous and exogenous contrast,	Reproducibility and standardization of the images
Multimodality imaging	Combining the advantages of various imaging modalities	High costs, Complexity design of Contrast agent, The long-term effects on the human body need further study	Nanoparticles