Table 4. ¹³C-labeled probes and their potential applications.

Probes	Potential clinical applications
[1-13C]pyruvate*	Glycolysis
[2-13C]pyruvate* [59,60,61]	Glycolysis, TCA cycle
[13C, 15N2]urea* [62,63]	Perfusion
[1-13C]α-ketoglutarate* [64]	TCA cycle, IDH
[1-13C]1,2-glycerol carbonate* [65]	pH imaging
[13C]bicarbonate [66]	pH imaging
[2-13C]dihydroxyacetone [67]	Hepatic glycolysis, gluconeogenesis, and glycerol synthesis
[1,4-13C2]fumarate [68]	Necrosis

^*Indicate probes that have been clinically validated for human use.

TCA = tricarboxylic acid cycle, IDH = isocitrate dehydrogenase