Table 1 Summary of salient properties of immune and peptide-associated tracers and radioisotopes matching their half-life
From: Promise and challenges of clinical non-invasive T-cell tracking in the era of cancer immunotherapy
|  | IgG | F(ab′)2 | Fab′ | Diabody | scFv | Nanobodies and affibodies |
|---|---|---|---|---|---|---|
Molecular weight | 150 kDa | 110 kDa | 55 kDa | 40–50 kDa | 28 kDa | 13–16 kDa |
Biol. T1/2 blood (h) | 110 | 48 | 4 | < 4 | 1 | < 1 |
Metabolic target organ | Liver | Liver | Kidney | Kidney | Kidney | Kidney |
Optimal accumulation time | Days | Day | Hours | Hours | Hour | < Hour |
Radionuclides of interest for PET | 64Cu 89Zr | 64Cu 89Zr | 64Cu 18F | 68Ga 18F | 68Ga 18F | 68Ga 18F |
Half-life | 12.7Â h 78.4Â h | 12.7Â h 78.4Â h | 12.7Â h 110Â min | 68Â min 110Â min | 68Â min 110Â min | 68Â min 110Â min |
Emaxβ + (MEV) | 0.653 0.902 | 0.653 0.902 | 0.653 0.634 | 1.890 0.634 | 1.890 0.634 | 1.890 0.634 |
Branching (β+) % | 17.5 22.7 | 17.5 22.7 | 17.5 96.9 | 87.7 96.9 | 87.7 96.9 | 87.7 96.9 |
Intrinsic spatial resolution loss (mm) | 0.7 1.0 | 0.7 1.0 | 0.7 0.7 | 2.4 0.7 | 2.4 0.7 | 2.4 0.7 |