Table 1.
Summary of salient properties of immune and peptide-associated tracers and radioisotopes matching their half-life
| 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 |
12.7 h 78.4 h |
12.7 h 78.4 h |
12.7 h 110 min |
68 min 110 min |
68 min 110 min |
68 min 110 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 |