TABLE 1.
Examples of brain SPECT and PET radiotracers previously developed and associated BPND values in healthy humans.
| Radiotracer | Target (high to low density) | BPND | References |
| 123I-Iomazenil | GABA receptors | 12.50 ± 0.05 (n = 10) | Abi-Dargham et al., 1994 |
| 123I-(R,R)l-QNB | mACh receptors | 4.85 (n = 11) | Norbury et al., 2004 |
| 123I-5-IA85380 | α4β2-nACh receptors | 4.43 ± 0.06 (n = 6) | Fujita et al., 2003 |
| 123I-β-CIT | Dopamine transporters | 6.66 ± 1.54 (n = 5) | Laruelle et al., 1994 |
| 11C-Raclopride | D2/3 receptors | 2.19 ± 0.18 (n = 40) | Berry et al., 2018 |
| 123I-IBZM | D2/3 receptors | 0.86 ± 0.11 (n = 10) | Meyer et al., 2008 |
| 11C-DASB | Serotonin transporters | 2.68 ± 0.68 (n = 5) | Ginovart et al., 2001 |
| 123I-ADAM | Serotonin transporters | 1.62 ± 0.57 (n = 7) | Yang et al., 2008 |
| 11C-PK11195 | TSPO | 1.60 ± 0.40 (n = 13) | Kropholler et al., 2005 |
| 11C-PIB | β-amyloid plaques | 0.11 ± 0.15 (n = 13) | Tolboom et al., 2009 |
| 18F-FDDNP | β-amyloid plaques | 0.05 ± 0.03 (n = 13) | Tolboom et al., 2009 |
BPND reduces as a function of target density and radiotracer affinity (e.g., dopamine receptor, serotonin transporter and β-amyloid plaques ligands). The results also depend on method of quantification used, i.e., kinetic modeling with or without input function (details in sections below). Legend: α4β2-nACh receptor = alpha-4 beta-2 nicotinic acetylcholine receptor; mACh receptors = muscarinic acetylcholine receptors; D2 receptors = dopamine type 2 and 3 receptors; TSPO = 18 kDa translocator protein.