Table 1

Comparison of radioligands for imaging of 5-HTT in humans

Properties	[¹²³I]β-CIT SPECT	[¹¹C](+)McN5652 PET	[¹¹C]DASB PET	[¹²³I]ADAM SPECT
Selectivity	Nonselective, near 1:1 affinity for 5-HTT to DAT22^,23	Likely selective 10:1 to 100:1 affinity for 5-HTT over NET24^,25	Highly selective 1000:1 affinity for 5-HTT over NET or DAT^* 26^,27	Highly selective 1000:1 affinity for 5-HTT over NET or DAT28^,29
Displaceability of specific binding	Incomplete30^,31	In most, but not all, reports19^,32^,33	Highly displaceable26^,27^,34^,35	Highly displaceable28^,29^,36
Reversibility^†	Good37^,38	Not adequate to adequate, depending on region^‡18^,19^,39	Adequate in midbrain, good to very good in other regions20^,21^,40	Adequate in midbrain36^,41
Brain uptake	Adequate37^,38	Good19^,39	Very good20^,21^,40	Adequate36^,41
Specific binding to free and nonspecific binding ratio^†	Good	Not adequate in most regions, adequate in thalamus39^,42	Adequate to very good^‡20^,21	Not adequate in most regions; adequate in midbrain36^,41
Reliability of 5-HTT BP^†	Not measured	Modest32	Very good to excellent34^,43	Most regions reasonable41
5-HTT BP measurability in multiple regions	Brainstem only37^,38	Measurable in thalamus,39 not measurable in cortex19	Yes20^,21	Measurable in midbrain; unclear for other regions36^,41

↵* [¹¹C]DASB is also highly selective for 5-HTT over several other targets tested in vitro.
↵† For humans (radiotracer performance differs across species.)
↵‡ Depending on brain region.