Table 1.

Neuroimaging Techniques to Measure Central Dopamine Function in Humans

Technique	Description	Outcome measures	Strengths	Limitations	Used in pediatric samples?
Positron Emission Tomography (PET)	A radioactive ligand is administered intravenously to index DA release or receptor binding	Metabolic increases or decreases measured in discrete brain regions of interest where the ligand has bound	Responsivity of the DA system is directly measured	Poor spatial resolution as compared to fMRI; poor temporal resolution; complex procedure is ethically challenging when used with vulnerable populations	No
MR-spectroscopy	Single or multiple voxels are targeted for neurochemical examination in an MR environment	Levels of neurochemicals are measured; these reflect cellular processes involved in energy expenditure	Relative ease of data collection; non-invasive; impairments at the cellular level can be assessed in the living brain	Difficult to examine whole-brain; resolution limited at low field strengths; only chemicals present in large concentrations can be measured	Yes
Structural MRI	Whole-brain or regional brain volumes are measured	White matter volumes, indices of white matter connectivity, and gray matter volumes in areas known to be innervated by DA	Relative ease of data collection; non-invasive	Links between structure and function are indirect and unclear in relation to neurochemical function	Yes
Functional MRI	Whole-brain or regional brain activations are measured through blood-oxygenation-level-Dependent (BOLD) signals during a behavioral task or at rest	Activations are measured in areas known to be innervated by DA; these activations can be provoked through the use of well-designed behavioral probes	Ease of data collection; non-invasive; use of behavioral probes in the scanner allows function to be directly linked to neural signals	BOLD signal cannot resolve increases or decreases in activation at the neurochemical level; interpretation is challenging	Yes
Pharmacological Challenge During fMRI or PET	Individuals systemically ingest drugs that activate (agonists) or inhibit (antagonists) DA release or receptor activity; can be combined with fMRI or PET	Behavioral functions typically compared pre-versus post-ingestion; some recent studies combine with neuroimaging to index brain function following drug challenge	Probes can be utilized that have selective effects on various aspects of DA synthesis or receptor function; many treatment applications	Most studies are conducted under acute challenge conditions; long-range effects of drug ingestion less well-studied; systemic administration has poor specificity for regional brain effects	No