Equivocal Dopamine Transporter Imaging: Integrating Visual Assessment, Quantification, and Clinical Follow-Up

Dopamine transporter (DAT) imaging is widely used to determine whether parkinsonian symptoms reflect presynaptic nigrostriatal degeneration. Although most examinations can be confidently classified as normal or abnormal, a clinically important subset remains equivocal. Such scans may show subtle posterior putaminal reduction, mild asymmetry, preserved comma-shaped morphology despite low quantitative values, or disagreement between visual and semiquantitative assessments. These findings may result from early neurodegeneration, physiological variation, medication effects, structural lesions, technical artifacts, or limitations of image processing and normative databases. This narrative review examines visual criteria, the complementary role and limitations of quantification, longitudinal outcomes of scans without evidence of dopaminergic deficit (SWEDD), common interpretive pitfalls, and the roles of clinical follow-up and repeat imaging. No universal quantitative cutoff can be applied across scanners, reconstruction methods, tracers, and software platforms. Expert visual interpretation remains the primary basis for assessment, while age- and platform-matched quantification is most useful as an adjunct in borderline cases. Integrating image quality, regional uptake pattern, quantitative findings, structural imaging, medication history, and clinical evolution may reduce diagnostic error and premature labeling of neurodegenerative parkinsonism.