DaT (I-123 Ioflupane) scan is the most definitive diagnostic imaging tool for Parkinsonism, identifying dopaminergic neuron loss in Parkinsonism syndrome, including parkinson disease, multisystem atrophy (MSA), progressive supranuclear palsy (PSP), corticobasilar degeneration (CBD), and diffuse Lewy body disease (DLBD). It is commonly used in distinguishing Parkinsonism tremor from other causes of tremor, such as essential tremor.

Lugol solution or sodium iodide solution is used prior to DaT scan to prevent radioiodine absorption by the thyroid gland. Many medications that interfere with ioflupane absorption, including stimulants (ephedrine, cocaine, methamphetamine, amphetamine), benztropine, fentanyl, bupropion, and phentermine need to be discontinued prior to DaT scan imaging.

The normal DaT scan findings in this case suggest a non-Parkinsonism etiology for the patient's tremor, such as essential tremor.