Is ¹⁸F-DOPA a valid cardiac sympathetic neuroimaging agent?

Area of Science:

• Nuclear medicine
• Neuroimaging
• Cardiology

Background:

• Cardiac noradrenergic deficiency is a hallmark of Lewy body forms of neurogenic orthostatic hypotension.
• 18F-Dopamine positron emission tomography (PET) is a validated research tool for assessing this deficiency.
• Brain 18F-DOPA PET is FDA-approved and 18F-DOPA converts to 18F-dopamine in the heart.

Purpose of the Study:

• To evaluate the potential of 18F-DOPA as a cardiac sympathetic neuroimaging agent.
• To compare 18F-DOPA and 18F-dopamine in patients with and without low 18F-dopamine cardiac radioactivity.

Main Methods:

• 18F-DOPA and 18F-dopamine PET scans of the brain and heart were performed in patients with neurogenic orthostatic hypotension, Parkinsonism, and controls.
• Cardiac 18F-dopamine radioactivity lower limit of normal was established at 6000 Bq-kg/cc-MBq.
• Inter-relationships between cardiac 18F-DOPA, cardiac 18F-dopamine, brain 18F-DOPA ratios (putamen/occipital cortex), and Parkinson Disease Rating Scale scores were analyzed.

Main Results:

• Cardiac 18F-DOPA radioactivity did not differentiate subjects with normal versus decreased cardiac 18F-dopamine radioactivity and showed no correlation with it.
• Left ventricular 18F-DOPA radioactivity was poorly resolved from the cardiac chamber.
• Brain 18F-DOPA putamen/occipital cortex ratios correlated negatively with Unified Parkinson Disease Rating Scale scores (r = -0.67, p = 0.0015).

Conclusions:

• 18F-DOPA is not suitable as a cardiac sympathetic neuroimaging agent.
• Brain 18F-DOPA PET remains a valuable biomarker for Parkinsonism.