The primary objective of this protocol is to analyze the sensitivity and specificity of 18F-DTBZ PET to the differential diagnosis of Parkinson's Disease (PD) and normality. Secondary, the investigators will analyze the correlation between the 18F-DTBZ binding and the severity of disease of PD and the role of 18F-DTBZ PET in the monitoring disease severity.

25 age-matched healthy volunteers will be enrolled. For assessing the correlation between the 18F-DTBZ binding and the severity of disease, the patients with PD will be divided into three groups according to their motor scores: mild, moderate, and advanced. We will enroll 25 patients in each group. Each evaluable subject involved in this study must fulfill all the inclusion and exclusion criteria according the subject grouping, each subject will have 3 visits in this study, as one screening visit, one imaging visit, and one safety evaluation visit.

Safety measurement will be evaluated by medical history, vital signs, physical examinations, laboratory examinations and collecting of adverse events.

Inclusion Criteria:

1. Both genders and 50~80 years old.
2. Written and dated informed consent by self or by legal representative, to be obtained before any of the study procedures
3. Healthy male or female subjects with no evidence of significant neurologic impairment by history.
4. Seventy-five PD subjects will be divided as three subgroups according to the severity of disease: mild (Modified Hoehn and Yahr stage 1 to 2), moderate (Modified Hoehn and Yahr stage 2.5 to 3), and advanced (Modified Hoehn and Yahr stage 4 to 5).
5. All the PD subjects should be fulfilled the UK Parkinson's Disease Society Brain Bank criteria of "possible" or "probable" PD. The age of disease onset should be older than 50 years.

Exclusion Criteria:

1. Pregnant or becoming pregnant during the study (as documented by pregnancy testing at screening or at any date during the study according to the PI discretion) or current breast feeding.
2. Any subject who has a clinically significant abnormal laboratory values, and/or clinically significant or unstable medical or psychiatric illness.
3. History of drug or alcohol abuse within the last year, or prior prolonged history of abuse.
4. History or presence of QTc prolongation.
5. History of intracranial operation, including thalamotomy, pallidotomy, and/or deep brain stimulation.
6. Any documented abnormality in the brain by CT or MRI of brain, which might contribute to the motor function, such as hydrocephalus, multiple infarction and encephalomalacia, will be excluded. Mild cortical atrophy and non-specific white matter changes will be allowed.
7. Patients who have the evidence of secondary