Investigating the Microstructural and Functional Alterations of Brain in Parkinson's Disease Patients

Inclusion Criteria: 1. PD group: 35 subjects with a diagnosis of PD whom must: * Male or female patients, age range 20\~80. * Patients should not have any clinical evidence of cognitive impairment or ICD. * Patients who provide a written informed consent prior to study entry. If the patient is incapable of informed consent, the caregiver may consent on behalf of the patient (the patient must still confirm assent). 2. PD-MCI group: 35 subjects with a diagnosis of PD with mild cognitive impairment whom must: * Male or female patients, age range 20\~80. * Patients should be fulfilled the"Diagnostic Criteria for Mild Cognitive Impairment in Parkinson's Disease: Movement Disorder Society Task Force Guidelines" as PD-MCI. (Litvan, 2012; Appendix II). * Patients should not have any clinical evidence of ICD. * Patients who provide a written informed consent prior to study entry. If the patient is incapable of informed consent, the caregiver may consent on behalf of the patient (the patient must still confirm assent). 3. PDD group: 35 subjects with a diagnosis of PD with dementia whom must: * Male or female patients, age range 20\~80. * Patients should be fulfilled the "Movement Disorders Society diagnostic criteria of PDD as "possible" or "probable" PDD (Emre, 2006). (Appendix III) * Patients should not have any clinical evidence of ICD. iv.Patients who provide a written informed consent prior to study entry. If the patient is incapable of informed consent, the caregiver may consent on behalf of the patient (the patient must still confirm assent). 4. PD-ICD group: 35 subjects with a diagnosis of PD with ICD whom must: * Male or female patients, age range 20\~80. * Patients should be fulfilled one of the diagnostic criteria or definition in these ICDs: pathological gambling, hypersexuality, compulsive shopping, compulsive eating, punding, and compulsive medication use (Voon, 2009). (Appendix IV). * Patients should not have any clinical evidence of dementia or cognitive impairment. * Patients who provide a written informed consent prior to study entry. If the patient is incapable of informed consent, the caregiver may consent on behalf of the patient (the patient must still confirm assent). 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 of intracranial operation, including thalamotomy, pallidotomy, and/or deep brain stimulation. 5. 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. 6. Any evidence of secondary parkinsonism (multiple infarcts, intoxication, and hydrocephalus, etc) or other neurodegenerative diseases (multiple system atrophy, progressive supranuclear palsy). 7. History of allergy to radioligands that contain 18F isotope.