[18F] LBT-999 PET Compared to [123I]-FP/CIT SPECT to Distinguish Between Parkinson's Diseases and Essential Tremor

Inclusion Criteria:

• Patients aged 35 to 80 (male or female)
• Patients:
• suffering from an essential tremor as defined by Elble's criteria from 2000 (excluding head tremor in decubitus and compatible with the study by theinvestigator)
• or with Parkinson's disease as defined by the United Kingdom Parkinson's DiseaseSociety Brain Bank (UKPDSBB)
• Patients diagnosed over 18 months ago
• Women of childbearing potential who must have effective contraception at baseline andup to 30 days after the last administration of the radiopharmaceutical (investigational medicinal product or comparator)
• Patients affiliated with or receiving a social security scheme
• Patients who have been fully informed about the organization of the research and whohave signed their informed consent

Exclusion Criteria:

• Patients with atypical non-idiopathic Parkinson's syndrome (multi system atrophy,progressive supranuclear palsy, etc.)
• Patients treated with deep brain stimulation
• Patients with functional psychogenic movements
• Patients with severe and progressive psychiatric disorders
• Patients with disabling dyskinesia or essential tremor that are incompatible withimaging studies
• Patients who have had an ionizing radiation examination on the brain within the last 3months
• Individuals with a contraindication to PET or SPECT imaging:
• Patients with claustrophobia
• Patients refusing to be informed in case of abnormalities detected during imagingtests
• Patients treated with amphetamines, benzatropine, amfebutamone, cocaine,mazindol, methylphenidate, phentermine or sertraline
• Individuals with a known allergy to the active substance or one of the excipientsof the product under investigation or to the reference product or to or tothyroid treatment
• Woman of childbearing age without effective contraception in the opinion of theinvestigator
• Any other serious unstabilized chronic condition deemed incompatible with the study bythe investigator
• Patients unable to sign the informed consent
• Patients participating in a protocol or in a period of exclusion from a protocol
• Patients who received compensation of more than 6000 € in the last 12 months prior toenrollment in clinical studies
• Patients in a period of exclusion from the national volunteer database during whichthey cannot participate in another clinical study
• Patients not affiliated with a social security scheme
• Patients refusing to participate
• Individuals referred to in articles L. 1121-5 to L. 1121-8 and L1122-2 of the FrenchPublic Health Code