The purpose of this study is to find a biomarker for Parkinson's disease (PD). A biomarker is an indicator of the presence of a disease, that can be measured, and that is able to give information about the progression, or severity, of it.~The study visits will take place in London. There are three locations on Hammersmith hospital campus, that are located near to each other. The NIHR Imperial Clinical Research Facility and Invicro London for clinical and MRI and PET assessments, and Imperial Healthcare Nuclear Medicine Department for the SPECT scan.~Participants will attend 5 visits in a 3 month period. These visits include an initial consent and assessment visit where some blood samples will also be taken. The second visit involves a PET scan with the tracer DASB along with an MRI scan. The third visit involves two PET scans one in the morning, with CIMBI tracer, an injection of Dexamphetamine, and then a second with CIMBI tracer to make a comparison. The fourth visit involves a SPECT scan, and the fifth visit is optional and would be for a lumbar puncture visit. Each visit will last around 6 hours.
In this study, the investigators aim to provide a deeper understanding of Parkinson's disease and find a biomarker of Parkinson's disease. This is done using imaging scans called Positron Emission tomography (PET), Single Photon Emission Computed Tomography (SPECT), and Magnetic Resonance Imaging (MRI). The findings will provide a deeper understanding of the brain changes in Parkinson's disease. More importantly, this study will help with the discovery and development of new medications aiming to delay progression of Parkinson's disease symptoms