Research Applications of Positron Emission Tomography/Magnetic Resonance (PET/MR) Imaging in Parkinson’s Disease (PD)

Abstract

PD is a common neurodegenerative disease affecting the elderly, with a prevalence of 15–328/100,000 people, approximately 1.7% of those over 65 years of age, and an incidence of 10–21/100,000 people each year. The etiology and pathogenesis of PD remain poorly understood, and it is currently believed to be caused by a combination of genetic and environmental factors. Typical pathological changes that occur in PD include the degeneration of dopaminergic neurons in the substantia nigra and the appearance of Lewy bodies within neurons. Lewy bodies are eosinophilic inclusions formed by the abnormal aggregation of alpha (α)-synuclein. The most common clinical presentation of PD is progressive motor dysfunction, with major motor symptoms including bradykinesia, resting tremor, muscle rigidity, and postural instability, accompanied by a wide range of non-motor symptoms, such as olfactory dysfunction, depression, constipation, sleep disorders, and cognitive impairment. Partial improvements in clinical symptoms can be achieved through pharmacological (primarily levodopa) and surgical (primarily deep brain stimulation, DBS) treatments, but to date, there has been no cure for PD. At present, the diagnosis of PD is primarily dependent on clinical examinations, and its diagnostic criteria are based on the presence of two or more core motor symptoms, bradykinesia plus resting tremor, and/or muscle rigidity. Owing to the lack of objective diagnostic methods, the rate of early diagnosis for PD is relatively low; therefore, the main challenge of imaging in the research of PD is the development of imaging markers for the early and differential diagnosis of PD. Additionally, the neural mechanisms underlying the clinical symptoms of PD remain unclear, which may be further elucidated with the help of imaging studies, thereby facilitating the development of effective treatment methods and targets.