Jiaying Lu

1 Introduction Parkinson’ s disease (PD) is a common progressive neurodegenerative disorder affecting approximately 1% of individuals over the age of 60 (Collaborators 2018; de Rijk et al. 2000; Ravenhill et al. 2023). A decline in dopamine transmitter synthesis disrupts the normal functioning of the striatum, subsequently preventing the rest of the brain from effectively coordinating muscle movements (Ota et al. 2006; Zemel et al. 2022).

Abstract Parkinson’s disease (PD) exhibits a characteristic posterior-to-anterior gradient of striatal dopamine loss, yet the underlying upstream mechanisms remain unclear. We combined in vivo ¹⁸F-FPCIT dopamine transporter (DaT) PET/MRI, quantitative susceptibility mapping, and diffusion MRI tractography in 48 PD patients and 10 healthy controls to test whether substantia nigra pars compacta (SNc) iron and microstructural disruption mediate posterior putaminal vulnerability.

Abstract Quantitative PET underpins diagnosis and treatment monitoring in neurodegenerative disease, yet systematic biases between PET-MRI and PET-CT preclude threshold transfer and cross-site comparability. We developed and validated the first unified, anatomically guided deep-learning framework to harmonize PET-MRI quantification to PET-CT standards across multiple tracers and scanner manufacturers.