NM-MRI for treatment evaluation of Parkinson’s Disease patients

Abstract

T1-weighted fast spin echo magnetic resonance imaging (MRI) sequences are able to depict neuromelanin (NM)-containing structures, such as the Substantia nigra (SN), as hyper-intense signal areas. NM-MRI can accurately discriminate Parkinson’s Disease (PD) patients from controls and could potentially be used to evaluate the effects of PD treatment - either surgery or medication. PD patients that are treated with Deep Brain Stimulation (DBS) can only undergo 1.5T MRI sequences with specific conditions that prevent the tissues surrounding the neurostimulators from overheating. However, NM-MRI sequences are usually not applied at 1.5T due to worse image quality. Nevertheless, it would be interesting to study how DBS and medication influence the NM signal as a path for a better understanding of the disease and to potentially evaluate the progression of PD after the surgical intervention. Firstly in this work, a NM-MRI sequence was adapted for scanning patients with implanted DBS systems at 1.5T. To evaluate the performance of the sequence, images were taken on the same day with 1.5T and 3T MRI systems. The contrast ratio of both sequences was evaluated and SN areas were measured resorting to a semi-automatic segmentation algorithm. The assessment of these measurements revealed a good agreement between the developed sequence and the original 3T sequence. A second study was carried out, in which SN areas of PD de novo patients were evaluated before and after two months of initiating pharmacological treatment. The median SN area tended to be increased after treatment, suggesting a potential increase of NM related to dopamine therapy. In conclusion, this work presented the first 1.5T NM-MRI sequence that enables SN area measurement of patients with implanted neurostimulators, for further investigation of this method as a diagnostic tool for assessment of disease progression and to better understand clinical effects on NM-MRI and PD itself.