Fig. 1.

Flow chart inclusion of study participants. 258 participants (173 patients with Parkinson's disease and 85 age and sex-matched controls) were recruited at baseline. An image quality analysis protocol was established in this study. This protocol allowed us to carry out our current study only on 98 Parkinson’s disease patients (60 males and 38 females) and 65 age and sex-matched healthy subjects (35 males and 30 females). Parkinson’s disease patients were stratified in four groups according to the duration of the disease (Group1 < 5 years; Group2 > 5 and < 10 years; Group3 > 10 and < 15 years and Group4 > 15 years).