Iron content is one of the physiological variables that can be estimated with magnetic resonance imaging (MRI) in the basal ganglia of patients with Parkinson's disease (PD). Brain iron is relatively independent from total body iron content since it is excluded by the blood-brain barrier. The microstructural and physiological organization of tissue plays an important role in determining the local magnetic field behavior of a given region in the brain. Recent work has extended previous observations by using a multimodal approach that combines MRI techniques for imaging iron content with other MRI sequences. MR-based measurements that are directly related to magnetic susceptibility changes should be closely related to iron content and less dependent on its microscopic spatial distribution. Susceptibility-weighted imaging (SWI) is a technique that uses magnetic susceptibility differences between different regions to generate image contrast. Deep brain stimulation (DBS) plays an important role in the treatment of PD.