This chapter provides an overview of magnetic resonance imaging (MRI) methods. The focus on iron in Parkinson's disease (PD) imaging has remained an important topic and researchers have often utilized T2*, or its reciprocal R2*, in nigral imaging protocols. Some iron-sensitive methods have been recently developed. These include adiabatic T2ρ, magnetization transfer (MT) imaging, and susceptibility-weighted imaging (SWI). The authors have developed a novel rotating frame relaxation experiment called relaxation along a fictitious field (RAFF). There has been greater refinement with the utilization of methods that do not employ a-priori regions of interest (ROIs). One such method is voxel-based morphometry (VBM), in which there is standardization of data and then voxel-by-voxel comparison between group data to determine if there are differences in signal intensity. Diffusion tensor imaging (DTI) provides structural data based on the directionally restrained diffusion of water within fiber tracts.

Ultrasmall paramagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) imaging is a promising noninvasive method to identify high-risk atheromatous plaques. Iron oxide particles function as contrast-enhancing agents by creating a large dipolar magnetic field gradient that acts on the water molecules that diffuse close to the particles. Howarth reported that USPIO appeared to show a dual contrast effect with signal enhancement being seen in plaques with little inflammation and large fibrous caps. The contralateral side of symptomatic patients given USPIO were also analyzed. It was found that 95% patients showed bilateral USPIO uptake suggesting an inflammatory burden within their carotid atheroma bilaterally. Three different approaches have been adopted to make the seemly impossible task a reality: ultrashort echo times (uTE), inversion recovery on-resonance water suppression (IRON) imaging, and Gradient echo acquisition for superparamagnetic particles with positive contrast (GRASP).