The substantia nigra was evaluated on three levels as shown here in a normal control (male, 61 years old).

<p>The delineation of the substantia nigra was poor on the maps of mean diffusivity, given by the mean apparent diffusion coefficient (ADC) in 12 directions as well as on the maps of the relaxation rates R2 and R2*. However, the mean b 1000 images, the FA maps and the proton-density weighted images provided the best contrast for the accurate demarcation of the substantia nigra (SN), which is marked by white arrows. These three different modalities were used for the segmentation of SN.</p

The R2* maps are derived from the substantia nigra of a representative healthy control and several PD patients with increasing disease duration as given on the upper margin of each image.

<p>Images belong to the same subjects included in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145493#pone.0145493.g005" target="_blank">Fig 5</a>. The white arrows point out increased signals on R2* maps, indicating iron overload. With increasing disease duration the areas of elevated R2* become inhomogeneous.</p

The R2* and the MD maps of the basal ganglia indicate relatively high iron concentrations in patients at early stages of Parkinson's disease (PD).

<p>The disease durations are marked on the upper margin of the R2* maps. The corresponding MD maps are just below the R2* maps. The high signals on the R2* maps within the basal ganglia indicate high iron concentrations and pointed out by white arrows. PD patients with longer disease durations show less signal on R2* maps compared to PD patients at early disease stage. Differences in MD can be hardly detected visually, but with the help of a ROI analysis.</p

The sagittal reconstructions of the co-registered maps show the excellent coherence in one normal control (A) and in two PD patients (B and C).

<p>In four subjects the R2* maps showed distinct signal loss near to the base of the skull as demonstrated in B.</p

The regions-of-interest (ROIs) were manually drawn by an experienced radiologist by using the b 1000 images, averaged for all measured directions, the FA maps and the proton-density weighted images.

<p>For that purpose, the maps of ADC, FA, R2 and R2* as well as the proton-density weighted images were first co-registered. The ROIs were segmented by syncing the b 1000 images, averaged for all measured directions, the FA maps and the proton-density weighted images in ImageJ. The ROIs were stored in the ROI manager and transferred to the co-registered maps. The segmented brain regions were highlighted in different colors: CN—black; PU—red; GP—green; TH—white; SN—blue; CC—cyan.</p