Article

Connectivity-based segmentation of the substantia Nigra in human and its implications in Parkinson's disease.

FMRIB Centre, John Radcliffe Hospital, University of Oxford, Oxford, UK.
NeuroImage (Impact Factor: 6.25). 06/2010; DOI: 10.1016/j.neuroimage.2010.05.086
Source: PubMed

ABSTRACT The aim of this study was to i) identify substantia nigra subregions i.e. pars reticulata (SNr) and pars compacta (SNc), in human, and ii) to assess volumetric changes in these subregions in the diagnosis of Parkinson's disease. Current MR imaging techniques are unable to distinguish SNr and SNc. Segmentation of these regions may be clinically useful in Parkinson's disease (PD) as substantia nigra is invariably affected in PD. We acquired quantitative T1 as well as diffusion tensor imaging (DTI) data from ten healthy subjects and ten PD patients. For each subject, the left and right SN were manually outlined on T1 images and then classified into two discrete regions based on the characteristics of their connectivity with the rest of the brain using an automated clustering method on the DTI data. We identified two regions in each subjects' SN: an internal region that is likely to correspond with SNc because it was mainly connected with posterior striatum, pallidum, anterior thalamus, and prefrontal cortex; and an external region that correspond with SNr because it was chiefly connected with posterior thalamus, ventral thalamus, and motor cortex. Volumetric study of these regions in PD patients showed a general atrophy in PD particularly in the right SNr. This pilot study showed that automated DTI-based parcellation of SN subregions may provide a useful tool for in-vivo identification of SNc and SNr and might therefore assist to detect changes that occur in patients with PD.

0 Bookmarks
 · 
83 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Deep brain stimulation an effective treatment of many neurologic conditions such as Parkinson disease, essential tremor, dystonia, and obsessive-compulsive disorder. Structural and functional neuroimaging studies provide the opportunity to visualize the dysfunctional nodes and networks underlying neurologic and psychiatric disease, and to thereby realize new targets for neuromodulation as well as personalize current therapy. This article reviews contemporary advances in neuroimaging in the basic sciences and how they can be applied to redirect and propel functional neurosurgery toward a goal of functional localization of targets with individualized maps and identification of novel targets for other neuropsychiatric diseases.
    Neurosurgery clinics of North America 01/2014; 25(1):173-185. · 1.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Diffusion tensor imaging (DTI) is a form of MRI that has been used extensively to map in vivo the white matter architecture of the human brain. It is also used for mapping subcortical nuclei because of its general sensitivity to tissue orientation differences and effects of iron accumulation on the diffusion signal. While DTI provides excellent spatial resolution in individual subjects, a challenge is visualizing consistent patterns of diffusion orientation across subjects. Here we present a simple method for averaging direction-encoded color anisotropy maps in standard space, explore this technique for visualizing the substantia nigra (SN) in relation to other midbrain structures, and show with signal-to-noise analysis that averaging improves the direction-encoded color signature. SN is distinguished on averaged maps from neighboring structures, including red nucleus (RN) and cerebral crus, and is proximal to SN location from existing brain atlases and volume of interest (VOI) delineation on individual scans using two blinded raters.
    Computers in biology and medicine. 05/2014; 51C:104-110.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose To evaluate the anatomy of the substantia nigra (SN) in healthy subjects by performing 7-T magnetic resonance (MR) imaging of the SN, and to prospectively define the accuracy of 7-T MR imaging in distinguishing Parkinson disease (PD) patients from healthy subjects on an individual basis. Materials and Methods The 7-T MR imaging protocol was approved by the Italian Ministry of Health and by the local competent ethics committee. SN anatomy was described ex vivo on a gross brain specimen by using highly resolved proton-density (spin-echo proton density) and gradient-recalled-echo (GRE) images, and in vivo in eight healthy subjects (mean age, 40.1 years) by using GRE three-dimensional multiecho susceptibility-weighted images. After training on appearance of SN in eight healthy subjects, the SN anatomy was evaluated twice by two blinded observers in 13 healthy subjects (mean age, 54.7 years) and in 17 PD patients (mean age, 56.9 years). Deviations from normal SN appearance were described and indicated as abnormal, and both diagnostic accuracy and intra- and interobserver agreement for diagnosis of PD with 7-T MR imaging were calculated. Results Three-dimensional multiecho susceptibility-weighted 7-T MR imaging reveals a three-layered organization of the SN allowing readers to distinguish pars compacta ventralis and dorsalis from pars reticulata. The abnormal architecture of the SN allowed a discrimination between PD patients and healthy subjects with sensitivity and specificity of 100% and 96.2% (range, 92.3%-100%), respectively. Intraobserver agreement (κ = 1) and interobserver agreement (κ = 0.932) were excellent. Conclusion MR imaging at 7-T allows a precise characterization of the SN and visualization of its inner organization. Three-dimensional multiecho susceptibility-weighted images can be used to accurately differentiate healthy subjects from PD patients, which provides a novel diagnostic opportunity. © RSNA, 2014.
    Radiology 02/2014; · 6.34 Impact Factor