The Neuromelanin-related T2* Contrast in Postmortem Human Substantia Nigra with 7T MRI

Sci Rep. 2016 Sep 6:6:32647. doi: 10.1038/srep32647.

Abstract

High field magnetic resonance imaging (MRI)-based delineation of the substantia nigra (SN) and visualization of its inner cellular organization are promising methods for the evaluation of morphological changes associated with neurodegenerative diseases; however, corresponding MR contrasts must be matched and validated with quantitative histological information. Slices from two postmortem SN samples were imaged with a 7 Tesla (7T) MRI with T1 and T2* imaging protocols and then stained with Perl's Prussian blue, Kluver-Barrera, tyrosine hydroxylase, and calbindin immunohistochemistry in a serial manner. The association between T2* values and quantitative histology was investigated with a co-registration method that accounts for histology slice preparation. The ventral T2* hypointense layers between the SNr and the crus cerebri extended anteriorly to the posterior part of the crus cerebri, which demonstrates the difficulty with an MRI-based delineation of the SN. We found that the paramagnetic hypointense areas within the dorsolateral SN corresponded to clusters of neuromelanin (NM). These NM-rich zones were distinct from the hypointense ventromedial regions with high iron pigments. Nigral T2* imaging at 7T can reflect the density of NM-containing neurons as the metal-bound NM macromolecules may decrease T2* values and cause hypointense signalling in T2* imaging at 7T.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Contrast Media / chemistry*
  • Female
  • Humans
  • Iron / metabolism
  • Magnetic Resonance Imaging*
  • Male
  • Melanins / metabolism*
  • Middle Aged
  • Postmortem Changes*
  • Substantia Nigra / metabolism*
  • Substantia Nigra / pathology*

Substances

  • Contrast Media
  • Melanins
  • neuromelanin
  • Iron