Contrast mechanisms associated with neuromelanin-MRI

Paula Trujillo, Paul E. Summers, Emanuele Ferrari, Fabio A. Zucca, Michela Sturini, Luca T. Mainardi, Sergio Cerutti, Alex K. Smith, Seth A. Smith, Luigi Zecca, Antonella Costa

Research output: Contribution to journalArticlepeer-review


Purpose: To investigate the physical mechanisms associated with the contrast observed in neuromelanin MRI. Methods: Phantoms having different concentrations of synthetic melanins with different degrees of iron loading were examined on a 3 Tesla scanner using relaxometry and quantitative magnetization transfer (MT). Results: Concentration-dependent T1 and T2 shortening was most pronounced for the melanin pigment when combined with iron. Metal-free melanin had a negligible effect on the magnetization transfer spectra. On the contrary, the presence of iron-laden melanins resulted in a decreased magnetization transfer ratio. The presence of melanin or iron (or both) did not have a significant effect on the macromolecular content, represented by the pool size ratio. Conclusion: The primary mechanism underlying contrast in neuromelanin-MRI appears to be the T1 reduction associated with melanin-iron complexes. The macromolecular content is not significantly influenced by the presence of melanin with or without iron, and thus the MT is not directly affected. However, as T1 plays a role in determining the MT-weighted signal, the magnetization transfer ratio is reduced in the presence of melanin-iron complexes. Magn Reson Med 78:1790–1800, 2017.

Original languageEnglish
Pages (from-to)1790-1800
Number of pages11
JournalMagnetic Resonance in Medicine
Issue number5
Publication statusPublished - Nov 1 2017


  • magnetization transfer
  • MRI
  • neuromelanin
  • relaxation

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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