Contrast mechanisms associated with neuromelanin-MRI.

Trujillo P, Summers PE, Ferrari E, Zucca FA, Sturini M, Mainardi LT, Cerutti S, Smith AK, Smith SA, Zecca L, Costa A
Magn Reson Med. 2017 78 (5): 1790-1800

PMID: 28019018 · DOI:10.1002/mrm.26584

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 T and T 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 T 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 T 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. © 2016 International Society for Magnetic Resonance in Medicine.

© 2016 International Society for Magnetic Resonance in Medicine.

MeSH Terms (7)

Humans Iron Magnetic Resonance Imaging Melanins Models, Biological Phantoms, Imaging Substantia Nigra

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