Open AccessDirect visualization of the subthalamic nucleus and its iron distribution using high‐resolution susceptibility mapping
Author(s) -
Schäfer Andreas,
Forstmann Birte U.,
Neumann Jane,
Wharton Sam,
Mietke Alexander,
Bowtell Richard,
Turner Robert
Publication year - 2012
Publication title -
human brain mapping
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.005
H-Index - 191
eISSN - 1097-0193
pISSN - 1065-9471
DOI - 10.1002/hbm.21404
Subject(s) - subthalamic nucleus , quantitative susceptibility mapping , nuclear magnetic resonance , visualization , orientation (vector space) , artificial intelligence , magnetic resonance imaging , thresholding , pattern recognition (psychology) , chemistry , physics , computer science , mathematics , deep brain stimulation , pathology , parkinson's disease , image (mathematics) , radiology , medicine , geometry , disease
Histological studies have shown a relatively high iron concentration in the subthalamic nucleus (STN). T2‐ and T2*‐weighted sequences have previously been used to visualize the STN in vivo . The phase information of gradient‐echo images reflects the magnetic tissue properties more directly, e.g., iron is more paramagnetic than water. Unfortunately, phase images suffer from non‐local effects and orientation dependency. The goal of this study is to delineate the STN more precisely using susceptibility maps, calculated from phase images, which directly index magnetic tissue properties while removing the non‐local effects and orientation dependency. Use of 7T MRI enables high spatial resolution with good signal to noise ratio (SNR). Eight healthy subjects were scanned at 7T using a high‐resolution 3D gradient‐echo sequence. Susceptibility maps were calculated from phase data using a thresholding Fourier approach and a regularization approach using spatial priors. The susceptibility maps clearly distinguish the STN from the adjacent substantia nigra (SN). Their susceptibilities are quantitatively different (0.06 and 0.1 ppm for the STN and SN, respectively). These maps allowed the STN, SN, and the red nucleus to be manually segmented, thus providing 3D visualization of their boundaries. In sum, the STN can be more clearly distinguished from adjacent structures in susceptibility maps than in T2*‐weighted images or phase images. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.