American Journal of Neuroradiology 2009;30:1717.
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American Journal of Neuroradiology
DOI 10.3174/ajnr.A1669
BRAIN
Localization of the Subthalamic Nucleus: Optimization with Susceptibility-Weighted Phase MR Imaging
From the Department of Radiology (A.T.V., D.J.L., D.L.) and Surgical Center for Movement Disorders (V.A.C., C.R.H.), Division of Neurosurgery, Department of Physics and Astronomy (S.K.), and UBC MRI Research Centre (A.R.), University of British Columbia, Vancouver, British Columbia, Canada; and Department of Neurosurgery (V.A.C.), Bonn University, Bonn, Germany.
Please address correspondence to: Alexander Rauscher, PhD, MRI Research Center, University of British Columbia, M10-Purdy Pavilion, 2221 Wesbrook Mall, Vancouver, BC, Canada V5T 2B5; e-mail address: rauscher{at}physics.ubc.ca
BACKGROUND AND PURPOSE: On clinical MR images, the subthalamic nuclei (STN) are poorly delineated from adjacent structures, impeding safe direct targeting for placement of electrodes in the treatment of Parkinson disease. Susceptibility-weighted MR phase imaging offers improved contrast and spatial resolution at reduced imaging times relative to clinically used T2-weighted spin-echo imaging for STN visualization. Our purpose was to assess STN visibility by using phase imaging, comparing phase and magnitude images obtained concurrently by using susceptibility-weighted imaging (SWI). The goal was to identify an efficient scanning protocol for high-quality phase images of STN.
MATERIALS AND METHODS: Seventy-eight SWI scans were acquired at 3T by using different TEs and acceleration factors. STN visibility and delimitation from adjacent structures were scored from 0 (not interpretable) to 5 (excellent). Regression analyses assessed the relationship of STN visibility to scanning parameters
RESULTS: STN were identified at all studied TEs on phase images. Visibility and delimitation of STN were consistently superior on phase images compared with magnitude images. Good visualization (score of 
4) of STN on phase imaging occurred at a mean TE of 20.0 ms and a sensitivity encoding (SENSE) of 1.40. Scores of STN visualization on phase images were dependent on SENSE (P < .002) and TE (P < .031). Good delimitation of the STN on phase imaging occurred at a mean TE of 21.6 ms and a SENSE of 1.36.
CONCLUSIONS: Visualization and delimitation of STN was superior on phase images and was achieved at 3T in <2.5 minutes. A TE of 20 ms and an acceleration factor of 
1.5 are recommended to visualize STN by using this method.