High-Resolution 3-Dimensional T2*-Weighted Angiography (HR 3-D SWAN): An Optimized 3-T Magnetic Resonance Imaging Sequence for Targeting the Subthalamic Nucleus BACKGROUND: Subthalamic nucleus deep brain stimulation (STN-DBS) is an estab- lished treatment for Parkinson’s disease. OBJECTIVE: To characterize an optimized magnetic resonance imaging (MRI) sequence (high-resolution 3-dimensional T2*-weighted angiography [HR 3-D SWAN]) for direct STN targeting. METHODS: Sequence distortions were measured using the Leksell stereotactic phan- tom. Eight consecutive candidates for STN-DBS underwent HR 3-D SWAN MRI for direct identification of the 16 STN. Two senior neurosurgeons independently determined the boundaries of STN on a semiquantitative scale (ranging from 1 [identification very easy] to 4 [identification very difficult]) and the anatomic target within the nucleus. The anatomic data were compared with electrophysiological recordings (48 micro- recordings). We examined the anatomic location of the active contacts on MRI. RESULTS: The mean distortion error over the phantom was 0.16 mm. For the 16 STNs, identification of the upper, internal, anterior, and external edges was considered to be easy (scores of 1 or 2). The distinction between the substantia nigra and the STN was rated 1 or 2 for all but 6 nuclei. In the mediolateral axis, electrophysiological recordings covered perfectly anatomic data. In the craniocaudal axis, the mean differences between the electrophysiological data and the anatomic data were 0.8 mm and 0.19 mm for the “entry” and “exit” of the STN, respectively. All active contacts were located within the STN on MRI. CONCLUSION: HR 3-D SWAN allows easy visualization of the STN. Adapted to ste- reotactic requirement, the sequence simplifies direct targeting in STN-DBS surgery. KEY WORDS: Deep brain stimulation, Magnetic resonance imaging, Subthalamic nucleus, Targeting Neurosurgery 74:615–627, 2014 DOI: 10.1227/NEU.0000000000000319 www.neurosurgery-online.com D eep brain stimulation (DBS) of the subtha- lamic nucleus (STN) is an established treatment for advanced Parkinson’ s dis- ease. 1-3 The efficacy of DBS is directly related to correct positioning of the electrode within the STN. 4 However, the STN varies significantly in terms of its volume, shape, and boundaries. 5 The STN’ s oblique orientation and small size and the use of a coil that is appropriate for a stereotactic frame make it difficult to identify with conventional 1.5-T magnetic resonance imaging (MRI). 5-7 High- field MRI enables direct visualization of the STN and thus may be particularly relevant (given the STN’ s anatomic variability) for planning the implan- tation of STN-DBS electrodes. 8,9 Here, we present a high-resolution 3-dimensional T2*-weighted angi- ography (HR 3-D SWAN) sequence that we adapted to meet the requirements of stereotactic surgery and direct identification of the STN. METHODS Imaging Protocol We adapted the HR 3-D SWAN sequence to limit distortion and improve resolution. In particular, the Michel Lefranc, MD* Ste ´phane Derrey, MD, PhD# Philippe Merle, MD‡ Me ´lissa Tir, MD, PhD§ Jean-Marc Constans, MD, PhD¶ Dominique Montpellier, MDk Jean Michel Macron, MD, PhD‡ Daniel Le Gars, MD, PhD* Johan Peltier, MD, PhD* Olivier Baledentt, PhD¶ Pierre Krystkowiak, MD, PhD§ Departments of *Neurosurgery, ‡Func- tional Exploration of the Central Nervous System, §Neurology, ¶Neuroradiology, kAnesthesiology, Amiens University Medical Center, Amiens, France; #Depart- ment of Neurosurgery, Rouen University Medical Center, Rouen, France Correspondence: Michel Lefranc, MD, Service de Neurochirurgie, CHU Amiens, 5 place Victor Pauchet, F-80054 Amiens cedex, France. E-mail: lefrancm@me.com Received, October 31, 2013. Accepted, January 29, 2014. Published Online, February 14, 2014. Copyright © 2014 by the Congress of Neurological Surgeons. ABBREVIATIONS: AC, anterior commissure; DBS, deep brain stimulation; fpCT, flat-panel computed tomography; HR 3-D SWAN, high-resolution 3-dimensional T2*-weighted angiography; PC, pos- terior commissure; SD, standard deviation; STN, subthalamic nucleus RESEARCH—HUMAN—CLINICAL STUDIES TOPIC RESEARCH—HUMAN—CLINICAL STUDIES NEUROSURGERY VOLUME 74 | NUMBER 6 | JUNE 2014 | 615 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited.