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 established 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 phantom. 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 microrecordings). 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 stereotactic requirement, the sequence simplifies direct targeting in STN-DBS surgery.