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Accuracy of Magnetic Resonance ImagingDirected Frame-Based Stereotaxis

Thani, Nova B. MBBS*,†; Bala, Arul FRACS*; Lind, Christopher R. P. FRACS*,†

doi: 10.1227/NEU.0b013e3182320bd6
Technique Assessment

BACKGROUND: Accurate placement of a probe to the deep regions of the brain is an important part of neurosurgery. In the modern era, magnetic resonance image (MRI)-based target planning with frame-based stereotaxis is the most common technique.

OBJECTIVE: To quantify the inaccuracy in MRI-guided frame-based stereotaxis and to assess the relative contributions of frame movements and MRI distortion.

METHODS: The MRI-directed implantable guide-tube technique was used to place carbothane stylettes before implantation of the deep brain stimulation electrodes. The coordinates of target, dural entry point, and other brain landmarks were compared between preoperative and intraoperative MRIs to determine the inaccuracy.

RESULTS: The mean 3-dimensional inaccuracy of the stylette at the target was 1.8 mm (95% confidence interval [CI], 1.5-2.1. In deep brain stimulation surgery, the accuracy in the x and y (axial) planes is important; the mean axial inaccuracy was 1.4 mm (95% CI, 1.1-1.8). The maximal mean deviation of the head frame compared with brain over 24.1 ± 1.8 hours was 0.9 mm (95% CI, 0.5-1.1). The mean 3-dimensional inaccuracy of the dural entry point of the stylette was 1.8 mm (95% CI, 1.5-2.1), which is identical to that of the target.

CONCLUSION: Stylette positions did deviate from the plan, albeit by 1.4 mm in the axial plane and 1.8 mm in 3-dimensional space. There was no difference between the accuracies at the dura and the target approximately 70 mm deep in the brain, suggesting potential feasibility for accurate planning along the whole trajectory.

*West Australian Neurosurgical Service, Sir Charles Gairdner Hospital, Perth, Australia

School of Surgery, University of Western Australia, Nedlands, Australia

Correspondence: Christopher Lind, FRACS, Consultant Neurosurgeon, 1st Floor, G Block, Sir Charles Gairdner Hospital, Hospital Ave, Nedlands, WA 6009, Australia. E-mail:

Received July 15, 2010

Accepted June 6, 2011

Copyright © by the Congress of Neurological Surgeons