Deformable brain atlas

Estimation of brain internal structures by deforming brain atlas using finite element method

This paper presents a method for estimating the internal structures of a patient brain by deforming a standard brain atlas. Conventional deformation methods need several landmarks from the brain surface contour to fit the atlas to the patient brain shape. However, since the number and shapes of small sulci on the brain surface are different from each other, the determination of the accurate correspondence between small sulcus is difficult for experienced neurosurgeons. Moreover, the relationship between the surface shape and internal structure of the brain is unclear. Therefore, even if the deformed atlas is fitted to the patient brain shape exactly, the use of the deformed atlas does not always guarantee the reliable estimation of the internal structure of the patient brain. To solve these problems, we propose a new method for estimate the internal structure of a patient brain by the finite element method (FEM). In the deformation, our method select the landmarks from the contours of both the brain surface and the detectable internal structures from MR images.

Magnetic resonance imaging techniques for visualization of the subthalamic nucleus

The authors reviewed 70 publications on MR imaging-based targeting techniques for identifying the subthalamic nucleus (STN) for deep brain stimulation in patients with Parkinson disease. Of these 70 publications, 33 presented quantitatively validated results. There is still no consensus on which targeting technique to use for surgery planning; methods vary greatly between centers. Some groups apply indirect methods involving anatomical landmarks, or atlases incorporating anatomical or functional data. Others perform direct visualization on MR imaging, using T2-weighted spin echo or inversion recovery protocols. The combined studies do not offer a straightforward conclusion on the best targeting protocol. Indirect methods are not patient specific, leading to varying results between cases. On the other hand, direct targeting on MR imaging suffers from lack of contrast within the subthalamic region, resulting in a poor delineation of the STN. These deficiencies result in a need for intraoperative adaptation of the original target based on test stimulation with or without microelectrode recording. It is expected that future advances in MR imaging technology will lead to improvements in direct targeting. The use of new MR imaging modalities such as diffusion MR imaging might even lead to the specific identification of the different functional parts of the STN, such as the dorsolateral sensorimotor part, the target for deep brain stimulation.