Date of Thesis

Spring 2022


Deep brain stimulation (DBS) modeling can be used to improve understanding of how DBS elicits therapeutic effects by quantifying the spatial extent of stimulation relative to subcortical structures of interest. A certain degree of model complexity is required to obtain accurate predictions, particularly complexity involving the electrical properties of the tissue around the DBS electrodes. The objective of this study was to evaluate the effect of anisotropy on the volume of tissue activation (VTA) in an individualized manner. Individualized tissue activation models incorporating patient-specific tissue conductivity derived from diffusion tensor imaging were built for 40 Parkinson disease patients who had received bilateral subthalamic nucleus (STN) DBS. To assess the impact of local changes in tissue anisotropy on VTA predictions, one VTA was computed at each electrode using the same clinical stimulation parameters. VTAs were also computed assuming an isotropic tissue conductivity for comparison. Stimulation location was taken into account by classifying VTAs based on their locations relative to the STN. VTAs were characterized based on size and shape using volume, spread in the lateral-medial, anterior-posterior, and dorsal-ventral directions, sphericity, and the Dice coefficient. Incorporating anisotropy generated significantly larger and less spherical VTAs overall. However, its effect on VTA size and shape was variable and more nuanced at the individual patient and implantation level. The influence of anisotropy on VTA predictions is not negligible and varies across patients and stimulation locations. This study highlights the importance of considering individualized factors in DBS modeling to accurately characterize the VTA.


deep brain stimulation, Parkinson disease, subthalamic nucleus, diffusion tensor imaging, electric field modeling, volume of tissue activation

Access Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science in Biomedical Engineering


Biomedical Engineering

Minor, Emphasis, or Concentration


First Advisor

Karlo A. Malaga

Second Advisor

James Baish