Figure 1.
Specification of paddle-array and reference electrode and illustration of the paddle-array in the brain.
The shape of a paddle-array having 5 metal electrodes and reference electrode (a). All metal electrodes of the paddle-array are disc type with a diameter of 4 mm. Also, only the contact side of the electrode (subsurface) is exposed. Illustration of the paddle-array on the gray matter in the brain (b) and our 3D computational model including the chest (c).
Figure 2.
Diagram describing the procedure of volume mesh generation.
Figure 3.
Geometric structure of the brain model.
A realistic upper body model (a), realistic full brain-only model (b), and simplified extruded slab model (c).
Table 1.
Impedance and output current of each model.
Figure 4.
Effect of types of stimulation electrodes on variation of the effective depth of penetration and effective volume with stimulation voltage (V) and current (mA).
Paddle-array and single electrode stimulations are compared quantitatively. Paddle-array (effect per electrode) is calculated using the effective depth of penetration and volume for the paddle-array divided by the number of electrodes (5).
Figure 5.
Current density distribution in the brain.
A 3D visualization of the brain with implanted paddle-array (left). The red line is the tangential slice of the right top and right bottom electrodes. The current density map is of the tangential slice (log scale) in the brain. We visualized only over the motor cortex threshold (2.5 A/m2); the thin black line is the edge of the threshold.
Figure 6.
The influence of the geometry of the brain model on the effective depth and effective volume with stimulation voltage (V) and current (mA).
Anisotropic conductivity in the white matter and a single electrode configuration were applied.
Figure 7.
Current density distribution and flow in the brain.
Realistic upper head (a) and simplified extruded slab model (b). The anisotropic conductivity in the white matter and a single electrode configuration were applied.
Figure 8.
The influence of white matter anisotropy on the effective depth and effective volume of single electrode stimulation with stimulation voltage (V) and current (mA).
Figure 9.
The coronal slice of the fractional anisotropy (FA) map and current direction for the isotropic and anisotropic models.
A realistic upper body model and single electrode configuration were applied. Dotted area encircles the corpus callosum.
Figure 10.
The spatial distribution of current density of 1V using right and left reference electrode model.
The results in the brain are the same with the reference electrode on the right (left) and the left (right). However, the distribution of current density is flipped horizontally only under the neck.