Fig. 1

Schematic representation of different multiple-electrodes arrays inserted in a solid tumor. a Four collinear electrodes with alternating polarities inserted perpendicularly along the largest diameter of the tumor. Electrodes 1 and 3 (positive) and 2 and 4 (negative) were identified (C-I). b Four electrode pairs were arranged in the tumor to 45° (electrode pair 1–2), 135° (electrode pair 3–4), 225° (electrode pair 5–6) and 325° (electrode pair 7–8). Electrodes 1, 4, 5 and 8 were positives whereas electrodes 2, 3, 6 and 7 negatives (C-II). c Four electrode pairs were arranged in the tumor to 0° (electrode pair 1–2), 90° (electrode pair 3–4), 180° (electrode pair 5–6) and 270° (electrode pair 7–8). Electrodes 2, 3, 5 and 8 were positives whereas electrodes 1, 4, 6 and 7 negatives (C-III). Furthermore, the direction of insertion depth along the z-direction and the central plane represented by z = 0 were shown for each geometry of electrode array