Pranav Bhagirath

152 Chapter 8 volume, the FEM is typically more efficient for this purpose. Especially when the number of model compartments is high or when anisotropic conductivity is modelled, the FEM is recommended [11]. Although the application of BVP has been studied previously [12-13], it has never advanced into clinical practice due to its time consuming and elaborative nature. Increased computational power and the introduction of open source software enable the calculation of BVP for clinical purposes. In this study the explanatory power of BVP is illustrated by experiments performed in a simple rectangular tank. In addition, simulations in a 3D patient specific model demonstrate the possible advantage of using BVP. METHODS Rectangular tank A rectangular tank of 33 x 25 x 25 cm filled with an electrolytic conductor was used. Electrodes with a surface of 2 x 2 cm were positioned in the middle of opposing sides. To block interference from nearby power sources, a 1000 Hz 8 V peak-to-peak sinusoidal power source was used. Measurements were performed using a dual beamoscilloscope, enabling monitoring the source voltage while measuring the resulting potential in the tank. The accuracy of the measurements approximated 2%, which was considered sufficient for validation purposes. MRI images MRI images of the rectangular tank and the patient were acquired using a Turbo Spin Echo (Black Blood) sequence in three orthogonal directions (slice thickness 8mm). Electrode positions in the tank and on the body surface were marked using liquid-filled vitamin D capsules, appearing hyper intense on MRI. The MRI scan was performed on a Siemens Aera 1.5 Tesla MRI scanner (Siemens Healthcare, Erlangen, Germany). The study complied with the declaration of Helsinki and received approval from the local ethical committee and the institutional scientific board. Written informed consent was obtained from the patient. Meshing In order to achieve topological propriety, MRI images were segmented in 3D using bounding planes. No spatial smoothing was applied. The Gmsh tool [14], freely available on the Internet for non-commercial use, was used for mesh generation.