Abstract
Electroporation-based treatments rely on increasing the permeability of the cell membrane by high voltage electric pulses applied to tissue via electrodes. To ensure that the whole tumor is covered with sufficiently high electric field, accurate numerical models are built based on individual patient anatomy. Extraction of patient's anatomy through segmentation of medical images inevitably produces some errors. In order to ensure the robustness of treatment planning, it is necessary to evaluate the potential effect of such errors on the electric field distribution. In this work we focus on determining the effect of errors in automatic segmentation of hepatic vessels on the electric field distribution in electroporation-based treatments in the liver. First, a numerical analysis was performed on a simple 'sphere and cylinder' model for tumors and vessels of different sizes and relative positions. Second, an analysis of two models extracted from medical images of real patients in which we introduced variations of an error of the automatic vessel segmentation method was performed. The results obtained from a simple model indicate that ignoring the vessels when calculating the electric field distribution can cause insufficient coverage of the tumor with electric fields. Results of this study indicate that this effect happens for small (10 mm) and medium-sized (30 mm) tumors, especially in the absence of a central electrode inserted in the tumor. The results obtained from the real-case models also show higher negative impact of automatic vessel segmentation errors on the electric field distribution when the central electrode is absent. However, the average error of the automatic vessel segmentation did not have an impact on the electric field distribution if the central electrode was present. This suggests the algorithm is robust enough to be used in creating a model for treatment parameter optimization, but with a central electrode.
Highlights
Exposing a biological cell to a sufficiently high electric field causes increased permeability of the cell membrane
We used three different sphere diameters: 10 mm, 30 mm and 50 mm. Such choice of sphere size was made because colorectal metastases in the liver that are most often treated with ECT have a diameter 10–30 mm [20], while primary tumors in the liver can be as large as 50 mm
The red line in all of the figures indicates a threshold of the tumor coverage required for a successful treatment, which is set to 99.9%
Summary
Through these experiments we aimed to establish if ignoring the vessels in the numerical calculations could potentially have negative effects on the tumor coverage with a sufficiently high electric field
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