Irreversible electroporation has seen increasing use for ablation of deep-seated tumors, for example in the liver. Patients with recurring metastases often have metallic surgical clips present in the liver due to previous treatment, which may cause a decrease in efficiency of an electroporation-based treatment. The aim of this master thesis was to numerically evaluate the potential influence of metallic surgical clips in vicinity of the ablation zone on the efficacy of treatment of liver tumors with irreversible electroporation.
Nine clinical cases of liver tumors were used for this numerical study – four with metallic surgical clips present in vicinity of the ablation zone and five without clips. For each case an anatomically correct numerical model was built based on patients' medical images and the irreversible electroporation treatment was reconstructed using the patient specific clinical data. The analysis was based on electric field distribution in the tumor and safety margin, since complete coverage with sufficiently high electric field is a prerequisite for successful ablation with irreversible electroporation. A previously designed numerical framework for treatment planning of electroporation-based therapies was used for the numerical computations.
Numerical calculations showed distortions in electric field only in the immediate vicinity of the clip in a range of a few millimeters. Surgical clips were not present directly in the tumor volume but rather on the margin or more often near the tumor. Due to a very local influence on the field, the presence of clips did not drastically affect the tumor coverage itself. However, distortions in electric field were more evident in the ablation safety margin, which can also be critical for treatment success, since micrometastases can be present in vicinity of the tumor. Despite some limitations of the reconstructed models, a good concordance between clinical and numerically calculated outcomes has been achieved. According to calculations, the presence of clips was not the major or sole cause for treatment failure in the majority of cases. However, based on our results we can conclude that in some cases the presence of metallic surgical clips can negatively affect the treatment outcome and is therefore not desired.
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