Irreversible Electroporation for the Treatment of Aggressive High-Grade Glioma
Garcia, Paulo A
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Malignant gliomas (MG), most notably glioblastoma multiforme (GBM), are among the most aggressive of all malignancies. High-grade variants of this type of brain cancer are generally considered incurable with singular or multimodal therapies. Many patients with GBM die within one year of diagnosis, and the 5-year survival rate in people is approximately 10%. Despite extensive research in diagnostic and therapeutic technologies, very few developments have emerged that significantly improve survival over the last seven decades. Irreversible electroporation (IRE) is a new non-thermal focal tissue ablation technique that uses low-energy electric pulses to destabilize cell membranes, thus achieving tissue death. The procedure is minimally invasive and is performed through small electrodes inserted into the tissue with treatment duration of about one minute. The pulses create an electric field that induces an increase in the resting transmembrane potential (TMP) of the cells in the tissue. The induced increase in the TMP is dependent on the electric pulse parameters. Depending on the magnitude of the induced TMP the electric pulses can have no effect, transiently increase membrane permeability or cause spontaneous death. In this dissertation we hypothesize that irreversible electroporation is capable of ablating normal (gray and white matter) and pathological (MG and/or GBM) brain tissue in a highly focused non-thermal manner that is modulated through pulse parameters and electrode configuration. Through a comprehensive experimental and numerical investigation, we tested and attained results strongly supporting our hypothesis. Specifically, we developed numerical models that were capable of simulating an entire IRE treatment protocol and would take into account pulse parameters (e.g. duration, frequency, repetition rate and strength) in addition to the dynamic changes in tissue electrical conductivity due to electroporation and joule heating, as well as biologically relevant processes such as blood perfusion and metabolic heat. We also provided a method to isolate the IRE effects from undesired thermal damage in models that were validated with real-time temperature measurements during the delivery of the pulses. Finally we outlined a procedure to use 3D volumetric reconstructions of IRE lesions using patient specific MRI scans in conjunction with the models described for establishing field thresholds or performing treatment planning prior to the surgical procedure; thus supplying the readers with the tools and understanding necessary to design appropriate treatment protocols for their specific application. Experimentally we presented the first systematic in vivo study of IRE in normal canine brain and the multimodal treatment of a canine MG patient. We confirmed that the procedure can be applied safely in the brain and was well tolerated clinically. The lesions created with IRE were sub-millimeter in resolution and we achieved 75% tumor volume reduction within 3 days post-IRE in the patient. In addition to the sharp delineation between necrotic and normal brain, the treatments spared the major blood vessels, making it appropriate for treatment of tumors adjacent to, or enveloping critical vascular structures. We believe that irreversible electroporation will play a key role in the treatment of intracranial disorders including malignant brain cancer in which the intent is to focally kill undesired tissue while minimizing damage to surrounding healthy tissue.
- Doctoral Dissertations