Anze Zupanic

Towards treatment planning and treatment of deep-seated solid tumors by electrochemotherapy

BackgroundElectrochemotherapy treats tumors by combining specific chemotherapeutic drugs with an intracellular target and electric pulses, which increases drug uptake into the tumor cells. Electrochemotherapy has been successfully used for treatment of easily accessible superficial tumor nodules. In this paper, we present the first case of deep-seated tumor electrochemotherapy based on numerical treatment planning.MethodsThe aim of our study was to treat a melanoma metastasis in the thigh of a patient. Treatment planning for electrode positioning and electrical pulse parameters was performed for two different electrode configurations: one with four and another with five long needle electrodes. During the procedure, the four electrode treatment plan was adopted and the patient was treated accordingly by electrochemotherapy with bleomycin. The response to treatment was clinically and radiographically evaluated. Due to a partial response of the treated tumor, the metastasis was surgically removed after 2 months and pathological analysis was performed.ResultsA partial response of the tumor to electrochemotherapy was obtained. Histologically, the metastasis showed partial necrosis due to electrochemotherapy, estimated to represent 40-50% of the tumor. Based on the data obtained, we re-evaluated the electrical treatment parameters in order to correlate the treatment plan with the clinical response. Electrode positions in the numerical model were updated according to the actual positions during treatment. We compared the maximum value of the measured electric current with the current predicted by the model and good agreement was obtained. Finally, tumor coverage with an electric field above the reversible threshold was recalculated and determined to be approximately 94%. Therefore, according to the calculations, a small volume of tumor cells remained viable after electrochemotherapy, and these were sufficient for tumor regrowth.ConclusionsIn this, the first reported clinical case, deep-seated melanoma metastasis in the thigh of the patient was treated by electrochemotherapy, according to a treatment plan obtained by numerical modeling and optimization. Although only a partial response was obtained, the presented work demonstrates that treatment of deep-seated tumor nodules by electrochemotherapy is feasible and sets the ground for numerical treatment planning-based electrochemotherapy.Trial registrationEudraCT:2008-008290-54

Electrochemotherapy: A New Technological Approach in Treatment of Metastases in the Liver

Electrochemotherapy is now in development for treatment of deep-seated tumors, like in bones and internal organs, such as liver. The technology is available with a newly developed electric pulse generator and long needle electrodes; however the procedures for the treatment are not standardized yet. In order to describe the treatment procedure, including treatment planning, within the ongoing clinical study, a case of successful treatment of a solitary metastasis in the liver of colorectal cancer is presented. The procedure was performed intraoperatively by inserting long needle electrodes, two in the center of the tumor and four around the tumor into the normal tissue. The insertion of electrodes proved to be feasible and was done according to the treatment plan, prepared by numerical modeling. After intravenous bolus injection of bleomycin the tumor was exposed to electric pulses. The delivery of the electric pulses did not interfere with functioning of the heart, since the pulses were synchronized with electrocardiogram in order to be delivered outside the vulnerable period of the ventricles. Also the post treatment period was uneventful without side effects. Re-operation of the treated metastasis demonstrated feasibility of the reoperation, without secondary effects of electrochemotherapy on normal tissue. Good antitumor effectiveness with complete tumor destruction was confirmed with histological analysis. The patient is disease-free 16 months after the procedure. In conclusion, treatment procedure for electrochemotherapy proved to be a feasible technological approach for treatment of liver metastasis. Due to the absence of the side effects and the first complete destruction of the treated tumor, treatment procedure for electrochemotherapy seems to be a safe method for treatment of liver metastases with good treatment effectiveness even in difficult-to-reach locations.

The endothelial cytoskeleton as a target of electroporation-based therapies

Electroporation-based therapies, such as electrochemotherapy and electrogene therapy, result in the disruption of blood vessel networks in vivo and cause changes in blood flow and vascular permeability. The effects of electroporation on the cytoskeleton of cultured primary endothelial cells and on endothelial monolayer permeability were investigated to elucidate possible mechanisms involved. Human umbilical vein endothelial cells (HUVECs) were electroporated in situ and then immunofluorescence staining for filamentous actin, β-tubulin, vimentin, and VE-cadherin as well as Western blotting analysis of levels of phosphorylated myosin light chain and cytoskeletal proteins were performed. Endothelial permeability was determined by monitoring the passage of FITC-coupled dextran through endothelial monolayers. Exposure of endothelial cells to electric pulses resulted in a profound disruption of microfilament and microtubule cytoskeletal networks, loss of contractility, and loss of vascular endothelial cadherin from cell-to-cell junctions immediately after electroporation. These effects were voltage dependent and reversible because cytoskeletal structures recovered within 60 min of electroporation with up to 40 V, without any significant loss of cell viability. The cytoskeletal effects of electroporation were paralleled by a rapid increase in endothelial monolayer permeability. These results suggest that the remodeling of the endothelial cytoskeleton and changes in endothelial barrier function could contribute to the vascular disrupting actions of electroporation-based therapies and provide an insight into putative mechanisms responsible for the observed increase in permeability and cessation of blood flow in vivo. [Mol Cancer Ther 2006;5(12):3145–52]

Robustness of Treatment Planning for Electrochemotherapy of Deep-Seated Tumors

Treatment of cutaneous and subcutaneous tumors with electrochemotherapy has become a regular clinical method, while treatment of deep-seated tumors is still at an early stage of development. We present a method for preparing a dedicated patient-specific, computer-optimized treatment plan for electrochemotherapy of deep-seated tumors based on medical images. The treatment plan takes into account the patient’s anatomy, tissue conductivity changes during electroporation and the constraints of the pulse generator. Analysis of the robustness of a treatment plan made with this method shows that the effectiveness of the treatment is not affected significantly by small single errors in electrode positioning. However, when many errors occur simultaneously, the resulting drop in effectiveness is larger, which means that it is necessary to be as accurate as possible in electrode positioning. The largest effect on treatment effectiveness stems from uncertainties in dielectric properties and electroporation thresholds of treated tumors and surrounding tissues, which emphasizes the need for more accurate measurements and more research. The presented methods for treatment planning and robustness analysis allow quantification of the treatment reproducibility and enable the setting of suitable safety margins to improve the likelihood of successful treatment of deep-seated tumors by electrochemotherapy.

Treatment planning of electroporation-based medical interventions: electrochemotherapy, gene electrotransfer and irreversible electroporation

In recent years, cancer electrochemotherapy (ECT), gene electrotransfer for gene therapy and DNA vaccination (GET) and tissue ablation with irreversible electroporation (IRE) have all entered clinical practice. We present a method for a personalized treatment planning procedure for ECT, GET and IRE, based on medical image analysis, numerical modelling of electroporation and optimization with the genetic algorithm, and several visualization tools for treatment plan assessment. Each treatment plan provides the attending physician with optimal positions of electrodes in the body and electric pulse parameters for optimal electroporation of the target tissues. For the studied case of a deep-seated tumour, the optimal treatment plans for ECT and IRE require at least two electrodes to be inserted into the target tissue, thus lowering the necessary voltage for electroporation and limiting damage to the surrounding healthy tissue. In GET, it is necessary to place the electrodes outside the target tissue to prevent damage to target cells intended to express the transfected genes. The presented treatment planning procedure is a valuable tool for clinical and experimental use and evaluation of electroporation-based treatments.

Numerical Modeling and Optimization of Electric Field Distribution in Subcutaneous Tumor Treated With Electrochemotherapy Using Needle Electrodes

Electrochemotherapy (ECT) is an effective antitumor treatment employing locally applied high-voltage electric pulses in combination with chemotherapeutic drugs. For successful ECT, the entire tumor volume needs to be subjected to a sufficiently high local electric field, whereas, in order to prevent damage, the electric field within the healthy tissue has to be as low as possible. To determine the optimum electrical parameters and electrode configuration for the ECT of a subcutaneous tumor, we combined a 3-D finite element numerical tumor model with a genetic optimization algorithm. We calculated and compared the local electric field distributions obtained with different geometrical and electrical parameters and different needle electrode geometries that have been used in research and clinics in past years. Based on this, we established which model parameters had to be taken into account for the optimization of the local electric field distribution and included them in the optimization algorithm. Our results showed that parallel array electrodes are the most suitable for the spherical tumor geometry, because the whole tumor volume is subjected to sufficiently high electric field while requiring the least electric current and causing the least tissue damage. Our algorithm could be a useful tool in the treatment planning of clinical ECT as well as in other electric field mediated therapies, such as gene electrotransfer, transdermal drug delivery, and irreversible tissues ablation.

Numerical optimization of gene electrotransfer into muscle tissue.

BackgroundElectroporation-based gene therapy and DNA vaccination are promising medical applications that depend on transfer of pDNA into target tissues with use of electric pulses. Gene electrotransfer efficiency depends on electrode configuration and electric pulse parameters, which determine the electric field distribution. Numerical modeling represents a fast and convenient method for optimization of gene electrotransfer parameters. We used numerical modeling, parameterization and numerical optimization to determine the optimum parameters for gene electrotransfer in muscle tissue.MethodsWe built a 3D geometry of muscle tissue with two or six needle electrodes (two rows of three needle electrodes) inserted. We performed a parametric study and optimization based on a genetic algorithm to analyze the effects of distances between the electrodes, depth of insertion, orientation of electrodes with respect to muscle fibers and applied voltage on the electric field distribution. The quality of solutions were evaluated in terms of volumes of reversibly (desired) and irreversibly (undesired) electroporated muscle tissue and total electric current through the tissue.ResultsLarge volumes of reversibly electroporated muscle with relatively little damage can be achieved by using large distances between electrodes and large electrode insertion depths. Orienting the electrodes perpendicular to muscle fibers is significantly better than the parallel orientation for six needle electrodes, while for two electrodes the effect of orientation is not so pronounced. For each set of geometrical parameters, the window of optimal voltages is quite narrow, with lower voltages resulting in low volumes of reversibly electroporated tissue and higher voltages in high volumes of irreversibly electroporated tissue. Furthermore, we determined which applied voltages are needed to achieve the optimal field distribution for different distances between electrodes.ConclusionThe presented numerical study of gene electrotransfer is the first that demonstrates optimization of parameters for gene electrotransfer on tissue level. Our method of modeling and optimization is generic and can be applied to different electrode configurations, pulsing protocols and different tissues. Such numerical models, together with knowledge of tissue properties can provide useful guidelines for researchers and physicians in selecting optimal parameters for in vivo gene electrotransfer, thus reducing the number of animals used in studies of gene therapy and DNA vaccination.

Planning of electroporation-based treatments using Web-based treatment-planning software.

Electroporation-based treatment combining high-voltage electric pulses and poorly permanent cytotoxic drugs, i.e., electrochemotherapy (ECT), is currently used for treating superficial tumor nodules by following standard operating procedures. Besides ECT, another electroporation-based treatment, nonthermal irreversible electroporation (N-TIRE), is also efficient at ablating deep-seated tumors. To perform ECT or N-TIRE of deep-seated tumors, following standard operating procedures is not sufficient and patient-specific treatment planning is required for successful treatment. Treatment planning is required because of the use of individual long-needle electrodes and the diverse shape, size and location of deep-seated tumors. Many institutions that already perform ECT of superficial metastases could benefit from treatment-planning software that would enable the preparation of patient-specific treatment plans. To this end, we have developed a Web-based treatment-planning software for planning electroporation-based treatments that does not require prior engineering knowledge from the user (e.g., the clinician). The software includes algorithms for automatic tissue segmentation and, after segmentation, generation of a 3D model of the tissue. The procedure allows the user to define how the electrodes will be inserted. Finally, electric field distribution is computed, the position of electrodes and the voltage to be applied are optimized using the 3D model and a downloadable treatment plan is made available to the user.

11th Mediterranean Conference on Medical and Biomedical Engineering and Computing 2007

Continuous patient monitoring during daily life can provide valuable information to different medical specialties. Indeed, long recording of related cardiac signals such as ECG, respiration and also other information such as body motion can improve diagnosis and monitor the evolution of many widespread diseases. Key-issues for portable or even wearable biomedical devices are: power consumption, longterm sensors, comfortable wearing, easy and wireless connectivity. Within this scenario, is valuable to realize prototypes making use of novel electronic technologies and common available communication technologies to assess practical use of long-term personal monitoring and foster new ways to provide healthcare services. We realized a small, battery powered, portable monitor capable to record ECG and body three-axes acceleration and continuously wireless transmit to any Bluetooth device including PDA or cellular phone. The ECG front end offers ultra-high input impedance allowing use of dry, long-lasting electrodes such conductive rubbers or novel textile electrodes that can be embedded in clothes. A small size MEMS 3-axes accelerometer was also integrated. Patient monitor incorporate a microprocessor that controls 12-bit ADC of signals at programmable sampling frequencies (e.g. 100 Hz) and drives a Bluetooth module capable to reliable transmit real-time signals within 10 m range. All circuitry can be powered by a standard mobile phone like Ni-MH 3.6V battery that can sustain more than seven day continuous functioning utilizing the Bluetooth Sniff mode to reduce TX power. At the moment we are developing dedicated software to process data and to extract concise parameters valuable for medical studies.

Optimization of induction heating using numerical modeling and genetic algorithm

Induction heating is a complex interplay of electromagnetic, thermal and metallurgic phenomena. It is therefore not surprising that only few numerical optimization approaches for solving induction heating problems have been published. The aim of our study was to determine the optimal coil position and the optimal amplitude and frequency of the electric current in order to attain the desired temperature profile in a non-ferromagnetic steel cylinder workpiece. The finite-element numerical modeling in combination with genetic algorithm optimization method was used for this purpose. The heated workpiece was surrounded by a copper coil consisting of four loops. In our calculations the workpieces temperature-dependent material properties were taken into account. Using a genetic algorithm the following parameters were optimized: position of the single-coil loop, the amplitude and the frequency of the electric current in the coil. Our numerical model was experimentally validated by comparison of measurement and simulation results. The optimized solution and the global optimum had comparable temperature profiles due to a better selection of the electric current parameters compared to the profile obtained by solving the problem intuitively. We demonstrated that the proposed approach can be used for planning of induction heating of steel materials at low-energy consumption and high time-efficiency.