Genetically engineered HEK cells as a valuable tool for studying electroporation in excitable cells.

Electric pulses used in electroporation-based treatments have been shown to affect the excitability of muscle and neuronal cells. However, understanding the interplay between electroporation and electrophysiological response of excitable cells is complex, since both ion channel gating and electroporation depend on dynamic changes in the transmembrane voltage (TMV). In this study, a genetically engineered human embryonic kidney cells expressing NaV1.5 and Kir2.1, a minimal complementary channels required for excitability (named S-HEK), was characterized as a simple cell model used for studying the effects of electroporation in excitable cells. S-HEK cells and their non-excitable counterparts (NS-HEK) were exposed to 100 µs pulses of increasing electric field strength. Changes in TMV, plasma membrane permeability, and intracellular Ca2+ were monitored with fluorescence microscopy. We found that a very mild electroporation, undetectable with the classical propidium assay but associated with a transient increase in intracellular Ca2+, can already have a profound effect on excitability close to the electrostimulation threshold, as corroborated by multiscale computational modelling. These results are of great relevance for understanding the effects of pulse delivery on cell excitability observed in context of the rapidly developing cardiac pulsed field ablation as well as other electroporation-based treatments in excitable tissues.

Nuclear Cogeneration of Methanol and Acetaldehyde from Ethylene Glycol Using Ionizing Radiation.

Despite offering low-carbon and reliable energy, the utilization of nuclear energy is declining globally due to high upfront capital costs and longer returns on investments. Nuclear cogeneration of valuable chemicals from waste biomass-derived feedstocks could have beneficial impacts while harnessing the underutilized resource of ionizing energy. Here, we demonstrate selective methanol or acetaldehyde production from ethylene glycol, a feedstock derived from glycerol, a byproduct of biodiesel, using irradiations from a nuclear fission reactor. The influence of radiation quality, dose rate, and the absorbed dose of irradiations on radiochemical yields (G-value) has been studied. Under low-dose-rate, γ-only radiolysis during reactor shutdown rate (<0.018 kGy min-1), acetaldehyde is produced at a maximum G-value of 8.28 ± 1.05 µmol J-1 and a mass productivity of 0.73 ± 0.06% from the 20 kGy irradiation of neat ethylene glycol. When exposed to a high-dose-rate (6.5 kGy min-1), 100 kGy mixed-field of neutron + γ-ray radiations, the radiolytic selectivity is adjusted from acetaldehyde to generate methanol at a G-value of 2.91 ± 0.78 µmol J-1 and a mass productivity of 0.93 ± 0.23%. Notably, utilizing 422 theoretical systems could contribute to 4.96% of worldwide acetaldehyde production using a spent fuel pool γ-ray scheme. This research reports G-values and production capacities for acetaldehyde for high-dose scenarios and shows the potential selectivity of a nuclear cogeneration process to synthesize chemicals based on their irradiation conditions from the same reagent.

Determination of lethal electric field threshold for pulsed field ablation in ex vivo perfused porcine and human hearts.

Introduction: Pulsed field ablation is an emerging modality for catheter-based cardiac ablation. The main mechanism of action is irreversible electroporation (IRE), a threshold-based phenomenon in which cells die after exposure to intense pulsed electric fields. Lethal electric field threshold for IRE is a tissue property that determines treatment feasibility and enables the development of new devices and therapeutic applications, but it is greatly dependent on the number of pulses and their duration. Methods: In the study, lesions were generated by applying IRE in porcine and human left ventricles using a pair of parallel needle electrodes at different voltages (500-1500 V) and two different pulse waveforms: a proprietary biphasic waveform (Medtronic) and monophasic 48 × 100 µs pulses. The lethal electric field threshold, anisotropy ratio, and conductivity increase by electroporation were determined by numerical modeling, comparing the model outputs with segmented lesion images. Results: The median threshold was 535 V/cm in porcine ((N = 51 lesions in n = 6 hearts) and 416 V/cm in the human donor hearts ((N = 21 lesions in n = 3 hearts) for the biphasic waveform. The median threshold value was 368 V/cm in porcine hearts ((N = 35 lesions in n = 9 hearts) cm for 48 × 100 µs pulses. Discussion: The values obtained are compared with an extensive literature review of published lethal electric field thresholds in other tissues and were found to be lower than most other tissues, except for skeletal muscle. These findings, albeit preliminary, from a limited number of hearts suggest that treatments in humans with parameters optimized in pigs should result in equal or greater lesions.

Optimization of Transpedicular Electrode Insertion for Electroporation-Based Treatments of Vertebral Tumors.

Electroporation-based treatments such as electrochemotherapy and irreversible electroporation ablation have sparked interest with respect to their use in medicine. Treatment planning involves determining the best possible electrode positions and voltage amplitudes to ensure treatment of the entire clinical target volume (CTV). This process is mainly performed manually or with computationally intensive genetic algorithms. In this study, an algorithm was developed to optimize electrode positions for the electrochemotherapy of vertebral tumors without using computationally intensive methods. The algorithm considers the electric field distribution in the CTV, identifies undertreated areas, and uses this information to iteratively shift the electrodes from their initial positions to cover the entire CTV. The algorithm performs successfully for different spinal segments, tumor sizes, and positions within the vertebra. The average optimization time was 71 s with an average of 4.9 iterations performed. The algorithm significantly reduces the time and expertise required to create a treatment plan for vertebral tumors. This study serves as a proof of concept that electrode positions can be determined (semi-)automatically based on the spatial information of the electric field distribution in the target tissue. The algorithm is currently designed for the electrochemotherapy of vertebral tumors via a transpedicular approach but could be adapted for other anatomic sites in the future.

Effects of Electrode-Tissue Proximity on Cardiac Lesion Formation Using Pulsed Field Ablation.

BACKGROUND: Pulsed field ablation (PFA) is a novel energy modality for treatment of cardiac arrhythmias. The impact of electrode-tissue proximity on lesion formation by PFA has not been conclusively assessed. The objective of this investigation was to evaluate the effects of electrode-tissue proximity on cardiac lesion formation with a biphasic, bipolar PFA system. METHODS: PFA was delivered on the ventricular epicardial surface in an isolated porcine heart model (n=8) via a 4-electrode prototype catheter. An offset tool was designed to control the distance between electrodes and target tissue; deliveries were placed 0 mm (0 mm offset), 2 mm (2 mm offset), and 4 mm away from the tissue (4 mm offset). Lesions were assessed using tetrazolium chloride staining. Numerical models for the experimental setup with and without the offset tool validated and supported results. RESULTS: Cardiac lesion dimensions decreased proportional to the distance between epicardial surface and electrodes. Lesion depth averaged 4.3±0.4 mm, 2.7±0.4 mm, and 1.3±0.4 mm for the 0, 2, and 4 mm and lesion width averaged 9.4±1.1 mm, 7.5±0.8 mm and 5.8±1.4 mm for the 0, 2, and 4 mm offset distances, respectively. Numerical modeling matched ex vivo results well and predicted lesion creation with and without the offset tool. CONCLUSIONS: Using a biphasic, bipolar PFA system resulted in cardiac lesions even in the 0 mm offset distance case. The relationship between lesion depth and offset distance was linear, and the deepest lesions were created with 0 mm offset distance, that is, with electrodes in contact with tissue. Therefore, close electrode-tissue proximity increases the likelihood of achieving transmural lesions by maximizing the electric field penetration into the target tissue.

Numerical mesoscale tissue model of electrochemotherapy in liver based on histological findings.

Electrochemotherapy (ECT) and irreversible electroporation (IRE) are being investigated for treatment of hepatic tumours. The liver is a highly heterogeneous organ, permeated with a network of macro- and microvasculature, biliary tracts and connective tissue. The success of ECT and IRE depends on sufficient electric field established in whole target tissue; therefore, tissue heterogeneity may affect the treatment outcome. In this study, we investigate electroporation in the liver using a numerical mesoscale tissue model. We numerically reconstructed four ECT experiments in healthy porcine liver and computed the electric field distribution using our treatment planning framework. We compared the computed results with histopathological changes identified on microscopic images after treatment. The mean electric field threshold that best fitted the zone of coagulation necrosis was 1225 V/cm, while the mean threshold that best fitted the zone of partially damaged liver parenchyma attributed to IRE was 805 V/cm. We evaluated how the liver macro- and microstructures affect the electric field distribution. Our results show that the liver microstructure does not significantly affect the electric field distribution on the level needed for treatment planning. However, major hepatic vessels and portal spaces significantly affect the electric field distribution, and should be considered when planning treatments.

Effects of Time Delay Between Unipolar Pulses in High Frequency Nano-Electrochemotherapy.

OBJECTIVE: this work focuses on bleomycin electrochemotherapy using new modality of high repetition frequency unipolar nanosecond pulses. METHODS: As a tumor model, Lewis lung carcinoma (LLC1) cell line in C57BL mice (n = 42) was used. Electrochemotherapy was performed with intertumoral injection of bleomycin (50 µL of 1500 IU solution) followed by nanosecond and microsecond range electrical pulse delivery via parallel plate electrodes. The 3.5 kV/cm pulses of 200 and 700 ns were delivered in a burst of 200 at frequencies of 1 kHz and 1 MHz. For comparison of treatment efficiency, a standard 1.3 kV/cm x 100 µs x 8 protocol was used. RESULTS: It was shown that it is possible to manipulate the efficacy of unipolar sub-microsecond electrochemotherapy solely by the time delay between the pulses. SIGNIFICANCE: the results suggest that the sub-microsecond range pulses can be as effective as the protocols in European Standard Operating Procedures on Electrochemotherapy (ESOPE) using 100 µs pulses.

Retrospective Study for Validation and Improvement of Numerical Treatment Planning of Irreversible Electroporation Ablation for Treatment of Liver Tumors.

OBJECTIVE: The aims of this study were to determine the electric field threshold that best fits the local response to irreversible electroporation (IRE) ablation of hepatic tumors as seen in follow-up MRI; to numerically evaluate the heat generating effect of IRE; and to demonstrate the utility of treatment planning to improve procedures in the future. METHODS: 18 cases of hepatic tumors treated with IRE ablation were numerically reconstructed and treatment outcome was computed with a numerical treatment planning framework. Simulated ablation volumes were compared to ablation volumes segmented from 6-week follow-up MRI. Two cases with a high thermal component were selected for numerical optimization. RESULTS: The best fit between segmented and simulated ablation zones was obtained at 900 V/cm threshold with the average absolute error of 5.6 ± 1.5 mm. Considerable heating was observed in 7/18 cases, where >50% of tumor volume experienced heating likely to cause thermal damage. In the selected two cases, thermal damage was eliminated with adjustment of applied voltages. CONCLUSION: Lesions visible on MRI 6 weeks post IRE represent areas that experienced an electric field of 900 V/cm or higher. This threshold is higher than previously reported for IRE of hepatic tumors. It is likely the 6-week follow-up period was too long and the ablation zone has already shrunk considerably, resulting in overestimation of the threshold. SIGNIFICANCE: We developed a sophisticated method for validation of the numerical treatment planning framework. A future prospective study can be effectively designed based on the findings of this study.

Safety and chronic lesion characterization of pulsed field ablation in a Porcine model.

BACKGROUND: Pulsed field ablation (PFA) has been identified as an alternative to thermal-based ablation systems for treatment of atrial fibrillation patients. The objective of this Good Laboratory Practice (GLP) study was to characterize the chronic effects and safety of overlapping lesions created by a PFA system at intracardiac locations in a porcine model. METHODS: A circular catheter with nine gold electrodes was used for overlapping low- or high-dose PFA deliveries in the superior vena cava (SVC), right atrial appendage (RAA), and right superior pulmonary vein (RSPV) in six pigs. Electrical isolation was evaluated acutely and chronic lesions were assessed via necropsy and histopathology after 4-week survival. Acute and chronic safety data were recorded peri- and post-procedurally. RESULTS: No animal experienced ventricular arrhythmia during PFA delivery, and there was no evidence of periprocedural PFA-related adverse events. Lesions created in all anatomies resulted in electrical isolation postprocedure. Lesions were circumferential, contiguous, and transmural, with all converting into consistent lines of chronic replacement fibrosis, regardless of trabeculated or smooth endocardial surface structure. Ablations were non-thermally generated with only minimal post-delivery temperature rises recorded at the electrodes. There was no evidence of extracardiac damage, stenosis, aneurysms, endocardial disruption, or thrombus. CONCLUSION: PFA deliveries to the SVC, RAA, and RSPV resulted in complete circumferential replacement fibrosis at 4-week postablation with an excellent chronic myocardial and collateral tissue safety profile. This GLP study evaluated the safety and efficacy of a dosage range in preparation for a clinical trial and characterized the non-thermal nature of PFA.

Nuclear-driven production of renewable fuel additives from waste organics.

Non-intermittent, low-carbon energy from nuclear or biofuels is integral to many strategies to achieve Carbon Budget Reduction targets. However, nuclear plants have high, upfront costs and biodiesel manufacture produces waste glycerol with few secondary uses. Combining these technologies, to precipitate valuable feedstocks from waste glycerol using ionizing radiation, could diversify nuclear energy use whilst valorizing biodiesel waste. Here, we demonstrate solketal (2,2-dimethyl-1,3-dioxolane-4-yl) and acetol (1-hydroxypropan-2-one) production is enhanced in selected aqueous glycerol-acetone mixtures with γ radiation with yields of 1.5 ± 0.2 µmol J-1 and 1.8 ± 0.2 µmol J-1, respectively. This is consistent with the generation of either the stabilized, protonated glycerol cation (CH2OH-CHOH-CH2OH2+ ) from the direct action of glycerol, or the hydronium species, H3O+, via water radiolysis, and their role in the subsequent acid-catalyzed mechanisms for acetol and solketal production. Scaled to a hypothetically compatible range of nuclear facilities in Europe (i.e., contemporary Pressurised Water Reactor designs or spent nuclear fuel stores), we estimate annual solketal production at approximately (1.0 ± 0.1) × 104 t year-1. Given a forecast increase of 5% to 20% v/v% in the renewable proportion of commercial petroleum blends by 2030, nuclear-driven, biomass-derived solketal could contribute towards net-zero emissions targets, combining low-carbon co-generation and co-production.

Dose rate calculations at beam tube no. 5 of the JSI TRIGA mark II research reactor using Monte Carlo method.

Monte Carlo N-Particle (MCNP) transport code accelerated by AutomateD VAriaNce reducTion Generator (ADVANTG) code was used to simulate neutron and prompt gamma particles emitted from TRIGA research reactor during operation. Firstly, the method was validated by measuring dose rates around open beam port number 5 was unplugged. Neutron and gamma dose rates inside the reactor hall in the vicinity of the beam port were calculated and compared to the measurements. Due to the satisfactory agreement, the method was later used to design external shielding for the same beam port when it was upgraded - special mechanism was installed that allows irradiation of larger samples. Computational analysis of the proposed shielding configuration provided acceptable dose rate levels inside the reactor hall. When the shield was constructed, calculated dose rates were confirmed by the actual measurements. No modifications were needed.

A Prospective Phase II Study Evaluating Intraoperative Electrochemotherapy of Hepatocellular Carcinoma.

The aim of this clinical study was to investigate the effectiveness and long-term safety of electrochemotherapy as an emerging treatment for HCC in patients not suitable for other treatment options. A prospective phase II clinical study was conducted in patients with primary HCC who were not suitable for other treatment options according to the Barcelona Clinic Liver Cancer classification. A total of 24 patients with 32 tumors were treated by electrochemotherapy. The procedure was effective, feasible, and safe with some procedure-related side effects. The responses of the 32 treated nodules were: 84.4% complete response (CR), 12.5% partial response (PR), and 3.1% stable disease (SD). The treatment was equally effective for nodules located centrally and peripherally. Electrochemotherapy provided a durable response with local tumor control over 50 months of observation in 78.0% of nodules. The patient responses were: 79.2% CR and 16.6% PR. The median progression-free survival was 12 months (range 2.7-50), and the overall survival over 5 years of observation was 72.0%. This prospective phase II clinical study showed that electrochemotherapy was an effective, feasible, and safe option for treating HCC in patients not suitable for other treatment options.

Investigation of safety for electrochemotherapy and irreversible electroporation ablation therapies in patients with cardiac pacemakers.

BACKGROUND: The effectiveness of electrochemotherapy of tumors (ECT) and of irreversible electroporation ablation (IRE) depends on different mechanisms and delivery protocols. Both therapies exploit the phenomenon of electroporation of the cell membrane achieved by the exposure of the cells to a series of high-voltage electric pulses. Electroporation can be fine-tuned to be either reversible or irreversible, causing the cells to either survive the exposure (in ECT) or not (in IRE), respectively. For treatment of tissues located close to the heart (e.g., in the liver), the safety of electroporation-based therapies is ensured by synchronizing the electric pulses with the electrocardiogram. However, the use of ECT and IRE remains contraindicated for patients with implanted cardiac pacemakers if the treated tissues are located close to the heart or the pacemaker. In this study, two questions are addressed: can the electroporation pulses interfere with the pacemaker; and, can the metallic housing of the pacemaker modify the distribution of electric field in the tissue sufficiently to affect the effectiveness and safety of the therapy? RESULTS: The electroporation pulses induced significant changes in the pacemaker ventricular pacing pulse only for the electroporation pulses delivered during the pacing pulse itself. No residual effects were observed on the pacing pulses following the electroporation pulses for all tested experimental conditions. The results of numerical modeling indicate that the presence of metal-encased pacemaker in immediate vicinity of the treatment zone should not impair the intended effectiveness of ECT or IRE even when the casing is in direct contact with one of the active electrodes. Nevertheless, the contact between the casing and the active electrode should be avoided due to significant tissue heating at the site of the other active electrode for the IRE protocol and may cause the pulse generator to fail to deliver the pulses due to excessive current draw. CONCLUSIONS: The observed effects of electroporation pulses delivered in close vicinity of the pacemaker or its electrodes do not indicate adverse consequences for either the function of the pacemaker or the treatment outcome. These findings should contribute to making electroporation-based treatments accessible also to patients with implanted cardiac pacemakers.

Safety and Feasibility of Electrochemotherapy of the Pancreas in a Porcine Model.

OBJECTIVES: The use of thermal ablative therapies in the pancreatic tumors is limited because of the risk of the vessel injury and potential pancreatitis or fistula formation. Electrochemotherapy (ECT) is an ablative therapy with an established role in the treatment of cutaneous and liver tumors. This study was designed to evaluate the safety and feasibility of ECT of the pancreas in a porcine survival model. METHODS: In the first group, 4 animals underwent computed tomography (CT)-guided percutaneous ECT with bleomycin of the pancreatic tail. In the second group (4 animals), the intraoperative ECT with bleomycin of pancreatic tail and head was performed. Animals were followed for 7 days and then killed. Clinical parameters, CT imaging, laboratory, and histologic analysis were performed. RESULTS: All pigs survived the ECT procedure and none of them developed clinical signs of acute pancreatitis or related complications. There were no signs of acute pancreatitis or damage to the large vessels present in the follow-up CT scans. No significant change in laboratory parameters was obtained after procedure. CONCLUSIONS: This study shows that ECT with bleomycin is feasible and safe in the pancreatic parenchyma. Clinical studies are needed to evaluate the efficacy of ECT in pancreatic cancer.

Percutaneous image guided electrochemotherapy of hepatocellular carcinoma: technological advancement.

Background Electrochemotherapy is an effective treatment of colorectal liver metastases and hepatocellular carcinoma (HCC) during open surgery. The minimally invasive percutaneous approach of electrochemotherapy has already been performed but not on HCC. The aim of this study was to demonstrate the feasibility, safety and effectiveness of electrochemotherapy with percutaneous approach on HCC. Patient and methods The patient had undergone the transarterial chemoembolization and microwave ablation of multifocal HCC in segments III, V and VI. In follow-up a new lesion was identified in segment III, and recognized by multidisciplinary team to be suitable for minimally invasive percutaneous electrochemotherapy. The treatment was performed with long needle electrodes inserted by the aid of image guidance. Results The insertion of electrodes was feasible, and the treatment proved safe and effective, as demonstrated by control magnetic resonance imaging. Conclusions Minimally invasive, image guided percutaneous electrochemotherapy is feasible, safe and effective in treatment of HCC.

Intraoperative electrochemotherapy of colorectal liver metastases: A prospective phase II study.

BACKGROUND AND OBJECTIVES: A previous pilot study proved the feasibility, safety and efficacy of electrochemotherapy in the treatment of colorectal liver metastases. The aim of this study was to evaluate long-term effectiveness and safety of electrochemotherapy in the treatment of unresectable colorectal liver metastases. PATIENTS AND METHODS: In this prospective phase II study, patients with metachronous colorectal liver metastases were included. In all patients, at least one metastasis was unresectable due to its central location or a too-small future remnant liver volume. Patients were treated by electrochemotherapy using intravenously administered bleomycin during open surgery. Treated were 84 metastases in 39 patients. Local tumor control, progression-free survival and overall survival were evaluated. RESULTS: The objective response was 75% (63% CR, 12% PR). The median duration of the response was 20.8 months for metastases in CR and 9.8 months for metastases in PR. The therapy was significantly more effective for metastases smaller than 3 cm in diameter than for larger ones. There was no difference in response according to the metastatic location, i.e., metastases in central vs. peripheral locations. Progression-free survival was better in patients who responded well to electrochemotherapy compared to those metastases that had a partial response or progressive disease. However, there was no difference in overall survival, with a median of 29.0 months. CONCLUSIONS: Electrochemotherapy has proven to be safe and effective in the treatment of colorectal liver metastases, with a durable response. It provides local tumor control that enables patients with unresectable metastases to receive further treatments.

Peri-tumoral Metallic Implants Reduce the Efficacy of Irreversible Electroporation for the Ablation of Colorectal Liver Metastases.

PURPOSE: To evaluate the effect of peri-tumoral metallic implants (MI) on the safety and efficacy of percutaneous irreversible electroporation (IRE) of colorectal liver metastasis (CRLM). MATERIALS AND METHODS: In this retrospective study, 25 patients (12 women, 13 men; MI: 13, no MI: 12) were treated for 29 CRLM. Patient characteristics, tumor location and size, treatment parameters and the presence of MI were evaluated as determinants of local tumor progression (LTP) with the competing risks model (univariate and multivariate analyses). Patient-specific computer models were created to examine the effect of the MI on the electric field used to induce IRE, probability of cell kill and potential thermal effects. RESULTS: Patients had a median follow-up of 25 months, during which no IRE-related major complications were reported. Univariate analysis showed that tumor size (> 2 cm), probe spacing (> 20 mm) and the presence of MI (p < 0.05) were significant predictors of time to LTP, but only the latter was found to be an independent predictor on multivariate analysis (sub-hazard ratio = 6.5; [95% CI 1.99, 21.4]; p = 0.002). The absence of peri-tumoral MI was associated with higher progression-free survival at 12 months (92.3% [56.6, 98.9] vs 12.5% [2.1, 32.8]). Computer simulations indicated significant distortions and reduction in electric field strength near MI, which could have contributed to under-treatment of the tumor. CONCLUSIONS: Peri-tumoral MI increases the risk of treatment failure following IRE of CRLM.

Radiological findings of porcine liver after electrochemotherapy with bleomycin.

Background Radiologic findings after electrochemotherapy of large hepatic blood vessels and healthy hepatic parenchyma have not yet been described. Materials and methods We performed a prospective animal model study with regulatory approval, including nine grower pigs. In each animal, four ultrasound-guided electroporated regions were created; in three regions, electrodes were inserted into the lumen of large hepatic vessels. Two types of electrodes were tested; variable linear- and fixed hexagonal-geometry electrodes. Ultrasonographic examinations were performed immediately and up to 20 minutes after the procedure. Dynamic computed tomography was performed before and at 60 to 90 minutes and one week after the procedure. Results Radiologic examinations of the treated areas showed intact vessel walls and patency; no hemorrhage or thrombi were noted. Ultrasonographic findings were dynamic and evolved from hyperechogenic microbubbles along electrode tracks to hypoechogenicity of treated parenchyma, diffusion of hyperechogenic microbubbles, and hypoechogenicity fading. Contrast-enhanced ultrasound showed decreased perfusion of the treated area. Dynamic computed tomography at 60 to 90 minutes after the procedure showed hypoenhancing areas. The total hypoenhancing area was smaller after treatment with fixed hexagonal electrodes than after treatment with variable linear geometry electrodes. Conclusions Radiologic findings of porcine liver after electrochemotherapy with bleomycin did not show clinically significant damage to the liver, even if a hazardous treatment strategy, such as large vessel intraluminal electrode insertion, was employed, and thus further support safety and clinical use of electrochemotherapy for treatment of hepatic neoplasia.

Large Liver Blood Vessels and Bile Ducts Are Not Damaged by Electrochemotherapy with Bleomycin in Pigs.

The first clinical studies on the use of electrochemotherapy to treat liver tumours that were not amenable to surgery or thermal ablation techniques have recently been published. However, there is still a lack of data on the effects of electrochemotherapy on normal liver tissue. Therefore, we designed a translational animal model study to test whether electrochemotherapy with bleomycin causes clinically significant damage to normal liver tissue, with emphasis on large blood vessels and bile ducts. We performed electrochemotherapy with bleomycin or delivered electric pulses alone using a potentially risky treatment strategy in eight pigs. Two and seven days after treatment, livers were explanted, and histological analysis was performed. Blood samples were collected before treatment and again before euthanasia to evaluate blood biomarkers of liver function and systemic inflammatory response. We found no thrombosis or other clinically significant damage to large blood vessels and bile ducts in the liver. No clinical or laboratory findings suggested impaired liver function or systemic inflammatory response. Electrochemotherapy with bleomycin does not cause clinically significant damage to normal liver tissue. Our study provides further evidence that electrochemotherapy with bleomycin is safe for treatment of patients with tumours near large blood vessels in the liver.

Ultrasonographic changes in the liver tumors as indicators of adequate tumor coverage with electric field for effective electrochemotherapy.

Background The aim of the study was to characterize ultrasonographic (US) findings during and after electrochem-otherapy of liver tumors to determine the actual ablation zone and to verify the coverage of the treated tumor with a sufficiently strong electric field for effective electrochemotherapy. Patients and methods US findings from two representative patients that describe immediate and delayed tumor changes after electrochemotherapy of colorectal liver metastases are presented. Results The US findings were interrelated with magnetic resonance imaging (MRI). Electrochemotherapy-treated tumors were exposed to electric pulses based on computational treatment planning. The US findings indicate immediate appearance of hyperechogenic microbubbles along the electrode tracks. Within minutes, the tumors became evenly hyperechogenic, and simultaneously, an oedematous rim was formed presenting as a hypoechogenic formation which persisted for several hours after treatment. The US findings overlapped with computed electric field distribution in the treated tissue, indicating adequate coverage of tumors with sufficiently strong electric field, which may predict an effective treatment outcome. Conclusions US provides a tool for assessment of appropriate electrode insertion for intraoperative electrochemo-therapy of liver tumors and assessment of the appropriate coverage of a tumor with a sufficiently strong electric field and can serve as predictor of the response of tumors.