Non-thermal Ablation Technique Research Articles

Irreversible electroporation of the pancreas: Definitive local therapy without systemic effects

The use of thermal tumor ablative techniques in the pancreas is limited due to the risk of pancreatitis and damage to major vascular structures. Irreversible electroporation (IRE) is a non-thermal ablation technique that could allow ablation in the pancreas while preserving vital surrounding blood vessels. The aim of this study was to assess the safety and ablation volume of IRE in porcine pancreatic tissue. IRE of swine pancreases was performed using an open technique and ultrasound guidance and the animals were followed for 72 hr, 7 days, and 14 days post-IRE. All pigs underwent IRE, with one pig was unsuccessful after three attempts using at 3,000 V due to inability to achieve a stable current. All animals recovered well and revealed only mild adhesions, no ascites, and no pancreatic necrosis. All animals had transient increases in amylase and lipase that normalized on post-IRE day 3. Pathologic analysis revealed that ablation defects (median size 3 cm × 2.8 cm) were seen in electroporated areas with significant destruction of the pancreatic tissue with patent vascular structures. This animal model demonstrates that IRE of the pancreas performed at an optimal voltage is well tolerated, with rapid resolution of pancreatic inflammation and preservation of vascular structures.

Current and future technology for minimally invasive ablation of renal cell carcinoma

Purpose of Review:To provide an overview of the technologic advancements in the field of ablative therapy, focusing on the treatment of renal neoplasms.Materials and Methods:A MEDLINE search was performed using each specific ablative technique name as the search term. Articles written in the English language were selected for review. In cases of multiple reports by a single institution, the most recent report was utilized. Pertinent articles specific to the technologic advancement in ablative therapy were selected for review.Recent Findings:Intermediate-term oncologic outcomes of radiofrequency ablation (RFA) and cryoablation (CA) for the treatment of small renal masses are encouraging. For thermal therapies, molecular adjuvants to enhance cellular kill and local control have been developed. Improvements in microwave technology have allowed for reductions in antenna size and increases in ablation size. Laparoscopic high-intensity focused ultrasound (HIFU) probes have been developed to overcome the limitations of transcutaneous energy delivery, but HIFU remains experimental for the treatment of renal lesions. Irreversible electroporation (IRE), a novel nonthermal ablative technique, is currently undergoing clinical investigation in human subjects. Histotripsy causes mechanical destruction of targeted tissue and shows promise in treating renal and prostate pathology.Summary:Ablative techniques are commonly utilized in the primary treatment of urologic malignancies. The purpose of this review is to discuss technologic advances in ablative therapies with emphasis on the treatment of renal masses. RFA and CA show acceptable intermediate-term efficacy and technical refinement continues. Emerging technologies, including microwave thermotherapy, IRE, HIFU and histotripsy, are described with emphasis on the mechanism of cellular kill, energy delivery, and stage in clinical development.

Laser interventions in otorhinolaryngology – Current techniques and future developments

Abstract Following the rapid pace at which laser applications and interventions evolved during the 1980s and 1990s, laser systems are now being used extensively in all fields of otorhinolaryngology. Surgical techniques have been refined and adapted to standards of minimally invasive operations. As long-term results are now widely available, especially in endolaryngeal and endopharyngeal laser surgery for malignant lesions, the indications for laser interventions versus conventional surgery are more clearly defined and have become less controversial. The original diversity of laser systems has now been concentrated into fewer systems for which the clinical experience is equally widespread. Current developments are focused on the application of laser energy and intelligent laser power control. This allows surgeons to concentrate on the actual resection task at hand. Future developments include precise non-thermal ablation techniques with femtosecond and picosecond lasers but also feedback-controlled systems which rely on diagnostic parameters that are evaluated automatically during the resection process. Another field of application is the non-destructive stimulation of inner ear hair cells or auditory neurons which has opened up new perspectives for the development of hearing aids or cochlear implants.

A Preliminary Study to Delineate Irreversible Electroporation From Thermal Damage Using the Arrhenius Equation

Intense but short electrical fields can increase the permeability of the cell membrane in a process referred to as electroporation. Reversible electroporation has become an important tool in biotechnology and medicine. The various applications of reversible electroporation require cells to survive the procedure, and therefore the occurrence of irreversible electroporation (IRE), following which cells die, is obviously undesirable. However, for the past few years, IRE has begun to emerge as an important minimally invasive nonthermal ablation technique in its own right as a method to treat tumors and arrhythmogenic regions in the heart. IRE had been studied primarily to define the upper limit of electrical parameters that induce reversible electroporation. Thus, the delineation of IRE from thermal damage due to Joule heating has not been thoroughly investigated. The goal of this study was to express the upper bound of IRE (onset of thermal damage) theoretically as a function of physical properties and electrical pulse parameters. Electrical pulses were applied to THP-1 human monocyte cells, and the percentage of irreversibly electroporated (dead) cells in the sample was quantified. We also determined the upper bound of IRE (onset of thermal damage) through a theoretical calculation that takes into account the physical properties of the sample and the electric pulse characteristics. Our experimental results were achieved below the theoretical curve for the onset of thermal damage. These results confirm that the region to induce IRE without thermal damage is substantial. We believe that our new theoretical analysis will allow researchers to optimize IRE parameters without inducing deleterious thermal effects.

Tumor Ablation with Irreversible Electroporation

We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 µs at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%), in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation.

A Study of the Immunological Response to Tumor Ablation with Irreversible Electroporation

Immune cell recruitment during the treatment of sarcoma tumors in mice with irreversible electroporation was studied by immunohistochemistry. Irreversible electroporation is a non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the membrane. Employing irreversible electroporation parameters known to completely ablate the tumors without thermal effects we did not find infiltration of immune cells probably because of the destruction of infiltration routes. We confirm here that immune response is not instrumental in irreversible electroporation efficacy, and we propose that irreversible electroporation may be, therefore, a treatment modality of interest to immunodepressed cancer patients.

The use of a “Liquid” electrode in hepatic electrolysis

Background The use of direct current electrolysis as a local nonthermal ablative technique for colorectal liver metastases promises to be a simple, safe, and effective therapy. Under general anesthesia, electrolysis is presently limited to tumors smaller than 5 cm, due to the protracted nature of its administration. In an attempt to enhance the effect of electrolysis, a direct current was passed through a preinjected bolus of acetic acid. Methods The effect of a combination of electrolysis and an injection of acetic acid was tested in the liver of eight normal pigs. The volumes of necrosis caused were analyzed. Results Acetic acid independently produced a volume of necrosis but did not provide a volumetric or rate advantage when used in combination with a direct current. Statistically, the only main effect on the volume of necrosis was a result of electrolysis. Conclusion The use of 50% acetic acid to augment the efficacy of direct current electrolysis cannot be recommended.