Cryosurgery with Pulsed Electric Fields

Abstract

This study explores the hypothesis that combining the minimally invasive surgical techniques of cryosurgery and pulsed electric fields will eliminate some of the major disadvantages of these techniques while retaining their advantages. Cryosurgery, tissue ablation by freezing, is a well-established minimally invasive surgical technique. One disadvantage of cryosurgery concerns the mechanism of cell death; cells at high subzero temperature on the outer rim of the frozen lesion can survive. Pulsed electric fields (PEF) are another minimally invasive surgical technique in which high strength and very rapid electric pulses are delivered across cells to permeabilize the cell membrane for applications such as gene delivery, electrochemotherapy and irreversible electroporation. The very short time scale of the electric pulses is disadvantageous because it does not facilitate real time control over the procedure. We hypothesize that applying the electric pulses during the cryosurgical procedure in such a way that the electric field vector is parallel to the heat flux vector will have the effect of confining the electric fields to the frozen/cold region of tissue, thereby ablating the cells that survive freezing while facilitating controlled use of the PEF in the cold confined region. A finite element analysis of the electric field and heat conduction equations during simultaneous tissue treatment with cryosurgery and PEF (cryosurgery/PEF) was used to study the effect of tissue freezing on electric fields. The study yielded motivating results. Because of decreased electrical conductivity in the frozen/cooled tissue, it experienced temperature induced magnified electric fields in comparison to PEF delivered to the unfrozen tissue control. This suggests that freezing/cooling confines and magnifies the electric fields to those regions; a targeting capability unattainable in traditional PEF. This analysis shows how temperature induced magnified and focused PEFs could be used to ablate cells in the high subzero freezing region of a cryosurgical lesion.

Rapid Dramatic Alterations to The Tumor Microstructure in Pancreatic Cancer Following Irreversible Electroporation Ablation

“…IRE disrupts cellular physiology, producing nearly complete cell kill within the targeted areas of ablation [22]. Preclinical studies in subcutaneous tumor models, human cancer cells, normal liver and liver-implanted tumor tissues, and prostate tissues have each demonstrated the feasibility of using IRE as a new ablation option with negligible thermal side effects [14,19,23–25]. …”

Combined pulsed field ablation with ultra‐low temperature cryoablation: A preclinical experience

“…The concept of augmenting cryoablation with pulsed electric fields has been explored before 18 . The increased impedance of cold and frozen tissue may concentrate the electrical field in the low‐temperature regions which could further improve the selectivity of the PFA and enabling the ablation of cells on the outer edges of the cryothermy lesions which may not be irreversibly damaged by the cold.…”

Novel Ablation Catheters for Atrial Fibrillation

“…A combination of PFA and cryoablation (PFCA) is one of the concepts to circumvent this issue. The increased impedance of cooled and frozen tissue might concentrate the electrical field in the low-temperature areas, potentially enhancing the selectivity of the PFA [ 35 ].…”