Study of enhanced radiofrequency heating by pre-freezing tissue

Abstract

In our previous animal model study, we found that radiofrequency (RF) ablation of pre-frozen tumor resulted in improved therapeutic effects. To understand the underlying mechanisms and optimize the treatment protocol, the RF heating pattern in pre-frozen tissue was studied in this paper. Both ex vivo and in vivo experiments were conducted to compare the temperature profiles of RF heating with or without pre-freezing. Results showed that the heating rate of in vivo tissues was significantly higher with pre-freezing. However, little difference was observed in the heating rate of ex vivo tissues with or without pre-freezing. In the histopathologic analysis of in vivo tissues, both a larger ablation area and a wider transitional zone were found in the tissue with pre-freezing. To investigate the cause for the enhancement in RF heating, the parameters affecting the tissue temperature rise were studied. It was found that the electrical conductivity of in vivo tissue with pre-freezing was much higher at low frequencies, but little difference was found at the 460 kHz frequency commonly used in clinical applications. A finite element model for RF heating was developed and validated to fit the thermal conductivity of in vivo tissue including effects of pre-freezing and the associated blood perfusion rate. Results showed that the enhancement of the heating rate was primarily attributed to the decreased blood perfusion rate in the tissue with vascular damage caused by pre-freezing. The ablation volume was increased by 104% due to the reduced heat dissipation.

Tumor-related HSP70 released after cryo-thermal therapy targeted innate immune initiation in the antitumor immune response

“…The thermal and mechanical stresses caused by cryo-thermal therapy facilitated tumor cell membrane disruption, which led to the acute release of tumor-derived DAMPs in situ [24]. In addition, cryo-thermal therapy could damage blood vessels and increase the permeability of blood vessels [23], which helped locally released DAMPs enter the peripheral circulation and subsequently induced a systemic immune response.…”

“…In our previous study, a novel local cryo-thermal therapy was developed to stimulate systemic antitumor immunity in animal models [23]. The therapeutic effect of local cryo-thermal therapy was clearly demonstrated by using mice bearing subcutaneous 4T1 murine mammary carcinomas or experimental lung metastases of murine B16F10 melanoma, and the mice had long-term survival rates over 70% and 80%, respectively [24,25].…”

Co‐ablation versus cryoablation for the treatment of stage III–IV non‐small cell lung cancer: A prospective, noninferiority, randomized, controlled trial (RCT)

“…reported that alternate cold and heat ablation (using ethanol and water as cooling and heating fluid) could result in severe vascular injury and a large area of tumor cell debris. Zhang et al . 16 utilized both the cryoablation system and RFA to achieve the combined ablation goal.…”

Liquid Metal Microparticles Phase Change Medicated Mechanical Destruction for Enhanced Tumor Cryoablation and Dual‐Mode Imaging

“…Actually, cryoablation, which continuously delivers cold energy to tissues via intracellular and extracellular ice formation to destroy tumors, is demonstrated with both therapeutic effects, broad adaptation and immune response. [49][50][51] The C8161 tumor model was established in female nude mice. When the cul tured tumor cells were in the logarithmic growth phase, cells were collected and injected into the subcutaneous sites.…”