Effects of a Thermal Accelerant Gel on Microwave Ablation Zone Volumes in Lung: A Porcine Study

Abstract

Background: Thermal ablation of cancers may be associated with high rates of local tumor progression. A thermal accelerant gel has been developed to improve the transmission of microwave energy in biologic tissues with the aim of enlarging the thermal ablation zone. Purpose: To determine the effects of a thermal accelerant gel on microwave ablation zone volumes in porcine lung and to compare percutaneous and endobronchial delivery methods. Materials and Methods: Thirty-two consecutive microwave lung ablations were performed in nine 12-week-old domestic male swine under general anesthesia by using fluoroscopic guidance between September 2017 and April 2018. Experimental ablations were performed following percutaneous injection of thermal accelerant into the lung (n = 16) or after endobronchial injection by using a flexible bronchoscope (n = 8). Control ablations were performed without accelerant gel (n = 8). Lung tissue was explanted after the animals were killed, and ablation zone volumes were calculated as the primary outcome measure by using triphenyltetrazolium chloride vital staining. Differences in treatment volumes were analyzed by generalized mixed modeling. Results: Thermal accelerant ablation zone volumes were larger than control ablations (accelerant vs control ablation, 4.3 cm 3 [95% confidence interval: 3.4, 5.5] vs 2.1 cm 3 [95% confidence interval: 1.4, 2.9], respectively; P , .001). Among ablations with the thermal accelerant, those performed following percutaneous injection had a larger average ablation zone volume than those performed following endobronchial injection (percutaneous vs endobronchial, 4.8 cm 3 [95% confidence interval: 3.6, 6.4] vs 3.3 cm 3 [95% confidence interval: 2.9, 3.8], respectively; P = .03). Ablation zones created after endobronchial gel injection were more uniform in size distribution (standard error, percutaneous vs endobronchial: 0.13 vs 0.07, respectively; P = .03). Conclusion: Use of thermal accelerant results in larger microwave ablation zone volumes in normal porcine lung tissue. Percutaneous thermal accelerant injection leads to a larger ablation zone volume compared with endobronchial injection, whereas a more homogeneous and precise ablation zone size is observed by using the endobronchial approach.

Survival benefit of thermal ablation therapy for patients with stage II-III non-small cell lung cancer: A propensity-matched analysis

“…TA is considered a safe treatment for primary lung cancer ( 7 , 20 , 21 ). As an alternative therapy to surgical resection, TA causes irreversible damage to tumor cells using thermal energy ( 14 , 31 , 32 ). While previous studies have shown that TA is beneficial for stage I NSCLC patients ( 7 , 18 , 33 ), however, there is minimal data on the use of TA in stage II-III NSCLC patients.…”

“…TA includes radiofrequency ablation (RFA), microwave ablation (MWA), and ultrasound ablation using various energy sources ( 12 , 13 ). As a minimally invasive treatment technique, TA utilizes thermal energy to cause injuries to the targeted tissue ( 14 ). Of the ablation technologies in clinical use, RFA is the most widely used for the treatment of multiple conditions, including cardiac arrhythmias and liver, lung, kidney, and other tumors ( 12 ).…”

Ablation for Single Pulmonary Nodules, Primary or Metastatic. Εndobronchial Ablation Systems or Percutaneous

“…Microwave technology was observed to be more efficient than radiofrequency 15 . Currently the thermal effect of microwave application has been enhanced by adding transbronchial thermal gel 16 . Moreover; thermosphere technology combined with microwave ablation has increased the efficiency of the method 13 .…”

Simulation of Image-Guided Microwave Ablation Therapy Using a Digital Twin Computational Model

“…Additionally, ex vivo liver experiments revealed larger ablation zones in the forward direction when compared with prior designs [13] , [14] . Another experimental approach is the use of thermal accelerants that are designed to augment microwave energy transmission, resulting in faster heating and larger ablation volumes [15] , [16] . In a study by Maxwell et al, the use of thermal accelerants was associated with an average 40% increase in ablation volumes compared to standard ablations in in vivo swine (22.2 cm 3 vs 15.9 cm 3 ) as well as producing more spherical ablation volumes [17] .…”