Thermal Field Distributions of Ablative Experiments Using Cyst-mimicking Phantoms: Comparison of Microwave and Radiofrequency Ablation

Effects of microwave ablation on cysts and cystic neoplasms with tissue-mimicking model: an ex vivo study

BACKGROUND AND PURPOSE

Microwave ablation (MWA) is a promising modality that needs to be further investigated for cystic lesions. The present study aimed to determine the effects of MWA on cysts and cystic neoplasms with a tissue-mimicking model.

METHODS

Twenty New Zealand White rabbits were randomly divided into Group A (cyst mimic models, n = 10, φ = 5 cm) and Group B (cystic neoplasm mimicking models, n = 10, φ = 5 cm). For each group, ex vivo rabbit healthy bladder and VX2-implanted tumor bladder were fixed and embedded in agarose gel to mimic cyst and cystic neoplasm. In the MWA experimental subgroups, microwave antennas guided by computed tomography (CT) were introduced into these models. A system thermometer was placed at the outer edge of the bladder wall to monitor temperature changes. Immediately after MWA, ex vivo rabbit healthy bladders and VX2-implanted tumor bladders were harvested for gross anatomy and prepared for pathological evaluation.

RESULTS

A total of twenty cyst and cystic neoplasm mimicking models were successfully developed. Ninety percent of the MWA procedures were successful, and no peri-procedural complications were encountered. The temperature of the cystic wall increased with duration in both MWA experimental subgroups and an effective ablation temperature (>60 °C) was achieved. Pathological examination of the cyst and cystic neoplasm mimic models revealed degenerative necrosis of the bladder wall mucosal epithelial cells, loss of bladder wall tissue structure and coagulative necrosis of VX2 tumor cells.

CONCLUSION

Our data indicate that MWA could cause thermal damage to the tissue structure of cyst and cystic neoplasm, and it is an effective technique for treating cystic diseases.HIGHLIGHTSex vivo rabbit healthy bladder and VX2-implanted tumor bladder were fixed and embedded in agarose gel to mimic cyst and cystic neoplasm.The temperature of the cystic wall increased with MWA duration and an effective ablation temperature (> 60 °C) was achieved.MWA could cause thermal damage to the tissue structure of the cyst and cystic neoplasm and it is effective in treating cystic diseases, as assessed by histopathology.

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

Background

Thermal ablation (TA) is considered a safe alternative to surgical resection for the treatment of non-small cell lung cancer (NSCLC). While previous studies have shown that TA is beneficial for stage I NSCLC patients, however, few have reported on TA efficacy in patients with stage II-III NSCLC. The current study investigated the impact of TA on the overall survival (OS) and cancer-specific survival (CSS) of patients with stage II-III NSCLC.

Methods

Data on patients with stage II-III NSCLC who did not undergo surgical resection between 2004 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Propensity score matching (PSM), Kaplan-Meier survival curves, and Cox regression were used for statistical analyses.

Results

A total of 57,959 stage II-III NSCLC patients who did not undergo surgical resection were included in this study, 261 of whom received TA. Overall, TA was associated with a longer OS (p = 0.035) and CSS (p = 0.005) than non-ablation. After 1:3 PSM, 252 patients receiving TA and 732 patients not receiving ablation were enrolled in the matched cohort. The OS (p = 0.047) and CSS (p = 0.029) remained higher in the TA group than in the non-ablation group after PSM. Cox regression analysis showed that age, sex, primary tumor site, pathological type, tumor size, radiotherapy, chemotherapy, and thermal ablation were independently associated with OS and CSS (p <0.05). Subgroup analysis found that the advantages of TA were more pronounced among individuals ≥70 years of age, with tumor size ≤3.0 cm, or who did not receive radiotherapy.

Conclusion

TA could be an effective alternative treatment for stage II-III NSCLC patients unsuitable for surgical resection, particularly those ≥70 years of age, with tumor size ≤3.0 cm, or who have not received radiotherapy.

Computed Tomography-Guided Microwave Ablation of Cystic Renal Cell Carcinoma: Assessment of Technique and Complications

This report evaluates the techniques and complications of microwave ablation of cystic renal cell carcinoma. Five patients with cystic renal cell carcinoma were treated with microwave ablation between October 2015 and June 2020. Medical records were reviewed to evaluate technique and complications. Technical success and primary technique efficacy both were 100%. There were no complications. Mean follow-up time was 18 months (range, 6-36 months). No local recurrence was identified during the follow-up period. Renal function remained stable at 1 month and the last follow-up. Percutaneous microwave ablation is promising for the nonsurgical management of cystic renal cell carcinoma.

How large is the periablational zone after radiofrequency and microwave ablation? Computer-based comparative study of two currently used clinical devices

Purpose:

To compare the size of the coagulation (CZ) and periablational (PZ) zones created with two commercially available devices in clinical use for radiofrequency (RFA) and microwave ablation (MWA), respectively.

Methods:

Computer models were used to simulate RFA with a 3-cm Cool-tip applicator and MWA with an Amica-Gen applicator. The Arrhenius model was used to compute the damage index (Ω). CZ was considered when Ω> 4.6 (>99% of damaged cells). Regions with 0.6<Ω< 2.1 were considered as the PZ (tissue that has undergone moderate sub-ablative hyperthermia). The ratio of PZ volume to CZ volume (PZ/CZ) was regarded as a measure of performance, since a low value implies achieving a large CZ while keeping the PZ small.

Results:

Ten-min RFA (51 W) created smaller periablational zones than 10-min MWA (11.3 cm³ vs. 17.2 22.9 cm³, for 60 100 W MWA, respectively). Prolonging duration from 5 to 10 min increased the PZ in MWA more than in RFA (2.7 cm³ for RFA vs. 8.3–11.9 cm³ for 60–100 W MWA, respectively). PZ/CZ for RFA were relatively high (65–69%), regardless of ablation time, while those for MWA were highly dependent on the duration (increase of up to 25% between 5 and 10 min) and on the applied power (smaller values as power was raised, 102% for 60 W vs. 81% for 100 W, both for 10 min). The lowest PZ/CZ across all settings was 56%, obtained with 100 W-5 min MWA.

Conclusions:

Although RFA creates smaller periablational zones than MWA, 100 W-5 min MWA provides the lowest PZ/CZ.

Microwave ablation combining surgery for the treatment of multiorgan cystic echinococcosis: A case report

Cystic echinococcosis (CE) is a global public health problem associated with a high overall disease burden. Multiple organ systems are involved in approximately 20% of cases, and treatment is challenging and rarely reported. In this study, we described microwave ablation (MWA) combining surgery for the treatment of a multiorgan CE patient. The patient underwent percutaneous MWA for a hepatic CE3b lesion and exploratory resection of the pelvic cavity lesions. The hepatic lesion was effectively treated by MWA, and invasiveness was reduced by avoiding hepatectomy. The patient had a favorable prognosis at a 20-month's follow-up. More studies are needed to evaluate its usefulness in CE treatment.