Finite Element Analysis of the Microwave Ablation Method for Enhanced Lung Cancer Treatment

The influence of microwave ablation parameters on the positioning of trocar in different cancerous tissues: a numerical study

The present study analyzed the microwave ablation of cancerous tumors located in six major cancer-prone organs and estimated the significance of input power and treatment time parameters in the apt positioning of the trocar into the tissue during microwave ablation. The present study has considered a three-dimensional two-compartment tumour-embedded tissue model. FEA based COMSOL Multiphysics software with inbuilt bioheat transfer, electromagnetic waves, heat transfer in solids and fluids, and laminar flow physics has been used to obtain the numerical results. Based on the mortality rates caused by cancer, the present study has considered six major organs affected by cancer, viz. lung, breast, stomach/gastric, liver, liver (with colon metastasis), and kidney for MWA analysis. The input power (100 W) and ablation times (4 minutes) with apt and inapt positioning of the trocar have been considered to compare the ablation volume of various cancerous tissues. The present study addresses one of the major problems clinicians face, i.e. the proper placement of the trocar due to poor imaging techniques and human error, resulting in incomplete tumor ablation and increased surgical procedures. The highest values of the ablation region have been observed for the liver, colon metastatic liver and breast cancerous tissues compared with other organs at the same operating conditions.

Optimized strategies of ROS-based nanodynamic therapies for tumor theranostics

Reactive oxygen species (ROS) play a crucial role in regulating the metabolism of tumor growth, metastasis, death and other biological processes. ROS-based nanodynamic therapies (NDTs) are becoming attractive due to non-invasive, low side effects and tumor-specific advantages. NDTs have rapidly developed into numerous branches, such as photodynamic therapy, chemodynamic therapy, sonodynamic therapy and so on. However, the complexity of the tumor microenvironment and the limitations of existing sensitizers have greatly restricted the therapeutic effects of NDTs, which heavily rely on ROS levels. To address the limitations of NDTs, various strategies have been developed to increase ROS yield, which is an urgent aspect for the positive development of NDTs. In this review, the nanodynamic potentiation strategies in terms of unique properties and universalities of NDTs are comprehensively outlined. We mainly summarize the current dilemmas faced by each NDT and the respective solutions. Meanwhile, the NDTs universalities-based potentiation strategies and NDTs-based combined treatments are elaborated. Finally, we conclude with a discussion of the key issues and challenges faced in the development and clinical transformation of NDTs.

Microwave ablation of the lung: Comparison of 19G with 14G and 16G microwave antennas in ex vivo porcine lung

Background

Percutaneous image-guided thermal ablation has an increasing role in the treatment of primary and metastatic lung tumors. Although microwave ablation (MWA) has emerged advantageous as a new ablation technology, more research is needed to improve it. This study aims to investigate the ablation zone of three microwave antennas in ex vivo porcine lung.

Materials and Methods

In the ex vivo standard model and porcine lung model, MWA was performed in three power output settings (50 W, 60 W, and 70 W) for 3, 6, 9, and 12 min using three microwave antennas, with outer diameter of 1.03 mm (19G), 1.6 mm (16G), and 2.0 mm (14G). A total of 108 and 216 sessions were performed (3 or 6 sessions per time setting with the 14G, 16G, and 19G microwave antennas). After the MWA was complete, we evaluated the shape and extent of the coagulation zone and measured the maximum long-axis (along the needle axis; length [L]) and maximum short-axis (perpendicular to the needle; diameter [D]) of the ablation zones using a ruler; subsequently, the sphericity index (L/D) was calculated. The sphericity index can be simplified as long-axis/short-axis.

Results

In the ex vivo standard model study, the long- and short-axis diameters and sphericity indices were not statistically different between the 14G, 16G, and 19G groups. In the ex vivo porcine lung study, the long- and short-axis diameters did not differ statistically between the 14G, 16G, and 19G groups (P < 0.05 each). The sphericity index for the 19G microwave antenna was higher than the sphericity indices for the 14G and 16G microwave antennas (P < 0.05); however, the index for the 14G microwave antenna was not statistically different than that for the 16G microwave antenna (P > 0.05).

Conclusions

The ablation zone of the 19G antenna was the same as those of the 14G and 16G antennas in vitro. Thus, the 19G antenna may reduce the incidence of complications in lung tumor ablation.

The Effect of Microwave Ablation Combined with Anti-PD-1 Monoclonal Antibody on T Cell Subsets and Long-Term Prognosis in Patients Suffering from Non-Small-Cell Lung Cancer

Objective

This research is aimed at studying the effect of microwave ablation combined with the antiprogrammed death- (PD-) 1 monoclonal antibody on T cell subsets and long-term prognosis in patients suffering from non-small-cell lung cancer (NSCLC).

Methods

Employing the random number table technique, a total of 122 NSCLC patients who received treatment at our hospital between May 2015 and June 2019 were selected and assigned to the observation group and the control group, and each group comprised 61 patients (n = 61). While the control group received only anti-PD-1 monoclonal antibody treatment, the observation group received microwave ablation in combination with anti-PD-1 monoclonal antibody. The clinical efficacy was observed for both groups. The levels of T cell subsets (CD3+, CD4+, and CD8+), serum tumor markers (squamous cell carcinoma antigen (SCCA), cytokeratin Ig fragment (CYFRA21-1), and serum carcinoembryonic antigen (CEA)), nuclear factor kappa B (NF-κB), protease C (PKC), and mitogen-activated protein kinase (MAPK) mRNA expression between the two groups were compared. The frequency of adverse reactions was observed in both groups. The survival time of both the groups was recorded over the course of three years of follow-up. The Kaplan-Meier method was employed for analyzing the survival of both the control and the observation group.

Results

The response rate (RR) of the observation group (80.33%) was considerably greater in comparison to that of the control group (62.30%) (P < 0.05). Following treatment, the observation group's levels of CD3+, CD4+, CD8+, SCCA, CyFRA21-1, and CEA and the mRNA expressions of NF-κB, PKC, and MAPK were superior to those of the control group, with statistical significances (all P < 0.05). Between the two groups, there was no significant difference in the occurrence of adverse reactions (P > 0.05). The observation group had greater 1-, 2-, and 3-year survival rates (57.38%, 39.34%, and 29.51%) than the control group (32.79%, 18.03%, and 8.20%), with statistically significant differences (all P < 0.05).

Conclusion

Microwave ablation in combination with an anti-PD-1 monoclonal antibody could effectively improve the level of T cell subsets and serum tumor markers in NSCLC patients, resulting in a long-term prognosis of patients with good therapeutic effect and safety.

An Analysis of Microwave Ablation Parameters for Treatment of Liver Tumors from the 3D-IRCADb-01 Database

Simulation techniques are powerful tools for determining the optimal conditions necessary for microwave ablation to be efficient and safe for treating liver tumors. Owing to the complexity and computational resource consumption, most of the existing numerical models are two-dimensional axisymmetric models that emulate actual three-dimensional cancers and the surrounding tissue, which is often far from reality. Different tumor shapes and sizes require different input powers and ablation times to ensure the preservation of healthy tissues that can be determined only by the full three-dimensional simulations. This study aimed to tailor microwave ablation therapeutic conditions for complete tumor ablation with an adequate safety margin, while avoiding injury to the surrounding healthy tissue. Three-dimensional simulations were performed for a multi-slot microwave antenna immersed in two tumors obtained from the 3D-IRCADb-01 liver tumors database. The temperature dependence of the dielectric and thermal properties of healthy and tumoral liver tissues, blood perfusion, and water content are crucial for calculating the correct ablation time and, thereby, the correct ablation process. The developed three-dimensional simulation model may help practitioners in planning patient-individual procedures by determining the optimal input power and duration of the ablation process for the actual shape of the tumor. With proper input power, necrotic tissue is placed mainly in the tumor, and only a small amount of surrounding tissue is damaged.

Study on the Microwave Ablation Effect of Inflated Porcine Lung

(1) Background: Microwave ablation (MWA) has an efficient killing effect on primary and metastatic lung cancer. However, the treatment effect will be affected by the air in the lung, which makes it very difficult to accurately predict and control the ablation area; (2) Methods: In this paper, in vitro experiments combined with simulations are used to study the microwave ablation area of inflated porcine lung. The in vitro experiment is divided into inflated group and deflated group, combined with different ablation power (40 W, 50 W, 60 W) and ablation time (100 s, 200 s, 300 s) for experiment, each power and time combination are repeated five times. A total of 90 ablation experiments were performed. The simulation experiment uses COMSOL Multiphysics software to simulate the microwave ablation area of the inflated lung; (3) Results and Conclusions: When the ablation power is 40 W, 50 W, and 60 W, the average long diameter of the deflated group are 20.8–30.9%, 7.6–22.6%, 10.4–19.8% larger than those of the inflated group, respectively; the average short diameter of the deflated group is 24.5–41.4%, 31.6–45.7%, 27.3–42.9% larger than that of the inflated group. The results show that the ablation area of inflated lung is smaller than deflated lung, which is mainly due to the smaller ablation short diameter.

Impact of Residential Concentration of PM2.5 Analyzed as Time-Varying Covariate on the Survival Rate of Lung Cancer Patients: A 15-Year Hospital-Based Study in Upper Northern Thailand

Air pollutants, especially particulate matter (PM) ≤ 2.5 µm (PM2.5) and PM ≤ 10 µm (PM10), are a major concern in upper northern Thailand. Data from a retrospective cohort comprising 9820 lung cancer patients diagnosed from 2003 to 2018 were obtained from the Chiang Mai Cancer Registry, and used to evaluate mortality and survival rates. Cox proportional hazard models were used to identify the association between the risk of death and risk factors including gender, age, cancer stage, smoking history, alcohol-use history, calendar year of enrollment, and time-updated PM2.5, PM10, NO₂ and O₃ concentrations. The mortality rate was 68.2 per 100 persons per year of follow-up. In a multivariate analysis, gender, age, cancer stage, calendar year of enrollment, and time-varying residential concentration of PM2.5 were independently associated with the risk of death. The lower the annually averaged PM2.5 and PM10 concentrations, the higher the survival probability of the patient. As PM2.5 and PM10 were factors associated with a higher risk of death, lung cancer patients who are inhabitant in the area should reduce their exposure to high concentrations of PM2.5 and PM10 to increase survival rates.

On Efficacy of Microwave Ablation in the Thermal Treatment of an Early-Stage Hepatocellular Carcinoma

Microwave ablation at 2.45 GHz is gaining popularity as an alternative therapy to hepatic resection with a higher overall survival rate than external beam radiation therapy and proton beam therapy. It also offers better long-term recurrence-free overall survival when compared with radiofrequency ablation. To improve the design and optimization of microwave ablation procedures, numerical models can provide crucial information. A three-dimensional model of the antenna and targeted tissue without homogeneity assumptions are the most realistic representation of the physical problem. Due to complexity and computational resources consumption, most of the existing numerical studies are based on using two-dimensional axisymmetric models to emulate actual three-dimensional cancers and surrounding tissue, which is often far from reality. The main goal of this study is to develop a fully three-dimensional model of a multislot microwave antenna immersed into liver tissue affected by early-stage hepatocellular carcinoma. The geometry of the tumor is taken from the 3D-IRCADb-01 liver tumors database. Simulations were performed involving the temperature dependence of the blood perfusion, dielectric and thermal properties of both healthy and tumoral liver tissues. The water content changes during the ablation process are also included. The optimal values of the input power and the ablation time are determined to ensure complete treatment of the tumor with minimal damage to the healthy tissue. It was found that a multislot antenna is designed to create predictable, large, spherical zones of the ablation that are not influenced by varying tissue environments. The obtained results may be useful for determining optimal conditions necessary for microwave ablation to be as effective as possible for treating early-stage hepatocellular carcinoma, with minimized invasiveness and collateral damages.

A Computational Study on Magnetic Nanoparticles Hyperthermia of Ellipsoidal Tumors

The modelling of magnetic hyperthermia using nanoparticles of ellipsoid tumor shapes has not been studied adequately. To fill this gap, a computational study has been carried out to determine two key treatment parameters: the therapeutic temperature distribution and the extent of thermal damage. Prolate and oblate spheroidal tumors, of various aspect ratios, surrounded by a large healthy tissue region are assumed. Tissue temperatures are determined from the solution of Pennes’ bio-heat transfer equation. The mortality of the tissues is determined by the Arrhenius kinetic model. The computational model is successfully verified against a closed-form solution for a perfectly spherical tumor. The therapeutic temperature and the thermal damage in the tumor center decrease as the aspect ratio increases and it is insensitive to whether tumors of the same aspect ratio are oblate or prolate spheroids. The necrotic tumor area is affected by the tumor prolateness and oblateness. Good comparison is obtained of the present model with three sets of experimental measurements taken from the literature, for animal tumors exhibiting ellipsoid-like geometry. The computational model enables the determination of the therapeutic temperature and tissue thermal damage for magnetic hyperthermia of ellipsoidal tumors. It can be easily reproduced for various treatment scenarios and may be useful for an effective treatment planning of ellipsoidal tumor geometries.