Application Of Microwave Ablation Research Articles

Clinical Application of Microwave Ablation in Potentially Resectable Colorectal Cancer With Simultaneously Multiple Liver Metastases

Objective To analyze the clinical efficacy of microwave ablation in the colorectal cancer with simultaneously multiple liver metastases that was initially evaluated as potentially resectable. Methods The patients with potentially resectable colorectal cancer with simultaneous multiple liver metastases treated in the Department of General Surgery of the First Affiliated Hospital of Hebei North University,the Center of Minimally Invasive Therapy in Oncology of Traditional Chinese and Western Medicine in Dongzhimen Hospital of Beijing University of Chinese Medicine,and the Second Department of General Surgery in the Fourth Hospital of Hebei Medical University from October 1,2018 to October 1,2020 were selected in this study.The general data,pathological features,treatment methods,and clinical efficacy of the patients were collected.According to the treatment methods,the patients were assigned into a surgical resection group(conversion therapy+laparoscopic primary resection+hepatectomy)and a microwave ablation group(conversion therapy+laparoscopic primary resection+microwave ablation).The surgical indicators(operation duration,time to first postoperative anal exhaust,hospital stay,etc.)and postoperative complications(anastomotic stenosis,anastomotic hemorrhage,incision infection,etc.)were compared between the two groups.The survival period was followed up,including the overall survival period and disease-free survival period,and the survival curves were drawn to analyze the clinical efficacy of the two treatment regimens. Results A total of 198 patients with potentially resectable colorectal cancer with simultaneous multiple liver metastases were included in this study.Sixty-six patients were cured by neoadjuvant chemotherapy(FOLFOX or FOLFIRI),including 30 patients in the surgical resection group and 36 patients in the microwave ablation group(with 57 tumors ablated).After the first ablation,54(94.74%)tumors achieved complete ablation,and all of them reached no evidence of disease status after re-ablation.The microwave ablation group had shorter operation duration,less intraoperative blood loss,shorter time to first postoperative anal exhaust,shorter time of taking a liquid diet,shorter hospital stay,and lower hospitalization cost than the surgical resection group(all P<0.001).In addition,the microwave ablation group had lower visual analogue scale score(P<0.001)than the surgical resection group.The incidences of complications such as incision infection(P=0.740),anastomotic fistula(P=1.000),and anastomotic stenosis(P=1.000),the overall survival period(P=0.191),and the disease-free survival period(P=0.934)showed no significant differences between the two groups. Conclusions For patients with colorectal cancer with simultaneous multiple liver metastases initially assessed as potentially resectable,laparoscopic primary resection+surgical resection/microwave ablation after conversion therapy was safe,effective,and had similar survival outcomes.Microwave ablation outperformed surgical resection in postoperative recovery,economy,and tolerability,being worthy of clinical promotion.

Image-based computer modeling assessment of microwave ablation for treatment of adrenal tumors

Purpose To assess the feasibility of delivering microwave ablation for targeted treatment of aldosterone producing adenomas using image-based computational models. Methods We curated an anonymized dataset of diagnostic 11C-metomidate PET/CT images of 14 patients with aldosterone producing adenomas (APA). A semi-automated approach was developed to segment the APA, adrenal gland, and adjacent organs within 2 cm of the APA boundary. The segmented volumes were used to implement patient-specific 3D electromagnetic-bioheat transfer models of microwave ablation with a 2.45 GHz directional microwave ablation applicator. Ablation profiles were quantitatively assessed based on the extent of the APA target encompassed by an ablative thermal dose, while limiting thermal damage to the adjacent normal adrenal tissue and sensitive critical structures. Results Across the 14 patients, adrenal tumor volumes ranged between 393 mm3 and 2,395 mm3. On average, 70% of the adrenal tumor volumes received an ablative thermal dose of 240CEM43, while limiting thermal damage to non-target structures, and thermally sparing 83.5–96.4% of normal adrenal gland. Average ablation duration was 293 s (range: 60–600 s). Simulations indicated coverage of the APA with an ablative dose was limited when the axis of the ablation applicator was not well aligned with the major axis of the targeted APA. Conclusions Image-based computational models demonstrate the potential for delivering microwave ablation to APA targets within the adrenal gland, while limiting thermal damage to surrounding non-target structures.

Numerical Optimization of an Open-Ended Coaxial Slot Applicator for the Detection and Microwave Ablation of Tumors.

Simple SummaryIn this work, a parametric analysis of a dual-mode applicator for microwave ablation treatments is proposed to optimize the geometric parameters of the structure. The dual-mode concept means that the applicator comprises an additional sensing mode to determine the dielectric properties of the surrounding tissue before and during the ablation procedure. Based on numerical electromagnetic-thermal coupled simulations the most optimal design in terms of applicator efficiency as well as ablation zone volume and shape is determined that further fulfills the sensitivity requirements of the sensing mode. The multiobjective optimization problem is solved graphically with the so-called Pareto-optimization method. The resulting Pareto-optimal dual-mode applicator designs are characterized by electromagnetic and thermal simulations and discussed.A multiobjective optimization method for a dual-mode microwave applicator is proposed. Dual-modality means that microwaves are used apart from the treatment, and also for the monitoring of the microwave ablation intervention. (1) The use of computational models to develop and improve microwave ablation applicator geometries is essential for further advances in this field. (2) Numerical electromagnetic–thermal coupled simulation models are used to analyze the performance of the dual-mode applicator in liver tissue; the sensitivity evaluation of the dual-mode applicator’s sensing mode constrains the set of optimal solutions. (3) Three Pareto-optimal design parameter sets are derived that are optimal in terms of applicator efficiency as well as volume and sphericity of the ablation zone. The resulting designs of the dual-mode applicator provide a suitable sensitivity to distinguish between healthy and tumorous liver tissue. (4) The optimized designs are presented and numerically characterized. An improvement on the performance of previously proposed dual-mode applicator designs is achieved. The multiphysical simulation model of electromagnetic and thermal properties of the applicator is applicable for future comprehensive design procedures.

A novel ISM band reflector type applicator design for microwave ablation systems

ABSTRACT In this paper, a radiation performance improved novel applicator is proposed which is called as reflector type microwave applicator as a part of microwave ablation (MWA) system operating at 2.45 GHz with experimentally measured bandwidth of 300 MHz in Industrial Scientific Medical (ISM) band for the local extermination of tumor with highly localized microwave power. The design principle of MW applicator is based on the structural formation of coaxial transmission line fed dielectric loaded with the metallic circular reflector for the near field energy concentration inside the tumorous tissue. To generate localized electromagnetic waves, a novel reflector type microwave applicator is designed by placing an aluminum disk near the 10 mm dielectric radiator section. The proposed applicator design has been numerically studied with finite integration technique (FIT) in CST Microwave Studio to develop the near field radiation pattern affecting the ablation level of tumorous tissue. In the light of performed numerical calculations, maximum SAR (Specific Absorption Rate) value on 1.76 g tumorous sample can be achieved to 208 W/kg under 15 W microwave power accepted by proposed probe. The experimental results confirm that proposed applicator can be utilized highly localized MWA applicator for cancer treatment hence the surface temperature of cylindrical shaped tumor sample which has the dimensions of 14.4 mm diameter and 8 mm height reaches from 25 to 68.3°C in 10 min.

Bronchoscopically delivered microwave ablation in an in vivo porcine lung model.

BackgroundPercutaneous microwave ablation is clinically used for inoperable lung tumour treatment. Delivery of microwave ablation applicators to tumour sites within lung parenchyma under virtual bronchoscopy guidance may enable ablation with reduced risk of pneumothorax, providing a minimally invasive treatment of early-stage tumours, which are increasingly detected with computed tomography (CT) screening. The objective of this study was to integrate a custom microwave ablation platform, incorporating a flexible applicator, with a clinically established virtual bronchoscopy guidance system, and to assess technical feasibility for safely creating localised thermal ablations in porcine lungs in vivo.MethodsPre-ablation CTs of normal pigs were acquired to create a virtual model of the lungs, including airways and significant blood vessels. Virtual bronchoscopy-guided microwave ablation procedures were performed with 24–32 W power (at the applicator distal tip) delivered for 5–10 mins. A total of eight ablations were performed in three pigs. Post-treatment CT images were acquired to assess the extent of damage and ablation zones were further evaluated with viability stains and histopathologic analysis.ResultsThe flexible microwave applicators were delivered to ablation sites within lung parenchyma 5–24 mm from the airway wall via a tunnel created under virtual bronchoscopy guidance. No pneumothorax or significant airway bleeding was observed. The ablation short axis observed on gross pathology ranged 16.5–23.5 mm and 14–26 mm on CT imaging.ConclusionWe have demonstrated the technical feasibility for safely delivering microwave ablation in the lung parenchyma under virtual bronchoscopic guidance in an in vivo porcine lung model.

Clinical Guideline for Microwave Ablation of Bone Tumors in Extremities.

Microwave ablation has been used to treat bone tumors in extremities for more than 30 years. With improved recognition, updated microwave equipment, and expanded clinical application, microwave ablation has recently been widely used to treat bone tumors. To standardize the application of microwave ablation in the clinical treatment of bone tumors in the limbs, research results and clinical experience involving the use of microwave ablation to treat bone tumors in the limbs have been summarized, and a clinical guideline has been designed. This guideline is aimed at providing a reliable clinical basis for indications, preoperative evaluation and decision‐making, perioperative treatment, complications, and other issues via evidence‐based medicine. Two aspects are considered—percutaneous microwave ablation and intraoperative microwave ablation of bone tumors in extremities. Ultimately, the guideline is intended to standardize treatment and improve the clinical efficacy of microwave ablation of bone tumors in extremities.

In-Silico study of microwave ablation applicators of different size for breast cancer treatment

Breast cancer is one of the most common types of cancer in females around the world, surgery is the preferred treatment for this disease in early stages, however there are some emergent treatment options with less clinical and cosmetically repercussions, being one of these the microwave ablation. Microwave ablation is a minimally invasive technique used to treat tumors in different organs of the human body, mainly in liver, lung and kidney. It consist on the destruction of the tumor by rising the temperature of the cells until necrosis is achieve. In breast tumors, this technique has been rarely used in human patients. Depending on the type of tissue, an applicator must be made to be coupled to ensure that energy used is not reflected, so the standing wave ratio is closest to 1. In order to determine an appropriate design for the applicators that could be used for the treatment of breast cancer, an in-silico study of microwave ablation of breast cancer was made to show the difference between micro-coaxial applicators constructed with two different types of coaxial cable (UT-47 and UT-85) utilizing the same design in three possible scenarios breast tissue, tumor tissue and tumor surrounded by breast tissue. The simulation was realized using COMSOL Multiphysics commercial software, due to its capabilities to simulate the electromagnetics and thermals effects. A slot type applicator was selected because of its ease of manufacture and the available literature on it. The results shows a better coupling for the applicator constructed with the UT-47 cable, especially in the tumor phantom surrounded by breast phantom test.

The application of magnetic resonance imaging-guided microwave ablation for lung cancer.

It is necessary to explore a minimally invasive, effective, and efficient treatment for those lung cancer patients who are poor candidates for surgery. This study aimed to investigate the application of microwave ablation (MWA) in the treatment of lung cancer. A total of 43 patients with 44 pulmonary lesions were examined following identical procedures before being randomly divided into two groups. The experimental group consists of 17 patients with a total of 18 pulmonary lesions, while the control group consists of 26 patients with a total of 26 pulmonary lesions. The experimental group was treated using magnetic resonance imaging (MRI)-guided MWA while the control group was treated using computer tomography (CT)-guided MWA. A transverse relaxation time-turbo spin echo (T2-TSE) sequence was used for signal collection in the experimental group to determine puncture location and microwave needle position while T2-TSE, T1-turbo field echo, and diffusion-weighted MRI (DWI) sequences were used for timely efficacy evaluation. Whereas in the control group, CT axial scanning was performed to serve similar purposes. A nonparametric Wilcoxon test, median (M [25%, 75%]). All of the 44 lesions were successfully located on the first attempt. The mean time for scanning and locating lung lesions under MRI and CT guidance were 64.53 and 42.96 min, the mean times of positioning were 12 and 18 min, and the mean durations of MWA were 12.48 and 15.06 min, respectively. As a minimally invasive method for treating lung tumors, MRI-guided MWA requires fewer localization scans, a shorter MWA duration, no radiation, real-time observation of the curative effect, and it prevents overtreatment.

Evaluation of tissue deformation during radiofrequency and microwave ablation procedures: Influence of output energy delivery.

The purpose of this study was to quantitatively analyze tissue deformation during radiofrequency (RF) and microwave ablation for varying output energy levels. A total of 46 fiducial markers which were classified into outer, middle, and inner lines were positioned into a single plane around an RF or microwave ablation applicator in each ex vivo bovine liver sample (8cm×6cm×4cm, n=18). Radiofrequency (500kHz; ~35W average) or microwave (2.4GHz; 50-100W output, ~35-70W delivered) ablation was performed for 10min (n=4-6 each setting). CT images were acquired over the entire liver volume every 15s. Principle strain magnitude and direction were determined from fiducial marker displacement. Normal and shear strain were then calculated such that negative strain denoted contraction and positive strain denoted expansion. Temporal variations, the final magnitudes, and angles of the strain were compared across energy delivery settings, using one-way ANOVA with post hoc Tukey's tests. On average, tissue strain rates peak at around 1min and decayed exponentially over time. No evidence of tissue expansion was observed. The tissue strains from RF and 50W, 75W, and 100W microwave ablation at 10min were -8.5%, -38.9%, -54.4%, and -65.7%, respectively, from the inner region and -3.6%, -23.7%, -41.8%, and -44.3%, respectively, from the outer region. Negative strain magnitude was positively correlated to energy delivery in the inner region (Spearman's =-0.99). Microwaves at higher powers (75-100W) induced significantly more strain than at lower power (50W) or after RF ablation (P<0.01). Principal strain angles ranged from 0.8° to -8.1°, indicating that tissue deformed more in the direction transverse to the applicator than along the direction of the applicator. The influence of output energy on tissue deformation during RF and microwave ablation was analyzed. Microwave ablation created significantly greater contraction than RF ablation with similar energy delivery. During microwave ablation, more contraction was noted at higher power levels and in proximity to the antenna. Contraction primarily transverse to the antenna produces ablation zones that are more elongated than the original tissue volume.

Forty-five consecutive cases of complicated monochorionic multiple pregnancy treated with microwave ablation: A single-center experience.

To describe our preliminary experience in the application of microwave ablation for selective fetal reduction in complicated monochorionic multiple pregnancies. In this prospective study, 45 consecutive complicated monochorionic multiple pregnancies that underwent microwave ablation for selective fetal reduction from July 2015 to February 2017 were analyzed from the first case onward. All patients were managed at the Peking University Third Hospital in Beijing, China. There were 45 cases (twins in 40 and triplets in five) treated by microwave ablation. The median gestational age at surgery was 21.3weeks (range, 15.9-25.7wk), with a mean total ablation time of 8.5±4.2(7.2-9.7)minutes. There were 12 (26.7%) cases of postprocedural fetal loss. Thirty-three women delivered alive at a median gestational age of 37.6weeks (range, 28.6-40.4wk). There were no neonatal deaths in our cohort, and the overall survival rate was 73.3% (33/45). Preterm premature rupture of membranes occurred in 9 (20.0%) cases with a median of 7.0weeks (range, 0.9-16.3wk) after the surgery. None of the surviving cotwins had evidence of thermal injury or neurological abnormalities. Microwave ablation appears to be a safe and effective method for selective feticide in complicated monochorionic pregnancies.

Preliminary experience in the management of brain and skull-base tumors with microwave ablation; feasibility guided by ultrasound, report from 23 cases.

Background:In surgery involving brain tumors, the use of new tools or equipment that allows for better results and improvement in the quality of life of the patients is mandatory. Microwave ablation (MWA) is a technique that has been used effectively since 1994 in the management of different kinds of tumors. The authors present their surgical experience with 23 cases of brain and skull-base tumors using MWA technique.Methods:In all, 23 cases diagnosed with brain and skull-base tumors are described; all of these were treated with MWA as unique technique as a complement to conventional microsurgical tumor resection. In all cases, ultrasound imaging guidance was used. A thin antenna (caliber 14.5; MedWaves) was positioned through ultrasound images to a central intratumoral area, and then energy was applied for 1–3 min until the temperature sensor in the proximal position of the antenna reached 80–100°C. Through transoperative Doppler ultrasound images and surgical microscopy, changes in the generated ablation were observed. The said ablation led to a decrease in intratumoral blood flow, and the adjacent vascular and cerebral structures were preserved.Results:The application of MWA during brain surgery was regarded as safe in all cases, as no permanent additional neurological deficit was detected. Intratumoral vascular flow was also reduced and tumor resection was facilitated. Likewise, a reduction in tumor volume was noted, and in others in whom the ablation was applied as a single therapy, a progressive destruction of the tumor was observed.Conclusion:MWA can be a useful tool as a single therapy or as a complement to conventional techniques for the surgical resection of brain and skull-base tumors. It was a safe method in all cases, producing a decrease in intratumoral blood flow, and this procedure facilitates the microsurgical resection of the lesion.

Feasibility of Using a Novel 2.45 GHz Double Short Distance Slot Coaxial Antenna for Minimally Invasive Cancer Breast Microwave Ablation Therapy: Computational Model, Phantom, and In Vivo Swine Experimentation.

Microwave ablation (MWA) by using coaxial antennas is a promising alternative for breast cancer treatment. A double short distance slot coaxial antenna as a newly optimized applicator for minimally invasive treatment of breast cancer is proposed. To validate and to analyze the feasibility of using this method in clinical treatment, a computational model, phantom, and breast swine in vivo experimentation were carried out, by using four microwave powers (50 W, 30 W, 20 W, and 10 W). The finite element method (FEM) was used to develop the computational model. Phantom experimentation was carried out in breast phantom. The in vivo experimentation was carried out in a 90 kg swine sow. Tissue damage was estimated by comparing control and treated micrographs of the porcine mammary gland samples. The coaxial slot antenna was inserted in swine breast glands by using image-guided ultrasound. In all cases, modeling, in vivo and phantom experimentation, and ablation temperatures (above 60°C) were reached. The in vivo experiments suggest that this new MWA applicator could be successfully used to eliminate precise and small areas of tissue (around 20–30 mm2). By modulating the power and time applied, it may be possible to increase/decrease the ablation area.

Application of microwave ablation in the emergent control of intraoperative life-threatening tumor hemorrhage during hepatic surgeries

Purpose: This study was designed to evaluate the efficacy and safety of microwave ablation (MWA) in the treatment of intraoperative life-threatening tumour haemorrhage during hepatic surgeries.Methods: Three cases of MWA application in the emergent control of life-threatening hepatic tumour haemorrhage were analysed and reported.Results: Satisfactory hemostasis for hepatic tumour rupture was achieved by MWA in all three cases. No major complications, such as post-operative haemorrhage, bile duct injury, liver abscess, colon perforation, skin burns, tumour seeding or renal dysfunction, were identified.Conclusions: MWA may be a feasible, effective and simple strategy for the emergent control of intraoperative hepatic tumour bleeding. To the best of our knowledge, this study represents the first reported cases of this novel application of MWA.

Application of Microwave Ablation at a Frequency of 2.45 GHz to the Uterus: Present and Future

Application of Microwave Ablation at a Frequency of 2.45 GHz to the Uterus: Present and Future

Mikrowellenablation

The majority of patients with hepatic malignancies are not amenable to surgical resection. In some of these cases minimally invasive ablative therapies are a treatment option. Besides radiofrequency ablation, the most common ablative therapies are cryoablation, laser ablation and microwave ablation. The classic fields of application of microwave ablation are the treatment of malignancies of the liver, kidneys and lungs. Furthermore, cases of treatment of bone tumors and tumors of the adrenal gland have been reported as well as treatment of secondary hypersplenism. The manufacturers of microwave systems pursue different strategies to reach an optimal ablation zone, such as water or gas cooling of the antenna, the simultaneous use of different antennas or an automatic modulation of the microwave energy and frequency. In contrast to other tumor ablation methods microwave ablation causes a direct heating of a tissue volume, thus this method is less vulnerable to the cooling effect of vessels in the ablation zone. Moreover the electric conductivity of the treated tissue does not influence microwave radiation so that microwave ablation has advantages for the treatment of high-resistance organs, such as the lungs or bone. Some publications have shown that microwave ablation causes larger ablation zones in less time in comparison to radiofrequency ablation. Classic indications for microwave ablation are the treatment of malignancies of the liver, lungs and kidneys. Initial technical problems have been solved, so that an increasing significance of the microwave ablation among the ablative therapies is to be expected.

Pulmonary Thermal Ablation: Comparison of Radiofrequency and Microwave Devices by Using Gross Pathologic and CT Findings in a Swine Model

To compare the performance of equivalently sized radiofrequency and microwave ablation applicators in a normal porcine lung model. All experiments were approved by an institutional animal care and use committee. A total of 18 ablations were performed in vivo in normal porcine lungs. By using computed tomographic (CT) fluoroscopic guidance, a 17-gauge cooled triaxial microwave antenna (n = 9) and a 17-gauge cooled radiofrequency (RF) electrode (n = 9) were placed percutaneously. Ablations were performed for 10 minutes by using either 125 W of microwave power or 200 W of RF power delivered with an impedance-based pulsing algorithm. CT images were acquired every minute during ablation to monitor growth. Animals were sacrificed after the procedure. Ablation zones were then excised and sectioned transverse to the applicator in 5-mm increments. Minimum and maximum diameter, cross-sectional area, length, and circularity were measured from gross specimens and CT images. Comparisons of each measurement were performed by using a mixed-effects model; P < .05 was considered to indicate a significant difference. Mean diameter (3.32 cm +/- 0.19 [standard deviation] vs 2.70 cm +/- 0.23, P < .001) was 25% larger with microwave ablation and mean cross-sectional area (8.25 cm(2) +/- 0.92 vs 5.45 cm(2) +/- 1.14, P < .001) was 50% larger with microwave ablation, compared with RF ablation. With microwave ablation, the zones of ablation were also significantly more circular in cross section (mean circularity, 0.90 +/- 0.06 vs 0.82 +/- 0.09; P < .05). One small pneumothorax was noted during RF ablation but stabilized without intervention. Microwave ablation with a 17-gauge high-power triaxial antenna creates larger and more circular zones of ablation than does a similarly sized RF applicator in a preclinical animal model. Microwave ablation may be a more effective treatment of lung tumors.