Feasibility Assessment of Microwave Ablation for Treating Esophageal Varices

Esophageal varices are a significant complication of portal hypertension. Endoscopic variceal ligation (EVL) is one of the clinical standards for treating these varices and preventing their hemorrhage. Limitations of EVL include the risk of stricture formation and postband ulcer bleeding due to the damage caused to the esophageal mucosa, as well as the need for multiple endoscopic treatment sessions to eradicate the varices. The goal of this study is to develop a device and evaluate the technical feasibility of microwave ablation to seal esophageal varices, while preventing thermal damage to the surface mucosal tissue. A microwave applicator with a directional radiation pattern was developed for endoscopic ablation of esophageal varices. Electromagnetic and bioheat transfer computational models were employed to optimize the design of the microwave applicator and evaluate energy delivery strategies for this application. Experiments in ex vivo and in vivo tissue were employed to verify simulation results. Simulations predicted enhanced heating performance of the antenna using an angled monopole radiating element. Further, simulations indicate that while the endoscopic cap attenuated electric fields in tissue, it also enhanced surface cooling of tissue, increasing the likelihood of preserving mucosal tissue. Experiments in ex vivo tissue indicated the feasibility of sealing veins with 77 W microwave power delivered for 30 s. In vivo experiments demonstrated the ability to seal veins, while preserving surface tissue. This study demonstrated the technical feasibility of microwave thermal ablation for treating esophageal varices using a 2.45 GHz water-cooled directional microwave applicator.

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A comparison of microwave ablation and bipolar radiofrequency ablation both with an internally cooled probe: Results in ex vivo and in vivo porcine livers

European Journal of Radiology ◽

10.1016/j.ejrad.2009.12.009 ◽

2011 ◽

Vol 79 (1) ◽

pp. 124-130 ◽

Cited By ~ 88

Author(s):

Jie Yu ◽

Ping Liang ◽

Xiaoling Yu ◽

Fangyi Liu ◽

Lei Chen ◽

...

Keyword(s):

Radiofrequency Ablation ◽

Microwave Ablation ◽

Ex Vivo ◽

Bipolar Radiofrequency ◽

Internally Cooled

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A feasibility study of photoacoustic imaging of ex vivo endoscopic mucosal resection tissues from Barrett’s esophagus patients

Endoscopy International Open ◽

10.1055/s-0043-111790 ◽

2017 ◽

Vol 05 (08) ◽

pp. E775-E783 ◽

Cited By ~ 3

Author(s):

Liang Lim ◽

Catherine Streutker ◽

Norman Marcon ◽

Maria Cirocco ◽

Alexandra Lao ◽

...

Keyword(s):

Barrett’S Esophagus ◽

Endoscopic Mucosal Resection ◽

Feasibility Study ◽

Barrett's Esophagus ◽

Ex Vivo ◽

Photoacoustic Imaging ◽

Esophageal Mucosa ◽

Mucosal Resection ◽

Total Hemoglobin

Abstract Background and study aims Accurate endoscopic detection of dysplasia in patients with Barrett’s esophagus (BE) remains a major clinical challenge. The current standard is to take multiple biopsies under endoscopic image guidance, but this leaves the majority of the tissue unsampled, leading to significant risk of missing dysplasia. Furthermore, determining whether there is submucosal invasion is essential for proper staging. Hence, there is a clinical need for a rapid in vivo wide-field imaging method to identify dysplasia in BE, with the capability of imaging beyond the mucosal layer. We conducted an ex vivo feasibility study using photoacoustic imaging (PAI) in patients undergoing endoscopic mucosal resection (EMR) for known dysplasia. The objective was to characterize the esophageal microvascular pattern, with the long-term goal of performing in vivo endoscopic PAI for dysplasia detection and therapeutic guidance. Materials and methods EMR tissues were mounted luminal side up. The tissues were scanned over a field of view of 14 mm (width) by 15 mm (depth) at 680, 750, and 850 nm (40 MHz acoustic central frequency). Ultrasound and photoacoustic images were simultaneously acquired. Tissues were then sliced and fixed in formalin for histopathology with hematoxylin and eosin staining. A total of 13 EMR specimens from eight patients were included in the analysis, which consisted of co-registration of the photoacoustic images with corresponding pathologist-classified histological images. We conducted mean difference test of the total hemoglobin distribution between tissue classes. Results Dysplastic and nondysplastic BE can be distinguished from squamous tissue in 84 % of region-of-interest comparisons (42/50). However, the ability of intrinsic PAI to distinguish dysplasia from NDBE, which is the clinically important challenge, was only about 33 % (10/30). Conclusion We demonstrated the technical feasibility of this approach. Based on our ex vivo data, changes in total hemoglobin content from intrinsic PAI (i. e. without exogenous contrast) can differentiate BE from squamous esophageal mucosa. However, most likely intrinsic PAI is unable to differentiate dysplastic from nondysplastic BE with adequate sensitivity for clinical translation.

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Bronchoscopically delivered microwave ablation in an in vivo porcine lung model

ERJ Open Research ◽

10.1183/23120541.00146-2020 ◽

2020 ◽

Vol 6 (4) ◽

pp. 00146-2020

Author(s):

Jan Sebek ◽

Steve Kramer ◽

Rob Rocha ◽

Kun-Chang Yu ◽

Radoslav Bortel ◽

...

Keyword(s):

Microwave Ablation ◽

Early Stage ◽

Lung Parenchyma ◽

Lung Model ◽

Guidance System ◽

Lung Tumour ◽

Virtual Bronchoscopy ◽

Invasive Treatment ◽

Technical Feasibility

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.

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