Liver Cancer: Increased Microwave Delivery to Ablation Zone with Cooled-Shaft Antenna—Experimental and Clinical Studies

Kuang, Ming; Lu, Min‐Shan; Xie, Xiaowen; Xu, Hui; Mo, Li Q; Liu, Guang J; Xu, Zuo Feng; Zheng, Yan L; Liang, Jin

doi:10.1148/radiol.2423052028

Cited by 161 publications

(115 citation statements)

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“…In vivo blood flow or an effective cooling system along the antenna shaft would likely reduce or eliminate this tail completely. 33 In conclusion, parametric analysis of a dual-slot antenna revealed that both the antenna reflection coefficient and spatial heating profile are highly sensitive to antenna geometry. A two-term sigmoidal cost function including both reflection coefficient and heating aspect ratio identified the most optimal design.…”

Section: Discussionmentioning

confidence: 92%

Dual‐slot antennas for microwave tissue heating: Parametric design analysis and experimental validation

Brace

2011

Medical Physics

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Purpose: Design and validate an efficient dual-slot coaxial microwave ablation antenna that produces an approximately spherical heating pattern to match the shape of most abdominal and pulmonary tumor targets. Methods: A dual-slot antenna geometry was utilized for this study. Permutations of the antenna geometry using proximal and distal slot widths from 1 to 10 mm separated by 1-20 mm were analyzed using finite-element electromagnetic simulations. From this series, the most optimal antenna geometry was selected using a two-term sigmoidal objective function to minimize antenna reflection coefficient and maximize the diameter-to-length aspect ratio of heat generation. Sensitivities to variations in tissue properties and insertion depth were also evaluated in numerical models. The most optimal dual-slot geometry of the parametric analysis was then fabricated from semirigid coaxial cable. Antenna reflection coefficients at various insertion depths were recorded in ex vivo bovine livers and compared to numerical results. Ablation zones were then created by applying 50 W for 2-10 min in simulations and ex vivo livers. Mean zone diameter, length, aspect ratio, and reflection coefficients before and after heating were then compared to a conventional monopole antenna using ANOVA with post-hoc t-tests. Statistical significance was indicated for P < 0.05. Results: Antenna performance was highly sensitive to dual-slot geometry. The best-performing designs utilized a proximal slot width of 1 mm, distal slot width of 4 mm 6 1 mm and separation of 8 mm 6 1 mm. These designs were characterized by an active choking mechanism that focused heating to the distal tip of the antenna. A dual-band resonance was observed in the most optimal design, with a minimum reflection coefficient of À20.9 dB at 2.45 and 1.25 GHz. Total operating bandwidth was greater than 1 GHz, but the desired heating pattern was achieved only near 2.45 GHz. As a result, antenna performance was robust to changes in insertion depth and variations in relative permittivity of the surrounding tissue medium. In both simulations and ex vivo liver, the dual-slot antenna created ablations greater in diameter than a coaxial monopole (35 mm 6 2 mm versus 31 mm 6 2 mm; P < 0.05), while also shorter in length (49 mm 6 2 mm versus 60 mm 6 6 mm; P < 0.001) after 10 min. Similar results were obtained after 2 and 5 min as well. Conclusions: Dual-slot antennas can produce more spherical ablation zones while retaining low reflection coefficients. These benefits are obtained without adding to the antenna diameter. Further evaluation for clinical microwave ablation appears warranted.

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Section: Discussionmentioning

confidence: 92%

Dual‐slot antennas for microwave tissue heating: Parametric design analysis and experimental validation

Brace

2011

Medical Physics

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“…12 Moreover, because of the self-heating of the applicator by the excessive microwave power, additional means for cooling the applicator are required to avoid the damage of healthy tissues near the passage of the applicator. 13 Besides, the conventional low-frequency spectrum ablation has poor material selectivity when compared to the alternative high-frequency spectrum proposed in our work.To overcome the limitations of the existing microwave ablation methods, we have investigated the properties of microwaves up to 30 GHz with emphasis on the ablation efficiency and material selectivity between normal and cancerous tissues. On the basis of our study, we propose a safe, efficient, low-powered (1-3 W), minimally invasive and cancer-specific microwave ablation system by identifying alternative microwave frequency spectrum optimized for material selectivity and heating efficiency.…”

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confidence: 76%

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confidence: 76%

High‐frequency microwave ablation method for enhanced cancer treatment with minimized collateral damage

Yoon

Cho

Kim

et al. 2011

Intl Journal of Cancer

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To overcome the limits of conventional microwave ablation, a new frequency spectrum above 6 GHz has been explored for low-power and low collateral damage ablation procedure. A planar coaxial probe-based applicator, suitable for easy insertion into the human body, was developed for our study to cover a wideband frequency up to 30 GHz. Thermal ablations with small input power (1-3 W) at various microwave frequencies were performed on nude mice xenografted with human breast cancer. Comparative study of ablation efficiencies revealed that 18-GHz microwave results in the largest difference in the temperature rise between cancer and normal tissues as well as the highest ablation efficiency, reaching 20 times that of 2 GHz. Thermal profile study on the composite region of cancer and fat also showed significantly reduced collateral damage using 18 GHz. Application of low-power (1 W) 18-GHz microwave on the nude mice xenografted with human breast cancer cells resulted in recurrence-free treatment. The proposed microwave ablation method can be a very effective process to treat small-sized tumor with minimized invasiveness and collateral damages.Breast cancer is a major threat to women's health psychologically as well as physically. 1 Despite the high potential of fatality, most women show reluctance for large-scale breast removal due to cosmetic concerns, which brings about the need for local surgical control. For this reason, minimally invasive techniques to achieve better local surgical control have collected extensive attention as a possible first-line treatment in lieu of conservative breast surgery procedures such as lumpectomy. 2,3 Among several alternative methods, microwave ablation entails many benefits in comparison with the others such as laser ablation, cryoablation and ethanol ablation. [4][5][6][7][8] Microwave ablation method is much safer and easily manageable 9 and can, in principle, offer material-specific responsiveness, where tissues with high water content such as cancer are preferentially heated and damaged. 10,11 This characteristic of microwaves makes microwave ablation well suited for local treatment of early stage of breast cancer. So far, the frequencies used in the existing microwave ablation systems have been limited to the low-frequency spectrum such as 915 MHz or 2.4 GHz. Because of the inherent low radiation efficiency, very high microwave input power of several tens of Watts is required at these frequencies, thus greatly increasing the cost and size of the equipment. 12 Moreover, because of the self-heating of the applicator by the excessive microwave power, additional means for cooling the applicator are required to avoid the damage of healthy tissues near the passage of the applicator. 13 Besides, the conventional low-frequency spectrum ablation has poor material selectivity when compared to the alternative high-frequency spectrum proposed in our work.To overcome the limitations of the existing microwave ablation methods, we have investigated the properties of microwaves up to 30 GHz wit...

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“…[10][11][12][13][14][15][16] Microwave ablation has been developed in the current decade as a new tumor ablation technique and is widely used to treat many types of malignant carcinomas including liver cancer, lung cancer, metastatic bone tumors, and renal tumors. [16][17][18][19][20] Microwave ablation of the adrenal gland is a promising technique for percutaneous treatment of adrenal malignant tumors, although there is limited experience reported in the literature. 16,21,22 We retrospectively analyzed patients with adrenal carcinomas who underwent microwave ablation in our department with the goal to evaluate the safety, practicality, and efficacy of CT-guided microwave ablation of adrenal carcinomas.…”

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confidence: 99%

CT‐guided percutaneous microwave ablation of adrenal malignant carcinoma

Fan

Zhang

et al. 2011

Cancer

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BACKGROUND:Microwave ablation has recently been developed as a safe and effective treatment for a variety of tumors. The authors evaluated the safety and efficacy of computed tomography (CT)‐guided percutaneous microwave ablation of adrenal malignant tumors.METHODS:Nine patients between 41 and 83 years of age (average age, 54 years) with adrenal carcinoma (a total of 10 lesions) received CT‐guided percutaneous water‐cooled microwave ablation. The 9 cases included 1 primary adrenocortical carcinoma and 8 metastatic carcinomas (4 from lung cancer, 2 from hepatocellular carcinoma, 1 from intrahepatic cholangiocarcinoma, and 1 from left tibial osteosarcoma). Of the 8 metastatic cases, 7 were unilateral, and 1 was bilateral. All cases were pathologically confirmed by aspiration biopsy or postsurgical biopsy. The tumor diameters ranged from 2.1 cm to 6.1 cm (average, 3.8 cm). The average number of ablation sites was 1.5 sites (1‐3 sites), and the average accumulated ablation time was 7.7 minutes (4‐15 minutes). The procedures were performed using a cooled‐shaft antenna.RESULTS:The patients were followed for 3‐37 months, with an average of 11.3 months. Nine of 10 lesions were completely necrotized after first treatment. The other lesion was completely necrotized after 2 treatments. One of the patients experienced hypertensive crisis during treatment. No patient experienced recurrent tumor at the treated site, and this lack of recurrence indicated effective local control. All patients had progression of metastatic disease at extra‐adrenal sites.CONCLUSIONS:CT‐guided percutaneous water‐cooled microwave ablation is a minimally invasive and effective method for the treatment of adrenal carcinoma. Cancer 2011;. © 2011 American Cancer Society.

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Liver Cancer: Increased Microwave Delivery to Ablation Zone with Cooled-Shaft Antenna—Experimental and Clinical Studies

Abstract: Delivery of greater microwave energy with cooled-shaft antennas yielded large ablation zones in ex vivo and in vivo livers and in liver cancers. Effective local tumor control was achieved during one microwave ablation session.

Cited by 161 publications

References 29 publications

Dual‐slot antennas for microwave tissue heating: Parametric design analysis and experimental validation

Dual‐slot antennas for microwave tissue heating: Parametric design analysis and experimental validation

High‐frequency microwave ablation method for enhanced cancer treatment with minimized collateral damage

CT‐guided percutaneous microwave ablation of adrenal malignant carcinoma

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