Analysis and experimental validation of a triaxial antenna for microwave tumor ablation

Brace, Chris; Weide, Daniel W. van der; Lee, F.T.; Laeseke, Paul F.; Sampson, Lisa A.

doi:10.1109/mwsym.2004.1338842

Cited by 20 publications

(24 citation statements)

References 9 publications

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“…Usually, within 2 cm of the probe, vessels smaller than 1 mm in diameter are easily damaged and occluded (36,37); however, even vessels up to 7 mm in diameter have been coagulated (14). Such results are similar to those obtained by Mectalfe et al (38) for RF and electrolytic therapy in close proximity to hepatic veins.…”

Section: Clinical Studiessupporting

confidence: 73%

Hepatic microwave ablation: a review of the histological changes following thermal damage

Gravante

Ong

Metcalfe

et al. 2008

Liver International

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Microwave (MW) ablation therapy is a local treatment by which tumours are destroyed by coagulation from the passage of MWs into cells. The aim of this review is to examine histological results obtained from preclinical and clinical studies. A literature search was undertaken for all studies focusing on MW therapy and in which lesions were excised for a complete histopathological examination after treatment. Two main zones were described after ablative therapy (central and transitional Microwave (MW) coagulation therapy is a form of local ablation where tumours are destroyed by thermal coagulation that develops from the passage of MWs into cells and the production of frictional movement between molecules (1). Initially developed in the early 1980s to achieve haemostasis along the plane of transection during hepatic resections (2), MW coagulation of tissue surfaces proved slower than electrocautery units and produced deeper areas of tissue necrosis. These two characteristics, while making MW unsuitable for operative haemostasis, are potentially useful in the ablation of liver tumours. Like radiofrequency (RF) ablation and laser-induced interstitial thermotherapy, MW is very versatile and can be performed percutaneously using ultrasound or computed tomography (CT) guidance, or at laparoscopy or laparotomy with intra-operative ultrasound guidance.The formation of the thermal lesion during the ablation process is a complex combination of MW energy absorption, heating conduction and possible tissue water evaporation, condensation and movement. In 2002, Izzo (3) suggested that the production of very small zones of coagulative necrosis by the intratumoral MW-emitting needle electrodes would require frequent repositioning at 5-10 mm intervals to create multiple overlapping zones of coagulative necrosis. He also suggested that MW should not be performed near major bile ducts and blood vessels because of the description of vascular and biliary complications in these locations. However, since the appearance of that review, numerous technical advances have been introduced in MW engineering and subsequently evaluated histologically in a number of preclinical and clinical studies.The aim of this review is to examine those studies and determine the factors that influence the production of an area of ablation and the evidence for its use under different circumstances. Materials and methodsA literature search was undertaken for all studies focusing on MW ablative therapy where lesions were excised for a complete histopathological examination after the treatment.Articles were selected from the MEDLINE, EMBASE and Cochrane Library databases, using the key words microwave, ablation or ablative therapy, liver, hepatic, in vivo, ex vivo, clinical, experimental. Only articles published in the English literature were used. We

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Section: Clinical Studiessupporting

confidence: 73%

Hepatic microwave ablation: a review of the histological changes following thermal damage

Gravante

Ong

Metcalfe

et al. 2008

Liver International

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“…1) [19]. The active length of the antenna loaded in tissue (see Table I for material properties) is nominally , where is an integer.…”

Section: A Antenna Designmentioning

confidence: 99%

Microwave ablation with a triaxial antenna: results in ex vivo bovine liver

Brace

Laeseke

Weide

et al. 2005

IEEE Trans. Microwave Theory Techn.

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110

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Abstract-We apply a new triaxial antenna for microwave ablation procedures to an ex vivo bovine liver. The antenna consists of a coaxial monopole inserted through a biopsy needle positioned one quarter-wavelength from the antenna base. The insertion needle creates a triaxial structure, which enhances return loss more than 10 dB, maximizing energy transfer to the tissue while minimizing feed cable heating and invasiveness. Numerical electromagnetic and thermal simulations are used to optimize the antenna design and predict heating patterns. Numerical and ex vivo experimental results show that the lesion size depends strongly on ablation time and average input power, but not on peak power. Pulsing algorithms are also explored. We were able to measure a 3.8-cm lesion using 50 W for 7 min, which we believe to be the largest lesion reported thus far using a 17-gauge insertion needle.

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“…The microwave ablation system (Micrablate, Madison, Wis) used in this study has a 17-gauge tunable triaxial antenna specifically developed to minimize power reflection without adding to the diameter of the antenna (11,12). A biopsy insertion needle is used to introduce the antenna.…”

Section: Advances In Knowledgementioning

confidence: 99%

“…All microwave ablations in this study were performed by using a single 17-gauge triaxial antenna as previously designed and characterized in an ex vivo liver model (11,12). Microwave power originated from a commercially available 2.45-GHz magnetron generator (MG0300D; Cober-Muegge, Norwalk, Conn) capable of delivering up to 300 W of continuous-wave power.…”

Section: Microwave Ablationmentioning

confidence: 99%

Microwave Ablation with a Single Small-Gauge Triaxial Antenna: In Vivo Porcine Liver Model

Brace¹,

Laeseke²,

Sampson³

et al. 2007

Radiology

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Purpose-To evaluate the performance of a 17-gauge triaxial antenna at microwave ablation in an in vivo porcine liver model. Materials and Methods-This study was approved by the institutional animal care and use committee. Thirteen female domestic pigs (mean weight, 45 kg) were used. Ablations were performed with a prototype microwave ablation system and triaxial antenna by using a constant, continuous-wave power of 68 W for 2 (n = 6), 3 (n = 6), 4 (n = 6), 5 (n = 6), 6 (n = 6), 7 (n = 13), 10 (n = 7), and 12 (n = 8) minutes. Animals were euthanized after ablation, livers were removed, and ablation zones were sliced and measured for size and roundness. A mixed linear model with animals modeled as random effects was used to test for significant differences in ablation zone metrics among time groups; post hoc tests were used to detect significant differences between time groups.Results-Mean ablation zone diameters ranged from 2.05 cm ± 0.23 (standard deviation) at 2 minutes to 2.59 cm ± 0.53 at 12 minutes. Thirteen (32%) of 40 ablation zones with mean maximum diameters greater than 3.0 cm were observed at the 5-12-minute time groups. No significant differences in ablation zone diameter were observed among all groups (P > .05), but a trend of increasing diameter with time was noted. Mean isoperimetric ratio (a measure of roundness) for all ablation zones was 0.88 ± 0.02, which indicates minimal heat sinking near vessels. Conclusion-The triaxial microwave ablation system is capable of creating relatively large, circular zones of ablation in minutes with minimal effects from local blood flow.Thermal tumor ablation is a rapidly expanding treatment option for neoplasms of many organs, including the lung, liver, bone, and kidney (1-6). Tumor ablation has gained considerable attention due to its minimally invasive nature and the large number of patients who are not candidates for potentially curable surgical resection because of comorbidities or tumor number, size, or location. Radiofrequency (RF) ablation accounts for most of the clinical and experimental studies in heat-based ablation techniques (7). Unfortunately, current RF ablation systems are limited by the need to keep temperatures below 100°C to prevent charring, long Advances in Knowledge• To our knowledge, we reported the first preclinical experience of microwave ablation with a triaxial antenna. • A functional relationship between application time and ablation diameter in a normal in vivo liver model was defined.• We described a way to quantify perfusion in a zone of ablation (perfusion score).• We quantified the limited heat-sink effect with the triaxial microwave ablation antenna through circularity measurements.Microwave ablation shares many of the advantages of RF ablation but has additional theoretic advantages that may offer better and more consistent destruction of tumors. Microwaves have a much broader field of power density and a correspondingly larger zone of active heating (8). This may allow for more uniform tumor killing within a targeted ...

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Analysis and experimental validation of a triaxial antenna for microwave tumor ablation

Cited by 20 publications

References 9 publications

Hepatic microwave ablation: a review of the histological changes following thermal damage

Hepatic microwave ablation: a review of the histological changes following thermal damage

Microwave ablation with a triaxial antenna: results in ex vivo bovine liver

Microwave Ablation with a Single Small-Gauge Triaxial Antenna: In Vivo Porcine Liver Model

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