Tissue Contraction Caused by Radiofrequency and Microwave Ablation: A Laboratory Study in Liver and Lung

Brace, Christopher L.; Diaz, Teresa A.; Hinshaw, J. Louis; Lee, Fred T.

doi:10.1016/j.jvir.2010.02.038

Cited by 141 publications

(151 citation statements)

References 27 publications

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“…Comparisons between ex vivo and in vivo studies were consistent with these previous studies, where the in vivo ablation zones were noticeably smaller than those created in ex vivo tissue. One exception was with the HinesPeralta study (27), where the in vivo ablation zones were larger than the ex vivo ablation zones for all 150-W ablations less than 10 minutes long. These variations could potentially have been attributed to the condition of the liver or more rapid tissue contraction, which were not evaluated.…”

Section: Experimental Studies: a Dual-slot Microwave Antenna Chiang Ementioning

confidence: 98%

A Dual-Slot Microwave Antenna for More Spherical Ablation Zones: Ex Vivo and in Vivo Validation

Chiang¹,

Hynes²,

Bedoya³

et al. 2013

Radiology

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Purpose:To compare the performance of a microwave antenna design with two annular slots to that of a monopole antenna design in creating a more spherical ablation zone. Materials and Methods:Animal care and use committee approval was obtained before in vivo experiments were performed. Microwave ablation zones were created by using dual-slot and monopole control antennas for 2, 5, and 10 minutes at 50 and 100 W in ex vivo bovine livers. Dual-slot and monopole antennas were then used to create ablation zones at 100 W for 5 minutes in in vivo porcine livers, which also underwent intraprocedural imaging. Ablation diameter, length, and aspect ratio (diameter 4 length) were measured at gross pathologic examination and compared at each combination of power and time by using the paired Student t test. A P value less than .05 was considered to indicate a significant difference. Aspect ratios closer to 1 reflected a more spherical ablation zone. Results:The dual-slot antenna created ablation zones with a higher aspect ratio at 50 W for 2 minutes (0.75 vs 0.53, P = .003) and 5 minutes (0.82 vs 0.63, P = .053) than did the monopole antenna in ex vivo liver tissue, although the difference was only significant at 2 minutes. At 100 W, the dual-slot antenna had a significantly higher aspect ratio at 2 minutes (0.52 vs 0.42, P = .002). In vivo studies showed significantly higher aspect ratios at 100 W for 5 minutes (0.63 vs 0.53, respectively, P = .029). Intraprocedural imaging confirmed this characterization, showing higher rates of ablation zone growth and heating primarily at the early stages of the ablation procedure when the dual-slot antenna was used. Conclusion:The dual-slot microwave antenna created a more spherical ablation zone than did the monopole antenna both in vivo and ex vivo liver tissue. Greater control over power delivery can potentially extend the advantages of the dualslot antenna design to higher power and longer treatment times.q RSNA, 2013 1

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Section: Experimental Studies: a Dual-slot Microwave Antenna Chiang Ementioning

confidence: 98%

A Dual-Slot Microwave Antenna for More Spherical Ablation Zones: Ex Vivo and in Vivo Validation

Chiang¹,

Hynes²,

Bedoya³

et al. 2013

Radiology

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“…Finally, some ablation technologies, most notably microwave ablation and to a lesser extent important to acknowledge variability in postablation size measurements, which can be more or less significant depending on the ablation modality. For example, microwave ablation and, to a lesser degree, RF ablation can lead to significant tissue contraction after ablation, resulting in a smaller apparent ablation zone at postprocedure imaging (84). The visible "ice ball" during cryoablation likely overestimates the size of the ablation zone, as the cytotoxic isotherm is several millimeters inside the ice-ball margin (85).…”

Section: Comparing Zones Of Coagulation Among Different Ablation Techmentioning

confidence: 99%

Image-guided Tumor Ablation: Standardization of Terminology and Reporting Criteria—A 10-Year Update

et al. 2014

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“…It was present in all ablations and corresponded to the region where vaporized water condensed after being driven from the ablation center [26][27][28]. Profiles were not extended to the ablation center, but the most critical region of the ablation to investigate was the region of low modulus contrast, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Rather, each profile was drawn perpendicular between the outer transition zone boundary in the indented, unstained image and the outer edge of the stained "ring" within the white zone of the ablation in the registered, stained image. The ring corresponded to the boundary where water condensed after being driven from the dehydrated ablation core and will be referred to as the condensation boundary [26][27][28]. The profile distance was normalized for all samples to show average changes between these landmarks.…”

Section: Image Analysismentioning

confidence: 99%

Quantifying local stiffness variations in radiofrequency ablations with dynamic indentation

DeWall

Varghese

Brace

2011

2011 IEEE International Ultrasonics Symposium

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Elastographic imaging can be used to monitor ablation procedures, however confident and clear determination of the ablation boundary is essential to ensure complete treatment of the pathological target. To investigate the potential for ablation boundary representation on elastographic images, local variations in the viscoelastic properties in radiofrequency ablated regions that were formed in vivo in porcine liver tissue were quantified using dynamic indentation. Spatial stiffness maps were then correlated to stained histology, the gold standard for determination of the ablation periphery or boundary. Regions of interest in eleven radiofrequency ablation samples were indented at 18-24 locations each, including the central zone of complete necrosis and more peripheral transition zones including normal tissue. Storage modulus and rate of stiffening were both greatest in the central ablation zone and decreased with radial distance away from the center. The storage modulus and modulus contrast at the ablation outer transition zone boundary were 3.1 ± 1.0 kPa and 1.6 ± 0.4, respectively, and 36.2 ± 9.1 kPa and 18.3 ± 5.5 at the condensation boundary within the ablation zone. Elastographic imaging modalities were then compared to gross pathology in ex vivo bovine liver tissue. Area estimated from strain, shear wave velocity, and gross pathology images were 470 mm 2 , 560 mm 2 , and 574 mm 2 , respectively, and ablation widths were 19.4 mm, 20.7 mm, and 23.0 mm. This study has provided insights into spatial stiffness distributions within radiofrequency ablations and suggests that low stiffness contrast on the ablation periphery leads to the observed underestimation of ablation extent on elastographic images.

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Tissue Contraction Caused by Radiofrequency and Microwave Ablation: A Laboratory Study in Liver and Lung

Cited by 141 publications

References 27 publications

A Dual-Slot Microwave Antenna for More Spherical Ablation Zones: Ex Vivo and in Vivo Validation

A Dual-Slot Microwave Antenna for More Spherical Ablation Zones: Ex Vivo and in Vivo Validation

Image-guided Tumor Ablation: Standardization of Terminology and Reporting Criteria—A 10-Year Update

Quantifying local stiffness variations in radiofrequency ablations with dynamic indentation

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