Ex situ quantification of the cooling effect of liver vessels on radiofrequency ablation

Lehmann, Kai S.; Ritz, J.‐P.; Valdeig, S.; Knappe, Verena; Schenk, Andrea; Weihusen, Andreas; Rieder, Christian; Holmer, Christoph; Zurbuchen, Urte; Hoffmann, P; Peitgen, Heinz O.; Buhr, H. J.; Frericks, Bernd

doi:10.1007/s00423-009-0480-1

Cited by 28 publications

(33 citation statements)

References 16 publications

(28 reference statements)

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“…In the experimental situation, our measurements showed a good reproducibility, but other influencing parameters can be expected in the clinical application. In particular, the cooling effect of the organ perfusion has a considerable influence on the lesion diameter [26] during in vivo applications and needs to be evaluated by comparing the ex vivo data and the yet to be obtained in vivo data. An application in clinical practice seems to be feasible on the basis of our data, but there are presently no results from large-animal studies with regard to the dose-effect relations in perfused organs or information on the capacity parameters of thyroid tissue necessary for optimal irradiation planning.…”

Section: Discussionmentioning

confidence: 99%

Bipolar Radiofrequency Ablation for Nodular Thyroid Disease—Ex Vivo and In Vivo Evaluation of a Dose-Response Relationship

Holmer

Lehmann

Knappe

et al. 2011

Journal of Surgical Research

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Section: Discussionmentioning

confidence: 99%

Bipolar Radiofrequency Ablation for Nodular Thyroid Disease—Ex Vivo and In Vivo Evaluation of a Dose-Response Relationship

Holmer

Lehmann

Knappe

et al. 2011

Journal of Surgical Research

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“…4. Another source of variability may be the heat sink effect due to blood flow within vessels carrying away the heat energy deposited [35–36]. It was possible to avoid forming ablations near major blood vessels in this study; however, the liver is a vascular structure, and smaller vessels could not be avoided in all cases.…”

Section: Discussionmentioning

confidence: 99%

Quantifying Local Stiffness Variations in Radiofrequency Ablations With Dynamic Indentation

DeWall

Varghese

Brace

2012

IEEE Trans. Biomed. Eng.

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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 mm2, 560 mm2, and 574 mm2, 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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“…The vascularization of tissue was missing in our study. It is known that the vascular perfusion of tissue has a high impact on its biophysiological properties (5). The absence of blood flow in the measured tissue presumably influences the electrical conductivity.…”

Section: Discussionmentioning

confidence: 99%

“…The mechanisms by which tissue is destroyed by RFA are well known (3,4). The area of the induced thermal necrosis is significantly influenced by the properties of the treated tissue, such as blood flow in the tissue (5) and its electrical conductivity (6).…”

Section: Introductionmentioning

confidence: 99%

Determination of the electrical conductivity of human liver metastases: impact on therapy planning in the radiofrequency ablation of liver tumors

et al. 2016

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Background Radiofrequency ablation is used to induce thermal necrosis in the treatment of liver metastases. The specific electrical conductivity of a liver metastasis has a distinct influence on the heat formation and resulting tumor ablation within the tissue. Purpose To examine the electrical conductivity σ of human colorectal liver metastases and of tumor-free liver tissue in surgical specimens. Material and Methods Surgical specimens from patients with resectable colorectal liver metastases were used for measurements (size of metastases <30 mm). A four-needle measuring probe was used to determine the electrical conductivity σ of human colorectal liver metastasis (n = 8) and tumor-free liver tissue (n = 5) in a total of five patients. All measurements were performed at 470 kHz, which is the relevant frequency for radiofrequency ablation. The tissue temperature was also measured. Hepatic resections were performed in accordance with common surgical standards. Measurements were performed in the operating theater immediately after resection. Results The median electrical conductivity σ was 0.57 S/m in human colorectal liver metastases at a median temperature of 35.1℃ and 0.35 S/m in tumor-free liver tissue at a median temperature of 34.9℃. The electrical conductivity was significantly higher in tumor tissue than in tumor-free liver tissue ( P = 0.005). There were no differences in tissue temperature between the two groups ( P = 0.883). Conclusion The electrical conductivity is significantly higher in human colorectal liver metastases than in tumor-free liver tissue at a frequency of 470 kHz.

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Ex situ quantification of the cooling effect of liver vessels on radiofrequency ablation

Cited by 28 publications

References 16 publications

Bipolar Radiofrequency Ablation for Nodular Thyroid Disease—Ex Vivo and In Vivo Evaluation of a Dose-Response Relationship

Bipolar Radiofrequency Ablation for Nodular Thyroid Disease—Ex Vivo and In Vivo Evaluation of a Dose-Response Relationship

Quantifying Local Stiffness Variations in Radiofrequency Ablations With Dynamic Indentation

Determination of the electrical conductivity of human liver metastases: impact on therapy planning in the radiofrequency ablation of liver tumors

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