A thermoelastic deformation model of tissue contraction during thermal ablation

Park, Chang Sub; Liu, Cong; Hall, Sheldon K.; Payne, Stephen J.

doi:10.1080/02656736.2017.1335441

Cited by 17 publications

(14 citation statements)

References 31 publications

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“…Further, the maximum values of volumetric strain in the coupled thermo-electro-mechanical model with and without the inclusion of tissue shrinkage have been found to be 34% and 1.4%, respectively, clearly highlighting the importance of tissue shrinkage term in the computational models of MWA. Moreover, one of the key observations from the coupled analysis is that the magnitude of tissue expansion is of the order of 10 -5 m, much smaller in magnitude compared to the combined expansion and shrinkage of tissue, i.e., order of 10 -3 to 10 -2 m. Again, such findings are in agreement with the previously reported thermo-elastic deformation model (see, e.g., [46]). The predicted damage volume of the MWA model without the mechanical coupling is 7.29% less as compared to the model with mechanical coupling after 10 min of 20 W MW heating.…”

Section: Discussionsupporting

confidence: 90%

“…where  is the stress tensor and ε = [(∇u T +∇u)/2] is the strain tensor (i,j = 1,2 15, β is the coefficient of volumetric protein denaturation shrinkage assumed to be equal to three [46], ξ is the relative shrinkage due to protein denaturation given by Eq. (20) and δ is the Kronecker delta function given by…”

Section: Modeling Of Mechanical Deformation Of Biological Tissuesmentioning

confidence: 99%

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Coupled thermo-electro-mechanical models for thermal ablation of biological tissues and heat relaxation time effects

Singh

Melnik

2019

Phys. Med. Biol.

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Section: Discussionsupporting

confidence: 90%

Section: Modeling Of Mechanical Deformation Of Biological Tissuesmentioning

confidence: 99%

Coupled thermo-electro-mechanical models for thermal ablation of biological tissues and heat relaxation time effects

Singh

Melnik

2019

Phys. Med. Biol.

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“…The initial swelling of ablated lesions, as observed in the first half hour after MWA, is a surprising observation, which stands in contrast to the findings of some previous ex vivo studies 7,8,15,16 . An ex vivo study in bovine livers performed by Amabile et al showed a linear correlation of shrinkage and time after ablation, while Brace et al also demonstrated a linear decrease in the lesion size 7,8 .…”

Section: Discussioncontrasting

confidence: 99%

Exploring Patterns of Dynamic Size Changes of Lesions after Hepatic Microwave Ablation in an In Vivo Porcine Model

Bressem

Vahldiek

Erxleben

et al. 2020

Sci Rep

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Microwave ablation (MWA) is a type of minimally invasive cancer therapy that uses heat to induce necrosis in solid tumours. Inter-and post-ablational size changes can influence the accuracy of control imaging, posing a risk of incomplete ablation. The present study aims to explore post-ablation 3D size dynamics in vivo using computed tomography (ct). ten MWA datasets obtained in nine healthy pigs were used. Lesions were subdivided along the z-axis with an additional planar subdivision into eight subsections. The volume of the subsections was analysed over different time points, subsequently colour-coded and three-dimensionally visualized. A locally weighted polynomial regression model (LoeSS) was applied to describe overall size changes, and Student's t-tests were used to assess statistical significance of size changes. The 3D analysis showed heterogeneous volume changes with multiple small changes at the lesion margins over all time points. the changes were pronounced at the upper and lower lesion edges and characterized by initially eccentric, opposite swelling, followed by shrinkage. In the middle parts of the lesion, we observed less dimensional variations over the different time points. LOESS revealed a hyperbolic pattern for the volumetric changes with an initially significant volume increase of 11.6% (111.6% of the original volume) over the first 32 minutes, followed by a continuous decrease to 96% of the original volume (p < 0.05). Microwave ablation (MWA) is a thermoablative procedure for the minimally invasive therapy of solid tumours, primarily in the lungs, kidneys and liver. It uses electromagnetic waves to induce local coagulation necrosis through heat 1-3. During the ablation procedure, high local temperatures of up to 120 °C can be achieved in the target tissue, not only causing protein denaturation but also for example evaporation of the water contained in the tissue and resulting in changes of dielectric and thermal properties as well as structural tissue changes 4-6. Overall, these structural changes can lead to dynamic alterations in lesion morphology and lesion size in the post-ablation period. Tissue shrinkage, primarily caused by dehydration, but also by tissue evaporation and carbonization, is an important change in the ablation area and ought to be considered in post-interventional imaging as it can cause a decrease in lesion volume of up to 30% and could therefore be of clinical relevance 7-9. Contrast-enhanced computed tomography (CECT) is often performed after MWA to determine the size and safety margin of the ablation area in order to ensure complete tumour ablation 10-13. CECT has been shown to allow identification of the central necrotic area of the ablated tissue, which displays little to no contrast medium uptake and thus appears hypodense compared to normal liver tissue (NLT) 14. Recent studies using CECT ex vivo or in vivo demonstrated the shrinkage of ablation zones in the first hours after MWA, but so far, no precise analysis of the dynamic size behaviour has been carried out ...

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“…In addition, tumor deformation during microwave ablation was not considered, which is another limitation of this study. The IS-54 model would, therefore, overestimate the actual treated tissue and the safety margin would be larger than the fixed 5 mm due to tissue contraction [45,46]. However, the tissue contraction during MWA could be evaluated using CT images [47] or measured using small specimens of ex vivo liver [48].…”

Section: Discussionmentioning

confidence: 99%

Conformal coverage of liver tumors by the thermal coagulation zone in 2450-MHz microwave ablation

Gao

Wang

et al. 2019

International Journal of Hyperthermia

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Purpose: To optimize treatment schemes using 2450-MHz microwave ablation (MWA), a novel conformal coverage method based on bipolar-angle mapping is proposed that determines whether a liver tumor is completely encompassed by thermal coagulation zones. Materials and methods: Firstly, three-dimensional (3-D) triangular mesh data of liver tumors were reconstructed from clinical computed tomography (CT) slices using the Marching cubes (MC) algorithm. Secondly, characterization models of thermal coagulation zones were established based on finite element simulation results of 40, 45, 50, 55, and 60 W ablations. Finally, coagulation zone models and tumor surface data were mapped and fused on a two-dimensional (2-D) plane to achieve conformal coverage of liver tumors by comparing the corresponding polar radii. Results: Optimal parameters for ablation treatment of liver tumors were efficiently obtained with the proposed conformal coverage method. Fifteen liver tumors were obtained with maximal diameters of 12.329-78.612 mm (mean ± standard deviation, 39.094 ± 19.447 mm). The insertion positions and orientations of the MWA antenna were determined based on 3-D reconstruction results of these tumors. The ablation patterns and durations of tumors were planned according to the minimum mean standard deviations between the ablative margin and tumor surface. Conclusion: The proposed method can be applied to computer-assisted MWA treatment planning of liver tumors, and is expected to guide clinical procedures in future.

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A thermoelastic deformation model of tissue contraction during thermal ablation

Abstract: The model presented here will allow predictions of thermal ablation to be corrected for tissue contraction, which is an important effect, during comparison with post-procedural images, thus improving the accuracy of mathematical simulations for treatment planning.

Cited by 17 publications

References 31 publications

Coupled thermo-electro-mechanical models for thermal ablation of biological tissues and heat relaxation time effects

Coupled thermo-electro-mechanical models for thermal ablation of biological tissues and heat relaxation time effects

Exploring Patterns of Dynamic Size Changes of Lesions after Hepatic Microwave Ablation in an In Vivo Porcine Model

Conformal coverage of liver tumors by the thermal coagulation zone in 2450-MHz microwave ablation

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