Physical modeling of microwave ablation zone clinical margin variance

Deshazer, Garron; Merck, Derek; Hagmann, Mark J.; Dupuy, Damian E.; Prakash, Punit

doi:10.1118/1.4942980

Cited by 46 publications

(71 citation statements)

References 72 publications

(86 reference statements)

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“…By intermittently turning power off, we were able to correct for thermal conduction (equations 1, 2, 3) and thus calculate SAR both initially and during ablation, to characterize changes in SAR. We used the results of these experimental measurements to validate a prior multi-physics MWA model [9]. There was reasonable agreement in temperature, with an average error of 5.9 °C between model and experiment (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The spatial temperature changes captured by the infrared camera were compared to a previously validated simulation model using the Perseon ST antenna [9] that mimicked the same experimental setup (discussed in the next section). The initial and transient SAR profiles were compared to the simulation as well.…”

Section: Methodsmentioning

confidence: 99%

“…The FEM model was implemented in COMSOL Multiphysics v4.4 (Burlington, MA) to simulate the described experiment. The model used to simulate the ablation experiments for this study was used in a previous study to quantify clinical margin variability during MWA treatments [9]. …”

Section: Methodsmentioning

confidence: 99%

“…Table 1 presents the temperature dependent dielectric and thermal properties used in our simulations within liver. The parameterizations of permittivity and electrical conductivity in liver tissue were also employed in a prior investigation for modeling MWA procedures within liver at 915 MHz [9]. Moreover, a similar linear approximation for thermal conductivity was used, where k 0 is the thermal conductivity at the reference temperature, k 1 is a temperature coefficient, and T and T 0 are the transient and reference temperatures [28,29].…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, the use of 2D ablation zone predictions on 3D anatomy places a considerable burden on the physician’s spatial treatment planning skill, and treatment accuracy may be skewed by physician experience. To facilitate personalized treatment delivery and simplify planning for physicians, there has been renewed interest in the development of modeling and visualization techniques towards treatment planning of ablation treatments [9,10,11]. …”

Section: Introductionmentioning

confidence: 99%

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Experimental measurement of microwave ablation heating pattern and comparison to computer simulations

Deshazer

Prakash

Merck

et al. 2016

International Journal of Hyperthermia

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Introduction For computational models of microwave ablation (MWA), knowledge of the antenna design is necessary, but the proprietary design of clinical applicators is often unknown. We characterized the specific absorption rate (SAR) during MWA experimentally and compared to a multi-physics simulation. Methods An infrared (IR) camera was used to measure SAR during MWA within a split ex vivo liver model. Perseon Medical’s short-tip (ST) or long-tip (LT) MWA antenna were placed on top of a tissue sample (n=6), and microwave power (15W) was applied for 6 min, while intermittently interrupting power. Tissue surface temperature was recorded via IR camera (3.3 fps, 320×240 resolution). SAR was calculated intermittently based on temperature slope before and after power interruption. Temperature and SAR data were compared to simulation results. Results Experimentally measured SAR changed considerably once tissue temperatures exceeded 100 °C, contrary to simulation results. The ablation zone diameters were 1.28 cm and 1.30 ± 0.03 cm (transverse), and 2.10 cm and 2.66 ± −0.22 cm (axial), for simulation and experiment, respectively. The average difference in temperature between the simulation and experiment were 5.6 °C (ST) and 6.2 °C (LT). Dice coefficients for 1000 W/kg SAR iso-contour were 0.74 ± 0.01 (ST) and 0.77 (± 0.03) (LT), suggesting good agreement of SAR contours. Conclusion We experimentally demonstrated changes in SAR during MWA ablation, which were not present in simulation, suggesting inaccuracies in dielectric properties. The measured SAR may be used in simplified computer simulations to predict tissue temperature when the antenna geometry is unknown.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental measurement of microwave ablation heating pattern and comparison to computer simulations

Deshazer

Prakash

Merck

et al. 2016

International Journal of Hyperthermia

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Sensitivity analysis of critical parameters affecting the efficacy of microwave ablation using Taguchi method

Singh

Repaka

Al‐Jumaily

2018

Int J RF Microw Comput Aided Eng

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Microwave ablation (MWA) is a minimally invasive thermal treatment modality that has already evolved as a promising alternative to radiofrequency ablation for treating different types of malignant and benign tumors, especially ≥3 cm in diameter. The efficacy of thermal ablative therapies is mainly judged by the ablation volume attained post‐ablation. In this regards, the present study aims at analyzing the influence of six critical parameters, as follows, relative permittivity, electrical conductivity, volumetric heat capacity, thermal conductivity, blood perfusion rate, and applied power on the ablation volume attained during MWA. Taguchi's L27 orthogonal array has been adopted for the current problem with six input variables having three levels each. The electric and thermophysical properties considered in the study have been derived from liver, lung, breast, and kidney. Finite element method (FEM) based numerical simulations of MWA have been conducted on three‐dimensional homogeneous model of biological tissue using coaxial single slot microwave antenna. Further, the ranking and the contribution of each parameter on the ablation volume attained during MWA have been quantified using analysis of variance. The corollaries drawn from the study would be useful to the clinical practitioners during the treatment planning stage of the MWA.

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Computational modeling of 915 MHz microwave ablation: Comparative assessment of temperature‐dependent tissue dielectric models

Deshazer

Hagmann²,

Merck

et al. 2017

Medical Physics

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The inclusion of decreased electrical conductivity above 95 °C, implemented with model B as guided by our experimental measurements, may be a good approach for approximating the dynamic changes that occur during MWA at 915 MHz. Although a step toward more effectively modeling MWA at 915 MHz, further investigation of the transition in dielectric properties with temperature and tissue shrinkage, especially at high temperatures is needed for more accurate simulations.

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Physical modeling of microwave ablation zone clinical margin variance

Cited by 46 publications

References 72 publications

Experimental measurement of microwave ablation heating pattern and comparison to computer simulations

Experimental measurement of microwave ablation heating pattern and comparison to computer simulations

Sensitivity analysis of critical parameters affecting the efficacy of microwave ablation using Taguchi method

Computational modeling of 915 MHz microwave ablation: Comparative assessment of temperature‐dependent tissue dielectric models

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