Broadband lung dielectric properties over the ablative temperature range: Experimental measurements and parametric models

Šebek, Jan; Bortel, Radoslav; Prakash, Punit

doi:10.1002/mp.13704

Cited by 20 publications

(32 citation statements)

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“…The results indicated that the dielectric properties of human cancer tissues and the corresponding normal tissues are often quite different. On the basis of this difference, a variety of diagnostic and therapeutic techniques have been developed, including magnetic resonance electric properties tomography (MR‐EPT) [Liu et al, ; Ariturk and Ider, ], surgical margin detection [Summers et al, ], and microwave ablation [Sebek et al, ], etc. In this article, we use this method to measure the dielectric properties of ex vivo metastatic and non‐metastatic lymph nodes (LNs) from lung cancer surgeries, including pre‐vascular and retrotraccheal LNs, subaortic LNs, para‐aortic LNs, subcarinal LNs, paraesophageal LNs, pulmonary ligament LNs, hilar LNs, and interlobar LNs.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Properties of Normal and Metastatic Lymph Nodes Ex Vivo From Lung Cancer Surgeries

Sun

Cai

et al. 2020

Bioelectromagnetics

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The dielectric properties of normal and tumor human tissues have been widely reported in recent years. However, the dielectric properties of intrathoracic lymph nodes (LNs) have not been reported. In this communication, we measured the dielectric properties (i.e., permittivity and conductivity) of ex vivo intrathoracic LNs obtained from lung cancer surgeries. Results show that the permittivity and conductivity of metastatic LNs are higher than those of normal LNs over the frequency range of 1 MHz-4 GHz. Statistically significant differences are observed at single specific frequencies (64, 128, 298, 433, and 915 MHz and 2.45 GHz). Our study provides the basic data to support future-related research and fills the research gap on the dielectric properties of LNs in the lungs. Bioelectromagnetics. 2020;41:148-155.

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Section: Introductionmentioning

confidence: 99%

Dielectric Properties of Normal and Metastatic Lymph Nodes Ex Vivo From Lung Cancer Surgeries

Sun

Cai

et al. 2020

Bioelectromagnetics

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“…According to the 4thorder Cole-Cole model, the dielectric constant and electrical conductivity of the lung tissue at the end of expiration and inhalation at 2.45 GHz were calculated. The Cole-Cole model is described as follows [20]:…”

Section: Tissue Ablation Governing Equationsmentioning

confidence: 99%

Effect of changes in lung physical properties on microwave ablation zone during respiration

Yang

Cao

2020

Biomed. Eng. Lett.

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Microwave ablation is a promising minimally invasive treatment for cancer. However, due to the respiratory movement of the lungs, it is very difficult to accurately predict and control the microwave ablation zone. Therefore, the influence of the changes of the physical parameters of the respiratory process on the microwave ablation zone is studied. Firstly, based on the 4D-CT describing the respiratory process of the lungs, all the image data are from 100 non-small cell lung cancer radiotherapy patients (50 males and 50 females, average 58 years, range 55-61 years). According to the theory of porous media, the change of the effective thermal conductivity of the lung tissue during the breathing process is obtained. The effective thermal conductivity of the lung parenchyma during respiration varies from 0.16 to 0.20 W/m °C, with the lowest vale at the end of inspiration and the highest at the end of expiration. The transient problems during microwave ablation of pulmonary tissue are analyzed by finite element method. The changes of relative permittivity, conductivity and density changes during the breathing process are also considered. The results show that the microwave ablation zone is significantly larger under dynamic physical parameters. At the end of expiration, when the tissue parameter is set to constant, the ablation lesion area is more concentrated around the tip and slot of the antenna, and the backward heating effect is smaller, Ablation volume was superior in nonventilated lungs. Therefore, single-lung ventilation can be considered during pulmonary ablation to reduce the impact of breathing on the ablation area. These findings can be useful to further our understanding the MWA and hold promise towards achieving successful treatment objective as well as enhanced therapeutic output via improved treatment planning and strategy. This study provides the basis for clinical pulmonary ablation and can also be used as a preoperative plan to provide guidance to physicians.

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“…The overall measurement setup is depicted in Figure 3.1(a). The temperature sensor was placed 2 mm away from the dielectric probe tip to preclude interference with electromagnetic field of the probe [63] as shown in Figure 3.1(b). A polyimide sheath was slid over the fiber optic sensor for its protection and a rubber band was used to fix the sensor at an appropriate position over the dielectric probe.…”

Section: Measurement Of Dielectric Propertiesmentioning

confidence: 99%

“…The fibroid sample was taken out from the RPMI gauze and placed in a custom-designed sample holder shown in Figure 3.1(c). The sample holder was constructed from copper sheets with the objective of minimizing thermal gradients across the sample, similar to prior studies [63], [135]. First, the dielectric properties were recorded at room temperature (23 ºC).…”

Section: Measurement Of Dielectric Propertiesmentioning

confidence: 99%

“…First, the dielectric properties were recorded at room temperature (23 ºC). Then, to capture the temperature dependency of the dielectric data, the sample was heated using a ThermoScientific hot plate [63]. The initial temperature of hot plate was set at ~150-200 ºC to achieve similar heating rates as that of water cooled MWA applicators (at a point 10 mm away from the applicator surface) [63].…”

Section: Measurement Of Dielectric Propertiesmentioning

confidence: 99%

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Microwave Ablation for Uterine Fibroids

2019

CMR

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Uterine fibroids are the most common tumors of the uterus, with a ~70-80% lifetime prevalence in women of childbearing age. Uterus sparing procedures are of increasing interest for the treatment of fibroids to avoid surgical complications, preserve fertility, and reduce treatment costs.Image-guided microwave thermal ablation is under investigation as a minimally-invasive alternative to gold-standard hysterectomy, offering potential to provide symptom alleviation while preserving the patient's fertility. This dissertation presents studies towards the technical feasibility assessment of hysteroscopic transcervical microwave ablation (MWA) technology for treating uterine fibroids with the objective of achieving localized thermal destruction of fibroids while precluding thermal damage to adjacent healthy tissues.Computational models, a powerful tool for the design and evaluation of candidate ablation technologies, require accurate specification of tissue dielectric properties and how these properties vary as a function of temperature during an ablation procedure. The dielectric properties of uterine fibroids within the microwave frequency range have not been previously reported, thus stunting the development of accurate modeling tools. This study presents, for the first time, the dielectric properties within the microwave frequency range (500 MHz to 6 GHz) of human uterine fibroids excised following hysterectomy procedures, and their variation across temperatures ranging between 23-150 ºC. At room temperature (23 ºC), values of ɛr ranged between 44.5-57.5 units with a decreasing trend seen at higher frequencies and ơeff varied between 0.91-6.02 Sm -1 with an increasing trend at higher frequencies. At temperatures close to the water vaporization point, ɛr, drops considerably i.e. to 12-14% of its baseline values for all measured frequencies. The ơeff initially rises till 98 ºC and then falls to 11-13% of its baseline values at 125 ºC for frequencies ≤ 2.45 GHz. The ơeff follows a decreasing trend for frequencies > 2.45 GHz and drops to ~ 6 % of its room temperature values. Furthermore, parametric models of temperature and frequency dependent dielectric properties of uterine fibroids were presented, which can be readily used in computer simulations for accurate modeling of MWA.While MWA applicators are in clinical use for a variety of indications, existing antenna designs are not well suited to ablation of 1 -3 cm type 2 uterine fibroids. Currently 2.45 GHz applicators are used for the MWA of fibroid tissues; these antennas typically have longer active lengths (~7-15 mm) compared to the radius of type 2 fibroids. A higher frequency 5.8 GHz applicator, which was expected to reduce the antenna radiating length was investigated. A 5.8 GHz water-cooled MWA applicator, suitable for insertion into targeted fibroids via the instrument channel of a hysteroscope, was designed for the treatment of small fibroids (1-3 cm diameter) using electromagnetic-bioheat transfer simulations. The prominent features of this applicator are ap...

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Broadband lung dielectric properties over the ablative temperature range: Experimental measurements and parametric models

Cited by 20 publications

References 46 publications

Dielectric Properties of Normal and Metastatic Lymph Nodes Ex Vivo From Lung Cancer Surgeries

Dielectric Properties of Normal and Metastatic Lymph Nodes Ex Vivo From Lung Cancer Surgeries

Effect of changes in lung physical properties on microwave ablation zone during respiration

Microwave Ablation for Uterine Fibroids

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