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Zia G, Lintz A, Hardin C, Bottiglieri A, Sebek J, Prakash P. Assessment of thermochromic phantoms for characterizing microwave ablation devices. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.23.584886. [PMID: 38617290 PMCID: PMC11014477 DOI: 10.1101/2024.03.23.584886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Background and Purpose Thermochromic gel phantoms provide a controlled medium for visual assessment of thermal ablation device performance. However, there are limited studies reporting on the comparative assessment of ablation profiles assessed in thermochromic gel phantoms against those in ex vivo tissue. The objective of this study was to compare microwave ablation zones in a thermochromic tissue mimicking gel phantom and ex vivo bovine liver, and to report on measurements of the temperature dependent dielectric and thermal properties of the phantom. Methods Thermochromic polyacrylamide phantoms were fabricated following a previously reported protocol. Phantom samples were heated to temperatures in the range of 20 - 90 °C in a temperature-controlled water bath, and colorimetric analysis of images of the phantom taken after heating were used to develop a calibration between color changes and temperature to which the phantom was heated. Using a custom, 2.45 GHz water-cooled microwave ablation antenna, ablations were performed in fresh ex vivo liver and phantoms using 65 W applied for 5 min or 10 min ( n = 3 samples in each medium for each power/time combination). Broadband (500 MHz - 6 GHz) temperature-dependent dielectric and thermal properties of the phantom were measured over the temperature range 22 - 100 °C. Measured dielectric and thermal properties of the phantom were employed in a previously validated computational model of microwave ablation to comparatively assess model predicted extents of heating against experimental observations in the phantom. Results Colorimetric analysis showed that the sharp change in gel phantom color commences at a temperature of 57 °C. Short and long axes of the ablation zone in the phantom (as assessed by the 57 °C isotherm) for 65 W, 5 min ablations were aligned with extents of the ablation zone observed in ex vivo bovine liver. However, for the 65 W, 10 min setting, ablations in the phantom were on average 23.7% smaller in short axis and 7.4 % smaller in long axis than those observed in ex vivo liver. Measurements of the temperature dependent relative permittivity, thermal conductivity, and volumetric heat capacity of the phantom largely followed similar trends to published values for ex vivo liver tissue. After incorporating measured dielectric and thermal properties of the phantom, model predictions of ablation zone linear dimensions ranged between 16 - 50% larger than those observed experimentally. Conclusion Thermochromic tissue mimicking phantoms provide a suitable, controlled, and reproducible medium for comparative assessment of microwave ablation devices and energy delivery settings, though ablation zone size and shapes may not accurately represent ablation sizes and shapes observed in ex vivo liver tissue under similar conditions.
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Vidjak K, Farina L, Challapalli RS, Quinn AM, O'Halloran M, Lowery A, Ruvio G, Cavagnaro M. Histology-validated electromagnetic characterization of ex-vivo ovine lung tissue for microwave-based medical applications. Sci Rep 2024; 14:5940. [PMID: 38467672 PMCID: PMC10928158 DOI: 10.1038/s41598-024-55035-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 02/19/2024] [Indexed: 03/13/2024] Open
Abstract
Microwave thermal ablation is an established therapeutic technique for treating malignant tissue in various organs. Its success greatly depends on the knowledge of dielectric properties of the targeted tissue and on how they change during the treatment. Innovation in lung navigation has recently increased the clinical interest in the transbronchial microwave ablation treatment of lung cancer. However, lung tissue is not largely characterized, thus its dielectric properties investigation prior and post ablation is key. In this work, dielectric properties of ex-vivo ovine lung parenchyma untreated and ablated at 2.45 GHz were recorded in the 0.5-8 GHz frequency range. The measured dielectric properties were fitted to 2-pole Cole-Cole relaxation model and the obtained model parameters were compared. Based on observed changes in the model parameters, the physical changes of the tissue post-ablation were discussed and validated through histology analysis. Additionally, to investigate the link of achieved results with the rate of heating, another two sets of samples, originating from both ovine and porcine tissues, were heated with a microwave oven for different times and at different powers. Dielectric properties were measured in the same frequency range. It was found that lung tissue experiences a different behavior according to heating rates: its dielectric properties increase post-ablation while a decrease is found for low rates of heating. It is hypothesized, and validated by histology, that during ablation, although the tissue is losing water, the air cavities deform, lowering air content and increasing the resulting tissue properties.
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Affiliation(s)
- Klementina Vidjak
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University of Rome, Rome, Italy
| | | | - Ritihaas Surya Challapalli
- Discipline of Surgery, Lambe Institute for Translational Research, University of Galway, Galway, Ireland
| | - Anne Marie Quinn
- Department of Anatomic Pathology, University Hospital Galway, Galway, Ireland
| | - Martin O'Halloran
- Translational Medical Device Lab, National University of Ireland Galway, Galway, Ireland
| | - Aoife Lowery
- Discipline of Surgery, Lambe Institute for Translational Research, University of Galway, Galway, Ireland
| | | | - Marta Cavagnaro
- Department of Information Engineering, Electronics, and Telecommunications, Sapienza University of Rome, Rome, Italy.
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Lamhamdi M, Esmaeili A, Layes K, El Maaroufi Z, Rose G, Brensing A, Schweizer B. Determining of Ablation Zone in Ex Vivo Bovine Liver Using Time-Shift Measurements. Cancers (Basel) 2023; 15:5230. [PMID: 37958402 PMCID: PMC10650454 DOI: 10.3390/cancers15215230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 10/27/2023] [Accepted: 10/29/2023] [Indexed: 11/15/2023] Open
Abstract
This study presents a measurement principle for determining the size of the ablation zone in MWA, which could ultimately form an alternative to more expensive monitoring approaches like CT. The measurement method is based on a microwave transmission measurement. A MWA is performed experimentally on ex vivo bovine liver to determine the ablation zone. This setup uses a custom slot applicator performing the MWA at an operating frequency of 2.45 GHz and a custom bowtie antenna measuring the waves transmitted from the applicator. Furthermore, a custom measurement probe is used to determine the dielectric properties. A time-shift analysis is used to determine the radial extent of the ablation zone. Several measurements are carried out with a power of 50 W for 10 min to show the reproducibility. The results show that this method can provide reproducible outcomes to determine the ablation zone with a maximum error of 4.11%.
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Affiliation(s)
- Mohamed Lamhamdi
- Deparment of Engineering, RheinMain University of Applied Science, 65428 Rüsselsheim, Germany; (A.E.); (A.B.); (B.S.)
| | - Ali Esmaeili
- Deparment of Engineering, RheinMain University of Applied Science, 65428 Rüsselsheim, Germany; (A.E.); (A.B.); (B.S.)
| | - Kiyan Layes
- Deparment of Engineering, RheinMain University of Applied Science, 65428 Rüsselsheim, Germany; (A.E.); (A.B.); (B.S.)
| | - Zakaria El Maaroufi
- Deparment of Engineering, RheinMain University of Applied Science, 65428 Rüsselsheim, Germany; (A.E.); (A.B.); (B.S.)
| | - Georg Rose
- Institute of Medical Engineering and Research Campus STIMULATE, Otto Von Guericke University, 39106 Magdeburg, Germany;
| | - Andreas Brensing
- Deparment of Engineering, RheinMain University of Applied Science, 65428 Rüsselsheim, Germany; (A.E.); (A.B.); (B.S.)
| | - Bernd Schweizer
- Deparment of Engineering, RheinMain University of Applied Science, 65428 Rüsselsheim, Germany; (A.E.); (A.B.); (B.S.)
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In Vitro Measurement and Mathematical Modeling of Thermally-Induced Injury in Pancreatic Cancer Cells. Cancers (Basel) 2023; 15:cancers15030655. [PMID: 36765619 PMCID: PMC9913239 DOI: 10.3390/cancers15030655] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/16/2023] [Accepted: 01/18/2023] [Indexed: 01/24/2023] Open
Abstract
Thermal therapies are under investigation as part of multi-modality strategies for the treatment of pancreatic cancer. In the present study, we determined the kinetics of thermal injury to pancreatic cancer cells in vitro and evaluated predictive models for thermal injury. Cell viability was measured in two murine pancreatic cancer cell lines (KPC, Pan02) and a normal fibroblast (STO) cell line following in vitro heating in the range 42.5-50 °C for 3-60 min. Based on measured viability data, the kinetic parameters of thermal injury were used to predict the extent of heat-induced damage. Of the three thermal injury models considered in this study, the Arrhenius model with time delay provided the most accurate prediction (root mean square error = 8.48%) for all cell lines. Pan02 and STO cells were the most resistant and susceptible to hyperthermia treatments, respectively. The presented data may contribute to studies investigating the use of thermal therapies as part of pancreatic cancer treatment strategies and inform the design of treatment planning strategies.
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Sebek J, Park WKC, Geimer S, Van Citters DW, Farah A, Dupuy DE, Meaney PM, Prakash P. Computational modeling of microwave ablation with thermal accelerants. Int J Hyperthermia 2023; 40:2255755. [PMID: 37710404 DOI: 10.1080/02656736.2023.2255755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 08/30/2023] [Accepted: 08/31/2023] [Indexed: 09/16/2023] Open
Abstract
PURPOSE To develop a computational model of microwave ablation (MWA) with a thermal accelerant gel and apply the model toward interpreting experimental observations in ex vivo bovine and in vivo porcine liver. METHODS A 3D coupled electromagnetic-heat transfer model was implemented to characterize thermal profiles within ex vivo bovine and in vivo porcine liver tissue during MWA with the HeatSYNC thermal accelerant. Measured temperature dependent dielectric and thermal properties of the HeatSYNC gel were applied within the model. Simulated extents of MWA zones and transient temperature profiles were compared against experimental measurements in ex vivo bovine liver. Model predictions of thermal profiles under in vivo conditions in porcine liver were used to analyze thermal ablations observed in prior experiments in porcine liver in vivo. RESULTS Measured electrical conductivity of the HeatSYNC gel was ∼83% higher compared to liver at room temperature, with positive linear temperature dependency, indicating increased microwave absorption within HeatSYNC gel compared to tissue. In ex vivo bovine liver, model predicted ablation zone extents of (31.5 × 36) mm with the HeatSYNC, compared to (32.9 ± 2.6 × 40.2 ± 2.3) mm in experiments (volume differences 4 ± 4.1 cm3). Computational models under in vivo conditions in porcine liver suggest approximating the HeatSYNC gel spreading within liver tissue during ablations as a plausible explanation for larger ablation zones observed in prior in vivo studies. CONCLUSION Computational models of MWA with thermal accelerants provide insight into the impact of accelerant on MWA, and with further development, could predict ablations with a variety of gel injection sites.
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Affiliation(s)
- Jan Sebek
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas, USA
| | | | - Shireen Geimer
- Expeditionary School at Black River, Ludlow, Vermont, USA
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | | | | | | | - Paul M Meaney
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA
| | - Punit Prakash
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, Kansas, USA
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Matković A, Šarolić A. The Effect of Freezing and Thawing on Complex Permittivity of Bovine Tissues. SENSORS (BASEL, SWITZERLAND) 2022; 22:9806. [PMID: 36560174 PMCID: PMC9788127 DOI: 10.3390/s22249806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 11/29/2022] [Accepted: 12/10/2022] [Indexed: 06/17/2023]
Abstract
The aim of this study was to investigate how the freezing and thawing of biological tissues affect their complex permittivity in the microwave frequency range from 0.5 MHz to 18 GHz. We measured the complex permittivity of ex vivo bovine tissues, including brain white and grey matter, liver, and muscle, using an open-ended coaxial probe. Bovine tissues were chosen for their availability and similarity to human tissue permittivity. The samples were measured at 25 °C, before they were frozen either in a commercial freezer below -18 °C or in liquid nitrogen, nominally at -196 °C. The measured permittivity before freezing was compared to the permittivity measured after freezing and thawing the tissues back to 25 °C. Statistical analysis of the results showed a statistically significant change in permittivity after freezing and thawing by both methods for all the measured tissues, at least in some parts of the measured frequency range. The largest difference was observed for the white matter, while the liver had the smallest percent change.
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Di Meo S, Cannatà A, Morganti S, Matrone G, Pasian M. On the dielectric and mechanical characterization of tissue‐mimicking breast phantoms. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac7bcc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 06/23/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. In this paper, we focus on the dielectric and mechanical characterization of tissue-mimicking breast phantoms. Approach. Starting from recipes previously proposed by our research group, based on easy-to-handle, cheap and safe components (i.e. sunflower oil, deionized water, dishwashing liquid and gelatin), we produced and tested, both dielectrically and mechanically, more than 100 samples. The dielectric properties were measured from 500 MHz to 14 GHz, the Cole–Cole parameters were derived to describe the dielectric behaviour in a broader frequency range, and the results were compared with dielectric properties of human breast ex vivo tissues up to 50 GHz. The macroscale mechanical properties were measured by means of unconfined compression tests, and the impact of the experimental conditions (i.e. preload and test speed) on the measured Young’s moduli was analysed. In addition, the mechanical contrast between healthy- and malignant-tissue-like phantoms was evaluated. Main results. The results agree with the literature in the cases in which the experimental conditions are known, demonstrating the possibility to fabricate phantoms able to mimic both dielectric and mechanical properties of breast tissues. Significance. In this work, for the first time, a range of materials reproducing all the categories of breast tissues were experimentally characterized, both from a dielectric and mechanical point of view. A large range of frequency were considered for the dielectric measurements and several combinations of experimental conditions were investigated in the context of the mechanical characterization. The proposed results can be useful in the design and testing of complementary or supplementary techniques for breast cancer detection based on micro/millimetre-waves, possibly in connection with other imaging modalities.
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D’Alvia L, Carraro S, Peruzzi B, Urciuoli E, Palla L, Del Prete Z, Rizzuto E. A Novel Microwave Resonant Sensor for Measuring Cancer Cell Line Aggressiveness. SENSORS (BASEL, SWITZERLAND) 2022; 22:4383. [PMID: 35746165 PMCID: PMC9229881 DOI: 10.3390/s22124383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/01/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
The measurement of biological tissues' dielectric properties plays a crucial role in determining the state of health, and recent studies have reported microwave biosensing to be an innovative method with great potential in this field. Research has been conducted from the tissue level to the cellular level but, to date, cellular adhesion has never been considered. In addition, conventional systems for diagnosing tumor aggressiveness, such as a biopsy, are rather expensive and invasive. Here, we propose a novel microwave approach for biosensing adherent cancer cells with different malignancy degrees. A circular patch resonator was designed adjusting its structure to a standard Petri dish and a network analyzer was employed. Then, the resonator was realized and used to test two groups of different cancer cell lines, based on various tumor types and aggressiveness: low- and high-aggressive osteosarcoma cell lines (SaOS-2 and 143B, respectively), and low- and high-aggressive breast cancer cell lines (MCF-7 and MDA-MB-231, respectively). The experimental results showed that the sensitivity of the sensor was high, in particular when measuring the resonant frequency. Finally, the sensor showed a good ability to distinguish low-metastatic and high-metastatic cells, paving the way to the development of more complex measurement systems for noninvasive tissue diagnosis.
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Affiliation(s)
- Livio D’Alvia
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, 00184 Rome, Italy; (L.D.); (S.C.); (Z.D.P.)
| | - Serena Carraro
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, 00184 Rome, Italy; (L.D.); (S.C.); (Z.D.P.)
| | - Barbara Peruzzi
- Multifactorial Disease and Complex Phenotype Research Area, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy; (B.P.); (E.U.)
| | - Enrica Urciuoli
- Multifactorial Disease and Complex Phenotype Research Area, Bambino Gesù Children’s Hospital, IRCCS, 00146 Rome, Italy; (B.P.); (E.U.)
| | - Luigi Palla
- Department of Public Health and Infectious Diseases, University of Rome La Sapienza, 00185 Rome, Italy;
| | - Zaccaria Del Prete
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, 00184 Rome, Italy; (L.D.); (S.C.); (Z.D.P.)
| | - Emanuele Rizzuto
- Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, 00184 Rome, Italy; (L.D.); (S.C.); (Z.D.P.)
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Sebek J, Shrestha TB, Basel MT, Chamani F, Zeinali N, Mali I, Payne M, Timmerman SA, Faridi P, Pyle M, O’Halloran M, Dennedy MC, Bossmann SH, Prakash P. System for delivering microwave ablation to subcutaneous tumors in small-animals under high-field MRI thermometry guidance. Int J Hyperthermia 2022; 39:584-594. [DOI: 10.1080/02656736.2022.2061727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Affiliation(s)
- Jan Sebek
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, USA
- Department of Circuit Theory, Czech Technical University in Prague, Prague, Czech Republic
| | - Tej B. Shrestha
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Matthew T. Basel
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Faraz Chamani
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, USA
| | - Nooshin Zeinali
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, USA
| | - Ivina Mali
- Department of Chemistry, Kansas State University, Manhattan, KS, USA
| | - Macy Payne
- Department of Chemistry, Kansas State University, Manhattan, KS, USA
| | - Sarah A. Timmerman
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Pegah Faridi
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, USA
| | - Marla Pyle
- Department of Anatomy and Physiology, Kansas State University, Manhattan, KS, USA
| | - Martin O’Halloran
- College of Medicine, Nursing and Health Sciences, National University of Ireland Galway, Galway, Republic of Ireland
| | - M. Conall Dennedy
- College of Medicine, Nursing and Health Sciences, National University of Ireland Galway, Galway, Republic of Ireland
| | - Stefan H. Bossmann
- Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS, USA
| | - Punit Prakash
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, USA
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Sebek J, Cappiello G, Rahmani G, Zeinali N, Keating M, Fayemiwo M, Harkin J, McDaid L, Gardiner B, Sheppard D, Senanayake R, Gurnell M, O’Halloran M, Dennedy MC, Prakash P. Image-based computer modeling assessment of microwave ablation for treatment of adrenal tumors. Int J Hyperthermia 2022; 39:1264-1275. [PMID: 36137605 PMCID: PMC9820798 DOI: 10.1080/02656736.2022.2125590] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
PURPOSE To assess the feasibility of delivering microwave ablation for targeted treatment of aldosterone producing adenomas using image-based computational models. METHODS We curated an anonymized dataset of diagnostic 11C-metomidate PET/CT images of 14 patients with aldosterone producing adenomas (APA). A semi-automated approach was developed to segment the APA, adrenal gland, and adjacent organs within 2 cm of the APA boundary. The segmented volumes were used to implement patient-specific 3D electromagnetic-bioheat transfer models of microwave ablation with a 2.45 GHz directional microwave ablation applicator. Ablation profiles were quantitatively assessed based on the extent of the APA target encompassed by an ablative thermal dose, while limiting thermal damage to the adjacent normal adrenal tissue and sensitive critical structures. RESULTS Across the 14 patients, adrenal tumor volumes ranged between 393 mm3 and 2,395 mm3. On average, 70% of the adrenal tumor volumes received an ablative thermal dose of 240CEM43, while limiting thermal damage to non-target structures, and thermally sparing 83.5-96.4% of normal adrenal gland. Average ablation duration was 293 s (range: 60-600 s). Simulations indicated coverage of the APA with an ablative dose was limited when the axis of the ablation applicator was not well aligned with the major axis of the targeted APA. CONCLUSIONS Image-based computational models demonstrate the potential for delivering microwave ablation to APA targets within the adrenal gland, while limiting thermal damage to surrounding non-target structures.
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Affiliation(s)
- Jan Sebek
- Mike Wiegers Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA
| | - Grazia Cappiello
- Translational Medical Devices Lab, National University of Ireland, Galway, Republic of Ireland
| | - George Rahmani
- Department of Radiology, Galway University Hospitals, Galway, Republic Ireland
| | - Nooshin Zeinali
- Mike Wiegers Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA
| | - Muireann Keating
- School of Medicine, National University of Ireland, Galway, Republic Ireland
| | - Michael Fayemiwo
- School of Computing, Engineering, and Intelligent Systems, Ulster University, Londonderry, Northern Ireland
| | - Jim Harkin
- School of Computing, Engineering, and Intelligent Systems, Ulster University, Londonderry, Northern Ireland
| | - Liam McDaid
- School of Computing, Engineering, and Intelligent Systems, Ulster University, Londonderry, Northern Ireland
| | - Bryan Gardiner
- School of Computing, Engineering, and Intelligent Systems, Ulster University, Londonderry, Northern Ireland
| | - Declan Sheppard
- Department of Radiology, Galway University Hospitals, Galway, Republic Ireland
| | | | - Mark Gurnell
- Institute of Metabolic Science, University of Cambridge, United Kingdom
| | - Martin O’Halloran
- Translational Medical Devices Lab, National University of Ireland, Galway, Republic of Ireland
| | - M. Conall Dennedy
- School of Medicine, National University of Ireland, Galway, Republic Ireland
| | - Punit Prakash
- Mike Wiegers Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA.,Author to whom correspondence should be addressed: Punit Prakash, 3078 Engineering Hall, 1701D Platt St, Kansas State University, Manhattan, KS 66506, USA.
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Zia G, Sebek J, Prakash P. Temperature-dependent dielectric properties of human uterine fibroids over microwave frequencies. Biomed Phys Eng Express 2021; 7. [PMID: 34534970 DOI: 10.1088/2057-1976/ac27c2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 09/17/2021] [Indexed: 12/15/2022]
Abstract
Microwave ablation is under investigation as a minimally-invasive treatment for uterine fibroids. Computational models play a vital role in the development, evaluation and characterization of candidate ablation devices. The temperature-dependent dielectric properties of fibroid tissue are essential for accurate computational modeling.Objective:To measure the broadband temperature-dependent dielectric properties of uterine fibroids excised during hysterectomy procedures.Methods: The open-ended coaxial probe method was employed for measuring the broadband dielectric properties of freshly excised human uterine fibroid samples (n = 6) obtained from an IRB-approved tissue bank. The dielectric properties (relative permittivity,εr, and effective electrical conductivity,σeff) were evaluated at temperatures ranging from 23 °C-150 °C, over the frequency range of 0.5-6 GHz. Linear piecewise parametrization with respect to temperature and quadratic parametrization with respect to frequency was applied to characterize broadband temperature-dependent dielectric properties of fibroid tissue.Results: The baseline room temperature values ofεrvary from 57.5 ± 5.29 to 44.5 ± 5.77 units andσeffchanges from 0.91 ± 0.19 to 6.02 ± 0.7 S m-1over the frequency range of 0.5-6 GHz. At temperatures close to the water vaporization point,εr, drops considerably i.e. to 12%-14% of its baseline value for all measured frequencies.σeffvalues initially rise till 98 °C and then fall to 11%-13% of their baseline values at 125 °C for frequencies ≤2.45 GHz. Theσefffollows a decreasing trend for frequencies >2.45 GHz and drops to ∼6 % of their baseline room temperature values.Conclusion:The temperature dependent dielectric properties of uterine fibroid tissues over microwave frequency range are reported for the first time in this study. Parametric models of uterine fibroid dielectric properties are also presented for incorporation within computational models of microwave ablation of fibroids.
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Affiliation(s)
- Ghina Zia
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, United States of America
| | - Jan Sebek
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, United States of America.,Department of Circuit Theory, Czech Technical University in Prague, Prague, Czech Republic
| | - Punit Prakash
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS, United States of America
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Khan MS, Hawlitzki M, Taheri SM, Rose G, Schweizer B, Brensing A. Investigation of Microwave Ablation Process in Sweet Potatoes as Substitute Liver. SENSORS 2021; 21:s21113894. [PMID: 34200011 PMCID: PMC8200201 DOI: 10.3390/s21113894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 05/28/2021] [Accepted: 05/31/2021] [Indexed: 12/24/2022]
Abstract
The microwave ablation technique to destroy cancer tissues in liver is practiced clinically and is the subject of ongoing research, e.g., ablation monitoring. For studies, liver tissue from cattle or pigs is often used as a substitute material. In this work, sweet potato is presented as an alternative material for microwave ablation experiments in liver due to similar material properties. Sweet potatoes as a substitute for liver have the advantages of better handling, easy procurement and stable material properties over time for microwave ablation experiments. The dielectric constant and electrical conductivity of sweet potato are characterized for temperature variation with the help of high-temperature dielectric probe. Furthermore, a test setup is presented for microwave ablation experiments in which a bowtie slot antenna matched to sweet potato is placed on its surface to directly receive the microwave power from a self-developed microwave applicator inserted into a sweet potato 4 cm below the surface antenna. A high-power source was used to excite the microwave powers up to 80 W and a spectrum analyzer was used to measure the signal received by the surface antenna. The experiments were performed in an anechoic chamber for safety reasons. Power at 50 W and 80 W was stimulated for a maximum of 600 s at the 2.45 GHz ISM band in different sweet potato experiments. A correlation is found between the power received by the surface antenna and rise of temperature inside sweet potato; relative received power drops from 1 at 76 ∘C to 0.6 at 88 ∘C (max. temperature) represents a 40% relative change in a 50 W microwave ablation experiment. The received power envelope at the surface antenna is between 10 mW and 32 mW during 50 W microwave ablation. Other important results for 10 min, 80 W microwave ablation include: a maximum ablation zone short axis diameter of 4.5 cm and a maximum ablation temperature reached at 99 ∘C, 3 mm away from the applicator’s slot. The results are compared with the state of the art in microwave ablation in animal liver. The dielectric constant and electrical conductivity evolution of sweet potato with rising temperature is comparable to animal liver in 50–60 ∘C range. The reflection loss of self-developed applicator in sweet potato is below 15 dB which is equal to reflection loss in liver experiments for 600 s. The temperature rise for the first 90 s in sweet potato is 76 ∘C as compared to 73 ∘C in liver with 50 W microwave ablation. Similarly, with 80–75 W microwave ablation, for the first 60 s, the temperature is 98 ∘C in sweet potato as compared to 100 ∘C in liver. The ablation zone short-axis diameter after 600 s is 3.3 cm for 50 W microwave ablation in sweet potato as compared to 3.5 cm for 30 W microwave ablation in liver. The reasons for difference in microwave ablation results in sweet potato and animal liver are discussed. This is the first study to directly receive a signal from microwave applicator during a microwave ablation process with the help of a surface antenna. The work can be extended to multiple array antennas for microwave ablation monitoring.
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Affiliation(s)
- Muhammad Saad Khan
- Department of Engineering, RheinMain University of Applied Sciences, 65428 Ruesselsheim, Germany; (M.H.); (S.M.T.); (B.S.); (A.B.)
- Correspondence:
| | - Michael Hawlitzki
- Department of Engineering, RheinMain University of Applied Sciences, 65428 Ruesselsheim, Germany; (M.H.); (S.M.T.); (B.S.); (A.B.)
| | - Shadan Mofrad Taheri
- Department of Engineering, RheinMain University of Applied Sciences, 65428 Ruesselsheim, Germany; (M.H.); (S.M.T.); (B.S.); (A.B.)
| | - Georg Rose
- Institute of Medical Engineering and Research Campus STIMULATE, Otto Von Guericke University, 39106 Magdeburg, Germany;
| | - Bernd Schweizer
- Department of Engineering, RheinMain University of Applied Sciences, 65428 Ruesselsheim, Germany; (M.H.); (S.M.T.); (B.S.); (A.B.)
| | - Andreas Brensing
- Department of Engineering, RheinMain University of Applied Sciences, 65428 Ruesselsheim, Germany; (M.H.); (S.M.T.); (B.S.); (A.B.)
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