Experimental Validation of Computational Models of Microwave Tissue Heating with Magnetic Resonance Thermometry

Faridi, Pegah; Prakash, Punit

doi:10.1109/mwsym.2018.8439359

Cited by 4 publications

(4 citation statements)

References 11 publications

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“…By establishing the relationship between dosages and effects, mathematical models are of paramount importance for predicting the impact of deposited thermal energy via numerical simulations, especially because these issues are hard to assess experimentally. Specific clinical applications incorporating mathematical bioheat models include thermal damage and heat deposition models for microwave thermal ablations (Chiang, Wang, & Brace, 2013), interstitial laser thermal therapies (Fuentes et al, 2009), microwave thermal therapy systems (Faridi & Prakash, 2018), endoluminal and interstitial ultrasound thermotherapy (Prakash, Salgaonkar, & Diederich, 2013), and nanoparticle‐mediated hyperthermal cancer therapy (Kaddi, Phan, & Wang, 2013; Orthaber, Pristovnik, Skok, Perić, & Maver, 2017), to name only a few.…”

Section: Computational Thermoregulatory Modelsmentioning

confidence: 99%

Thermoregulation: A journey from physiology to computational models and the intensive care unit

Skok

Duh

Stožer

et al. 2020

WIREs Mechanisms of Disease

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Thermoregulation plays a vital role in homeostasis. Many species of animals as well as humans have evolved various physiological mechanisms for body temperature control, which are characteristically flexible and enable a fine‐tuned spatial and temporal regulation of body temperature in different environmental conditions and circumstances. Human beings normally maintain a core body temperature at around 37°C, and maintenance of this relatively high temperature is critical for survival. Therefore, principles of thermoregulatory control have also important clinical implications. Infections can cause the body temperature to rise internally and several diseases can cause a dysfunction of thermoregulatory mechanisms. Moreover, the utilization of thermotherapies in treating various diseases has been known for thousands of years with a recent resurgence of interest. An increasing amount of research suggests that targeted temperature management is of paramount importance to patient outcomes in certain clinical scenarios. We provide a concise summary of the basic concepts of thermoregulation. Emphasis is given to the principles of thermoregulation in humans in basic pathological states and to targeted temperature management strategies in the clinical environment, with special attention on therapeutic hypothermia in postcardiac arrest patients. Finally, the discussion is focused on the potential offered by computational thermophysiological models for predicting thermal responses of patients in various clinical circumstances, for proposing new perspectives in the design of novel thermal therapies, and to optimize targeted temperature management strategies.This article is categorized under: Cardiovascular Diseases > Computational Models Cardiovascular Diseases > Environmental Factors Cardiovascular Diseases > Biomedical Engineering

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Section: Computational Thermoregulatory Modelsmentioning

confidence: 99%

Thermoregulation: A journey from physiology to computational models and the intensive care unit

Skok

Duh

Stožer

et al. 2020

WIREs Mechanisms of Disease

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“…The DSC between the simulated and measured ΔT= 6 °C and 8 °C isotherms were 0.97 ± 0.02 and 0.98 ± 0.01, respectively, which suggests that computational model predicts temperatures that are in alignment with experimental measurements. We have previously comparatively assessed the validity of simulated transient temperature profiles in multiple ROIs with MR thermometry and the maximum error between simulated and MR measured temperatures were 0.7 °C [37].…”

Section: Experimental Assessment Of Computational Modelsmentioning

confidence: 99%

Simulation-based design and characterization of a microwave applicator for MR-guided hyperthermia experimental studies in small animals

Faridi

Bossmann

Prakash

2019

Biomed. Phys. Eng. Express

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Purpose:The objective of this study was to design and characterize a 2.45 GHz microwave hyperthermia applicator for delivering hyperthermia in experimental small animals to 2 -4 mm diameter targets located 1 -3 mm from the skin surface, with minimal heating of the surrounding tissue, under 14.1 T MRI real-time monitoring and feedback control. Materials and methods:An experimentally validated 3D computational model was employed to design and characterize a non-invasive directional water-cooled microwave hyperthermia applicator. We assessed the effects of: reflector geometry, monopole shape, cooling water temperature, and flow rate on spatial-temperature profiles. The system was integrated with realtime MR thermometry and feedback control to monitor and maintain temperature elevations in the range of 4 -5 °C at 1 -3 mm from the applicator surface. The quality of heating was quantified by determining the fraction of the target volume heated to the desired temperature, and the extent of heating in non-targeted regions.Results: Model-predicted hyperthermic profiles were in good agreement with experimental measurements (Dice Similarity Coefficient of 0.95 -0.99). Among the four considered criteria, a reflector aperture angle of 120 °, S-shaped monopole antenna with 0.6 mm displacement, and coolant flow rate of 150 ml/min were selected as the end result of the applicator design. The temperature of circulating water and input power were identified as free variables, allowing considerable flexibility in heating target sizes within varying distances from the applicator surface. 2 -4 mm diameter targets positioned 1 -3 mm from the applicator surface were heated to hyperthermic temperatures, with target coverage ratio ranging between 76 -93 % and 11 -26 % of non-targeted tissue heated. Conclusion:We have designed an experimental platform for MR-guided hyperthermia, incorporating a microwave applicator integrated with temperature-based feedback control to heat deep-seated targets for experimental studies in small animals.

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“…35 With advances in MR thermometry sequence development, multi-slice thermometry with update times of under 10 s are now available, offering a potential avenue for three-dimensional (3D) measurement of transient temperature profiles during ablation procedures. 23 In our earlier study, 36 we presented a preliminary assessment of 3D computational models of microwave thermal therapy (over the temperature range 20°C-45°C) in an agar phantom using a 14.1 T ultra-high field small-animal MR scanner. Due to the limited size of the high-field small-animal scanner, the phantom diameter was restricted to 27 mm, and the use of power levels typically used during ablative exposures was precluded.…”

Section: Introductionmentioning

confidence: 99%

“…In our earlier study, 36 we presented a preliminary assessment of 3D computational models of microwave thermal therapy (over the temperature range 20°C–45°C) in an agar phantom using a 14.1 T ultra‐high field small‐animal MR scanner. Due to the limited size of the high‐field small‐animal scanner, the phantom diameter was restricted to 27 mm, and the use of power levels typically used during ablative exposures was precluded.…”

Section: Introductionmentioning

confidence: 99%

Experimental assessment of microwave ablation computational modeling with MR thermometry

et al. 2020

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Computational models are widely used during the design and characterization of microwave ablation (MWA) devices, and have been proposed for pretreatment planning. Our objective was to assess three-dimensional (3D) transient temperature and ablation profiles predicted by MWA computational models with temperature profiles measured experimentally using magnetic resonance (MR) thermometry in ex vivo bovine liver. Materials and methods: We performed MWA in ex vivo tissue under MR guidance using a custom, 2.45 GHz water-cooled applicator. MR thermometry data were acquired for 2 min prior to heating, during 5-10 min microwave exposures, and for 3 min following heating. Fiber-optic temperature sensors were used to validate the accuracy of MR temperature measurements. A total of 13 ablation experiments were conducted using 30-50 W applied power at the applicator input. MWA computational models were implemented using the finite element method, and incorporated temperature-dependent changes in tissue physical properties. Model-predicted ablation zone extents were compared against MRI-derived Arrhenius thermal damage maps using the Dice similarity coefficient (DSC). Results: Prior to heating, the observed standard deviation of MR temperature data was in the range of 0.3-0.7°C. Mean absolute error between MR temperature measurements and fiber-optic temperature probes during heating was in the range of 0.5-2.8°C. The mean DSC between model-predicted ablation zones and MRI-derived Arrhenius thermal damage maps for 13 experimental setups was 0.95. When comparing simulated and experimentally (i.e. using MRI) measured temperatures, the mean absolute error (MAE %) relative to maximum temperature change was in the range 5%-8.5%. Conclusion: We developed a system for characterizing 3D transient temperature and ablation profiles with MR thermometry during MWA in ex vivo liver tissue, and applied the system for experimental validation of MWA computational models.

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Experimental Validation of Computational Models of Microwave Tissue Heating with Magnetic Resonance Thermometry

Cited by 4 publications

References 11 publications

Thermoregulation: A journey from physiology to computational models and the intensive care unit

Thermoregulation: A journey from physiology to computational models and the intensive care unit

Simulation-based design and characterization of a microwave applicator for MR-guided hyperthermia experimental studies in small animals

Experimental assessment of microwave ablation computational modeling with MR thermometry

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