Electromagnetic Power Distribution Research Articles

ODP638 Towards the development of treatment planning for microwave thermal ablation of adrenal adenomas

Abstract Primary aldosteronism (PA) is the principal cause of secondary hypertension and accounts for 5-12% of all hypertension. PA is characterized by unregulated aldosterone secretion from unilateral or bilateral nodules on the adrenal glands. High levels of aldosterone are associated with an increased risk of cardiovascular and cerebrovascular complications. Conventional therapy includes adrenalectomy and mineralocorticoid receptor antagonists. These carry the challenges of surgical complication and poor tolerability to medication side effects. Moreover, no definitive therapy exists for bilateral PA driven by nodular disease. Microwave thermal ablation (MTA) offers a percutaneous alternative to adrenalectomy for PA and with precision engineering of microwave antennae may also offer a definitive option for bilateral PA. MTA can be applied to select and localize therapy to aldosterone producing adenomas while preserving the surrounding functional adrenocortical tissue. Advance treatment planning is essential to optimize the following parameters (i) microwave power delivery, (ii) probe placement, (iii) heat-sink minimisation. We present a novel and state-of-the-art simulated treatment planning approach to adrenal MTA through 3D anatomic reconstruction and dielectric electromagnetic modeling to predict therapeutic response. MTA consists of a microwave applicator antenna to transfer the electromagnetic (EM) energy and induce cytotoxic hyperthermia. The EM power distribution across tissue is calculated by solving the Maxwell's equations. The Finite-Difference Time-Domain (FDTD) method computes the SAR (Specific Absorption Rate) patterns and the Pennes’ bio heat equation models the bioheat transfer within the adrenal gland. Treatment planning combines CT abdomen and 11C-metomidate PET/CT images to generate a 3D patient specific model using a segmentation routine in iSeg (version 3.1, Speag, Zurich, Switzerland)) which is combined with the applicator model in Sim4Life (version 6.2, Speag, Zurich, Switzerland). Electrical and thermal properties of the organ are assigned and the microwave power is modelled to optimally and selectively heat the target tissue while minimizing damage to adjacent cortical tissue. We present results from 3D computational modelling derived from patient imaging-scans employed to predict the thermal ablation zone in patients affected by PA. Using this system, anatomically, dielectrically and thermally accurate models of adrenal glands, nodules and adjacent sensitive structures were reconstructed and energy delivery strategies were evaluated. This method was used to assess the ability to inform appropriate power settings and probe placement for ablating adrenal gland nodules. Treatment planning not only represents an important tool to precisely deliver controlled doses of microwave thermal therapy in the context of adrenal ablation but also represents an important tool to inform future applicator probe design and appropriate imaging. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Mechanism of PV Generation System Damping Electromechanical Oscillations

For physically understanding the dynamic response of the photovoltaic (PV) integrated power system for electromechanical oscillations damping, firstly, this paper develops the linear mathematical model of a single machine infinite bus system integrated by the PV grid-tied inverter under the electromechanical time scale. Then, based on the electric torque analysis method, and the functional route of the PV grid-tied inverter variable active power control (P-control) and reactive power control (Q-control) with the power angle or grid frequency feedback as the input control signal, the key factors and influence laws of the integrated system inertia, damping level and synchronization capability are investigated. The developed model shows that enlarging the proportional-integral-derivative (PID) controller parameters of P and/or Q-control loop can effectively change electromagnetic power distribution to suppress the imbalance power, and equivalently improve the system damping level, synchronization capability and inertial effect, respectively, contributing to actively adjust the grid frequency oscillation amplitude, period and recovery speed to maintain the system control stability according to the grid code demand. Besides, under the same inverter capacity constraint, P-control mode is proved more advantageous than Q-control mode to damp electromechanical oscillations. Finally, the correctness of the physical mechanism analysis is verified by MATLAB simulations and RT-LAB experiments.

Distillation of essential oil and simulation of electromagnetic power distribution in a microwave oven

In the present study, the essential oil from the leaves of River Red Gum (Eucalyptus camaldulensis Dehnh) was distilled by microwave applied in situ hydrodistillation (MWHD) and the properties obtained were compared with hydrodistillation (HD) techniques. The chemical composition of essential oil obtained by the microwave method was analyzed by gas chromatography (GC) and GC–mass spectrometry (MS). The results showed that the essential oil from E. camaldulensis could successfully be distilled by using microwave irradiation power. Microwave power has been supplied from a cavity having a multimode microwave reactor 2455 MHz with a maximum power of 1000 W. Electromagnetic power distribution has been analyzed inside the cavity. The yield of essential oil increased with increasing microwave irradiation power. It was also found that the content of main compounds clearly varied according to methods applied. However, the yield of essential oil determined by MWHD was slightly lower than that of conventional HD method at conditions studied.

Scaling model experiments on propagation of electromagnetic waves using salt solution to simulate the Earth's crust: Loma Prieta and Kobe earthquakes

Propagation of electromagnetic (EM) waves from an earthquake focus in the conductive Earth has been investigated using 1/1,000,000 scaling models taking earth-ionosphere and ocean-Moho plane parallel-plate waveguides into account. Microwaves at a frequency, ω m, a million times higher than that of seismic EM signal (SEMS), ω, were generated at the model focus. They are propagated in a salt solution modeling the earth's crust and reflected by ocean, fault planes, ionosphere and Moho plane all made by aluminum. Distribution of EM power was mapped by scanning a detector antenna over the model Earth's surface. The skin depth, δ, calculated by the exact skin depth equation, 1/ δ= ω( με/2) 1/2 [(1+(1/ ωερ) 2) 1/2 −1] 1/2 where dielectric constant, ε and permeability, μ are the same but resistivity, ρ, 10 −6 times smaller than that of Earth, gave 10 −6 times small skin depth validating the model scaling index. Images for evanescent and wave-ripple standing waves disturbed by normal, strike-slip and dip-slip conductive fault planes have been obtained using an aluminum plate. The co-circular contour map above the epicenter due to evanescence was pushed to the north east direction from the epicenter by the presence of ocean for the Loma Prieta earthquake, while to north direction for the Kobe earthquake. The intensity of EM ULF emissions for the Loma Prieta earthquake is discussed quantitatively.

Calculation of change in brain temperatures due to exposure to a mobile phone

In this study we evaluated for a realistic head model the 3D temperature rise induced by a mobile phone. This was done numerically with the consecutive use of an FDTD model to predict the absorbed electromagnetic power distribution, and a thermal model describing bioheat transfer both by conduction and by blood flow. We calculated a maximum rise in brain temperature of 0.11 °C for an antenna with an average emitted power of 0.25 W, the maximum value in common mobile phones, and indefinite exposure. Maximum temperature rise is at the skin. The power distributions were characterized by a maximum averaged SAR over an arbitrarily shaped 10 g volume of approximately 1.6 W kg-1. Although these power distributions are not in compliance with all proposed safety standards, temperature rises are far too small to have lasting effects. We verified our simulations by measuring the skin temperature rise experimentally. Our simulation method can be instrumental in further development of safety standards.

Effect of the Near Field on the Electromagnetic Power Distribution in Annular Antenna Arrays

Effect of the Near Field on the Electromagnetic Power Distribution in Annular Antenna Arrays

Near-Field Effects in the Electromagnetic Power Distribution in the Vicinity of an Array of Hertzian Dipoles

Near-Field Effects in the Electromagnetic Power Distribution in the Vicinity of an Array of Hertzian Dipoles

Electromagnetic energy deposition inside a three-layer cylindrical human body model caused by near-field radiators

The electromagnetic power distribution inside a three-layer cylindrical model irradiated by a loop or an aperture antenna is examined. The cylindrical configuration has been adopted to represent parts of the human body with similar shape, such as the torso or limb. The complex electromagnetic problem is formulated with the aid of the Green's function theory. The Green's function for the three-layer cylindrical structure is determined as the response to a unit excitation located outside the cylinder. The response to the radiators under examination is found. Numerical results are presented for several radiator dimensions and locations. A new applicator with enhanced penetration depth is proposed. >