scholarly journals Optimization of an Endoscopic Radiofrequency Ablation Electrode

2018 ◽  
Vol 12 (3) ◽  
Author(s):  
Bradley Hanks ◽  
Mary Frecker ◽  
Matthew Moyer
Keyword(s):  
Radiofrequency Ablation ◽  
Thermal Ablation ◽  
Computational Models ◽  
Optimization Procedure ◽  
Pancreatic Tissue ◽  
Design Parameters ◽  
Electrode Design ◽  
Systematic Design ◽  
Spherical Tumor ◽  
Compliant Electrode

Radiofrequency ablation (RFA) is an increasingly used, minimally invasive, cancer treatment modality for patients who are unwilling or unable to undergo a major resective surgery. There is a need for RFA electrodes that generate thermal ablation zones that closely match the geometry of typical tumors, especially for endoscopic ultrasound-guided (EUS) RFA. In this paper, the procedure for optimization of an RFA electrode is presented. First, a novel compliant electrode design is proposed. Next, a thermal ablation model is developed to predict the ablation zone produced by an RFA electrode in biological tissue. Then, a multi-objective genetic algorithm is used to optimize two cases of the electrode geometry to match the region of destructed tissue to a spherical tumor of a specified diameter. This optimization procedure is then applied to EUS-RFA ablation of pancreatic tissue. For a target 2.5 cm spherical tumor, the optimal design parameters of the compliant electrode design are found for two cases. Cases 1 and 2 optimal solutions filled 70.9% and 87.0% of the target volume as compared to only 25.1% for a standard straight electrode. The results of the optimization demonstrate how computational models combined with optimization can be used for systematic design of ablation electrodes. The optimization procedure may be applied to RFA of various tissue types for systematic design of electrodes for a specific target shape.

Optimization of a Compliant Endoscopic Radiofrequency Ablation Electrode

2017 ◽  
Author(s):  
Bradley Hanks ◽  
Mary Frecker ◽  
Matthew Moyer
Keyword(s):  
Radiofrequency Ablation ◽  
Computational Models ◽  
Optimization Procedure ◽  
Pancreatic Tissue ◽  
Design Parameters ◽  
Electrode Design ◽  
Systematic Design ◽  
Objective Functions ◽  
Spherical Tumor ◽  
Compliant Electrode

Radiofrequency ablation (RFA) is a common cancer treatment modality for patients who are ineligible for open surgery. There is a need for RFA electrodes that generate heating zones that closely match the geometry of typical tumors, especially for endoscopic ultrasound-guided (EUS) RFA. In this paper, the procedure for optimization of an RFA electrode is presented. First, a novel compliant electrode design is proposed. Next, a thermal ablation model is developed to predict the ablation zone surrounding an RFA electrode in biological tissue. Then, a multi-objective genetic algorithm is used to optimize two cases of the electrode geometry to match the region of destructed tissue to a spherical tumor of specified diameter. This optimization procedure is applied to an EUS-RFA ablation of pancreatic tissue. For a target 2.5cm spherical tumor, the optimal design parameters of the compliant electrode design were found. After simulating 40 generations of 50 designs per generation, both cases converged to optimal solutions. The objective functions were useful for simple electrode designs. For more complex electrode designs, the objective functions were unable to direct the design toward a 2.5cm sphere. The results of the optimization demonstrate how computational models combined with optimization can be used for systematic design of ablation electrodes. The optimization procedure may be applied to RFA of various tissue types for systematic design of electrodes that generate spherical ablation zones.

Optimization of a Cemented Femoral Prosthesis Considering Bone Remodeling

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Leandro Luis Corso ◽  
Leandro de Freitas Spinelli ◽  
Fernando Schnaid ◽  
Crisley Dossin Zanrosso ◽  
Rogério José Marczak
Keyword(s):  
Bone Loss ◽  
Bone Remodeling ◽  
Hip Replacement ◽  
Computational Models ◽  
Three Dimensional ◽  
Femoral Stem ◽  
Optimization Procedure ◽  
Design Parameters ◽  
Femoral Bone ◽  
Bone Mass Loss

The study presents a numerical methodology for minimizing the bone loss in human femur submitted to total hip replacement (THR) procedure with focus on cemented femoral stem. Three-dimensional computational models were used to describe the femoral bone behavior. An optimization procedure using the genetic algorithm (GA) method was applied in order to minimize the bone loss, considering the geometry and the material of the prosthesis as well as the design of the stem. Internal and external bone remodeling were analyzed numerically. The numerical method proposed here showed that the bone mass loss could be reduced by 24%, changing the design parameters.

Optimization of Turbofan Propulsion Cycle Using a Genetic Algorithm

2010 ◽  
Author(s):  
Adel Ghenaiet
Keyword(s):  
Genetic Algorithm ◽  
Fuel Consumption ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Optimization Procedure ◽  
Specific Fuel Consumption ◽  
High Mass ◽  
Design Parameters ◽  
Inlet Temperature ◽  
Simplifying Assumptions

This paper presents an evolutionary approach as the optimization framework to design for the optimal performance of a high-bypass unmixed turbofan to match with the power requirements of a commercial aircraft. The parametric analysis had the objective to highlight the effects of the principal design parameters on the propulsive performance in terms of specific fuel consumption and specific thrust. The design optimization procedure based on the genetic algorithm PIKAIA coupled to the developed engine performance analyzer (on-design and off-design) aimed at finding the propulsion cycle parameters minimizing the specific fuel consumption, while meeting the required thrusts in cruise and takeoff and the restrictions of temperatures limits, engine size and weight as well as pollutants emissions. This methodology does not use engine components’ maps and operates on simplifying assumptions which are satisfying the conceptual or early design stages. The predefined requirements and design constraints have resulted in an engine with high mass flow rate, bypass ratio and overall pressure ratio and a moderate turbine inlet temperature. In general, the optimized engine is fairly comparable with available engines of equivalent power range.

scholarly journals Artificial neural networks for inverse design of resonant nanophotonic components with oscillatory loss landscapes

Nanophotonics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 385-392
Author(s):  
Joeri Lenaerts ◽  
Hannah Pinson ◽  
Vincent Ginis
Keyword(s):  
Machine Learning ◽  
Optimization Procedure ◽  
Linear Mapping ◽  
Inverse Design ◽  
Design Parameters ◽  
Second Step ◽  
Input Parameters ◽  
Novel Variant ◽  
Resonant Systems ◽  
The Fourier Transform

AbstractMachine learning offers the potential to revolutionize the inverse design of complex nanophotonic components. Here, we propose a novel variant of this formalism specifically suited for the design of resonant nanophotonic components. Typically, the first step of an inverse design process based on machine learning is training a neural network to approximate the non-linear mapping from a set of input parameters to a given optical system’s features. The second step starts from the desired features, e.g. a transmission spectrum, and propagates back through the trained network to find the optimal input parameters. For resonant systems, this second step corresponds to a gradient descent in a highly oscillatory loss landscape. As a result, the algorithm often converges into a local minimum. We significantly improve this method’s efficiency by adding the Fourier transform of the desired spectrum to the optimization procedure. We demonstrate our method by retrieving the optimal design parameters for desired transmission and reflection spectra of Fabry–Pérot resonators and Bragg reflectors, two canonical optical components whose functionality is based on wave interference. Our results can be extended to the optimization of more complex nanophotonic components interacting with structured incident fields.

scholarly journals Polyadic Cantor Fractal Ultrasonic Lenses: Design and Characterization

2018 ◽  
Vol 8 (8) ◽  
pp. 1389 ◽  
Author(s):  
Sergio Castiñeira-Ibáñez ◽  
Daniel Tarrazó-Serrano ◽  
Jose Fuster ◽  
Pilar Candelas ◽  
Constanza Rubio
Keyword(s):  
Thermal Ablation ◽  
Dynamic Control ◽  
Design Parameters ◽  
Medical Applications ◽  
Curved Surfaces ◽  
Ultrasonic Beam ◽  
Acoustic Lens ◽  
Acoustic Profile ◽  
Made In

Traditional acoustic lenses modulate the ultrasonic beam due to their curved surfaces and the refractive material of which they are made. In this work, a different type of acoustic lens, based on Polyadic Cantor Fractals (PCF), is presented and thoroughly analyzed. These new Polyadic Cantor Fractal Lenses (PCFLs) are completely flat and easy to build, and they present interesting modulation capabilities over the acoustic profile. The dependence of the focusing profile on the PCFL design parameters is fully characterized, and it is shown that certain design parameters provide a dynamic control, which is critical in many medical applications such as thermal ablation of tumors.

scholarly journals Radiofrequency Ablation for Treatment of Symptomatic Uterine Fibroids

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Siân Jones ◽  
Peter O'Donovan ◽  
David Toub
Keyword(s):  
Radiofrequency Ablation ◽  
Thermal Energy ◽  
Thermal Ablation ◽  
Mechanical Energy ◽  
Symptomatic Relief ◽  
Uterine Fibroids ◽  
Ultrasound Waves ◽  
Associated Symptoms ◽  
Fibroid Volume

The use of thermal energy-based systems to treat uterine fibroids has resulted in a plethora of devices that are less invasive and potentially as effective in reducing symptoms as traditional options such as myomectomy. Most thermal ablation devices involve hyperthermia (heating of tissue), which entails the conversion of an external electromagnetic or ultrasound waves into intracellular mechanical energy, generating heat. What has emerged from two decades of peer-reviewed research is the concept that hyperthermic fibroid ablation, regardless of the thermal energy source, can create large areas of necrosis within fibroids resulting in reductions in fibroid volume, associated symptoms and the need for reintervention. When a greater percentage of a fibroid's volume is ablated, symptomatic relief is more pronounced, quality of life increases, and it is more likely that such improvements will be durable. We review radiofrequency ablation (RFA), one modality of hyperthermic fibroid ablation.

scholarly journals Modified Koch Fractal Antenna for Multi and Wideband Wireless Applications

2021 ◽  
Vol 19 (2) ◽  
pp. 182-189
Author(s):  
Shweta Rani ◽  
Sushil Kakkar
Keyword(s):  
Numerical Simulations ◽  
Impedance Matching ◽  
Optimization Procedure ◽  
Design Parameters ◽  
Impedance Bandwidth ◽  
Fractal Antenna ◽  
Bacterial Foraging Optimization ◽  
Koch Curve ◽  
Wireless Applications ◽  
Koch Fractal

This paper focuses on the design and development of modified Koch fractal antenna. Compared to traditional Koch curve antenna, the presented antenna possesses a greater number of frequency bands and better impedance matching. Furthermore, the bacterial foraging optimization (BFO) approach is implemented to enhance the impedance bandwidth. The developed technique has been verified by employing various numerical simulations. The design parameters generated from the optimization procedure have been utilized to manufacture the antenna and the respective experimental and simulated results compared. The measured results show that the designed antenna exhibits multi and wideband behavior, covering WLAN, WIMAX, and various other wireless applications.

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