The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
Lei Dong - One of the best experts on this subject based on the ideXlab platform.
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Comparison of Temperature curve and ablation zone between 915 MHz and 2450 MHz cooled-shaft microwave antenna:results in ex vivo porcine livers
Chinese Journal of Ultrasonography, 2011Co-Authors: Lei DongAbstract:Objective To compare Temperature curve and ablation zone between 915 MHz and 2450 MHz cooled shaft microwave antenna in ex vivo porcine livers.Methods The 915 MHz and 2450 MHz microwave ablation and thermal monitor system were used in this study.A total of 56 ablation zones and 280 Temperature data were obtained in ex vivo porcine livers.The output powers were 50,60,70,and 80W and the setting time was 600s.The Temperature curve of every Temperature Spot,the short- and long-axis diameters of the coagulation zones were recorded and measured.Results At all four power output settings,the peak Temperatures of every Temperature Spot had a tendency to increase accordingly as the output power was increased,and except for 5 mm away from the antenna,the peak Temperatures for the 915 MHz cooledshaft antenna were significantly higher than those for the 2450 MHz cooled-shaft antenna (P ＜0.05).Meanwhile,the short- and long-axis diameters for the 915 MHz cooled-shaft antenna were significantly larger than those for the 2450 MHz cooled-shaft antenna ( P ＜0.05).Conclusions The 915 MHz cooledshaft antenna can yield a significantly larger ablation zone and achieve higher Temperature in ablation zone than 2450 MHz cooled-shaft antenna in ex vivo porcine livers. Key words: Microwaves/therapeuticuse; Liver; Catheter ablation
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Comparison of Temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna: Results in ex vivo porcine livers
European Journal of Radiology, 2011Co-Authors: Zhigang Cheng, Lei Dong, Guoming Zhang, Yang Wang, Ping LiangAbstract:Abstract Objective To compare Temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna in ex vivo porcine livers. Materials and methods The 915- and 2450-MHz microwave ablation and thermal monitor system were used in this study. A total of 56 ablation zones and 280 Temperature data were obtained in ex vivo porcine livers. The output powers were 50, 60, 70, and 80 W and the setting time was 600 s. The Temperature curve of every Temperature Spot, the short- and long-axis diameters of the coagulation zones were recorded and measured. Results At all four power output settings, the peak Temperatures of every Temperature Spot had a tendency to increase accordingly as the MW output power was increased, and except for 5 mm away from the antenna, the peak Temperatures for the 915 MHz cooled-shaft antenna were significantly higher than those for the 2450 MHz cooled-shaft antenna ( p p Conclusion The 915 MHz cooled-shaft antenna can yield a significantly larger ablation zone and achieve higher Temperature in ablation zone than a 2450 MHz cooled-shaft antenna in ex vivo porcine livers.
K G Strassmeier - One of the best experts on this subject based on the ideXlab platform.
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Light‐curve inversions with truncated least‐squares principal components: Tests and application to HD 291095 = V1355 Orionis
Astronomische Nachrichten, 2008Co-Authors: I S Savanov, K G StrassmeierAbstract:We present a new inversion code that reconstructs the stellar surface Spot configuration from the light curve of a rotating star. Our code employs a method that uses the truncated least-squares estimation of the inverse problem's objects principal components. We use Spot filling factors as the unknown objects. Various test cases that represent a rapidly-rotating K subgiant are used for the forward problem. Tests are then performed to recover the artificial input map and include data errors and input-parameter errors. We demonstrate the robustness of the solution to false input parameters like photospheric Temperature, Spot Temperature, gravity, inclination, unSpotted brightness and different Spot distributions and we also demonstrate the insensitivity of the solution to Spot latitude. Tests with Spots peppered over the entire stellar surface or with phase gaps do not produce fake active longitudes. The code is then applied to ten years of V and I -band light curve data of the Spotted sub-giant HD291095. A total of 22 light curves is presented. We find that for most of the time its Spots were grouped around two active longitudes separated on average by 180°. Switches of the dominant active region between these two longitudes likely occurred about every 3.15±0.23 years while the amplitude modulation of the brightness occurred with a possible period of 3.0±0.15 years. For the first time, we found evidence that the times of the activity flips coincide with times of minimum light as well as minimum photometric amplitude, i.e. maximum Spottedness. From a comparison with simultaneous Doppler images we conclude that the activity flips likely take place near the rotational pole of the star. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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light curve inversions with truncated least squares principal components tests and application to hd 291095 v1355 orionis
Astronomische Nachrichten, 2008Co-Authors: I S Savanov, K G StrassmeierAbstract:We present a new inversion code that reconstructs the stellar surface Spot configuration from the light curve of a rotating star. Our code employs a method that uses the truncated least-squares estimation of the inverse problem's objects principal components. We use Spot filling factors as the unknown objects. Various test cases that represent a rapidly-rotating K subgiant are used for the forward problem. Tests are then performed to recover the artificial input map and include data errors and input-parameter errors. We demonstrate the robustness of the solution to false input parameters like photospheric Temperature, Spot Temperature, gravity, inclination, unSpotted brightness and different Spot distributions and we also demonstrate the insensitivity of the solution to Spot latitude. Tests with Spots peppered over the entire stellar surface or with phase gaps do not produce fake active longitudes. The code is then applied to ten years of V and I -band light curve data of the Spotted sub-giant HD291095. A total of 22 light curves is presented. We find that for most of the time its Spots were grouped around two active longitudes separated on average by 180°. Switches of the dominant active region between these two longitudes likely occurred about every 3.15±0.23 years while the amplitude modulation of the brightness occurred with a possible period of 3.0±0.15 years. For the first time, we found evidence that the times of the activity flips coincide with times of minimum light as well as minimum photometric amplitude, i.e. maximum Spottedness. From a comparison with simultaneous Doppler images we conclude that the activity flips likely take place near the rotational pole of the star. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Anatoli Tumin - One of the best experts on this subject based on the ideXlab platform.
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Three-dimensional wave packets in a compressible boundary layer
Physics of Fluids, 2006Co-Authors: Eric Forgoston, Anatoli TuminAbstract:A three-dimensional wave packet generated by a local disturbance in a two-dimensional hypersonic boundary layer flow is studied with the aid of the previously solved initial-value problem. The solution to this problem can be expanded in a biorthogonal eigenfunction system as a sum of modes consisting of continuous and discrete spectra of temporal stability theory. A specific disturbance consisting of an initial Temperature Spot is considered, and the receptivity to this initial Temperature Spot is computed for both the two-dimensional and three-dimensional cases. Using previous analysis of the discrete and continuous spectrum, the inverse Fourier transform is computed numerically. The two-dimensional inverse Fourier transform is calculated for two discrete modes: Mode F and Mode S. The Mode S result is compared with an asymptotic approximation of the Fourier integral, which is obtained using the Gaussian model as well as the method of steepest descent. It is shown that the method of steepest descent provi...
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Numerical and Asymptotical Study of Three-Dimensional Wave Packets in a Compressible Boundary Layer
36th AIAA Fluid Dynamics Conference and Exhibit, 2006Co-Authors: Eric Forgoston, Michael Viergutz, Anatoli TuminAbstract:A three-dimensional wave packet generated by a local disturbance in a two-dimensional hypersonic boundary layer ∞ow is studied with the aid of the previously solved initialvalue problem. The solution can be presented as a sum of modes consisting of continuous and discrete spectra of temporal stability theory. Two discrete modes, known as Mode S and Mode F, are of interest in high-speed ∞ows since they may be involved in a laminarturbulent transition scenario. The continuous and discrete spectra are analyzed numerically for a hypersonic ∞ow. A comprehensive study of the spectrum is performed, including Reynolds number, Mach number and Temperature factor efiects. A speciflc disturbance consisting of an initial Temperature Spot is considered, and the receptivity to this initial Temperature Spot is computed for both the two-dimensional and three-dimensional cases. Using the analysis of the discrete and continuous spectrum, the inverse Fourier transform is computed numerically. The two-dimensional inverse Fourier transform is calculated for Mode F and Mode S. The Mode S result is compared with an asymptotic approximation of the Fourier integral, which is obtained using a Gaussian model as well as the method of steepest descent. Additionally, the three-dimensional inverse Fourier transform is found using an asymptotic approximation. Using the inverse Fourier transform computations, the development of the wave packet is studied, including efiects due to Reynolds number, Mach number and Temperature factor.
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THREE-DIMENSIONAL WAVE PACKET IN A HYPERSONIC BOUNDARY LAYER
43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005Co-Authors: Eric Forgoston, Anatoli TuminAbstract:A three-dimensional wave packet generated by a local disturbance in a hypersonic boundary layer flow is studied with the aid of the previously solved initialvalue problem. The solution to this problem can be expanded in a biorthogonal eigenfunction system as a sum of discrete and continuous modes. A specific disturbance consisting of an initial Temperature Spot is considered, and the receptiv ity to this initial Temperature Spot is computed for both the twodimensional and three-dimensional cases. Using previous analysis of the discrete and continuous spectrum, we numerically compute the inverse Fourier transform. The two-dimensional inverse Fourier transform is found for Mode S, and the result is compared with the asymptotic approximation of the Fourier integral. Due to the synchronism between Mode F and entropy/vorticity modes, it is necessary to d eform the path of integration around the associated branch cut. Additionally, the inverse Fourier transform for a prescribed spanwise wave number is computed for three-dimensional Mode S. Nomenclature A = vector function (direct problem) j A = j th component of vector A B = vector function (adjoint problem) j B = j th component of vector B
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initial value problem for hypersonic boundary layer flows
AIAA Journal, 2001Co-Authors: Alexander Fedorov, Anatoli TuminAbstract:An initial-value problem is analyzed for a two-dimensional wave packet induced by a local two-dimensional disturbance in a hypersonic boundary layer. The problem is solved using Fourier transform with respect to the streamwisecoordinateandLaplacetransform with respectto time. The temporal continuous spectrum isrevisited, and the uncertainty associated with the overlapping of continuous-spectrum branches is resolved. It is shown that thediscretespectrum’ s dispersion relationship isnonanalyticbecause of thesynchronization of thee rst mode with the vorticity/entropy waves of the continuous spectrum. However, the inverse Laplace transform is regular at the synchronism point. Characteristics of the wave packet generated by an initial Temperature Spot are numerically calculated. It is shown that the hypersonic boundary layer is highly receptive to vorticity/entropy disturbances in the synchronism region. The feasibility of experimental verie cation of this receptivity mechanism is discussed.
Ping Liang - One of the best experts on this subject based on the ideXlab platform.
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Comparison of Temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna: Results in ex vivo porcine livers
European Journal of Radiology, 2011Co-Authors: Zhigang Cheng, Lei Dong, Guoming Zhang, Yang Wang, Ping LiangAbstract:Abstract Objective To compare Temperature curve and ablation zone between 915- and 2450-MHz cooled-shaft microwave antenna in ex vivo porcine livers. Materials and methods The 915- and 2450-MHz microwave ablation and thermal monitor system were used in this study. A total of 56 ablation zones and 280 Temperature data were obtained in ex vivo porcine livers. The output powers were 50, 60, 70, and 80 W and the setting time was 600 s. The Temperature curve of every Temperature Spot, the short- and long-axis diameters of the coagulation zones were recorded and measured. Results At all four power output settings, the peak Temperatures of every Temperature Spot had a tendency to increase accordingly as the MW output power was increased, and except for 5 mm away from the antenna, the peak Temperatures for the 915 MHz cooled-shaft antenna were significantly higher than those for the 2450 MHz cooled-shaft antenna ( p p Conclusion The 915 MHz cooled-shaft antenna can yield a significantly larger ablation zone and achieve higher Temperature in ablation zone than a 2450 MHz cooled-shaft antenna in ex vivo porcine livers.
Kullervo Hynynen - One of the best experts on this subject based on the ideXlab platform.
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Mapping of Temperature elevation using focused ultrasound phased arrays
Proceedings of the Second Joint 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society] [Engineering in Medicine and, 2002Co-Authors: Elisa E. Konofagou, S. Sokka, Jonathan S. Thierman, Kullervo HynynenAbstract:Temperature monitoring is most important during the application of thermal treatment, such as in the case of Focused Ultrasound Surgery (FUS). Currently, Magnetic Resonance Imaging (MRI) is the predominant method for Temperature mapping of FUS. However, its high cost, low temporal resolution and limited availability and applicability often result in its restricted use. In this paper, a new device for Temperature mapping is introduced that only uses focused ultrasound to both apply and monitor the treatment temporally and spatially. By utilizing the principle of the recently introduced Ultrasound-Stimulated Acoustic Emission (USAE) as well as the phased array capability of steering the beam, the Temperature distribution at various instants during the application of the treatment could be assessed. The target used here was a silicone gel with tissue-mimicking properties. The Temperature Spot could be detected during the application of the treatment and the Temperature elevation could be both mapped spatially and monitored temporally. In conclusion, an all ultrasound-based system could serve as a more applicable alternative to MR techniques for thermal therapy monitoring. Our plan is to use the same array for the therapy sonication and monitoring of the treatment in the focal zone. This could provide a potential for realizing the ultimate clinical goal: an economic, fully integrated closed loop feedback system for therapy control.
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Temporal and spatial monitoring of Temperature-related tissue changes using focused ultrasound phased arrays
2002 IEEE Ultrasonics Symposium 2002. Proceedings., 2002Co-Authors: Elisa E. Konofagou, S. Sokka, Jonathan S. Thierman, Kullervo HynynenAbstract:Temperature monitoring is most important during the application of thermal treatment, such as in the case of Focused Ultrasound Surgery (FUS). Currently, Magnetic Resonance Imaging (MRI) is the predominant method for Temperature mapping of FUS. However, its high cost, low temporal resolution and limited availability and applicability often result in its restricted use. In this paper, a new device for Temperature mapping is introduced that only uses focused ultrasound to both apply and monitor the treatment temporally and spatially. By utilizing the principle of the recently introduced Ultrasound-Stimulated Acoustic Emission (USAE) as well as the phased array capability of steering the beam, the Temperature distribution at various instants during the application of the treatment could be assessed. The target used here was a silicone gel with tissue-mimicking properties. The Temperature Spot could be detected during the application of the treatment and the Temperature elevation could be both mapped spatially and monitored temporally. In conclusion, an all ultrasound-based system could serve as a more applicable alternative to MR techniques for thermal therapy monitoring. Our plan is to use the same array for the therapy sonication and monitoring of the treatment in the focal zone. This could provide a potential for realizing the ultimate clinical goal: an economic, fully integrated closed loop feedback system for therapy control.
