The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform

Dennis L. Parker - One of the best experts on this subject based on the ideXlab platform.

  • Simultaneous proton resonance frequency shift thermometry and T1 measurements using a single Reference Variable flip angle T1 method
    Magnetic resonance in medicine, 2019
    Co-Authors: Bryant T. Svedin, Allison Payne, Dennis L. Parker
    Abstract:

    Implement simultaneous proton resonance frequency (PRF) shift and T1 measurements with equivalent temporal resolution using a single Reference Variable flip angle method. This novel method allows for simultaneous thermometry in both aqueous and fatty tissue. This method acquires a single Reference image at the lower flip angle and all dynamic images at the higher angle. T1 is calculated using a single Reference Variable flip angle method, which accounts for the Reference image temperature remaining constant. Monte Carlo simulations determined the optimal dynamic flip angle for combined PRF and T1 measurements. This method was evaluated in MR-guided focused ultrasound heating experiments using a gelatin phantom and human cadaver breasts. In vivo measurement precision was demonstrated in healthy female volunteers under nonheating conditions. Temperature rise during MR-guided focused ultrasound heating was measured in aqueous tissue with both PRF and T1 . Both measures show good qualitative agreement in both space and time in aqueous tissue. The T1 change due to temperature increase was measured in fat, demonstrating the expected temporal response. The dynamic flip angle that produces optimal SNR for PRF measurements is lower than the optimal angle for T1 measurements, necessitating the selection of a compromise angle. The single Reference Variable flip angle method provides a reliable way to simultaneously measure PRF temperature and T1 change and overcomes PRF's inability to simultaneously monitor temperature in aqueous and adipose tissues. Future work will calibrate T1 change to temperature, enabling real-time temperature in fat and increasing patient safety and treatment efficacy during thermal interventional treatments. © 2018 International Society for Magnetic Resonance in Medicine.

  • simultaneous proton resonance frequency shift thermometry and t1 measurements using a single Reference Variable flip angle t1 method
    Magnetic Resonance in Medicine, 2019
    Co-Authors: Bryant T. Svedin, Allison Payne, Dennis L. Parker
    Abstract:

    A computer implemented method for measuring T1 in an anatomical region of interest during a dynamic procedure includes acquiring a Reference MR image of the anatomical region of interest using a first flip angle. A first set of dynamic MR images of the anatomical region of interest are acquired using a second flip angle. The Reference MR image and the first set are used to calculate a Reference T1 value for tissue in the anatomical region of interest. During an intervention where the T1 value may change, a second set of dynamic MR images of the anatomical region of interest is acquired using the second flip angle. The Reference MR image and the second set are used to calculate an estimated T1 value. The Reference T1 value, the estimated T1 value, and the first and second flip angles may then be used to correct the estimated T1 value.

Bryant T. Svedin - One of the best experts on this subject based on the ideXlab platform.

  • Simultaneous proton resonance frequency shift thermometry and T1 measurements using a single Reference Variable flip angle T1 method
    Magnetic resonance in medicine, 2019
    Co-Authors: Bryant T. Svedin, Allison Payne, Dennis L. Parker
    Abstract:

    Implement simultaneous proton resonance frequency (PRF) shift and T1 measurements with equivalent temporal resolution using a single Reference Variable flip angle method. This novel method allows for simultaneous thermometry in both aqueous and fatty tissue. This method acquires a single Reference image at the lower flip angle and all dynamic images at the higher angle. T1 is calculated using a single Reference Variable flip angle method, which accounts for the Reference image temperature remaining constant. Monte Carlo simulations determined the optimal dynamic flip angle for combined PRF and T1 measurements. This method was evaluated in MR-guided focused ultrasound heating experiments using a gelatin phantom and human cadaver breasts. In vivo measurement precision was demonstrated in healthy female volunteers under nonheating conditions. Temperature rise during MR-guided focused ultrasound heating was measured in aqueous tissue with both PRF and T1 . Both measures show good qualitative agreement in both space and time in aqueous tissue. The T1 change due to temperature increase was measured in fat, demonstrating the expected temporal response. The dynamic flip angle that produces optimal SNR for PRF measurements is lower than the optimal angle for T1 measurements, necessitating the selection of a compromise angle. The single Reference Variable flip angle method provides a reliable way to simultaneously measure PRF temperature and T1 change and overcomes PRF's inability to simultaneously monitor temperature in aqueous and adipose tissues. Future work will calibrate T1 change to temperature, enabling real-time temperature in fat and increasing patient safety and treatment efficacy during thermal interventional treatments. © 2018 International Society for Magnetic Resonance in Medicine.

  • simultaneous proton resonance frequency shift thermometry and t1 measurements using a single Reference Variable flip angle t1 method
    Magnetic Resonance in Medicine, 2019
    Co-Authors: Bryant T. Svedin, Allison Payne, Dennis L. Parker
    Abstract:

    A computer implemented method for measuring T1 in an anatomical region of interest during a dynamic procedure includes acquiring a Reference MR image of the anatomical region of interest using a first flip angle. A first set of dynamic MR images of the anatomical region of interest are acquired using a second flip angle. The Reference MR image and the first set are used to calculate a Reference T1 value for tissue in the anatomical region of interest. During an intervention where the T1 value may change, a second set of dynamic MR images of the anatomical region of interest is acquired using the second flip angle. The Reference MR image and the second set are used to calculate an estimated T1 value. The Reference T1 value, the estimated T1 value, and the first and second flip angles may then be used to correct the estimated T1 value.

Allison Payne - One of the best experts on this subject based on the ideXlab platform.

  • Simultaneous proton resonance frequency shift thermometry and T1 measurements using a single Reference Variable flip angle T1 method
    Magnetic resonance in medicine, 2019
    Co-Authors: Bryant T. Svedin, Allison Payne, Dennis L. Parker
    Abstract:

    Implement simultaneous proton resonance frequency (PRF) shift and T1 measurements with equivalent temporal resolution using a single Reference Variable flip angle method. This novel method allows for simultaneous thermometry in both aqueous and fatty tissue. This method acquires a single Reference image at the lower flip angle and all dynamic images at the higher angle. T1 is calculated using a single Reference Variable flip angle method, which accounts for the Reference image temperature remaining constant. Monte Carlo simulations determined the optimal dynamic flip angle for combined PRF and T1 measurements. This method was evaluated in MR-guided focused ultrasound heating experiments using a gelatin phantom and human cadaver breasts. In vivo measurement precision was demonstrated in healthy female volunteers under nonheating conditions. Temperature rise during MR-guided focused ultrasound heating was measured in aqueous tissue with both PRF and T1 . Both measures show good qualitative agreement in both space and time in aqueous tissue. The T1 change due to temperature increase was measured in fat, demonstrating the expected temporal response. The dynamic flip angle that produces optimal SNR for PRF measurements is lower than the optimal angle for T1 measurements, necessitating the selection of a compromise angle. The single Reference Variable flip angle method provides a reliable way to simultaneously measure PRF temperature and T1 change and overcomes PRF's inability to simultaneously monitor temperature in aqueous and adipose tissues. Future work will calibrate T1 change to temperature, enabling real-time temperature in fat and increasing patient safety and treatment efficacy during thermal interventional treatments. © 2018 International Society for Magnetic Resonance in Medicine.

  • simultaneous proton resonance frequency shift thermometry and t1 measurements using a single Reference Variable flip angle t1 method
    Magnetic Resonance in Medicine, 2019
    Co-Authors: Bryant T. Svedin, Allison Payne, Dennis L. Parker
    Abstract:

    A computer implemented method for measuring T1 in an anatomical region of interest during a dynamic procedure includes acquiring a Reference MR image of the anatomical region of interest using a first flip angle. A first set of dynamic MR images of the anatomical region of interest are acquired using a second flip angle. The Reference MR image and the first set are used to calculate a Reference T1 value for tissue in the anatomical region of interest. During an intervention where the T1 value may change, a second set of dynamic MR images of the anatomical region of interest is acquired using the second flip angle. The Reference MR image and the second set are used to calculate an estimated T1 value. The Reference T1 value, the estimated T1 value, and the first and second flip angles may then be used to correct the estimated T1 value.

Alexander Y. Klimenko - One of the best experts on this subject based on the ideXlab platform.

  • Modelling of a turbulent premixed flame series using a new MMC-LES model with a shadow position Reference Variable
    Proceedings of the Combustion Institute, 2020
    Co-Authors: Yashar Shoraka, S. Galindo-lopez, Fatemeh Salehi, Matthew J. Cleary, Assaad R. Masri, Alexander Y. Klimenko
    Abstract:

    Abstract A new multiple mapping conditioning model with a shadow position Reference Variable for localising mixing is implemented in a large eddy simulation solver and validated against three experimental turbulent premixed flames. The shadow position used here has diffusion coefficient which is linked to the turbulent propagation speed. Localisation of mixing produces a flamelet-like inner structure in shadow position space and the structure in physical space is determined by the subgrid dispersion of shadow and physical positions. The lengths of the predicted flames match the trends observed for the experimental flames, and the predicted inner structures are consistent with what is expected for these flames in the thin reaction zones regime. The statistical predictions are in very good quantitative agreement with the experimental data for velocity and major species. Errors for reaction progress Variable, turbulent kinetic energy and minor species (carbon monoxide) are generally larger yet mostly within the ranges reported in the literature.

  • An MMC-LES simulation of turbulent piloted flames using a shadow position Reference Variable
    2017
    Co-Authors: S. Galindo-lopez, Fatemeh Salehi, Matthew J. Cleary, Assaad R. Masri, Alexander Y. Klimenko
    Abstract:

    This paper presents large eddy simulations (LES) of piloted partially premixed turbulent flames with homogeneous inlets. It is a first attempt to implement Shadow Positions (SP) [1] as Reference Variable in the MMC-LES modelling framework. The Sydney piloted burner is employed here although, at this stage, without any compositional inhomogeneity at the exit plane. The Shadow Position vector is used as Reference Variable for conditioning in the mixing model and a flame sheet approximation is made to treat the chemistry. Comparisons between the predictions and the experimental measurements are made. The flame structure is adequately predicted and it serves as a good starting point to expand the use of SP in multiple mapping conditioning (MMC) to compute the structure of premixed flames [2] and hence mixed-mode flames similar to those produced in the Sydney Burner when composition inhomogeneity is introduced.

  • Matching the conditional variance as a criterion for selecting parameters in the simplest multiple mapping conditioning models
    Physics of Fluids, 2004
    Co-Authors: Alexander Y. Klimenko
    Abstract:

    The simplest model within the multiple mapping conditioning (MMC) approach, that involves a single mixture-fraction-like Reference Variable, is considered in the Brief Communication. An important parameter—the minor dissipation time—remains unknown in the probabilistic version of the model. The present work demonstrates by the specially developed asymptotic analysis that the simplest MMC possesses an ability (although somewhat limited) to match the physical intensity of the conditional fluctuations and this match represents the criterion for proper selection of the minor dissipation time.

Vincent C. Alfonso - One of the best experts on this subject based on the ideXlab platform.

  • a cross battery Reference Variable confirmatory factor analytic investigation of the chc taxonomy
    Journal of School Psychology, 2013
    Co-Authors: Matthew R. Reynolds, Timothy Z. Keith, Dawn P. Flanagan, Vincent C. Alfonso
    Abstract:

    The Cattell-Horn-Carroll (CHC) taxonomy has been used to classify and describe human cognitive abilities. The ability factors derived from the CHC taxonomy are often assumed to be invariant across multiple populations and intelligence batteries, which is an important assumption for research and assessment. In this study, data from five different test batteries that were collected during separate Kaufman Assessment Battery for Children-Second Edition (KABC-II; Kaufman & Kaufman, 2004) concurrent validity studies were factor-analyzed jointly. Because the KABC-II was administered to everyone in the validity studies, it was used as a Reference battery to link the separate test batteries in a "cross-battery" confirmatory factor analysis. Some findings from this analysis were that CHC-based test classifications based on theory and prior research were straightforward and accurate, a first-order Fluid/Novel Reasoning (Gf) factor was equivalent to a second-order g factor, and sample heterogeneity related to SES and sex influenced factor loadings. It was also shown that a Reference Variable approach, used in studies that incorporate planned missingness into data collection, may be used successfully to analyze data from several test batteries and studies. One implication from these findings is that CHC theory should continue to serve as a useful guide that can be used for intelligence research, assessment, and test development. Language: en

  • A cross-battery, Reference Variable, confirmatory factor analytic investigation of the CHC taxonomy
    Journal of school psychology, 2013
    Co-Authors: Matthew R. Reynolds, Timothy Z. Keith, Dawn P. Flanagan, Vincent C. Alfonso
    Abstract:

    The Cattell-Horn-Carroll (CHC) taxonomy has been used to classify and describe human cognitive abilities. The ability factors derived from the CHC taxonomy are often assumed to be invariant across multiple populations and intelligence batteries, which is an important assumption for research and assessment. In this study, data from five different test batteries that were collected during separate Kaufman Assessment Battery for Children-Second Edition (KABC-II; Kaufman & Kaufman, 2004) concurrent validity studies were factor-analyzed jointly. Because the KABC-II was administered to everyone in the validity studies, it was used as a Reference battery to link the separate test batteries in a "cross-battery" confirmatory factor analysis. Some findings from this analysis were that CHC-based test classifications based on theory and prior research were straightforward and accurate, a first-order Fluid/Novel Reasoning (Gf) factor was equivalent to a second-order g factor, and sample heterogeneity related to SES and sex influenced factor loadings. It was also shown that a Reference Variable approach, used in studies that incorporate planned missingness into data collection, may be used successfully to analyze data from several test batteries and studies. One implication from these findings is that CHC theory should continue to serve as a useful guide that can be used for intelligence research, assessment, and test development.