scholarly journals Newton Method to Recover the Phase Accumulated during MRI Data Acquisition

2012 ◽  
Vol 2012 ◽  
pp. 1-15
Author(s):  
Oh-In Kwon ◽  
Chunjae Park
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Newton Method ◽  
Image Data ◽  
Magnetic Flux Density ◽  
Impedance Tomography ◽  
Conductivity Image ◽  
Space Data ◽  
Internal Conductivity ◽  
Data Reading

For an internal conductivity image, magnetic resonance electrical impedance tomography (MREIT) injects an electric current into an object and measures the induced magnetic flux density, which appears in the phase part of the acquired MR image data. To maximize signal intensity, the injected current nonlinear encoding (ICNE) method extends the duration of the current injection until the end of the MR data reading. It disturbs the usual linear encoding of the MRk-space data used in the inverse Fourier transform. In this study, we estimate the magnetic flux density, which is recoverable from nonlinearly encoded MRk-space data by applying a Newton method.

scholarly journals Current Density Imaging Using Directly Measured HarmonicBzData in MREIT

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Chunjae Park ◽  
Oh In Kwon
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Flux ◽  
Flux Density ◽  
Current Density ◽  
Background Field ◽  
Magnetic Flux Density ◽  
Reconstruction Procedure ◽  
Phantom Experiment ◽  
Impedance Tomography ◽  
Space Data

Magnetic resonance electrical impedance tomography (MREIT) measures magnetic flux density signals through the use of a magnetic resonance imaging (MRI) in order to visualize the internal conductivity and/or current density. Understanding the reconstruction procedure for the internal current density, we directly measure the second derivative ofBzdata from the measuredk-space data, from which we can avoid a tedious phase unwrapping to obtain the phase signal ofBz. We determine optimal weighting factors to combine the derivatives of magnetic flux density data,∇2Bz, measured using the multi-echo train. The proposed method reconstructs the internal current density using the relationships between the induced internal current and the measured∇2Bzdata. Results from a phantom experiment demonstrate that the proposed method reduces the scanning time and provides the internal current density, while suppressing the background field inhomogeneity. To implement the real experiment, we use a phantom with a saline solution including a balloon, which excludes other artifacts by any concentration gradient in the phantom.

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

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