Current Injection Optimization for Magnetic Resonance-Electrical Impedance Tomography (MREIT)
01 Jan 2007-pp 504-507
TL;DR: In this paper, the current injection optimization problem for 2D cylindrical body with concentric inhomogeneity is analytically formulated, based on distinguishability definition for magnetic resonance-electrical impedance tomography (MREIT).
Abstract: Determining optimum current injection pattern is of interest in magnetic resonance-electrical impedance tomography (MREIT), since it helps in detecting smaller inhomogeneities within the body when total injected current into the body is limited. Based on this fact, for 2-D cylindrical body with concentric and cylindrical inhomogeneity, current injection optimization problem is analytically formulated, based on distinguishability definition for MREIT. The exterior penalty method is used to solve the optimization problem. In the second step, the same problem is considered for eccentric and cylindrical inhomogeneity and the best current injection pattern is obtained.
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TL;DR: MRCTI data acquisition is experimentally implemented and anisotropic conductivity images of test phantoms are reconstructed using recently proposed MRCTI reconstruction algorithms.
Abstract: Magnetic resonance conductivity tensor imaging (MRCTI) is an emerging modality which reconstructs images of anisotropic conductivity distribution within a volume conductor. Images are reconstructed based on magnetic flux density distribution induced by an externally applied probing current, together with a resultant surface potential value. The induced magnetic flux density distribution is measured using magnetic resonance current density imaging techniques. In this study, MRCTI data acquisition is experimentally implemented and anisotropic conductivity images of test phantoms are reconstructed using recently proposed MRCTI reconstruction algorithms.
9 citations
Cites methods from "Current Injection Optimization for ..."
...This could be possible adopting the optimized MREIT current injection strategies [16]....
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01 Jan 2008
TL;DR: In this article, the authors present a table of contents of a chapter and a list of FIGURES, including the following categories: 1) ACKNOWLEDGEMENTs 2)
Abstract: iv OZ vi ACKNOWLEDGEMENTS ix TABLE OF CONTENTS x LIST OF TABLES xiii LIST OF FIGURES xiv CHAPTER
2 citations
01 Jan 2009
TL;DR: In this article, an image reconstruction algorithm for magnetic resonance electrical impedance tomography (MREIT) is proposed to achieve maximum benefit of optimum current injection patterns, which can reduce the probing current amplitude.
Abstract: In this study, an image reconstruction algorithm for magnetic resonance electrical impedance tomography (MREIT) is proposed to achieve maximum benefit of optimum current injection patterns. By doing so, considerable reduction in probing current amplitude could be possible. In the proposed algorithm, field of view (FOV) is divided into a number of segments. Image of each segment is reconstructed separately, based on measurements obtained using the best (optimum) current patterns, which maximize distinguishability for the same segment. Images reconstructed individually for all segments are then merged to form an image of the entire FOV. The proposed regional image reconstruction (RIR) algorithm is evaluated with simulated measurements obtained from a conductivity phantom having Shepp-Logan head phantom geometry. Smaller reconstruction errors and perceptively better images are obtained by using RIR instead of conventional reconstruction (CR). Improvement is more significant for small inhomogeneities which are away from the outer surface. When SNR is 13 dB, conductivity error for small inhomogeneities reconstructed by RIR is almost half of the errors of CR.
1 citations
References
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TL;DR: Criteria for the distinguishability of two different conductivity distributions inside a body by electric current computed tomography (ECCT) systems with a specified precision are given.
Abstract: We give criteria for the distinguishability of two different conductivity distributions inside a body by electric current computed tomography (ECCT) systems with a specified precision. It is shown in a special case how these criteria can be used to determine the measurement precision needed to distinguish between two different conductivity distributions. It is also shown how to select the patterns of current to apply to the body in order to best distinguish given conductivity distributions with an ECCT system of finite precision.
443 citations
TL;DR: A detailed discussion of several ways to measure the ability of anImpedance imaging system to distinguish between two different conductivity distributions is given.
Abstract: Impedance imaging systems apply currents to the surface of a body, measure the induced voltages on the surface, and from this information reconstruct an approximation to the electrical conductivity in the interior. A detailed discussion of several ways to measure the ability of such a system to distinguish between two different conductivity distributions is given. The subtle differences between these related measures are discussed, and examples are provided to show that these different measures can give rise to different answers to various practical questions about system design. >
125 citations
TL;DR: This paper considers appropriate safety constraints and discusses how to find the optimal current patterns with those constraints.
Abstract: There are a number of constraints which limit the current and voltages which can be applied on a multiple drive electrical imaging system. One obvious constraint is to limit the maximum ohmic power dissipated in the body. Current patterns optimizing distinguishability with respect to this constraint are singular functions of the difference of transconductance matrices with respect to the power norm (the optimal currents of Isaacson). If one constrains the total current (L1 norm) the optimal patterns are pair drives. On the other hand if one constrains the maximum current on each drive electrode (an L(infinity) norm), the optimal patterns have each drive channel set to the maximum source or sink current value. In this paper we consider appropriate safety constraints and discuss how to find the optimal current patterns with those constraints.
85 citations
TL;DR: This paper describes how these current patterns may be determined and describes a system for achieving this in practice.
Abstract: It has been shown that there exists an optimum set of current patterns for distinguishing one conductivity distribution from another. Since the optimum set of current patterns depends on the conductivity distribution being imaged it must be determined for each object being imaged. This paper describes how these current patterns may be determined and describes a system for achieving this in practice.
83 citations
29 Feb 2000
TL;DR: In this article, a magnetic resonance-electrical impedance tomography (MREIT) technique was proposed for determining the local conductivity of an object, which combines magnetic resonance current density imaging (MRCDI) with EIT in order to obtain the benefits of both procedures.
Abstract: A magnetic resonance-electrical impedance tomography (MREIT) technique for determining the local conductivity of an object. The MREIT technique combines magnetic resonance current density imaging (MRCDI) with electrical impedance tomography (EIT) in order to obtain the benefits of both procedures. The MREIT technique includes the step of current density imaging by performing the steps of placing a series of electrodes around the patient or object to be imaged for the application of current, placing the patient or object in a strong magnetic field, and applying an MR imaging sequence which is synchronized with the application of current through the electrodes. Next, the electric potentials of the surface of the object or patient are measured simultaneously with the MR imaging sequence, as in EIT. Then, the MR imaging signal containing information about the current and the measured potential are processed to calculate the internal conductivity (impedance) of the object or patient.
78 citations