Numerical analysis of the magnetic field for arbitrary magnetic susceptibility distributions in 2D

Bhagwandien, Rohit; Ee, R. van; Beersma, R.; Bakker, Chris J.G.; Moerland, Marinus A.; Lagendijk, J J W

doi:10.1016/0730-725x(92)90489-m

Cited by 63 publications

(74 citation statements)

References 9 publications

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“…Spatial accuracy in MRI is limited by the inhomogeneity of the static magnetic eld B 0 and the nonlinearity of the imaging gradients G x , G y and G z . The nonlinearity of the gradients is often considered a matter of system and sequence design Bakker et al 1992;O'Donnell and Edelstein 1985;Kawanaka and Takagi 1986 and the inhomogeneity of the static eld is known to stem from the system Bakker et al 1992;Kawanaka and Takagi 1986;Sekihara et al 1984 and from the magnetic properties of the object itself L udeke et al 1985; Edmonds and Wormald 1988;Ericsson et al 1988;Chu et al 1990;Posse and Aue 1990;Bhagwandien et al 1992a. As has been recognized in previous studies L udeke et al 1985, the geometric distortion of MR images is a ected by the strength, direction and polarity of the imaging gradients.…”

Section: In-plane Image Distortions In Echo Planar Imaging Epimentioning

confidence: 81%

“…They demonstrated magnetic eld distortions in and around cylindrical and spherical objects. In our group, a numerical method was developed for calculation of the magnetic eld for arbitrary susceptibility distributions Bhagwandien et al 1992a;Bhagwandien et al 1994. As already mentioned above, this method was used for analysis of distortions in images of cylindrical phantoms, but also for analysis of image distortions caused by magnetic eld perturbations by the patient itself Bhagwandien et al 1992b;Bhagwandien 1994.…”

Section: Mr Image Distortionsmentioning

confidence: 99%

“…Firstly, a computer model was developed for calculating image distortions induced by the object. Theoretical analysis and simulations led to insight in the nature and severity of the object-related MR image distortions, which has been reported in the literature Bakker et al 1993;Bhagwandien et al 1992a;Bhagwandien et al 1994 and in a Ph.D. thesis Bhagwandien 1994. Secondly, the problems were approached experimentally.…”

mentioning

confidence: 99%

“…For better understanding of the objectinduced image distortions we developed a numerical technique for calculating the magnetic eld for arbitrary magnetic susceptibility distributions. This calculation method was validated against analytical solutions for a cylinder and a coaxial cylinder Bhagwandien et al 1992a. In this chapter our numerical technique will be brie y reviewed and applied to a clinical setup, namely to calculate the magnetic eld around the head xed by a cast in a home-built localization frame.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic resonance imaging in radiotherapy treatment planning

Moerland¹

1997

Medical Physics

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The aim of this study is to investigate the capabilities of magnetic resonance imaging (MRI) in radiotherapy treatment planning (RTP) and to explore the MR image distortions and how these distortions can be reduced or, if necessary, corrected in order to integrate MRI into RTP in a reliable manner. Image distortions and the efficacy of correction methods were evaluated in phantom, volunteer, and patient studies. From the measurement, analysis, and correction of machine‐related geometric distortions in MRI, it was concluded that MR image corrections are necessary in applications which require mm accuracy and that correction methods, based on 3D maps of static field inhomogeneity and gradient nonlinearity, are feasible in clinical practice. From the measurement and numerical analysis of object‐related geometric distortions, it was concluded that these distortions can be reduced to the order of the pixel size by imaging at 0.5 T and using gradients on the order of 3 mT normalm−1. Furthermore, in a study on volunteers, fast MRI scan techniques were used to measure the respiration induced kidney movement and in a study on patients with prostate cancer, the value of MRI for the evaluation of brachytherapy was demonstrated. The MR image artifacts induced by the I‐125 seeds were used to evaluate the dose distributions and dose volume histograms of permanent prostate implants.

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Section: In-plane Image Distortions In Echo Planar Imaging Epimentioning

confidence: 81%

Section: Mr Image Distortionsmentioning

confidence: 99%

mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magnetic resonance imaging in radiotherapy treatment planning

Moerland¹

1997

Medical Physics

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“…Based on these principles we propose electromagnetic phantoms as an additional tool for measurement and imaging quality testing using NMR imaging methods. Numerical analyses of the magnetic field for arbitrary magnetic susceptibility mapping were described in [4], [5], [6], [7]. Phantom design method for high-field MRI human and systems multilayered spherical head phantom excited by MRI coils were described in [8], [9].…”

Section: Introductionmentioning

confidence: 99%

Measurement and Imaging of Planar Electromagnetic Phantoms Based on NMR Imaging Methods

Frollo¹,

Andris²,

Přibil³

et al. 2010

Measurement Science Review

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Planar electromagnetic phantom design for measurement and imaging using NMR has been performed. Electromagnetic phantom computation and testing on a NMR 0.178 Tesla Esaote Opera imager were accomplished. The classical geometrical and chemical phantoms are generally used for testing of NMR imaging systems. They are simple cylindrical or rectangular objects with different dimensions and shapes with holes filled with specially prepared water solutions. In our experiments a homogeneous phantom (reference medium) -a container filled with water -was used. The resultant image represents the magnetic field distribution in the homogeneous phantom. An image acquired by this method is actually a projection of the sample properties onto the homogeneous phantom. The goal of the paper is to map and image the magnetic field deformation using NMR imaging methods. We are using a double slender rectangular vessel with constant thickness filled with specially prepared water solution in our experiments. For detection a carefully tailored gradient-echo imaging method, susceptible to magnetic field homogeneity, was used.

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