Clinical Magnetic Susceptibility Mapping of the Brain

Young, I. R.; Khenia, S; Thomas, D. G. T.; Davis, Courtland H.; Gadian, David G.; Cox, IJ; Ross, Brian D.; Bydder, Graeme M.

doi:10.1097/00004728-198701000-00002

Cited by 93 publications

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“…A common approach is to measure the MR frequency or phase shift due to the field deviation from the susceptibility effects (16 -20). However, for most of the existing methods magnetic susceptibility quantitation for macroscopically localized objects is limited to objects with regular shapes such as a sphere or a long cylinder (8,10,16 -18), and the static polarizing field is either assumed to be sufficiently homogeneous or accounted for with approximation methods such as an extra reference scan or polynomial fitting methods (17)(18)(19)(20). Wang et al (20) reported a susceptibility quantitation method which has no presumption of sample shape and only needs measurement of the magnetic field difference across an interface of two regions of different susceptibilities.…”

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Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields

Li¹

2001

Magn. Reson. Med.

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Magnetic susceptibility measurement has wide-ranging applications in MR technical development and medical applications. A general susceptibility quantitation method for objects of arbitrary shapes in inhomogeneous magnetic fields is presented in this study. Based on the mean value properties of magnetic fields, the polarizing magnetic field at the location of interest inside an object can be exactly obtained in situ from the field values on a spherical surface enclosing the object. With numerical computation of the self-demagnetizing field and correction of contact shifts, magnetic susceptibilities were quantitatively measured for CuSO 4 Magnetic susceptibility effects relate to wide-ranging MR applications, such as artifact corrections (1,2), blood/tumor oxygenation measurement (3,4), the BOLD (bloodoxygenation-level-dependent) signal contrast in functional MRI (5), medical diagnosis (6), and in vivo imaging of gene expression (7). Therefore, quantitative magnetic susceptibility measurement is important. A number of NMR methods exist to measure susceptibility or susceptibility related effects based on various mechanisms (8 -20). A common approach is to measure the MR frequency or phase shift due to the field deviation from the susceptibility effects (16 -20). However, for most of the existing methods magnetic susceptibility quantitation for macroscopically localized objects is limited to objects with regular shapes such as a sphere or a long cylinder (8,10,16 -18), and the static polarizing field is either assumed to be sufficiently homogeneous or accounted for with approximation methods such as an extra reference scan or polynomial fitting methods (17)(18)(19)(20). Wang et al. (20) reported a susceptibility quantitation method which has no presumption of sample shape and only needs measurement of the magnetic field difference across an interface of two regions of different susceptibilities. In practice, accuracy of the method is reduced because of the severe partial volume effects at the interface caused by abrupt field change and finite image resolution.The purpose of this article is to present a new susceptibility quantitation method that is theoretically rigorous in inhomogeneous polarizing fields and applicable to objects with arbitrary shapes. The susceptibility is quantified under a general condition: multiple localized distributions of materials with distinct susceptibilities are present in space permeated with a medium of known susceptibility o , and the inhomogeneous applied field H a . The goal is to determine the susceptibility value i of a localized region K (boundary denoted as ‫ץ‬K, with an arbitrary shape and uniform susceptibility inside) from the measurement of field distribution in space (Fig. 1).If one considers media in which magnetization M and magnetic field H are collinear and in proportion to each other, i.e., M ϭ H ( is the magnetic susceptibility), then the relationship between MR-measured magnetic induction field B nmr and magnetic field H at any point in space is given by the vect...

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Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields

Li¹

2001

Magn. Reson. Med.

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“…The presence of a patient in a MRI scanner leads to static magnetic eld inhomogeneity, since the magnetic eld is perturbed as the consequence of the di erence in susceptibility b e t ween the patient and the surrounding air. The severity of the eld perturbations outside the body depends on the susceptibility di erence with air, the shape of the body and the orientation of the body with respect to the applied magnetic eld Cox et al 1986;Young et al 1987;Yamada et al 1990;Yamada et al 1992;Mosher and Smith 1991;Bhagwandien et al 1994. For better understanding of the objectinduced image distortions we developed a numerical technique for calculating the magnetic eld for arbitrary magnetic susceptibility distributions.…”

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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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“…This was published in the immediate aftermath of World War II in an issue of the British Medical Bulletin celebrating the 50th anniversary of Roentgen's discovery of X-rays [3]. It was also a year before the discovery of nuclear magnetic resonance (NMR), 28 years before the discovery of MRI, and over 40 years before the general use of susceptibility-weighted imaging (SWI) [4,5] and the observation of the variation in bulk magnetic susceptibility of tendons, ligaments and menisci with orientation to the static magnetic field [6,7].…”

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The Agfa Mayneord lecture: MRI of short and ultrashortT₂andT₂* components of tissues, fluids and materials using clinical systems

Bydder¹

2011

BJR

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ABSTRACT. A variety of techniques are now available to directly or indirectly detect signal from tissues, fluids and materials that have short, ultrashort or supershort T 2 or T 2 * components. There are also methods of developing image contrast between tissues and fluids in the short T 2 or T 2 * range that can provide visualisation of anatomy, which has not been previously seen with MRI. Magnetisation transfer methods can now be applied to previously invisible tissues, providing indirect access to supershort T 2 components. Particular methods have been developed to target susceptibility effects and quantify them after correcting for anatomical distortion. Specific methods have also been developed to image the effects of magnetic iron oxide particles with positive contrast. Major advances have been made in techniques designed to correct for loss of signal and gross image distortion near metal. These methods are likely to substantially increase the range of application for MRI.

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Clinical Magnetic Susceptibility Mapping of the Brain

Cited by 93 publications

References 0 publications

Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields

Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields

Magnetic resonance imaging in radiotherapy treatment planning

The Agfa Mayneord lecture: MRI of short and ultrashortT₂andT₂* components of tissues, fluids and materials using clinical systems

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Clinical Magnetic Susceptibility Mapping of the Brain

Cited by 93 publications

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Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields

Magnetic susceptibility quantification for arbitrarily shaped objects in inhomogeneous fields

Magnetic resonance imaging in radiotherapy treatment planning

The Agfa Mayneord lecture: MRI of short and ultrashortT2andT2* components of tissues, fluids and materials using clinical systems

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Product

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The Agfa Mayneord lecture: MRI of short and ultrashortT₂andT₂* components of tissues, fluids and materials using clinical systems