Magnetic Field Homogeneity Adjustment for Magnetic Resonance Imaging Equipment

Frollo, Ivan; Andris, Peter; Krafčík, Andrej; Gogola, D.; Dermek, T.

doi:10.1109/tmag.2018.2804352

Cited by 7 publications

(6 citation statements)

References 27 publications

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“…Interesting example oriented to static magnetic field was published in [12]. Spatial distribution of magnetic field is determined by vector shape of the Laplace differential equation.…”

Section: Resultsmentioning

confidence: 99%

Measurement Science is the Science of Sciences - There is no Science without Measurement

Witkovský

Frollo

2020

Measurement Science Review

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Omnia in mensura et numero et pondere disposuisti is a famous Latin phrase from Solomon's Book of Wisdom, dated to the mid first century BC, meaning that all things were ordered in measure, number, and weight. Naturally, the wisdom is appearing in its relation to man. The Wisdom of Solomon is understood as the perfection of knowledge of the righteous as a gift from God showing itself in action. Consequently, a natural and obvious conjecture is that measurement science is the science of sciences. In fact, it is a basis of all experimental and theoretical research activities. Each measuring process assumes an object of measurement. Some science disciplines, such as quantum physics, are still incomprehensible despite complex mathematical interpretations. No phenomenon is a real phenomenon unless it is observable in space and time, that is, unless it is a subject to measurement. The science of measurement is an indispensable ingredient in all scientific fields. Mathematical foundations and interpretation of the measurement science were accepted and further developed in most of the scientific fields, including physics, cosmology, geology, environment, quantum mechanics, statistics, and metrology. In this year, 2020, Measurement Science Review celebrates its 20th anniversary and we are using this special opportunity to highlight the importance of measurement science and to express our faith that the journal will continue to be an excellent place for exchanging bright ideas in the field of measurement science. As an illustration and motivation for usage and further development of mathematical methods in measurement science, we briefly present the simple least squares method, frequently used for measurement evaluation, and its possible modification. The modified least squares estimation method was applied and experimentally tested for magnetic field homogeneity adjustment.

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“…Interesting example oriented to static magnetic field was published in [12]. Spatial distribution of magnetic field is determined by vector shape of the Laplace differential equation.…”

Section: Resultsmentioning

confidence: 99%

Measurement Science is the Science of Sciences - There is no Science without Measurement

Witkovský

Frollo

2020

Measurement Science Review

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“…Spherical harmonics (ie, active shimming) uses a computational technique that has the ability to correct the magnetic field to the maximum homogeneity. 11 Active shimming is mostly performed to rectify inhomogeneities caused by patients. 1 In order to implement this type of shimming, superconducting resistive (shim) coils are incorporated into the gradient coil of the MRI machine to increase the magnetic field homogeneity of the empty magnet.…”

Section: Ways Of Optimizing Magnetic Field Homogeneity Optimization O...mentioning

confidence: 99%

“…When a magnet is certified to exit a company after the production process is complete, the magnetic field inhomogeneity is generally in the range of approximately 500 ppm peak-to-peak over the maximum volume. 1 Disturbances caused by external ferromagnetic components 10,11 or certain site factors such as the presence of steel in building construction can, however, influence the magnetic field homogeneity. As a result, the field homogeneity is finetuned during the system installation using a technique known as shimming.…”

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confidence: 99%

Impact of Magnetic Field Inhomogeneity on the Quality of Magnetic Resonance Images and Compensation Techniques: A Review

Manson¹,

Inkoom²,

Mumuni³

2022

RMI

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Background: Magnetic field inhomogeneity in magnetic resonance imaging (MRI) is caused by the inherent properties of the main magnet, external ferromagnetic components surrounding the magnet, and the patient itself. Significant deviations from magnetic field inhomogeneity can create artifacts in MRI images, thereby compromising image quality. Optimizing magnetic field homogeneity improves image quality and helps to reduce artifacts. The goal of this article therefore is to help radiographers and operators of MRI understand the clinical basis of magnetic field inhomogeneity and its effects on MR images. This would assist them to appreciate the trade-offs between sequence parameters and image quality metrics towards optimizing magnetic field inhomogeneity. Methods: A narrative literature review was conducted from relevant databases using search terms such as MRI, magnetic field inhomogeneity, optimization, magnetic field inhomogeneity artifacts, and MRI shimming. Results: Minimizing field inhomogeneities in MRI is not straightforward but involves a multitude of factors and steps. Magnetic field homogeneity could be optimized to improve MR image quality by choosing the most appropriate pulse sequence/imaging parameters that could best minimize distortion and increase SNR based on the anatomical region of interest (or tissue types) while complementing it with shimming and use of dielectric pads. Conclusion: Future works to investigate the association between the MRI pulse sequence parameters and measurements of MR image quality metrics, based on individual tissue densities, could provide a new window for reducing magnetic field inhomogeneity due to susceptibility and chemical shift effects.

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“…Previous work for mitigating magnetic field imperfections led to magnetic cloaks for sensors [9,10], shim coils for magnetic resonance imaging [11] and nuclear magnetic resonance [12] applications, selective shields for field homogenization in solenoids [13]. Recently, persistent-current shims coils were introduced as a conceptual solution for improving the field quality in accelerator magnets [14,15].…”

Section: Introductionmentioning

confidence: 99%

Proof of Concept of High-Temperature Superconducting Screens for Magnetic Field-Error Cancellation in Accelerator Magnets

Bortot,

Mentink,

Petrone

et al. 2021

Preprint

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Accelerators magnets must have minimal magnetic field imperfections for reducing particle-beam instabilities. In the case of coils made of high-temperature superconducting (HTS) tapes, the field imperfections from persistent currents need to be carefully evaluated. In this paper we study the use of superconducting screens based on HTS tapes for reducing the magnetic field imperfections in accelerator magnets. The screens exploit the magnetization by persistent currents to cancel out the magnetic field error. The screens are aligned with the main field components, such that only the undesired field components are compensated. The screens are passive, self-regulating, and do not require any external source of energy. Measurements in liquid nitrogen at 77 K show for dipole-field configurations a significant reduction of the magnetic-field error up to a factor of four. The residual error is explained via numerical simulations, accounting for the geometrical imperfections in the HTS screens, thus achieving satisfactory agreement with experimental results. Simulations show that if screens are increased in width and thickness, and operated at 4.5 K, field errors may be eliminated almost entirely for the typical excitation cycles of accelerator magnets.

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Magnetic Field Homogeneity Adjustment for Magnetic Resonance Imaging Equipment

Cited by 7 publications

References 27 publications

Measurement Science is the Science of Sciences - There is no Science without Measurement

Measurement Science is the Science of Sciences - There is no Science without Measurement

Impact of Magnetic Field Inhomogeneity on the Quality of Magnetic Resonance Images and Compensation Techniques: A Review

Proof of Concept of High-Temperature Superconducting Screens for Magnetic Field-Error Cancellation in Accelerator Magnets

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