Fast MRI coil analysis based on 3-D electromagnetic and RF circuit co-simulation

Kozlov, Mikhail V.; Turner, Robert

doi:10.1016/j.jmr.2009.06.005

Cited by 198 publications

(167 citation statements)

References 10 publications

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“…The simulation model was meshed with 28.5 Mio mesh voxels for Duke and 26.1 Mio mesh voxels for Ella, and the voxel size was below (2 3 2 3 2) mm 3 in the region of the voxel model. The feeding points of the elements were modelled as discrete ports with a characteristic impedance of 50 V. The matching and tuning network was modelled using the built-in circuit simulator of CST Design Studio (26). For the determination of the values for the matching and tuning capacitors the resulting S-parameter matrix of the EMF simulations was fed to ADS (Agilent Technologies, Santa Clara, CA) circuit simulations for fast processing.…”

Section: Electromagnetic Field and Sar Simulationsmentioning

confidence: 99%

16‐channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

Oezerdem

Winter

Graessl

et al. 2015

Magnetic Resonance in Med

103

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Section: Electromagnetic Field and Sar Simulationsmentioning

confidence: 99%

16‐channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

Oezerdem

Winter

Graessl

et al. 2015

Magnetic Resonance in Med

103

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“…Final field results were accomplished by incorporating lumped tuning and matching capacitors in the built-in circuit simulator of CST Studio Suite (CST Design Studio) (26).…”

Section: Rf Safety Assessmentmentioning

confidence: 99%

Skin sodium measured with ²³Na MRI at 7.0 T

et al. 2014

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Objective: Skin-sodium storage, as a physiologically important regulatory mechanism for blood pressure, volume regulation, and indeed survival, has recently been rediscovered. This prompted the development of MRI methods to assess sodium storage in humans ( 23 Na-MRI) at 3.0 Tesla. This work examines the feasibility of high in-plane spatial resolution 23 Na MRI in skin at 7.0 T. Methods:A two-channel transceiver RF coil array tailored for skin MRI at 7.0 T (f=78.5MHz) is proposed. Specific absorption rate (SAR) simulations and a thorough assessment of RF power deposition were performed to meet the safety requirements. Human skin was examined in an in vivo feasibility study using 2D gradient echo imaging. Normal male adult volunteers (n=17, mean ± SD = 46 ± 18 years, range: 20-79 years) were investigated.Transverse slices of the calf were imaged with 23 Na MRI using a high in-plane resolution of (0.9 x 0.9) mm 2 . Skin Na + content was determined using external agarose standards covering a physiological-range of Na + concentrations. To assess the intra-subject reproducibility, each volunteer was examined three to five times with each session including a 5 min walk and repositioning/preparation of the subject. Age-dependence of skin Na + content was investigated. Results:The 23 Na RF coil provides improved sensitivity within a range of 1 cm from its surface versus a volume RF coil which facilitates high in-plane spatial resolution imaging of human skin. Intra-subject variability of human skin sodium content in the volunteer population was <10.3%. An age-dependent increase in skin Na + content was observed, r = 0.78). Short abstractThis work demonstrates the feasibility of sub-millimeter in-plane spatial resolution 23 Na MRI in skin at clinically acceptable acquisition times at 7.0 T. Intra-subject variability of human skin sodium content in the volunteer population was <10.3%. An age-dependent increase in skin Na + content was observed (r = 0.78). Assigning sodium stores with 23 Na-MRI techniques could be improved at 7.0 T compared to current 3.0 T technology.-6 -

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“…The feeding points of the elements were modeled as 50 Ω ports. Final field results were accomplished incorporating lumped tuning and matching capacitors in the built-in circuit simulator of CST Studio Suite (CST Design Studio), following a previously proposed workflow [31]. The capacitor values were optimized with respect to the Sparameter simulation and were used as a starting point for the practical realization.…”

Section: Numerical Electromagnetic Field Simulationsmentioning

confidence: 99%

Ophthalmic Magnetic Resonance Imaging at 7 T Using a 6-Channel Transceiver Radiofrequency Coil Array in Healthy Subjects and Patients With Intraocular Masses

Graessl¹,

Muhle²,

Schwerter³

et al. 2014

Investigative Radiology

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ObjectivesThis study is designed to examine the feasibility of ophthalmic MRI at 7.0 T using a local six-channel transmit/receive radiofrequency (RF) coil array in healthy volunteers and patients with intraocular masses. Materials and MethodsA novel six-element transceiver RF coil array that makes uses of loop elements and that is customized for eye imaging at 7.0 T is proposed. Considerations influencing the RF coil design and the characteristics of the proposed RF coil array are presented. Numerical electro-magnetic field (EMF) simulations were conducted to enhance the RF coil characteristics. Specific absorption rate (SAR) simulations and a thorough assessment of RF power deposition were performed to meet the safety requirements. Phantom experiments were carried out to validate the EMF simulations and to assess the real performance of the proposed transceiver array. Certified approval for clinical studies was provided by a local notified body prior to the in vivo studies. The suitability of the RF coil to image the human eye, optical nerve and orbit was examined in an in vivo feasibility study including (i) 3D gradient echo imaging (3D GRE), (ii) inversion recovery 3D gradient echo (3D IR-GRE) and (iii) 2D T2 weighted fast spin-echo (2D FSE) imaging. For this purpose healthy adult volunteers (n=17, mean age 3411 years) and patients with intraocular masses (uveal melanoma, n=5, mean age 576years) were investigated. ResultsAll subjects tolerated all examinations well with no relevant adverse events. The sixchannel coil array supports high resolution 3D GRE imaging with a spatial resolution as good as (0.2 x 0.2 x 1.0) mm 3 which facilitates the depiction of anatomical details of the eye. Rather uniform signal intensity across the eye was found. A mean signal-to-noise ratio (SNR) of approximately 35 was found for the lens while the vitreous humor showed an SNR of page 3 approximately 30. The lens-vitreous humor contrast-to-noise ratio was 8, which allows good differentiation between the lens and the vitreous compartment. Inversion recovery prepared 3D GRE using a spatial resolution of (0.4 x 0.4 x 1.0 mm) 3 was found to be feasible. T2-weighted 2D FSE imaging with the proposed RF coil afforded a spatial resolution of (0.25 x 0.25 x 0.7 mm) 3 . ConclusionsThis work provides valuable information on the feasibility of ophthalmic MRI at 7.0 T using a dedicated six-channel transceiver coil array that supports the acquisition of high contrast, high spatial resolution images in healthy volunteers and patients with intraocular masses. The results underscore the challenges of ocular imaging at 7.0 T and demonstrate that these issues can be offset by using tailored RF coil hardware. The benefits of such improvements would be in positive alignment with explorations that are designed to examine the potential of MRI for the assessment of spatial arrangements of the eye segments and their masses with the ultimate goal to provide imaging means for guiding treatment decisions in ophthalmological diseases.

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Fast MRI coil analysis based on 3-D electromagnetic and RF circuit co-simulation

Cited by 198 publications

References 10 publications

16‐channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

16‐channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

Skin sodium measured with ²³Na MRI at 7.0 T

Ophthalmic Magnetic Resonance Imaging at 7 T Using a 6-Channel Transceiver Radiofrequency Coil Array in Healthy Subjects and Patients With Intraocular Masses

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Fast MRI coil analysis based on 3-D electromagnetic and RF circuit co-simulation

Cited by 198 publications

References 10 publications

16‐channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

16‐channel bow tie antenna transceiver array for cardiac MR at 7.0 tesla

Skin sodium measured with 23Na MRI at 7.0 T

Ophthalmic Magnetic Resonance Imaging at 7 T Using a 6-Channel Transceiver Radiofrequency Coil Array in Healthy Subjects and Patients With Intraocular Masses

Contact Info

Product

Resources

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Skin sodium measured with ²³Na MRI at 7.0 T