Floating shield current suppression trap

Seeber, D. A.; Jevtic, Jovan; Menon, Aric Kumaran

doi:10.1002/cmr.b.20008

Cited by 73 publications

(79 citation statements)

References 2 publications

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“…The ability to attenuate common mode currents and to decouple the line is commonly measured by the transmission characteristics of S21. In this work, the attenuation of each cable trap was below the recommended − 30 dB and similar to previous reported values . This result is in concordance with the measured influence of the transmission line on the E‐ and H‐field, where only a small change could be determined.…”

Section: Discussionsupporting

confidence: 92%

Doppler ultrasound triggering for cardiac MRI at 7T

Kording

Ruprecht

Schoennagel

et al. 2017

Magnetic Resonance in Med

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Section: Discussionsupporting

confidence: 92%

Doppler ultrasound triggering for cardiac MRI at 7T

Kording

Ruprecht

Schoennagel

et al. 2017

Magnetic Resonance in Med

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“…RF traps (“Baluns”) tuned to the MRI frequency were placed at 0.30 m increments along the entire cable. We used “floating” RF traps 31 , positioned along the outside the cable, and inductively coupled to the cable, instead of filters placed within the cable (e.g. in-line filters, such as a band-reject filter), so that (i) these traps would not receive the full power of the defibrillation current and (ii) since their role was to attenuate waves at the MRI frequency, induced by the MRI scanner’s body-coil onto the cable during imaging, which are primarily common-mode in nature, for which such filters are sufficient.…”

Section: Methodsmentioning

confidence: 99%

A Magnetic Resonance Imaging–Conditional External Cardiac Defibrillator for Resuscitation Within the Magnetic Resonance Imaging Scanner Bore

Schmidt

Watkins

Zviman

et al. 2016

Circ: Cardiovascular Imaging

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Background Subjects undergoing cardiac arrest within an MRI scanner are currently removed from the bore and then from the MRI suite, prior to delivery of CPR and defibrillation, potentially increasing risk of mortality. This precludes many higher-risk (acute-ischemic, acute-stroke) patients from undergoing MRI imaging and MRI-guided intervention. An MRI-conditional cardiac defibrillator should enable scanning with defibrillation pads attached and the generator ON, enabling application of defibrillation within the MRI seconds after a cardiac event. An MRI-conditional external defibrillator may improve patient acceptance for MRI procedures. Methods and Results A commercial external defibrillator was rendered 1.5 Tesla MRI-conditional by addition of novel Radio-Frequency (RF) filters between the generator and commercial disposable surface-pads. The RF filters reduced emission into the MRI scanner, and prevented cable/surface-pad heating during imaging, while preserving all the defibrillator’s monitoring and delivery functions. Human volunteers were imaged using high Specific-Absorption-Rate sequences to validate MRI image quality (IQ) and lack of heating. Swine were electrically fibrillated (N=4) and thereafter defibrillated both outside and inside the MRI bore. MRI IQ was reduced by 0.8 or 1.6 dB, with the generator in monitoring mode and operating on battery or AC power, respectively. Commercial surface-pads did not create artifacts deeper than 6mm below the skin surface. RF heating was within FDA guidelines. Defibrillation was completely successful inside and outside the MRI bore. Conclusions A prototype MRI-conditional defibrillation system successfully defibrillated in the MRI without degrading image quality, or increasing the time needed for defibrillation. It can increase patient acceptance for MRI procedures.

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“…Coil resonance remained unperturbed when RF cables were touched by hand or by various parts of the animal body. The grounding of the birdcage RF shield to the drive cable jacket [22–24] removed interaction between the coil resonance and the common mode currents in the cable jacket, forgoing the baluns and cable traps that are often used in small animal coils [20, 21]. …”

Section: Resultsmentioning

confidence: 99%

A volume birdcage coil with an adjustable sliding tuner ring for neuroimaging in high field vertical magnets: Ex and in vivo applications at 21.1 T

Cui

Masad

Rosenberg

et al. 2012

Journal of Magnetic Resonance

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A tunable 900 MHz transmit/receive volume coil was constructed for 1H MR imaging of biological samples in a 21.1 T vertical bore magnet. To accommodate a diverse range of specimen and RF loads at such a high frequency, a sliding-ring adaptation of a low-pass birdcage was implemented through simultaneous alteration of distributed capacitance. To make efficient use of the constrained space inside the vertical bore, a modular probe design was implemented with a bottom-adjustable tuning and matching apparatus. The sliding ring coil displays good homogeneity and sufficient tuning range for different samples of various dimensions representing large span of RF loads. High resolution in vivo and ex vivo images of large rats (up to 350 g), mice and human postmortem tissues were obtained to demonstrate coil functionality and to provide examples of potential applications at 21.1 T.

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Floating shield current suppression trap

Cited by 73 publications

References 2 publications

Doppler ultrasound triggering for cardiac MRI at 7T

Doppler ultrasound triggering for cardiac MRI at 7T

A Magnetic Resonance Imaging–Conditional External Cardiac Defibrillator for Resuscitation Within the Magnetic Resonance Imaging Scanner Bore

A volume birdcage coil with an adjustable sliding tuner ring for neuroimaging in high field vertical magnets: Ex and in vivo applications at 21.1 T

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