Enhancing surface coil sensitive volume with hybridized electric dipoles at 17.2 T

Dubois, Marc; Gomez, Tania S. Vergara; Jouvaud, Camille; Ourir, Abdelwaheb; Rosny, Julien de; Kober, Frank; Abdeddaïm, Redha; Enoch, Stefan; Ciobanu, Luisa

doi:10.1016/j.jmr.2019.106567

Cited by 6 publications

(3 citation statements)

References 22 publications

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“…In general, higher static magnetic fields increase the signal-to-noise ratio (SNR), thereby leading to higher spatial resolution images 4,5 . The SNR at lower magnetic fields can also be increased by improving the sensitivity of the receiving coils used in the MRI scanner 6,7 . Typically, a large number (8 to 64) of receiver coils are placed close to the imaging region-of-interest for maximum sensitivity.…”

Section: A Smart Switching System To Enable Automatic Tuning and Detuning Of Metamaterials Resonators In Mri Scansmentioning

confidence: 99%

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

Saha

Pricci

Κουτσουπίδου

et al. 2020

Sci Rep

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We present a radio-frequency-activated switching system that can automatically detune a metamaterial resonator to enhance magnetic resonance imaging (MRI) performance. Local sensitivity-enhancing metamaterials typically consist of resonant components, which means that the transmitted radio frequency field is spatially inhomogeneous. The switching system shows for the first time that a metamaterial resonator can be detuned during transmission and tuned during reception using a digital circuit. This allows a resonating system to maintain homogeneous transmit field while maintaining an increased receive sensitivity. As a result, sensitivity can be enhanced without changing the system-provided specific absorption rate (SAR) models. The developed digital circuit consists of inductors sensitive to the transmit radio-frequency pulses, along with diodes acting as switches to control the resonance frequency of the resonator. We first test the automatic resonator detuning on-the-bench, and subsequently evaluate it in a 1.5 T MRI scanner using tissue-mimicking phantoms. The scan results demonstrate that the switching mechanism automatically detunes the resonator in transmit mode, while retaining its sensitivity-enhancing properties (tuned to the Larmor frequency) in receive mode. Since it does not require any connection to the MRI console, the switching system can have broad applications and could be adapted for use with other types of MRI scanners and field-enhancing resonators.

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Section: A Smart Switching System To Enable Automatic Tuning and Detuning Of Metamaterials Resonators In Mri Scansmentioning

confidence: 99%

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

Saha

Pricci

Κουτσουπίδου

et al. 2020

Sci Rep

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“…Volume coils with designs like the birdcage coil [9,10] and the transverse-electromagnetic coil (TEM) [11,12] are usually used as transmit coils due to their uniform eld distribution. Surface coils, such as loop coils or arrays of loops, are placed closely to the sample to detect the MR signal due to their high sensitivity [8, 13,14]. An RF front end in MRI uses the standard concepts of conjugate and noise matching for power delivery e ciency and lower noise performance, respectively.…”

Section: Introductionmentioning

confidence: 99%

Design of Standalone Wireless Impedance Matching (SWIM) System for RF Coils in MRI

Kandala

Sohn

2022

Preprint

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The radio frequency (RF) power transfer efficiency of transmit coils and the signal-to-noise ratio (SNR) at the receive signal chain are directly dependent on the impedance matching condition presented by a loaded coil, tuned to the Larmor frequency. Sub-optimal impedance condition of receive coils significantly reduce coil sensitivity and image quality. In this study we propose a Standalone Wireless Impedance Matching (SWIM) system for RF coils to automatically compensate for the impedance mismatch caused by the loading effect at the target frequency. SWIM uses a built-in RF generator to produce a calibration signal, measure reflected power as feedback for loading change, and determine an optimal impedance. The matching network consists of a capacitor array with micro-electromechanical system (MEMS) RF switches to electronically cycle through different input impedance conditions. Along with automatic calibration, SWIM can also perform software detuning of RF receive coils. An Android mobile application was developed to monitor reflected power in real-time and control the SWIM system wirelessly via Bluetooth. The SWIM system can automatically calibrate the coil to a 33 dB return loss in 3 seconds and the SNR was improved by 24% (26.85 dB to 34.15 dB) when compared to a loaded coil without retuning.

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“…Volume coils with designs like the birdcage coil 10,11 and the transverse-electromagnetic coil (TEM) 12,13 are usually used as transmit coils due to their uniform field distribution. Surface coils, such as loop coils or arrays of loops, are placed closely to the sample to detect the MR signal due to their high sensitivity 9,14,15 . An RF front end in MRI uses the standard concepts of conjugate and noise matching for power delivery efficiency and lower noise performance, respectively.…”

mentioning

confidence: 99%

Design of standalone wireless impedance matching (SWIM) system for RF coils in MRI

Kandala

Sohn

2022

Sci Rep

View full text Add to dashboard Cite

The radio frequency (RF) power transfer efficiency of transmit coils and the signal-to-noise ratio (SNR) at the receive signal chain are directly dependent on the impedance matching condition presented by a loaded coil, tuned to the Larmor frequency. Sub-optimal impedance condition of receive coils significantly reduces coil sensitivity and image quality. In this study we propose a Standalone Wireless Impedance Matching (SWIM) system for RF coils to automatically compensate for the impedance mismatch caused by the loading effect at the target frequency. SWIM uses a built-in RF generator to produce a calibration signal, measure reflected power as feedback for loading change, and determine an optimal impedance. The matching network consists of a capacitor array with micro-electromechanical system (MEMS) RF switches to electronically cycle through different input impedance conditions. Along with automatic calibration, SWIM can also perform software detuning of RF receive coils. An Android mobile application was developed for real-time reflected power monitoring and controlling the SWIM system via Bluetooth. The SWIM system can automatically calibrate an RF coil in 3 s and the saline sample SNR was improved by 24% when compared to a loaded coil without retuning. Four different tomatoes were imaged to validate the performance of SWIM.

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Enhancing surface coil sensitive volume with hybridized electric dipoles at 17.2 T

Cited by 6 publications

References 22 publications

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

Design of Standalone Wireless Impedance Matching (SWIM) System for RF Coils in MRI

Design of standalone wireless impedance matching (SWIM) system for RF coils in MRI

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Enhancing surface coil sensitive volume with hybridized electric dipoles at 17.2 T

Cited by 6 publications

References 22 publications

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

A smart switching system to enable automatic tuning and detuning of metamaterial resonators in MRI scans

Design of Standalone Wireless Impedance Matching (SWIM) System for RF Coils in MRI

Design of standalone wireless impedance matching (SWIM) system for RF coils in MRI

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Product

Resources

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Enhancing surface coil sensitive volume with hybridized electric dipoles at 17.2 T