Condition for Optimal Preamplifier Decoupling in One-turn Single- and Multi-gap Shielded Loop MRI Detectors

Wang, Wenjun; Sánchez‐Heredia, Juan D.; Zhurbenko, Vitaliy; Ardenkjær‐Larsen, Jan Henrik

doi:10.1109/ukrmw58013.2022.10037007

Cited by 4 publications

(3 citation statements)

References 16 publications

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“…Since the difference in SNR was below 10%, it could easily be compensated by a closer contact to the ROI in a wearable coil design, where the Rx elements are mounted on an elastic substrate instead of the firm holder as used here. To improve the twisted pair coils’ transmission decoupling, further research into how to optimize port impedance for maximum detuning efficiency may be of interest for future applications, similar to the method used by Wang et al for preamplifier decoupling [ 54 ]. Based on the excellent SNR results, interelement coupling was sufficiently mediated by the heavy loading of the Rx elements for both twisted pair and standard Rx loops.…”

Section: Resultsmentioning

confidence: 99%

Combining Dipole and Loop Coil Elements for 7 T Magnetic Resonance Studies of the Human Calf Muscle

Cap,

Rocha dos Santos,

Repnin

et al. 2024

Sensors

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Combining proton and phosphorus magnetic resonance spectroscopy offers a unique opportunity to study the oxidative and glycolytic components of metabolism in working muscle. This paper presents a 7 T proton calf coil design that combines dipole and loop elements to achieve the high performance necessary for detecting metabolites with low abundance and restricted visibility, specifically lactate, while including the option of adding a phosphorus array. We investigated the transmit, receive, and parallel imaging performance of three transceiver dipoles with six pair-wise overlap-decoupled standard or twisted pair receive-only coils. With a higher SNR and more efficient transmission decoupling, standard loops outperformed twisted pair coils. The dipoles with standard loops provided a four-fold-higher image SNR than a multinuclear reference coil comprising two proton channels and 32% more than a commercially available 28-channel proton knee coil. The setup enabled up to three-fold acceleration in the right–left direction, with acceptable g-factors and no visible aliasing artefacts. Spectroscopic phantom measurements revealed a higher spectral SNR for lactate with the developed setup than with either reference coil and fewer restrictions in voxel placement due to improved transmit homogeneity. This paper presents a new use case for dipoles and highlights their advantages for the integration in multinuclear calf coils.

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Section: Resultsmentioning

confidence: 99%

Combining Dipole and Loop Coil Elements for 7 T Magnetic Resonance Studies of the Human Calf Muscle

Cap,

Rocha dos Santos,

Repnin

et al. 2024

Sensors

View full text Add to dashboard Cite

show abstract

“…4). Using the equations for wire loop impedance [5] and assuming the conductivity of copper at 77K is 10 9 /3.5 S/m, the calculated Zcoil at 32.1 MHz is indicated in Fig. 3.…”

Section: Procedures and Resultsmentioning

confidence: 99%

Manipulating Bandwidth of Cryogenically Cooled Receive-Only MRI Detectors

et al. 2023

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Cryogenically cooled MRI coils demonstrate extremely high Q-factors leading to a very narrow bandwidth. This bandwidth can be increased in a controlled manner using a preamplifier decoupling. In this work, an MRI coil design procedure is explained and an example showing over 2 times bandwidth increase in a cryogenic coil for 13C isotope imaging in 3-tesla MRI systems is demonstrated. The achieved wider bandwidth preserves the spectral components of magnetic resonance signals and makes coils less susceptive to detuning due to parasitic coupling to surrounding structures. The presented method is also useful in other applications of high-Q coils, for instance, in low field magnetic resonance imaging systems.

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“…We also demonstrate how to use |𝐾𝐾(j𝜔𝜔)| ∝ 𝜔𝜔 to build a 13 C- 23 Na coil of which the current values at the resonant frequencies of 13 C (30.99 MHz) and 23 Na (32.59 MHz) are required equal to ensure identical coil sensitivity profiles [4]. This calibration method has been shown previously to measure preamplifier decoupling accurately [5], [6].…”

Section: Introductionmentioning

confidence: 93%

Calibrating Double-Loop H-Field Probe Measurements of RF Coil Current for MRI

Wang,

Sánchez-Heredia,

Maurouard

et al. 2023

IEEE J. Electromagn. RF Microw. Med. Biol.

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A double-loop H-field probe is used to measure current on RF coils for MRI. Direct S parameter measurement, denoted by 𝑆𝑆 21,𝑏𝑏 , is not proportional to coil current. After subtracting the coil-free S parameter, 𝑆𝑆 21,𝑎𝑎 , the quantity 𝑆𝑆 21,cal = 𝑆𝑆 21,𝑏𝑏 − 𝑆𝑆 21,𝑎𝑎 is proportional to coil current. The ratio �𝑆𝑆 21,cal /𝐼𝐼 coil � is plotted for several setups of different probe size, different coil size and different coil-to-probe distance. For double-loop H-field probes of ⌀1.3 cm probes and coil-to-probe distance no less than 5 cm, there is 𝑆𝑆 21,cal /𝐼𝐼 coil ≈ j𝜔𝜔𝜔𝜔 exp(j𝜔𝜔𝜔𝜔) up to 300 MHz, where 𝜔𝜔 < 0 and 𝜔𝜔 < 0 are setup-specific constants.

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Condition for Optimal Preamplifier Decoupling in One-turn Single- and Multi-gap Shielded Loop MRI Detectors

Cited by 4 publications

References 16 publications

Combining Dipole and Loop Coil Elements for 7 T Magnetic Resonance Studies of the Human Calf Muscle

Combining Dipole and Loop Coil Elements for 7 T Magnetic Resonance Studies of the Human Calf Muscle

Manipulating Bandwidth of Cryogenically Cooled Receive-Only MRI Detectors

Calibrating Double-Loop H-Field Probe Measurements of RF Coil Current for MRI

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