Power amplifier for magnetic resonance imaging using unconventional Cartesian feedback loop

Abuelhaija, Ashraf; Solbach, Klaus; Buck, Adam

doi:10.1109/gemic.2015.7107767

Cited by 9 publications

(7 citation statements)

References 29 publications

(39 reference statements)

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“…This can be achieved by first measuring the current within the transmit radiofrequency coil that is responsible for generating the 𝐵 field. In view of this, [18][19][20][21][22][23][24] integrated a current sensor into the transmit coil to measure its current flow. In [18], the obtained current sensing information was used to compute RF shim weights for minimizing 𝐵 non-uniformities, while Zanchi et al [19] controlled the coil current using a Cartesian feedback loop (FBL) without using any extra field sensor.…”

Section: Introductionmentioning

confidence: 99%

“…This design not only allowed control of the coil current but also offered coil decoupling. For coil current sensing using this design, the PA first uses an unconventional Cartesian FBL to compensate for cur-rent variations in the array coil by controlling the output voltage of the PA [24]. The PA output is connected to the coil using a tuned (N × half-wavelength) cable, with the current flowing into the coil being independent of load impedance and proportional to the voltage at the transformer's primary side.…”

Section: Introductionmentioning

confidence: 99%

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Built-In Coil Current Sensing for 7-Tesla 1H/23Na and 1H/31P Magnetic Resonance Imaging

Abuelhaija,

Saleh,

Issa

et al. 2024

J. Electromagn. Eng. Sci

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This article introduces two designs for dual-tuned built-in radio-frequency coil current sensing in 7-Tesla magnetic resonance imaging based on the current forcing property of the quarter-wave transmission line. The first design offers dual-tuned built-in coil current sensing at 1H/23Na resonant frequencies to probe the coil current consecutively at 298 MHz and 78.8 MHz, without the need for any integrated sensor on the coil. The second design enables dual-tuned built-in coil current sensing at 1H/31P resonant frequencies to probe the coil current at 298 MHz and 120 MHz consecutively. The first design achieved good matching (<-40 dB) and low insertion loss (<0.5 dB) for 1H and 23Na magnetic resonance signals. The 1H/31P design also exhibited good matching (<-30 dB) and low insertion loss (<0.67 dB). Therefore, both designs show promising potential for monitoring current flows in dual-tuned coils at the Larmor frequencies of different atomic nuclei.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Built-In Coil Current Sensing for 7-Tesla 1H/23Na and 1H/31P Magnetic Resonance Imaging

Abuelhaija,

Saleh,

Issa

et al. 2024

J. Electromagn. Eng. Sci

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“…A wide range of existing and emerging applications require the delivery of radio-frequency (rf) power into widely-varying loads at power levels up to several kilowatts and beyond. Examples include magnetic resonance imaging [1], [2], wireless communications [3], wireless power transfer [4]- [8], and plasma generation [9], [10]. The wide variation in load impedance in many of these applications makes it challenging to achieve efficient rf power generation while maintaining acceptable loading of the rf amplifier or inverter, and providing accurate control of power delivered to the load.…”

Section: Introductionmentioning

confidence: 99%

A 1.5 kW Radio-Frequency Tunable Matching Network Based on Phase-Switched Impedance Modulation

Bastami

Jurkov

Nguyen

et al. 2020

IEEE Open J. Power Electron.

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Dynamically-tunable impedance matching is a key feature in numerous radio-frequency (RF) applications at high frequencies (10 s of MHz) and power levels (100s-1000 s of Watts and above). This work develops techniques that enable the design of high power tunable matching networks (TMN) that can be tuned orders of magnitude faster than with conventional tunable impedance matching techniques, while realizing the high power levels required for many industrial applications. This is achieved by leveraging an emerging technique -known as phase-switched impedance modulation (PSIM), which involves switching passive elements at the rf operating frequency -that has previously been demonstrated at rf frequencies at up to a few hundred Watts. In this paper, we develop design approaches that enable it to be practically used at up to many kilowatts of power at frequencies in the 10 s of MHz. A detailed analysis of the factors affecting the losses as well as the tradeoffs of a basic PSIM-based element is provided. Furthermore, it is shown how incorporating additional stages to the PSIM-based element, including impedance scaling and / or the addition of series or shunt passive elements, influences the losses and enables the efficient processing of high power levels given the limitations of available switches. A PSIM-based TMN that matches load impedances to 50 and delivers up to 1.5 kW of power at frequencies centered around 13.56 MHz is implemented and tested over a load impedance range suitable for various industrial plasma processes.

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“…For example, Cartesian feedback loops were developed, and their performances were verified for 3 T [36] and 7 T [37] MRI systems. An unconventional Cartesian feedback loop was additionally developed and implemented in [38]. It has been used with a new concept of coil current sensing by using a special combination of power amplifiers and coils [39].…”

Section: Introductionmentioning

confidence: 99%

Port Decoupling vs Array Elements Decoupling for Tx/Rx System at 7-Tesla Magnetic Resonance Imaging

Abuelhaija¹,

Salama²,

Baldawi³

2020

PIER C

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Symmetrically excited meandered microstrip line RF coil elements are widely used in multichannel approaches; i.e., being integrated in ultra-high field magnetic resonance imaging (MRI) systems (i.e., 7-Tesla and higher). These elements have demonstrated strong magnetic field in deep areas through the object under imaging. Designing a radio frequency (RF) coil array that employs these elements without decoupling networks might cause non-optimized driving performance of coil array which in turn result in non-clear image. In this paper, two different methods of decoupling are studied: port decoupling and array elements decoupling. In the first one, the coil elements are designed at Larmor frequency (297.3 MHz), while in the other one, the coil elements are designed at higher frequencies but matched at Larmor frequency. Port decoupling does not always mean element decoupling. Conventional decoupling methods, such as single capacitor or inductor, face challenges to realize the coil element decoupling for meandered microstrip arrays. An optimized reactive (T-shaped) network is needed in order to achieve element decoupling which in turn prevents distortion of the EM field. All simulation results have been obtained using the CST time domain solver (CST AG, Darmstadt, Germany).

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Power amplifier for magnetic resonance imaging using unconventional Cartesian feedback loop

Cited by 9 publications

References 29 publications

Built-In Coil Current Sensing for 7-Tesla 1H/23Na and 1H/31P Magnetic Resonance Imaging

Built-In Coil Current Sensing for 7-Tesla 1H/23Na and 1H/31P Magnetic Resonance Imaging

A 1.5 kW Radio-Frequency Tunable Matching Network Based on Phase-Switched Impedance Modulation

Port Decoupling vs Array Elements Decoupling for Tx/Rx System at 7-Tesla Magnetic Resonance Imaging

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