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Characterization of SiN Integrated Optical Phased Arrays on a Wafer-Scale Test Station
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Optically controlled switch-mode current-source amplifiers for on-coil implementation in high-field parallel

Natalia Gudino1, Qi Duan1, Jacco A de Zwart1

  • 1Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.

Magnetic Resonance in Medicine
|August 11, 2015
PubMed
Summary
This summary is machine-generated.

Researchers developed a miniaturized radiofrequency (RF) amplifier for parallel transmission (pTX) in high-field MRI. This on-coil amplifier enables artifact-free imaging at 7T and 11.7T, facilitating advanced pTX array implementation.

Keywords:
RF amplifiershigh-field MRIparallel transmission

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Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Radiofrequency Engineering
  • Biomedical Engineering

Background:

  • Parallel transmission (pTX) in high-field MRI requires efficient and compact radiofrequency (RF) amplifiers.
  • Integrating RF amplifiers directly with transmit coils is challenging due to space and electromagnetic interference constraints.

Purpose of the Study:

  • To test the feasibility of implementing parallel transmission (pTX) for high-field MRI.
  • To design and evaluate a miniaturized RF amplifier for on-coil or near-coil placement.

Main Methods:

  • A current-source switch-mode amplifier using miniaturized, nonmagnetic electronics was designed.
  • Optical RF signals were used for amplifier control, derived from the scanner's RF source via a custom interface.
  • Performance was assessed through benchtop measurements and MRI imaging at 7T and 11.7T, evaluating interchannel coupling and phase adjustment.

Main Results:

  • The amplifier delivered over 44 W RF power with minimal MRI interference.
  • Accurate optical control signals were generated for carrier frequencies from 64 to 750 MHz.
  • Interchannel decoupling better than 14 dB was achieved between closely spaced coil loops (1 cm), enabling artifact-free 7T and 11.7T MRI.

Conclusions:

  • An optically controlled, miniaturized RF amplifier suitable for on-coil implementation at high magnetic fields was developed.
  • This technology facilitates the implementation of high-density pTX arrays for advanced MRI applications.