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Abstract #3441

Switching pTx: Time-Division Multiplexing for Improved kT Points Excitation with a Limited Number of RF Power Amplifiers

Felix Glang1, Georgiy A. Solomakha1, Dario Bosch1,2, Klaus Scheffler1,2, and Nikolai I. Avdievich1
1Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Department of Biomedical Magnetic Resonance, Eberhard Karls University Tübingen, Tübingen, Germany

Synopsis

Keywords: Parallel Transmit & Multiband, High-Field MRI, multiplexing, RF switch, SAR, flip angle homogeneity

Motivation: Parallel transmission is a key technology to mitigate B1+ inhomogeneity and increased power deposition in ultra-high field MRI. Its performance is limited by the number of available Tx channels.

Goal(s): Improving excitation homogeneity by time-division multiplexing of 16 Tx elements between 8 RF power amplifiers.

Approach: An RF switch was built to alternately route 8 RFPAs to each row of a double-row 16-element coil array. The setup was tested for kT points excitation at 9.4T.

Results: With the proposed time-division multiplexing, similar excitation fidelity as with 16 channels can be achieved with only 8 channels, but at the expense of increased SAR.

Impact: Time-division multiplexing allows driving a larger number of Tx elements with a smaller number of RFPAs, resulting in improved pTx performance. This opens up new possibilities for using advanced multi-row pTx coils in sites with only 8 RFPAs available.

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Keywords