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Abstract #1328

New method to characterize and correct with sub-µs precision gradient delays in bipolar multi-spoke RF pulses

Vincent Gras1, Alexandre Vignaud1, Alexis Amadon1, Franck Mauconduit2, Denis Le Bihan1, and Nicolas Boulant1

1UNIRS, CEA/DRF/I2BM/Neurospin, Gif-sur-Yvette, France, 2Siemens Healthcare, Saint Denis, France

Small gradient delays with respect to radiofrequency (RF) pulses can have disastrous effects on the performance of bipolar spokes RF pulses employed in parallel transmission (pTx) to mitigate RF field inhomogeneity problems. This work reports a new method to characterize this delay with a precision of ~20 ns, shown to appear necessary for high performance pTx. By the same token, the same physics principles underlying the method suggest a way to correct for it by simply phase-shifting every second spoke RF pulse. The technique is validated with measurements on a water phantom and on an adult volunteer at 7T.

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