pTx-Pulseq in hybrid sequences: Accessible and advanced hybrid open-source MRI sequences on Philips scanners

To enhance the accessibility of advanced pulse sequences, or parts thereof, through the open-source Pulseq framework. This work extends the Pulseq framework to Philips MRI systems and incorporates dynamic parallel-transmit (pTx) capabilities within the constraints of the existing Pulseq format. This enables the hybrid use of Pulseq sequences within the native vendor's scans, leveraging the combined strengths of both approaches. We showcase a new possibility of these techniques: the use of a portable cross-vendor universal pulse (UP) excitation in a native scan.

pTx-Pulseq was implemented to add full dynamic pTx within the Pulseq specification. We developed a Pulseq interpreter for Philips systems, supporting both Pulseq-only and hybrid sequences. The hybrid mode was used to integrate a UP from the PASTeUR package into a vendor's native scan. Simulation experiments, safety validations, field measurements, and imaging experiments in phantom and in vivo were conducted to verify the interpreter's and UP's functionality.

The interpreter executed Pulseq sequences on a Philips 7T system, accurately reproducing gradient waveforms and dynamic pTx sequences. The real-time safety systems operated correctly. Phantom and in vivo scans demonstrated comparable image quality to native sequences, validating the effectiveness of the interpreter and the successful cross-vendor use of universal pulses.

The successful cross-vendor application of a universal pulse through pTx-Pulseq in a hybrid sequence demonstrates how advanced MRI techniques can be made accessible. This not only highlights the flexibility and extensibility of Pulseq but also sets the stage for rapid clinical translation of innovative imaging techniques.