Open-source implementation of X-nuclear sequences using the Pulseq framework

Purpose: Create vendor-neutral modular sequences for X-nuclear acquisitions and build an X-nuclear-enabled Pulseq interpreter for GE (GE HealthCare, Waukesha, WI) scanners. Methods: We designed a modular 2D gradient echo spiral sequence to support several sequence formats and a modular metabolite-specific 3D balanced steady-state free precession sequence for hyperpolarized (HP) carbon-13 (C-13) MRI. In addition, we developed a new Pulseq interpreter for GE scanners, named TOPPE MNS (TOPPE Multi-Nuclear Spectroscopy), to implement X-nuclear acquisitions capabilities. We evaluated TOPPE MNS and the modular sequences through phantom studies using phosphorus-31 (31P), hydrogen-2 (2H), and C-13 coils, and in vivo studies including a human brain deuterium metabolic imaging study at natural abundance, HP C-13 animal studies, and human renal studies. Results: Data from the C-13 phantom showed the accuracy of designed modular sequences and consistent performance with the product sequences. 31P, 2H, and C-13 phantom studies and a multi-vendor/multi-version C-13 phantom study showed accurate excitation and spatial encoding functionalities. A 2H-MRS brain volunteer study, HP [1-C-13]pyruvate animal study, and human renal study showed good image quality with SNR comparable to those reported in the published literature. These results demonstrated the reproducibility of the TOPPE MNS GE interpreter and modular spiral sequences. Conclusion: We have designed a modular 2D gradient echo spiral sequence supporting several sequence formats and a modular metabolic-specific 3D balanced steady-state free precession sequence for C-13 acquisition, as well as developed a GE interpreter with X-nucleus capabilities. Our work paves the way for future multi-site studies with acquisitions for X-nuclei across MRI vendors and software versions.