Optimized Spatial-Spectral RF Pulse Design for High-Fidelity and Robust Hyperpolarized MRI

Hyperpolarized MRI (HP MRI) enables real-time metabolic imaging with dramatically enhanced signal-to-noise ratios [1], but current RF pulse sequences lack the precision needed for simultaneous spatial and spectral selectivity. We present a novel optimization framework that generates high-fidelity spatial-spectral RF pulses while minimizing both duration and power requirements. In contrast to existing approaches [2], our use of automatic differentiation incorporates realistic hardware constraints that are typically found in MRI machines. We further demonstrate robust pulse optimization that maintains performance despite B1 field inhomogeneities. This robustness is achieved through a multi-objective optimization that balances excitation fidelity against sensitivity to system imperfections. These advances enable more precise metabolic mapping in challenging applications such as real-time tumor metabolism studies [2], where both spatial precision and chemical specificity are crucial for clinical diagnosis.

[1] Ardenkjaer-Larsen JH, et al. Proc. Natl. Acad. Sci. U. S. A, 100, 10158−10163 (2003).

[2] Maximov, I. I., et al. Journal of Magnetic Resonance, 254, 110–120 (2015).

[3] Kurhanewicz J, et al. Neoplasia (2011).