Optimal Variable Flip Angle Schemes for Multi-Band Dynamic Acquisition of Hyperpolarized 13C MRSI

Yan Xing¹, Galen D. Reed¹, John M. Pauly², Adam B. Kerr², Peder E.Z. Larson¹

Hyperpolarized [1-13C]pyruvate to lactate conversion can be used to discern cancerous tissues from the healthy ones or to monitor cancer progression. Conventionally, the amount of nonrenewable non-equilibrium polarization rapidly diminishes over the duration of the scan, leading to decreased signal level particularly for dynamic acquisitions. We developed a novel approach with multi-band spectral-spatial RF excitation pulses to account for the metabolic conversion, losses due to RF excitation and T1 relaxation, so that a constant signal level can be maintained. Simulations of two approaches showed signal constancy; in vivo experiments also exhibited improved signal.