Hemodynamic Modeling and Phase-Adjustable Reconstruction of Hyperpolarized Cardiac 13C MRS Using 1H Cine and ECG Timing.

PURPOSE: To deconvolve cardiac phase and hemodynamic effects in hyperpolarized (HP) [1-13C]pyruvate and to develop a cardiac phase-adjustable reconstruction framework.

METHODS

Cardiac phase drift during dynamic acquisition of HP 13C MRS and its effect on dynamic signal fidelity were simulated using a digital cardiac phantom. A hemodynamic model describing ventricular passages of HP pyruvate was developed and applied to dynamic cardiac 13C MRS datasets acquired from healthy volunteers. Timecourses of HP pyruvate from multiphase 13C MRI and 13C MRS were fit to the hemodynamic model and were compared with multiphase 1H and ECG timing. Phase-adjustable reconstruction was demonstrated for ECG-gated and nongated HP 13C MRS.

RESULTS

Phantom simulations demonstrated that heart rate variability induces cardiac phase misalignment, causing substantial distortion of dynamic HP pyruvate timecourses. Human studies showed transient heart rate changes during pyruvate bolus arrival, resulting in phase shifts. Multiphase 13C MRI confirmed that pyruvate signal is correlated with ventricular volume (R2 = 0.88 ± 0.08), with diastolic signals exceeding systolic signals in both ventricles and LV peak less than half of RV. The hemodynamic model accurately depicted in vivo cardiac 13C MRS (R2 > 0.978), separating LV, RV, and recirculation components and estimating pulmonary transit times consistent with image-based measurements. Retrospective phase correction enabled reconstruction of dynamic HP pyruvate timecourses aligned to specific cardiac phases.

CONCLUSION

We present a volume-guided hemodynamic modeling and reconstruction framework that corrects cardiac phase misalignment. This approach improves quantitative robustness across varying heart rates and is applicable to both ECG-gated and nongated acquisitions.