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

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

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.

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.

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.