Correlating Pulmonary Hemodynamics With HP ¹²⁹ Xe Dissolved‐Phase MRSI in a Controlled Porcine Intervention Study

Purpose Pulmonary hypertension is related to a 1‐year mortality ranging from < 5% to > 20% in low‐ and high‐risk groups. Right heart catheterization is the diagnostic gold standard, associated with a 1.1% rate of severe adverse events, posing the need for a non‐invasive diagnostic tool. This study aims to delineate the effects of controlled changes on pulmonary hemodynamics by quantifying corresponding changes in hyperpolarized 129 Xe MRSI dissolved‐phase parameters, including RBC oscillations. Methods Seven Danish Landrace pigs underwent hyperpolarized 129 Xe dissolved‐phase 3D MRSI with interleaved MRS under baseline conditions and three vasoactive interventions, monitored with invasive catheters or phase‐contrast MRI. Results were evaluated using one‐way ANOVA or mixed‐effects analysis followed by Dunnett's multiple comparisons test. Results Hypoxia increased mPAP ( p = 0.038), reduced RBC:M (−31%, p = 0.007) and RBC:G (−34%, p = 0.009), while increasing RBC chemical shift (0.57%, p = 0.020). Adenosine and dobutamine increased RBC:M (22%, p = 0.003) and RBC:G (30%, p = 0.009), while decreasing RBC chemical shift (−0.38%, p = 0.11). Linear regression revealed an inverse correlation between mPAP and RBC oscillation amplitude ( R 2 = 0.158, p = 0.04), RBC:M ( R 2 = 0.25, p = 0.05), and RBC:G ( R 2 = 0.22, p = 0.01). Conclusion This study demonstrates that dissolved‐phase hyperpolarized 129 Xe MRSI parameters are sensitive to hemodynamic changes, exhibiting consistent inverse relationships with invasively measured mPAP. By leveraging concurrent invasive reference measurements, these findings provide physiological validation that dissolved‐phase 129 Xe metrics reflect pulmonary vascular pressure, supporting their further development as a non‐invasive adjunct to right heart catheterization.