Comparison of Hyperpolarized 3He and 129Xe MR Imaging in Cystic Fibrosis Patients

Purpose: In this study, we compared hyperpolarized He-3 and Xe-129 images from patients with cystic fibrosis using two commonly applied magnetic resonance sequences, standard gradient echo (GRE) and balanced steady-state free precession (TrueFISP) to quantify regional similarities and differences in signal distribution and defect analysis. Materials and Methods: Ten patients (7M/3F) with cystic fibrosis underwent hyperpolarized gas MR imaging with both He-3 and Xe-129. Six had MRI with both GRE, and TrueFISP sequences and four patients had only GRE seuence but not TrueFISP. Ventilation defect percentages (VDPs) were calculated as lung voxels with <60% of the whole-lung hyperpolarized gas signal mean and was measured in all datasets. The voxel signal distributions of both Xe-129 and He-3 gases were visualized and compared using violin plots. VDPs of hyperpolarized He-3 and Xe-129 were compared in Bland-Altman plots; Pearson correlation coefficients were used to evaluate the relationships between inter-gas and inter-scan to assess the reproducibility. Results: A significant correlation was demonstrated between Xe-129 VDP and He-3 VDP for both GRE and TrueFISP sequences (rho = 0.78, rho<0.0004). The correlation between the GRE and TrueFISP VDP for He-3 was rho = 0.98 and was rho = 0.91 for Xe-129. Overall, Xe-129 (27.2 +/- 9.4) VDP was higher than He-3 (24.3 +/- 6.9) VDP on average on cystic fibrosis patients. Conclusion: In patients with cystic fibrosis, the selection of hyperpolarized Xe-129 or He-3 gas is most likely inconsequential when it comes to measure the overall lung function by VDP although Xe-129 may be more sensitive to starker lung defects, particularly when using a TrueFISP sequence.