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

PURPOSE

In this study, we compared hyperpolarized He and Xe 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 and Xe. Six had MRI with both GRE, and TrueFISP sequences and four patients had only GRE sequence 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 and He gases were visualized and compared using violin plots. VDPs of hyperpolarized 3 He and 129 Xe 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 VDP and He VDP for both GRE and TrueFISP sequences (ρ = 0.78, p<0.0004). The correlation between the GRE and TrueFISP VDP for He was ρ = 0.98 and was ρ = 0.91 for Xe. Overall, Xe (27.2±9.4) VDP was higher than He (24.3±6.9) VDP on average on cystic fibrosis patients.

CONCLUSION

In patients with cystic fibrosis, the selection of hyperpolarized Xe or He gas is most likely inconsequential when it comes to measure the overall lung function by VDP although Xe may be more sensitive to starker lung defects, particularly when using a TrueFISP sequence.