Rapid pulmonary ¹²⁹Xe ventilation MRI of discharged COVID-19 patients with zigzag sampling

Purpose: To demonstrate the feasibility of zigzag sampling for 3D rapid hyperpolarized ¹²⁹Xe ventilation MRI in human.

Methods: Zigzag sampling in one direction was combined with gradient-recalled echo sequence (GRE-zigzag-Y) to acquire hyperpolarized ¹²⁹Xe ventilation images. Image quality was compared with a balanced SSFP (bSSFP) sequence with the same spatial resolution for 12 healthy volunteers (HVs). For another 8 HVs and 9 discharged coronavirus disease 2019 subjects, isotropic resolution ¹²⁹Xe ventilation images were acquired using zigzag sampling in two directions through GRE-zigzag-YZ. ¹²⁹Xe ventilation defect percent (VDP) was quantified for GRE-zigzag-YZ and bSSFP acquisitions. Relationships and agreement between these VDP measurements were evaluated using Pearson correlation coefficient (r) and Bland-Altman analysis.

Results: For 12 HVs, GRE-zigzag-Y and bSSFP required 2.2 s and 10.5 s, respectively, to acquire ¹²⁹Xe images with a spatial resolution of 3.96 × 3.96 × 10.5 mm³. Structural similarity index, mean absolute error, and Dice similarity coefficient between the two sets of images and ventilated lung regions were 0.85 ± 0.03, 0.0015 ± 0.0001, and 0.91 ± 0.02, respectively. For another 8 HVs and 9 coronavirus disease 2019 subjects, ¹²⁹Xe images with a nominal spatial resolution of 2.5 × 2.5 × 2.5 mm³ were acquired within 5.5 s per subject using GRE-zigzag-YZ. VDP provided by GRE-zigzag-YZ was strongly correlated (R² = 0.93, p < 0.0001) with that generated by bSSFP with minimal biases (bias = -0.005%, 95% limit-of-agreement = [-0.414%, 0.424%]).

Conclusion: Zigzag sampling combined with GRE sequence provides a way for rapid ¹²⁹Xe ventilation imaging.