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

Abstract Purpose To demonstrate the feasibility of zigzag sampling for 3D rapid hyperpolarized 129 Xe ventilation MRI in human. Methods Zigzag sampling in one direction was combined with gradient‐recalled echo sequence (GRE‐zigzag‐Y) to acquire hyperpolarized 129 Xe 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 129 Xe ventilation images were acquired using zigzag sampling in two directions through GRE‐zigzag‐YZ. 129 Xe 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 129 Xe images with a spatial resolution of 3.96 × 3.96 × 10.5 mm 3 . 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, 129 Xe images with a nominal spatial resolution of 2.5 × 2.5 × 2.5 mm 3 were acquired within 5.5 s per subject using GRE‐zigzag‐YZ. VDP provided by GRE‐zigzag‐YZ was strongly correlated ( R 2 = 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 129 Xe ventilation imaging.