Establishing standardized healthy reference distributions and values for multisite ¹²⁹Xe gas exchange MRI/MR...

To establish standardized reference distributions and values for 1-point Dixon ¹²⁹Xe gas exchange MRI/MR spectroscopy (MRS) in a multicenter healthy cohort of 18-30-year-olds scanned on three major 3T platforms. These distributions and values enable consistent, quantitative analysis and interpretation of images and spectra.

Healthy participants from three centers-Duke University (Siemens), Cincinnati Children's Hospital (Philips), and the University of Iowa (General Electric)-underwent pulmonary function testing and a standardized ¹²⁹Xe MRI/MRS protocol with dissolved-phase excitation at 208 ppm from the gas resonance. Raw data were converted to the ISMRMRD format, centrally processed, and used to construct reference values and distributions for each gas-exchange compartment. The combined reference values were compared to site-specific values and, with suitable transformation, to a cohort evaluated with 218 ppm excitation.

The reference distributions were consistent across sites and platforms for both imaging and spectroscopy. Combined imaging reference means were ventilation = 0.71 ± 0.14, membrane (M)/gas = 0.97 ± 0.27 × 10^-2, red blood cell (RBC)/gas = 0.48 ± 0.20 × 10^-2, and RBC:M = 0.49 ± 0.11. Spectroscopic chemical shifts were 197.6 ± 0.3 and 218.2 ± 0.5 ppm for membrane and RBC, with an RBC oscillation amplitude of 10.0 ± 2.5%. Estimated global T₂* values were 0.99 ± 0.04 ms (membrane) and 1.04 ± 0.03 ms (RBC). Quantitative maps showed no significant differences using site-specific versus combined distributions. Scaled 208-ppm distributions agreed well with single-site distributions acquired with 218-ppm excitation.

These reference distributions provide a robust benchmark for 3T ¹²⁹Xe gas exchange MRI/MRS, ensuring rigor, reproducibility, and cross-center comparability.