Rapid single-breath hyperpolarized noble gas MRI-based biomarkers of airspace enlargement.

Abstract

Multi-b diffusion-weighted hyperpolarized-gas MRI measures pulmonary airspace-enlargement using apparent diffusion coefficients (ADCs) and mean-linear-intercepts (Lm ). To develop single-breath 3D multi-b diffusion-weighted 3 He and 129 Xe MRI using k-space undersampling. Rapid, cost-efficient, single-breath acquisitions may facilitate clinical translation. Prospective. We evaluated 12 participants, including nine subjects (mean age = 69 ± 9) who were included in the retrospective experiment and three chronic pulmonary obstruction disease (COPD) patients (mean age = 81 ± 6) who participated in the prospective study. A whole-body 3 T 2D/3D fast gradient recall echo (FGRE) sequence. Hyperpolarized 3 He/129 Xe MRI, spirometry, plethysmography computed tomography (CT). We evaluated 129 Xe ADC/morphometry estimates by retrospectively undersampling previously acquired fully sampled multibreath, multi-b diffusion-weighted data. Next, we prospectively evaluated the feasibility of accelerated (AF = 7) 3 He MRI static-ventilation/T2 * (extra short-TE, b = 0 image) and ADC/morphometry (five b-values) maps using a single gas-dose and 16-second breath-hold. To conservatively evaluate cost-improvement, we compared total costs of single vs. multiple 129 Xe doses. Multivariate analysis of variance, independent t-tests and voxel-by-voxel basis difference test. For the retrospectively undersampled 129 Xe data, a nonsignificant mean difference for ADC/Lm of 14%/12%, 12%/8%, and 11%/9% was observed (all, P > 0.4) between the fully sampled and accelerated data for the never-smoker, COPD, and alpha-1 antitrypsin deficiency (AATD) groups, respectively. The control never-smoker group had significantly lower ADC (P < 0.001) and Lm (P < 0.001) than the COPD/AATD group for both fully sampled and accelerated data. For the prospectively acquired 3 He MRI data, static-ventilation, T2 *, ADC, and morphometry maps were acquired using a single 16-second breath-hold scan and single gas dose. Accelerated imaging resulted in cost savings of ~$US 1000/patient, a conservative estimate based on 129 Xe MRI dose savings (single vs. five doses). This is a proof-of-concept demonstration of accelerated (7×) morphometry that shows that less cost- and time-efficient multibreath methods that lead to variability and patient fatigue may be avoided in the future. 2 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018.