Whole lung morphometry with 3D multiple b-value hyperpolarized gas MRI and compressed sensing.

PurposeTo demonstrate three-dimensional (3D) multiple b-value diffusion-weighted (DW) MRI of hyperpolarized He-3 gas for whole lung morphometry with compressed sensing (CS). MethodsA fully-sampled, two b-value, 3D hyperpolarized He-3 DW-MRI dataset was acquired from the lungs of a healthy volunteer and retrospectively undersampled in the k(y) and k(z) phase-encoding directions for CS simulations. Optimal k-space undersampling patterns were determined by minimizing the mean absolute error between reconstructed and fully-sampled He-3 apparent diffusion coefficient (ADC) maps. Prospective three-fold, undersampled, 3D multiple b-value He-3 DW-MRI datasets were acquired from five healthy volunteers and one chronic obstructive pulmonary disease (COPD) patient, and the mean values of maps of ADC and mean alveolar dimension (Lm(D)) were validated against two-dimensional (2D) and 3D fully-sampled He-3 DW-MRI experiments. ResultsReconstructed undersampled datasets showed no visual artifacts and good preservation of the main image features and quantitative information. A good agreement between fully-sampled and prospective undersampled datasets was found, with a mean difference of +3.4% and +5.1% observed in mean global ADC and Lm(D) values, respectively. These differences were within the standard deviation range and consistent with values reported from healthy and COPD lungs. ConclusionsAccelerated CS acquisition has facilitated 3D multiple b-value He-3 DW-MRI scans in a single breath-hold, enabling whole lung morphometry mapping. Magn Reson Med 77:1916-1925, 2017. (c) 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.