Abstract
PurposeTo obtain whole lung morphometry measurements from 129Xe in a single breath‐hold with 3D multiple b‐value 129Xe diffusion‐weighted MRI (DW‐MRI) with an empirically optimized diffusion time and compressed sensing for scan acceleration.MethodsProspective three‐fold undersampled 3D multiple b‐value hyperpolarized 129Xe DW‐MRI datasets were acquired, and the diffusion time (Δ) was iterated so as to provide diffusive length scale (LmD) estimates from the stretched exponential model (SEM) that are comparable to those from 3He. The empirically optimized 129Xe diffusion time was then implemented with a four‐fold undersampling scheme and was prospectively benchmarked against 3He measurements in a cohort of five healthy volunteers, six ex‐smokers, and two chronic obstructive pulmonary disease patients using both SEM‐derived LmD and cylinder model (CM)‐derived mean chord length (Lm).ResultsGood agreement between the mean 129Xe and 3He LmD (mean difference, 2.2%) and Lm (mean difference, 1.1%) values was obtained in all subjects at an empirically optimized 129Xe Δ = 8.5 ms.ConclusionCompressed sensing has facilitated single‐breath 3D multiple b‐value 129Xe DW‐MRI acquisitions, and results at 129Xe Δ = 8.5 ms indicate that 129Xe provides a viable alternative to 3He for whole lung morphometry mapping with either the SEM or CM. Magn Reson Med 79:2986–2995, 2018. © 2017 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 Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Highlights
The apparent diffusion coefficient (ADC) calculated from hyperpolarized 3He diffusion-weighted MRI (DW-MRI) has been shown to be sensitive to changes in lung microstructure [1,2]
(0.0329 cm2/s) and fully sampled mean 129Xe ADC (0.0325 cm2/s) for one volunteer (HV1) was similar to the small differences we reported previously between fully sampled and Compressed sensing (CS) undersampled 2D and 3D 3He ADC values [10,28]
This indicates that any mismatch between 3He and 129Xe LmD values at the 129Xe D 1⁄4 8.5 ms is of the order of same-day reproducibility error, and we conclude that comparable lung morphometry maps can be obtained with 129Xe
Summary
The apparent diffusion coefficient (ADC) calculated from hyperpolarized 3He diffusion-weighted MRI (DW-MRI) has been shown to be sensitive to changes in lung microstructure [1,2]. The signal decay is determined by experimental and physiological factors including gas diffusivity, diffusion gradient strengths and timings, and the complexity of alveolar microstructure, which together influence the measurement of ADC [4,5] Theoretical diffusion models, such as the cylinder model (CM) [6,7], stretched exponential model (SEM) [8], and q-space analysis [9], have been proposed to model this non-Gaussian diffusion behavior and derive estimates of alveolar length scales (i.e., morphometry) from multiple b-value DW-MRI acquisitions. Lm is subsequently derived from the alveoli surface area and volume based upon the geometrical parameters of R and h [7]
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