Multiple breath washout of hyperpolarized 129 Xe and 3 He in human lungs with three-dimensional balanced steady-state free-precession imaging

Abstract

Purpose: To compare quantitative fractional ventilation measurements from multiple breath washout imaging (MBW-I) using hyperpolarized ³ He with both spoiled gradient echo (SPGR) and balanced steady-state free precession (bSSFP) three-dimensional (3D) pulse sequences and to evaluate the feasibility of MBW-I with hyperpolarized ¹²⁹ Xe.

Methods: Seven healthy subjects were scanned using ³ He MBW-I with 3D SPGR and bSSFP sequences. Five also underwent MBW-I with ¹²⁹ Xe. A dual-tuned coil was used to acquire MBW-I data from both nuclei in the same subject position, enabling direct comparison of regional information.

Results: High-quality MBW images were obtained with bSSFP sequences using a reduced dose (100 mL) of inhaled hyperpolarized ³ He. 3D MBW-I with ¹²⁹ Xe was also successfully demonstrated with a bSSFP sequence. Regional quantitative ventilation measures derived from ³ He and ¹²⁹ Xe MBW-I correlated well in all subjects (P < 0.001) with mean Pearson's correlation coefficients of r = 0.61 and r = 0.52 for ³ He SPGR-bSSFP and ¹²⁹ Xe-³ He (bSSFP) comparisons. The average intersubject mean difference (and standard deviation) in fractional ventilation in SPGR-bSSFP and ¹²⁹ Xe-³ He comparisons was 15% (28%) and 9% (38%), respectively.

Conclusions: Improved sensitivity in MBW-I can be achieved with polarization-efficient bSSFP sequences. Same scan-session 3D MBW-I with ³ He and ¹²⁹ Xe has been demonstrated using a dual-tuned coil. Magn Reson Med 77:2288-2295, 2017. © 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 Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Keywords: 129Xe; 3He; hyperpolarized gas; lung function; multiple breath washout.

Figure 1

Representative results from MBW‐I. Comparison of ³He MBW‐I with SPGR with bSSFP sequences (subject 4) and comparison of ¹²⁹Xe and ³He bSSFP MBW‐I (subject 3). Schematic lung volume curve during MBW‐I as derived from flow recordings at the mouth. Fractional ventilation maps of the slices shown in panel A. For all acquisitions, the time delay between images was fixed to 4 s to allow subjects to comfortably complete one breathing cycle.

Figure 2

(A, B) Comparative fractional ventilation maps from ³He MBW‐I using bSSFP and SPGR sequences (subject 6) (A) and from ¹²⁹Xe and ³He MBW‐I using bSSFP sequences (subject 3) (B). (C) Voxel‐by‐voxel correlation plots of the datasets in panel A (top, r = 0.56) and panel B (bottom, r = 0.81). The solid red line indicates the line of unity, and the color map represents the density of points, with blue <10 and red >30.

Figure 3

Comparison of fractional ventilation maps derived from subject 2 using low‐resolution SPGR and high‐resolution bSSFP imaging sequences with hyperpolarized ³He. The k‐space of the SPGR acquisition was zero‐filled before reconstruction to mimic the resolution of the bSSFP images. Fractional ventilation maps from selected slices (anterior to posterior) are shown, along with whole‐lung fractional ventilation histograms. Slight differences in the intensity of the maps from each acquisition result from using the same color map in both cases. Different average fractional ventilation values were obtained (SPGR average [standard deviation] r = 0.33 [0.10], bSSFP average [standard deviation] r = 0.28 [0.11]); see also the shift in peak position of the histograms.