Dose and pulse sequence considerations for hyperpolarized 129Xe ventilation MRI

Purpose: The aim of this study was to evaluate the effect of hyperpolarized Xe-129 dose on image signal-to-noise ratio (SNR) and ventilation defect conspicuity on both multi-slice gradient echo and isotropic 3D-radially acquired ventilation MRI. Materials and methods: Ten non-smoking older subjects (ages 60.8 +/- 7.9 years) underwent hyperpolarized (HP) Xe-129 ventilation MRI using both GRE and 3D-radial acquisitions, each tested using a 71 ml (high) and 24 ml (low) dose equivalent (DE) of fully polarized, fully enriched Xe-129. For all images SNR and ventilation defect percentage (VDP) were calculated. Results: Normalized SNR (SNRn), obtained by dividing SNR by voxel volume and dose was higher for high-DE GRE acquisitions (SNRn = 1.9 +/- 0.8 ml(-2)) than low-DE GRE scans (SNRn = 0.8 +/- 0.2 ml(-2)). Radially acquired images exhibited a more consistent, albeit lower SNRn (High-DE: SNRn = 0.5 +/- 0.1 ml(-2), low-DE: SNRn = 0.5 +/- 02 ml(-2)). VDP was indistinguishable across all scans. Conclusions: These results suggest that images acquired using the high-DE GRE sequence provided the highest SNRn, which was in agreement with previous reports in the literature. 3D-radial images had lower SNR, but have advantages for visual display, monitoring magnetization dynamics, and visualizing physiological gradients. By evaluating normalized SNR in the context of dose-equivalent formalism, it should be possible to predict Xe-129 dose requirements and quantify the benefits of more efficient transmit/receive coils, field strengths, and pulse sequences. (C) 2015 Elsevier Inc. All rights reserved.