He Mu, Robertson Scott H, Kaushik S Sivaram, Freeman Matthew S, Virgincar Rohan S, Davies John, Stiles Jane, Foster William M, McAdams H Page, Driehuys Bastiaan
Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, USA; Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA.
Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, USA; Medical Physics Graduate Program, Duke University, Durham, NC, USA.
Magn Reson Imaging. 2015 Sep;33(7):877-85. doi: 10.1016/j.mri.2015.04.005. Epub 2015 Apr 30.
The aim of this study was to evaluate the effect of hyperpolarized (129)Xe 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.
Ten non-smoking older subjects (ages 60.8±7.9years) underwent hyperpolarized (HP) (129)Xe ventilation MRI using both GRE and 3D-radial acquisitions, each tested using a 71ml (high) and 24ml (low) dose equivalent (DE) of fully polarized, fully enriched (129)Xe. For all images SNR and ventilation defect percentage (VDP) were calculated.
Normalized SNR (SNRn), obtained by dividing SNR by voxel volume and dose was higher for high-DE GRE acquisitions (SNRn=1.9±0.8ml(-2)) than low-DE GRE scans (SNRn=0.8±0.2ml(-2)). Radially acquired images exhibited a more consistent, albeit lower SNRn (High-DE: SNRn=0.5±0.1ml(-2), low-DE: SNRn=0.5±0.2ml(-2)). VDP was indistinguishable across all scans.
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 SNRn, 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 (129)Xe dose requirements and quantify the benefits of more efficient transmit/receive coils, field strengths, and pulse sequences.
本研究旨在评估超极化（129）Xe剂量对多层梯度回波和各向同性3D径向采集的通气MRI图像信噪比（SNR）和通气缺陷清晰度的影响。
10名非吸烟老年受试者（年龄60.8±7.9岁）接受了超极化（HP）（129）Xe通气MRI检查，采用GRE和3D径向采集方式，每种采集方式均使用71ml（高）和24ml（低）剂量当量（DE）的完全极化、完全富集的（129）Xe进行测试。计算所有图像的SNR和通气缺陷百分比（VDP）。
通过将SNR除以体素体积和剂量获得的归一化SNR（SNRn），高DE GRE采集（SNRn=1.9±0.8ml（-2））高于低DE GRE扫描（SNRn=0.8±0.2ml（-2））。径向采集的图像显示出更一致的SNRn，尽管较低（高DE：SNRn=0.5±0.1ml（-2），低DE：SNRn=0.5±0.2ml（-2））。所有扫描的VDP无明显差异。
这些结果表明，使用高DE GRE序列采集的图像提供了最高的SNRn，这与文献中先前的报道一致。3D径向图像的SNRn较低，但在视觉显示、监测磁化动力学和可视化生理梯度方面具有优势。通过在剂量当量形式的背景下评估归一化SNR，应该能够预测（129）Xe剂量需求，并量化更高效的发射/接收线圈、场强和脉冲序列的益处。
