Department of Medical Physics and Biomedical Engineering, Centre for Medical Image Computing (CMIC), University College London, London, UK.
Bioxydyn Limited, Manchester, UK.
Magn Reson Med. 2024 Mar;91(3):972-986. doi: 10.1002/mrm.29914. Epub 2023 Nov 27.
To demonstrate proof-of-concept of a T *-sensitized oxygen-enhanced MRI (OE-MRI) method at 3T by assessing signal characteristics, repeatability, and reproducibility of dynamic lung OE-MRI metrics in healthy volunteers.
We performed sequence-specific simulations for protocol optimisation and acquired free-breathing OE-MRI data from 16 healthy subjects using a dual-echo RF-spoiled gradient echo approach at 3T across two institutions. Non-linear registration and tissue density correction were applied. Derived metrics included percent signal enhancement (PSE), ∆R * and wash-in time normalized for breathing rate (τ-nBR). Inter-scanner reproducibility and intra-scanner repeatability were evaluated using intra-class correlation coefficient (ICC), repeatability coefficient, reproducibility coefficient, and Bland-Altman analysis.
Simulations and experimental data show negative contrast upon oxygen inhalation, due to substantial dominance of ∆R * at TE > 0.2 ms. Density correction improved signal fluctuations. Density-corrected mean PSE values, aligned with simulations, display TE-dependence, and an anterior-to-posterior PSE reduction trend at TE . ∆R * maps exhibit spatial heterogeneity in oxygen delivery, featuring anterior-to-posterior R * increase. Mean T * values across 32 scans were 0.68 and 0.62 ms for pre- and post-O inhalation, respectively. Excellent or good agreement emerged from all intra-, inter-scanner and inter-rater variability tests for PSE and ∆R *. However, ICC values for τ-nBR demonstrated limited agreement between repeated measures.
Our results demonstrate the feasibility of a T *-weighted method utilizing a dual-echo RF-spoiled gradient echo approach, simultaneously capturing PSE, ∆R * changes, and oxygen wash-in during free-breathing. The excellent or good repeatability and reproducibility on intra- and inter-scanner PSE and ∆R * suggest potential utility in multi-center clinical applications.
通过评估健康志愿者的动态肺部 OE-MRI 指标的信号特征、可重复性和再现性，证明 T*-敏化的氧增强 MRI（OE-MRI）方法在 3T 下的概念验证。
我们针对协议优化进行了序列特异性模拟，并在 3T 下使用双回波 RF 扰相梯度回波方法在两个机构中从 16 名健康志愿者中获取自由呼吸的 OE-MRI 数据。应用了非线性配准和组织密度校正。得出的指标包括信号增强百分比（PSE）、∆R*和呼吸率归一化的洗入时间（τ-nBR）。使用组内相关系数（ICC）、重复性系数、再现性系数和 Bland-Altman 分析评估了扫描仪间的再现性和扫描仪内的可重复性。
模拟和实验数据显示，由于在 TE > 0.2ms 时 ∆R的显著主导作用，吸氧后出现负对比。密度校正改善了信号波动。与模拟一致，经密度校正的平均 PSE 值在 TE 上显示出依赖性，并且在 TE 时出现从前向后的 PSE 降低趋势。∆R图显示了氧气输送的空间异质性，表现为从前向后的 R增加。32 次扫描的平均 T值分别为吸氧前和吸氧后的 0.68 和 0.62ms。PSE 和 ∆R*的所有内、扫描仪间和观察者间变异性测试均显示出极好或良好的一致性。然而，τ-nBR 的 ICC 值表明重复测量之间的一致性有限。
我们的结果表明，使用双回波 RF 扰相梯度回波方法同时捕获自由呼吸期间的 PSE、∆R变化和氧气洗入，T-加权方法是可行的。扫描仪内和扫描仪间 PSE 和 ∆R*的极好或良好的可重复性和再现性表明，该方法在多中心临床应用中具有潜在的应用价值。
