0.55T下的自由呼吸PDFF和R2*定量：降低的呼吸运动敏感性与时间分辨4D MRI方法
Free-Breathing PDFF and R2* Quantification at 0.55T: Reduced Respiratory Motion Sensitivity and a Time-Resolved 4D MRI Approach
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- New York University Grossman School of Medicine（纽约大学格罗斯曼医学院）
- Icahn School of Medicine at Mount Sinai（西奈山伊坎医学院）
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中文总结 AI 辅助
本研究在0.55T下开发了时间分辨4D自由呼吸MRI方法，发现R2*对呼吸运动敏感性低于3T，结合时间分辨重建可提高肝脏PDFF/R2*定量的运动稳健性。
中文摘要 AI 辅助
目的：自由呼吸多回波MRI能够在无需屏气的情况下实现肝脏PDFF/R2*定量，但呼吸运动可能通过运动引起的场变化影响R2*估计。我们研究了在0.55T下与3T相比，呼吸运动敏感性是否降低，并开发了一种无需呼吸分箱的时间分辨自由呼吸4D MRI方法。方法：实现了一种带有导航仪的多回波堆叠之星序列。在3T和0.55T下，对十名受试者在自由呼吸和故意体动期间进行了扫描。数据分别采用运动平均、运动分辨和时间分辨方法进行重建。还在PDFF/R2*体模中采用笛卡尔和径向采集评估了定量性能。结果：体模实验显示，在3T下R2*和PDFF的径向-笛卡尔结果高度一致。在0.55T下，R2*在低至中等范围内表现出良好的一致性，但在高R2*处不确定性更高，同时观察到较大的径向-笛卡尔PDFF差异。R2*在0.55T下对呼吸运动的敏感性显著低于3T，而PDFF在两种场强下均相对不敏感。在体动条件下，时间分辨重建提供了稳健的R2*和PDFF测量，特别是在0.55T下自由呼吸和体动采集之间的一致性非常高。结论：R2*定量在0.55T下对呼吸运动的敏感性低于3T，而PDFF保持相对不敏感。时间分辨重建为体动提供了额外的稳健性。0.55T下降低的磁化率效应和时间分辨重建可能为运动稳健的自由呼吸肝脏R2*和PDFF定量提供互补优势。
英文摘要
Purpose: Free-breathing multi-echo MRI enables hepatic PDFF/R2* quantification without breath-holds, but respiratory motion can affect R2* estimation through motion-induced field variations. We investigated whether respiratory motion sensitivity is reduced at 0.55T versus 3T and developed a time-resolved free-breathing 4D MRI approach without respiratory binning. Methods: A navigator-embedded multi-echo stack-of-stars sequence was implemented. Ten subjects were scanned during free breathing and deliberate bulk motion at both 3T and 0.55T. Data were reconstructed using motion-averaged, motion-resolved, and time-resolved approaches. Quantitative performance was also evaluated in a PDFF/R2* phantom using Cartesian and radial acquisitions. Results: Phantom experiments showed close radial-Cartesian agreement for R2* and PDFF at 3T. At 0.55T, R2* showed good agreement over the low-to-moderate range but higher uncertainty at high R2*, where larger radial-Cartesian PDFF differences were also observed. R2* was substantially less sensitive to respiratory motion at 0.55T than at 3T, whereas PDFF was relatively insensitive at both field strengths. Under bulk motion, time-resolved reconstruction provided robust R2* and PDFF measurements, with particularly high consistency between free-breathing and bulk-motion acquisitions at 0.55T. Conclusion: R2* quantification was less sensitive to respiratory motion at 0.55T than at 3T, while PDFF remained relatively insensitive. Time-resolved reconstruction provided additional robustness to bulk motion. Reduced susceptibility effects at 0.55T and time-resolved reconstruction may provide complementary advantages for motion-robust free-breathing hepatic R2* and PDFF quantification.
