超短回波时间图像定量高肝铁。
Ultra-short echo time images quantify high liver iron.
机构信息
Department of Biomedical Engineering, University of Southern California, Los Angeles, California, USA.
Division of Cardiology, Children's Hospital Los Angeles, Los Angeles, California, USA.
出版信息
Magn Reson Med. 2018 Mar;79(3):1579-1585. doi: 10.1002/mrm.26791. Epub 2017 Jun 22.
PURPOSE
1.5T gradient echo-based R2∗ estimates are standard-of-care for assessing liver iron concentration (LIC). Despite growing popularity of 3T, echo time (TE) limitations prevent 3T liver iron quantitation in the upper half of the clinical range (LIC ⪆20 mg/g). In this work, a 3D radial pulse sequence was assessed to double the dynamic range of 3T LIC estimates.
THEORY AND METHODS
The minimum TE limits the dynamic range of pulse sequences to estimate R2∗. 23 chronically-transfused human volunteers were imaged with 1.5T Cartesian gradient echo (1.5T-GRE), 3T Cartesian gradient echo (3T-GRE), and 3T ultrashort TE radial (3T-UTE) pulse sequences; minimum TEs were 0.96, 0.76, and 0.19 ms, respectively. R2∗ was estimated with an exponential signal model, normalized to 1.5T equivalents, and converted to LIC. Bland-Altman analysis compared 3T-based estimates to 1.5T-GRE.
RESULTS
LIC by 3T-GRE was unbiased versus 1.5T-GRE for LIC ≤ 25 mg/g (sd = 9.6%); 3T-GRE failed to quantify LIC > 25 mg/g. At high iron loads, 3T-UTE was unbiased (sd = 14.5%) compared to 1.5T-GRE. Further, 3T-UTE estimated LIC up to 50 mg/g, exceeding 1.5T-GRE limits.
CONCLUSION
3T-UTE imaging can reliably estimate high liver iron burdens. In conjunction with 3T-GRE, 3T-UTE allows clinical LIC estimation across a wide range of liver iron loads. Magn Reson Med 79:1579-1585, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
目的
基于 1.5T 梯度回波的 R2∗估计是评估肝脏铁浓度（LIC）的标准方法。尽管 3T 的应用越来越广泛，但由于回波时间（TE）的限制，无法在临床范围内的上半部分（LIC ⪆20mg/g）对 3T 肝脏铁进行定量。在这项工作中，评估了一种 3D 径向脉冲序列，以将 3T LIC 估计的动态范围扩大一倍。
理论与方法
最小 TE 限制了脉冲序列估计 R2∗的动态范围。23 名慢性输血志愿者分别接受 1.5T 笛卡尔梯度回波（1.5T-GRE）、3T 笛卡尔梯度回波（3T-GRE）和 3T 超短 TE 径向（3T-UTE）脉冲序列成像；最小 TE 分别为 0.96、0.76 和 0.19ms。R2∗ 采用指数信号模型进行估计，归一化为 1.5T 等效值，并转换为 LIC。Bland-Altman 分析比较了 3T 基于估计值与 1.5T-GRE 的估计值。
结果
对于 LIC≤25mg/g（sd=9.6%），3T-GRE 的 LIC 相对于 1.5T-GRE 是无偏的；对于 LIC＞25mg/g，3T-GRE 无法定量 LIC。在高铁负荷下，3T-UTE 与 1.5T-GRE 相比是无偏的（sd=14.5%）。此外，3T-UTE 可估计高达 50mg/g 的 LIC，超过了 1.5T-GRE 的限制。
结论
3T-UTE 成像可可靠地估计高肝脏铁负荷。与 3T-GRE 结合使用，3T-UTE 可在广泛的肝脏铁负荷范围内进行临床 LIC 估计。磁共振医学 79：1579-1585，2018。©2017 国际磁共振学会。
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