快速自动化肝脏定量磁化率映射。
Rapid automated liver quantitative susceptibility mapping.
机构信息
Meinig School of Biomedical Engineering, Cornell University, Ithaca, New York, USA.
Department of Radiology, Weill Medical College of Cornell University, New York, New York, USA.
出版信息
J Magn Reson Imaging. 2019 Sep;50(3):725-732. doi: 10.1002/jmri.26632. Epub 2019 Jan 13.
BACKGROUND
Accurate measurement of the liver iron concentration (LIC) is needed to guide iron-chelating therapy for patients with transfusional iron overload. In this work, we investigate the feasibility of automated quantitative susceptibility mapping (QSM) to measure the LIC.
PURPOSE
To develop a rapid, robust, and automated liver QSM for clinical practice.
STUDY TYPE
Prospective.
POPULATION
13 healthy subjects and 22 patients.
FIELD STRENGTH/SEQUENCES: 1.5 T and 3 T/3D multiecho gradient-recalled echo (GRE) sequence.
ASSESSMENT
Data were acquired using a 3D GRE sequence with an out-of-phase echo spacing with respect to each other. All odd echoes that were in-phase (IP) were used to initialize the fat-water separation and field estimation (T *-IDEAL) before performing QSM. Liver QSM was generated through an automated pipeline without manual intervention. This IP echo-based initialization method was compared with an existing graph cuts initialization method (simultaneous phase unwrapping and removal of chemical shift, SPURS) in healthy subjects (n = 5). Reproducibility was assessed over four scanners at two field strengths from two manufacturers using healthy subjects (n = 8). Clinical feasibility was evaluated in patients (n = 22).
STATISTICAL TESTS
IP and SPURS initialization methods in both healthy subjects and patients were compared using paired t-test and linear regression analysis to assess processing time and region of interest (ROI) measurements. Reproducibility of QSM, R *, and proton density fat fraction (PDFF) among the four different scanners was assessed using linear regression, Bland-Altman analysis, and the intraclass correlation coefficient (ICC).
RESULTS
Liver QSM using the IP method was found to be ~5.5 times faster than SPURS (P < 0.05) in initializing T *-IDEAL with similar outputs. Liver QSM using the IP method were reproducibly generated in all four scanners (average coefficient of determination 0.95, average slope 0.90, average bias 0.002 ppm, 95% limits of agreement between -0.06 to 0.07 ppm, ICC 0.97).
DATA CONCLUSION
Use of IP echo-based initialization enables robust water/fat separation and field estimation for automated, rapid, and reproducible liver QSM for clinical applications.
LEVEL OF EVIDENCE
1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:725-732.
背景
为了指导输血性铁过载患者的铁螯合治疗，需要准确测量肝脏铁浓度（LIC）。在这项工作中，我们研究了自动定量磁化率映射（QSM）测量 LIC 的可行性。
目的
开发一种快速、稳健且自动化的临床用肝脏 QSM。
研究类型
前瞻性。
人群
13 名健康受试者和 22 名患者。
磁场强度/序列：1.5T 和 3T/3D 多回波梯度回波（GRE）序列。
评估
使用具有相互相位失谐的 3D GRE 序列采集数据。所有同相（IP）奇数回波都用于在执行 QSM 之前进行脂肪-水分离和场估计（T * -IDEAL）初始化。肝脏 QSM 通过无人工干预的自动化流水线生成。在健康受试者（n=5）中，将这种基于 IP 回波的初始化方法与现有的图切割初始化方法（同时相位解缠和去除化学位移，SPURS）进行了比较。使用健康受试者（n=8），在两个制造商的两个场强的四台扫描仪上评估了可重复性。在 22 名患者中评估了临床可行性。
统计学检验
使用配对 t 检验和线性回归分析比较健康受试者和患者中的 IP 和 SPURS 初始化方法，以评估处理时间和感兴趣区域（ROI）测量值。使用线性回归、Bland-Altman 分析和组内相关系数（ICC）评估四台不同扫描仪之间的 QSM、R *和质子密度脂肪分数（PDFF）的可重复性。
结果
在对 T * -IDEAL 进行初始化时，使用 IP 方法的肝脏 QSM 发现比 SPURS 快约 5.5 倍（P<0.05），而输出结果相似。在所有四台扫描仪中，均能稳定地生成基于 IP 方法的肝脏 QSM（平均决定系数 0.95，平均斜率 0.90，平均偏差 0.002ppm，95%一致性区间在-0.06 到 0.07ppm 之间，ICC 0.97）。
数据结论
使用 IP 回波基初始化可实现稳健的水/脂肪分离和场估计，从而实现临床应用的自动化、快速和可重复的肝脏 QSM。
证据水平
1 技术功效：第 2 阶段 J. 磁共振成像 2019；50：725-732。
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