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.
J Magn Reson Imaging. 2019 Sep;50(3):725-732. doi: 10.1002/jmri.26632. Epub 2019 Jan 13.
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.
To develop a rapid, robust, and automated liver QSM for clinical practice.
Prospective.
13 healthy subjects and 22 patients.
FIELD STRENGTH/SEQUENCES: 1.5 T and 3 T/3D multiecho gradient-recalled echo (GRE) sequence.
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).
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).
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).
Use of IP echo-based initialization enables robust water/fat separation and field estimation for automated, rapid, and reproducible liver QSM for clinical applications.
1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:725-732.
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。
开发一种快速、稳健且自动化的临床用肝脏 QSM。
前瞻性。
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。
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。
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。
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）。
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。
1 技术功效：第 2 阶段 J. 磁共振成像 2019；50：725-732。
