Comparison of automated and manual protocols for magnetic resonance imaging assessment of liver iron concentration

Abstract Objective: To compare automated and manual magnetic resonance imaging protocols for estimating liver iron concentrations at 1.5 T. Materials and Methods: Magnetic resonance imaging examination of the liver was performed in 53 patients with clinically suspected hepatic iron overload and in 21 control subjects. Liver iron concentrations were then estimated by two examiners who were blinded to the groups. The examiners employed automated T2* and T1 mapping, as well as manual T2* and signal-intensity-ratio method. We analyzed accuracy by using ROC curves. Interobserver and intraobserver agreement were analyzed by calculating two-way intraclass correlation coefficients. Results: The area under the ROC curve (to discriminate between patients and controls) was 0.912 for automated T2* mapping, 0.934 for the signal-intensity-ratio method, 0.908 for manual T2*, and 0.80 for T1 mapping, the last method differing significantly from the other three. The level of interobserver and intraobserver agreement was good (intraclass correlation coefficient, 0.938-0.998; p < 0.05). Correlations involving T1 mapping, although still significant, were lower. Conclusion: At 1.5 T, T2* mapping is a rapid tool that shows promise for the diagnosis of liver iron overload, whereas T1 mapping shows less accuracy. The performance of T1 mapping is poorer than is that of T2* methods.

摘要 研究目的：对比1.5 T场强下自动化与手动磁共振成像（magnetic resonance imaging, MRI）方案估算肝脏铁浓度的效能。
材料与方法：纳入53例临床疑似肝脏铁过载患者及21例对照受试者，对其开展肝脏磁共振成像检查。随后由两名对分组信息设盲的检查者估算肝脏铁浓度，两名检查者分别采用自动化T2*映射（T2* mapping）、自动化T1映射（T1 mapping）、手动T2*映射以及信号强度比法进行评估。本研究通过受试者工作特征曲线（Receiver Operating Characteristic curve, ROC）分析诊断准确性，并通过计算双向组内相关系数（intraclass correlation coefficient, ICC）分析观察者间与观察者内一致性。
结果：用于区分患者与对照受试者的ROC曲线下面积分别为：自动化T2*映射0.912，信号强度比法0.934，手动T2*映射0.908，T1映射0.80；其中T1映射的曲线下面积与其余三种方法存在显著差异。观察者间及观察者内一致性水平良好（组内相关系数为0.938~0.998；p<0.05）。涉及T1映射的相关性虽仍具有统计学意义，但相关性程度较低。
结论：在1.5 T场强下，T2*映射是一种快速的检测手段，在肝脏铁过载的诊断中展现出应用前景；而T1映射的诊断准确性相对较低，其性能劣于各类T2*方法。