Wáng Yì Xiáng J, Li Yáo T, Chevallier Olivier, Huang Hua, Leung Jason Chi Shun, Chen Weitian, Lu Pu-Xuan
1 Department of Imaging and Interventional Radiology, Faculty of Medicine, The Chinese University of Hong Kong, New Territories, Hong Kong SAR.
2 Department of Vascular and Interventional Radiology, University of Bourgogne/Franche-Comté, François-Mitterrand Teaching Hospital, Dijon Cedex, France.
Acta Radiol. 2019 Jan;60(1):3-12. doi: 10.1177/0284185118774913. Epub 2018 May 9.
Intravoxel incoherent motion (IVIM) tissue parameters depend on the threshold b-value.
To explore how threshold b-value impacts PF ( f), D ( D), and D ( D*) values and their performance for liver fibrosis detection.
Fifteen healthy volunteers and 33 hepatitis B patients were included. With a 1.5-T magnetic resonance (MR) scanner and respiration gating, IVIM data were acquired with ten b-values of 10, 20, 40, 60, 80, 100, 150, 200, 400, and 800 s/mm. Signal measurement was performed on the right liver. Segmented-unconstrained analysis was used to compute IVIM parameters and six threshold b-values in the range of 40-200 s/mm were compared. PF, D, and D values were placed along the x-axis, y-axis, and z-axis, and a plane was defined to separate volunteers from patients.
Higher threshold b-values were associated with higher PF measurement; while lower threshold b-values led to higher D and D measurements. The dependence of PF, D, and D on threshold b-value differed between healthy livers and fibrotic livers; with the healthy livers showing a higher dependence. Threshold b-value = 60 s/mm showed the largest mean distance between healthy liver datapoints vs. fibrotic liver datapoints, and a classification and regression tree showed that a combination of PF (PF < 9.5%), D (D < 1.239 × 10 mm/s), and D (D < 20.85 × 10 mm/s) differentiated healthy individuals and all individual fibrotic livers with an area under the curve of logistic regression (AUC) of 1.
For segmented-unconstrained analysis, the selection of threshold b-value = 60 s/mm improves IVIM differentiation between healthy livers and fibrotic livers.
体素内不相干运动（IVIM）组织参数取决于阈值b值。
探讨阈值b值如何影响PF（f）、D（D）和D*（D*）值及其在肝纤维化检测中的性能。
纳入15名健康志愿者和33名乙型肝炎患者。使用1.5-T磁共振（MR）扫描仪并采用呼吸门控技术，采集10个b值（分别为10、20、40、60、80、100、150、200、400和800 s/mm²）下的IVIM数据。在肝脏右侧进行信号测量。采用分段无约束分析计算IVIM参数，并比较40 - 200 s/mm²范围内的6个阈值b值。将PF、D和D*值分别置于x轴、y轴和z轴上，并定义一个平面以区分志愿者和患者。
较高的阈值b值与较高的PF测量值相关；而较低的阈值b值导致较高的D和D测量值。PF、D和D对阈值b值的依赖性在健康肝脏和纤维化肝脏之间存在差异；健康肝脏的依赖性更高。阈值b值 = 60 s/mm²时，健康肝脏数据点与纤维化肝脏数据点之间的平均距离最大，分类回归树显示，PF（PF < 9.5%）、D（D < 1.239×10⁻³ mm²/s）和D*（D* < 20.85×10⁻³ mm²/s）的组合能够区分健康个体和所有纤维化肝脏个体，逻辑回归曲线下面积（AUC）为1。
对于分段无约束分析，选择阈值b值 = 60 s/mm²可改善IVIM对健康肝脏和纤维化肝脏的区分能力。
