From the Department of Radiology and Research Institute of Radiology (Y.L., S.S.L., N.K., E.K., Y.J.K., S.H.P., S.Y.K., M.G.L.) and Department of Clinical Epidemiology and Biostatistics (S.C.Y.), University of Ulsan College of Medicine, Asan Medical Center, 86 Asanbyeongwon-Gil, Songpa-Gu, Seoul 138-736, South Korea; Siemens AG, Healthcare, Oncology Applications Development, Erlangen, Germany (B.K.); and Siemens Healthcare Korea, Seoul, South Korea (I.S.K.).
Radiology. 2015 Feb;274(2):405-15. doi: 10.1148/radiol.14140759. Epub 2014 Sep 17.
To compare the influence of triggering methods for diffusion-weighted imaging (DWI) on apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) parameters in the liver, as well as regional variability and measurement repeatability.
In this institutional review board-approved prospective study, 12 healthy volunteers (six women, six men; mean age, 30 years) underwent 1.5-T DWI of the liver by using nine b values twice with free breathing (FB) without triggering (mean acquisition time ± standard deviation, 3.7 minutes ± 0), respiratory triggering (RT) (mean acquisition time, 6.8 minutes ± 1.4), and echocardiography triggering (ET) (mean acquisition time, 8.3 minutes ± 2.0) after providing written informed consent. ADC and IVIM parameters, including pure diffusion coefficient (D), perfusion fraction (f), and perfusion-related diffusion coefficient (D*), were measured by using 15 regions of interest (ROIs). Regional variability of ADC and IVIM parameters and measurement repeatability were evaluated by using the coefficient of variation (CV) across ROIs and within-subject CV, respectively.
ET DWI (range of CV across ROIs, 6.69%-20.0%) resulted in significantly decreased regional variability of ADC, D, and f, compared with FB DWI (13.86%-35.8%) and RT DWI (15.15%-35.91%, P ≤. 049). ET DWI showed better repeatability of ADC measurement (within-subject CV range, 3.17%-4.12% for ET DWI; 4.15%-4.74% for FB DWI; and 2.33%-6.96% for RT DWI), D (4.05%-5.34% for ET DWI, 4.11%-12.51% for FB DWI, and 3.19%-16.17% for RT DWI), and f (7.6%-9.86% for ET DWI, 13.83%-16.81% for FB DWI, and 10.05%-12.10% for RT DWI), compared with FB DWI and RT DWI, with significant differences in within-subject CV for D in the left hepatic lobe compared with RT DWI (P = .023) and for f compared with FB DWI (P ≤ .032). For all three imaging techniques, D* showed the worst repeatability (within-subject CV, 57.05%-156.61%) among ADC and IVIM parameters.
ET DWI is more effective for decreasing regional variability of ADC and IVIM parameters than FB DWI or RT DWI; it may improve measurement repeatability by reducing cardiac motion-induced measurement error.
比较触发式扩散加权成像（DWI）在肝脏表观扩散系数（ADC）和体素内不相干运动（IVIM）参数方面的影响，以及区域性变异性和测量重复性。
本研究为机构审查委员会批准的前瞻性研究，12 名健康志愿者（6 名女性，6 名男性；平均年龄，30 岁）使用 1.5-T 扫描仪进行两次肝脏 DWI 检查，两次检查均采用自由呼吸（FB）模式（平均采集时间±标准差，3.7 分钟±0 秒）、呼吸触发（RT）（平均采集时间，6.8 分钟±1.4 秒）和超声心动图触发（ET）（平均采集时间，8.3 分钟±2.0 秒）。在获得书面知情同意后，使用 15 个感兴趣区（ROI）测量 ADC 和 IVIM 参数，包括纯扩散系数（D）、灌注分数（f）和灌注相关扩散系数（D*）。通过 ROI 间的变异系数（CV）和个体内 CV 分别评估 ADC 和 IVIM 参数的区域性变异性和测量重复性。
与 FB DWI（13.86%-35.8%）和 RT DWI（15.15%-35.91%，P≤.049）相比，ET DWI（ROI 间 CV 范围，6.69%-20.0%）可显著降低 ADC、D 和 f 的 ROI 间变异性。ET DWI 显示 ADC 测量重复性更好（个体内 CV 范围，ET DWI 为 3.17%-4.12%；FB DWI 为 4.15%-4.74%；RT DWI 为 2.33%-6.96%），D（ET DWI 为 4.05%-5.34%，FB DWI 为 4.11%-12.51%，RT DWI 为 3.19%-16.17%）和 f（ET DWI 为 7.6%-9.86%，FB DWI 为 13.83%-16.81%，RT DWI 为 10.05%-12.10%），与 FB DWI 和 RT DWI 相比，左肝叶的 D 在个体内 CV 方面与 RT DWI 相比差异具有统计学意义（P=0.023），f 与 FB DWI 相比差异具有统计学意义（P≤0.032）。对于所有三种成像技术，ADC 和 IVIM 参数中 D*的重复性最差（个体内 CV 范围，57.05%-156.61%）。
与 FB DWI 或 RT DWI 相比，ET DWI 更有效地降低 ADC 和 IVIM 参数的 ROI 间变异性，通过减少心脏运动引起的测量误差，可能提高测量重复性。
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