Demonstration of nonlinearity bias in the measurement of the apparent diffusion coefficient in multicenter trials
Demonstration of nonlinearity bias in the measurement of the apparent diffusion coefficient in multicenter trials
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DOI：
10.1002/mrm.25754
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发表时间：
2016-03-01
影响因子：
3.3
通讯作者：
Chenevert, Thomas L.
中科院分区：
文献类型：
--
作者：
Malyarenko, Dariya I.;Newitt, David;Chenevert, Thomas L.
PurposeCharacterize系统特定的偏见在多中心trials.MethodsDiffusion加权成像（DWI）的定量扩散测量常见的磁共振成像（MRI）平台上进行了一个冰水幻影沿着上下（SI）和右左（RL）的方向跨越150毫米。相同的扫描协议在7个成像中心的14个MRI系统上实施。偏倚估计为沿沿着单个DWI方向测量的表观扩散系数（ADC）的偏差。独立评估梯度非线性、匀场误差、成像梯度和涡流的相对贡献。所观察到的偏差误差进行了比较与数值models.ResultsThe测量的系统ADC误差缩放平方与等中心偏移，范围在-55%（SI）和25%（RL）。非线性偏倚取决于系统设计和扩散梯度方向。与数值模型相一致，轻微的ADC误差（+/- 5%），由于垫片，成像和涡流减轻了双回波DWI和图像配准的个别gradientdirections.ConclusionThe分析确认梯度非线性作为一个主要来源的空间DW偏差和变异性偏离中心ADC测量的MRI平台，从垫片，成像梯度和涡流的微小贡献。所开发的方案能够对多中心定量DWI研究中的系统偏倚进行经验性描述。Magn Reson Med 75：1312-1323，2016年。(c)2015 Wiley Periodicals，Inc.
PurposeCharacterize system-specific bias across common magnetic resonance imaging (MRI) platforms for quantitative diffusion measurements in multicenter trials.MethodsDiffusion weighted imaging (DWI) was performed on an ice-water phantom along the superior-inferior (SI) and right-left (RL) orientations spanning 150 mm. The same scanning protocol was implemented on 14 MRI systems at seven imaging centers. The bias was estimated as a deviation of measured from known apparent diffusion coefficient (ADC) along individual DWI directions. The relative contributions of gradient nonlinearity, shim errors, imaging gradients, and eddy currents were assessed independently. The observed bias errors were compared with numerical models.ResultsThe measured systematic ADC errors scaled quadratically with offset from isocenter, and ranged between -55% (SI) and 25% (RL). Nonlinearity bias was dependent on system design and diffusion gradient direction. Consistent with numerical models, minor ADC errors (+/- 5%) due to shim, imaging and eddy currents were mitigated by double echo DWI and image coregistration of individual gradient directions.ConclusionThe analysis confirms gradient nonlinearity as a major source of spatial DW bias and variability in off-center ADC measurements across MRI platforms, with minor contributions from shim, imaging gradients and eddy currents. The developed protocol enables empiric description of systematic bias in multicenter quantitative DWI studies. Magn Reson Med 75:1312-1323, 2016. (c) 2015 Wiley Periodicals, Inc.