Quality assurance in MRI breast screening: comparing signal-to-noise ratio in dynamic contrast-enhanced imaging protocols.
Quality assurance in MRI breast screening: comparing signal-to-noise ratio in dynamic contrast-enhanced imaging protocols.
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DOI：
10.1088/0031-9155/61/1/37
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发表时间：
2016-01-07
影响因子：
3.5
通讯作者：
Schmidt MA
中科院分区：
文献类型：
--
作者：
Kousi E;Borri M;Dean J;Panek R;Scurr E;Leach MO;Schmidt MA
MRI已广泛用于乳腺癌分期、管理和高危筛查。检测灵敏度在乳腺筛查中是至关重要的，但信噪比（SNR）作为位置的函数的变化往往被忽视。我们提出并证明了实用的方法来评估动态对比增强（DCE）乳腺检查中的空间SNR变化，并将这些方法应用于不同的协议和系统。四种不同的协议在三个不同的MRI系统（1.5和3.0 T）与不同设计的接收器线圈被用于充油的测试对象，有和没有均匀性过滤器。每个协议采集20个3D数据集;每个数据集在60秒内采集，因此符合当前乳腺DCE指南。除了在逐像素的基础上计算的标准SNR之外，我们还提出了其他区域指数，这些指数考虑了以每个像素为中心的一个小的子区域上的信号的平均值和标准差。这些区域指数包括线圈灵敏度的空间变化和其他结构化伪影的影响。所提出的区域SNR指数表明SNR的空间变化以及伪影和灵敏度变化的存在，否则难以量化并且在临床环境中可能被忽略。SNR的空间变化取决于协议选择和硬件特性。均匀性滤波器的使用被证明会导致SNR值的上升，从而改变噪声分布。相邻像素中的噪声之间的相关性与沿相位编码方向的数据截断沿着。使用区域信息的空间信噪比变化的方法进行了演示，与乳腺癌筛查和多中心试验的质量保证的影响。
MRI has been extensively used in breast cancer staging, management and high risk screening. Detection sensitivity is paramount in breast screening, but variations of signal-to-noise ratio (SNR) as a function of position are often overlooked. We propose and demonstrate practical methods to assess spatial SNR variations in dynamic contrast-enhanced (DCE) breast examinations and apply those methods to different protocols and systems. Four different protocols in three different MRI systems (1.5 and 3.0 T) with receiver coils of different design were employed on oil-filled test objects with and without uniformity filters. Twenty 3D datasets were acquired with each protocol; each dataset was acquired in under 60 s, thus complying with current breast DCE guidelines. In addition to the standard SNR calculated on a pixel-by-pixel basis, we propose other regional indices considering the mean and standard deviation of the signal over a small sub-region centred on each pixel. These regional indices include effects of the spatial variation of coil sensitivity and other structured artefacts. The proposed regional SNR indices demonstrate spatial variations in SNR as well as the presence of artefacts and sensitivity variations, which are otherwise difficult to quantify and might be overlooked in a clinical setting. Spatial variations in SNR depend on protocol choice and hardware characteristics. The use of uniformity filters was shown to lead to a rise of SNR values, altering the noise distribution. Correlation between noise in adjacent pixels was associated with data truncation along the phase encoding direction. Methods to characterise spatial SNR variations using regional information were demonstrated, with implications for quality assurance in breast screening and multi-centre trials.