Measurement of signal-to-noise ratios in MR images: Influence of multichannel coils, parallel imaging, and reconstruction filters
Measurement of signal-to-noise ratios in MR images: Influence of multichannel coils, parallel imaging, and reconstruction filters
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DOI：
10.1002/jmri.20969
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发表时间：
2007-08-01
影响因子：
4.4
通讯作者：
Schoenberg, Stefan O.
中科院分区：
文献类型：
--
作者：
Dietrich, Olaf;Raya, Jose G.;Schoenberg, Stefan O.
目的：为了评价不同方法的有效性，以确定信噪比（SNR）在MRI实验与多元素表面线圈，并行成像，和不同的重建filter.Materials和方法：四种不同的方法计算信噪比进行了比较，在体模测量和在体内的基础上：1）像素的标准偏差（SD）在多次重复采集; 2）差分图像中的信号统计;以及3）和4）采用背景噪声的平均值或SD的单个图像的两个单独区域中的统计。不同的接收线圈系统（一个和八个通道）、有和没有并行成像的采集以及五种不同的重建滤波器进行了比较。所有体模测量的平均值与多次采集方法提供的参考值的偏差为2.7%（SD 1.6%）差异法，37.7%对背景噪声平均值的判断正确率为25.9%，对噪声平均值的判断正确率为34.0%评价背景噪声标准差的正确率为38.1%。基于单个图像中的分离的信号和噪声区域的常规确定的SNR通常将不与在图1中测量的真实SNR一致。在应用某些重建滤波器、多通道重建或并行成像之后的图像。
Purpose: To evaluate the validity of different approaches to determine the signal-to-noise ratio (SNR) in MRI experiments with multi-element surface coils, parallel imaging, and different reconstruction filters.Materials and Methods: Four different approaches of SNR calculation were compared in phantom measurements and in vivo based on: 1) the pixel-by-pixel standard deviation (SD) in multiple repeated acquisitions; 2) the signal statistics in a difference image; and 3) and 4) the statistics in two separate regions of a single image employing either the mean value or the SD of background noise. Different receiver coil systems (with one and eight channels), acquisitions with and without parallel imaging, and five different reconstruction filters were compared.Results: Averaged over all phantom measurements, the deviations from the reference value provided by the multiple-acquisitions method are 2.7% (SD 1.6%) for the difference method, 37.7% (25.9%) for the evaluation of the mean value of background noise, and 34.0% (38.1%) for the evaluation of the SD of background noise.Conclusion: The conventionally determined SNR based on separate signal and noise regions in a single image will in general not agree with the true SNR measured in images after the application of certain reconstruction filters, multichannel reconstruction, or parallel imaging.