Development of a novel estimation method for spatially varying noise levels in MR images

信噪比（Signal-to-Noise Ratio，SNR）是评价磁共振成像图像质量的重要指标，它对成像技术和硬件性能的变化非常敏感。SNR被定义为均匀感兴趣区域内的平均信号强度与作为其标准偏差估计的噪声的比率。然而，在MR图像中，信号均匀性差是相当普遍的，因此像素值的标准偏差受到图像均匀性的影响比真正的随机噪声更强烈。在这项研究中，我们已经开发出一个准确和强大的噪声估计方法计算可靠的SNR值。

Signal-to-noise ratio (SNR) is an important metric commonly used to evaluate image quality in magnetic resonance (MR) imaging, because it is quite sensitive to any change of imaging techniques and hardware performances. The SNR is defined as the ratio of the mean signal intensity within a homogeneous region of interest to noise estimated as its standards deviation. However, poor signal uniformity is fairly common in MR images, and thus standard deviation of pixel values is more strongly influenced by the image uniformity than true random noise. In this study, we have developed an accurate and robust noise estimation method for calculating reliable SNR values.